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+
+
+International Telecommunication Union
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**K.11**
+
+(01/2009)
+
+SERIES K: PROTECTION AGAINST INTERFERENCE
+
+# --- **Principles of protection against overvoltages and overcurrents**
+
+Recommendation ITU-T K.11
+
+ITU-T
+
+![ITU logo: A globe with a red lightning bolt striking it, next to the text 'ITU International Telecommunication Union'.](84a1d09fb489061482111515543b60dc_img.jpg)
+
+ITU logo: A globe with a red lightning bolt striking it, next to the text 'ITU International Telecommunication Union'.
+
+
+
+## **Recommendation ITU-T K.11**
+
+# **Principles of protection against overvoltages and overcurrents**
+
+## **Summary**
+
+Recommendation ITU-T K.11 deals with protection principles, e.g., risk management, safety and reliability, surge protective devices and surge protective components. It gives guidance for the protection of telecommunication equipment, installations and cable plants exposed to the results of external sources of interference such as overvoltages and overcurrents due to lightning or effects related to power lines and electric traction systems.
+
+It gives general information about:
+
+- the origin of overvoltages and overcurrents (lightning, power induction, power contacts, earth potential rises);
+- types of protective devices (voltage-limiting and current-limiting devices) and their residual effects;
+- risk assessment;
+- protection of telecommunication lines;
+- protection of exchange and transmission equipment;
+- protection in access networks.
+
+Reference is made, in the bibliography, to some ITU-T K-series Recommendations and IEC standards related to:
+
+- power supply effects and low frequency interference;
+- lightning effects;
+- surge protective devices and components;
+- resistibility of telecommunications equipment.
+
+## **Source**
+
+Recommendation ITU-T K.11 was approved on 13 January 2009 by ITU-T Study Group 5 (2009-2012) under Recommendation ITU-T A.8 procedures.
+
+## **Keywords**
+
+Maintenance, protection, protective measures.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2010
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+# CONTENTS
+
+|     |                                                                           | Page |
+|-----|---------------------------------------------------------------------------|------|
+| 1   | Scope .....                                                               | 1    |
+| 2   | References.....                                                           | 1    |
+| 3   | Definitions .....                                                         | 2    |
+| 4   | Abbreviations and acronyms .....                                          | 3    |
+| 5   | General considerations.....                                               | 3    |
+| 5.1 | Effects related to power lines and electric traction systems.....         | 4    |
+| 5.2 | Effects related to lightning effects.....                                 | 5    |
+| 5.3 | Methods of protection.....                                                | 5    |
+| 5.4 | Surge protective devices and surge protective components .....            | 6    |
+| 5.5 | Residual effects .....                                                    | 7    |
+| 5.6 | Risk management .....                                                     | 8    |
+| 5.7 | Protection principles.....                                                | 9    |
+| 5.8 | Decision on protection.....                                               | 10   |
+| 6   | Protection of telecommunication lines .....                               | 11   |
+| 6.1 | Protective measures external to the conductors themselves.....            | 11   |
+| 6.2 | Special cables and protective systems .....                               | 12   |
+| 6.3 | Use of protective devices.....                                            | 12   |
+| 6.4 | Installation of protective devices .....                                  | 12   |
+| 7   | Protection of exchange and transmission equipment.....                    | 13   |
+| 7.1 | Need for protection external to the equipment.....                        | 13   |
+| 7.2 | Need for equipment to have a minimum level of electrical robustness ..... | 13   |
+| 7.3 | Effect of switching conditions.....                                       | 14   |
+| 8   | Protection in access networks.....                                        | 14   |
+| 8.1 | Degree of exposure.....                                                   | 14   |
+| 8.2 | Use of SPDs and SPCs .....                                                | 14   |
+| 8.3 | Equipotential bonding .....                                               | 15   |
+| 8.4 | High isolation techniques .....                                           | 15   |
+| 8.5 | National regulations.....                                                 | 15   |
+| 8.6 | Maintenance of installations.....                                         | 16   |
+|     | Bibliography.....                                                         | 17   |
+
+# **Introduction**
+
+Overvoltage protection may be required for safety of persons and for protection of equipment. To provide this protection, it is necessary to interconnect the metallic parts (shield, sheath) along the line and to bond them to the local or building earth, conductors are installed via SPDs at the entrance of the entered structure. This will reduce the risk of injury to people using these services during a.c. fault conditions and during lightning storms. These methods will also provide a level of protection for equipment connected to one or more of these services.
+
+## Recommendation ITU-T K.11
+
+# Principles of protection against overvoltages and overcurrents
+
+# 1 Scope
+
+Current ITU-T publications recognize lightning and faults on nearby electrical installations as sources of dangerous disturbances in telecommunication lines, which may cause damage leading to interruptions in service and the need for repairs or even hazards to personnel.
+
+The objective of this Recommendation is to set out principles which enable the frequency and seriousness of such disturbances to be limited to levels which take account of quality of service, operating costs and safety of personnel. These principles are applicable to all parts of a telecommunications system and cover:
+
+- power supply effects and low frequency interference;
+- lightning effects;
+- surge protective devices and components.
+
+More details on risk calculation, certain methods of protection and protective devices are given in the Recommendations mentioned in the bibliography.
+
+The telecommunication network to be protected using this Recommendation is limited to telecommunication lines using metallic conductors (buried or aerial cables, shielded or unshielded cables, reference configuration, see [ITU-T K.72]). Responsibilities for protection at customer premises are given in [ITU-T K.66].
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [ITU-T K.66] Recommendation ITU-T K.66 (2004), *Protection of customer premises from overvoltages*.
+- [ITU-T K.72] Recommendation ITU-T K.72 (2008), *Protection of telecommunication lines using metallic conductors against lightning – Risk management*.
+- [IEC 61643-1] IEC 61643-1 (2005), *Low-voltage surge protective devices – Part 1: Surge protective devices connected to low-voltage power distribution systems – Requirements and tests*.
+- [IEC 61643-21] IEC 61643-21 (2009), *Low-voltage surge protective devices – Part 21: Surge protective devices connected to telecommunications and signalling networks – Performance requirements and testing methods*.
+
+ITU-T Recommendations and other documents containing deeper information and provisions, which are relevant to calculate the need of protective measures, the options of protective methods and protective devices are listed in the bibliography.
+
+# 3 Definitions
+
+This Recommendation defines the following terms:
+
+**3.1 active reduction system (ARS):** An active reduction system uses a transformer to compensate for induced voltages in the telecommunication cable system. It operates on the basis that, via a transformer, a voltage with a phase shift by 180°, but of the same amplitude, is coupled into the telecommunication cable to be protected. It consists of a coupling element (iron core with a primary winding, a control winding connected to a pilot conductor, a corresponding number of secondary windings) and an amplifier with a power supply.
+
+**3.2 inherent protection:** Inherent protection is that protection which is provided at an equipment interface either by virtue of its intrinsic characteristics or by specific design.
+
+**3.3 maintenance:** Combination of all technical and administrative actions, including supervision actions, intended to retain an item in, or restore it to, a state in which it can perform a required function.
+
+**3.4 multistage protection:** Multistage protection is the application of sequential protection stages to achieve the intended overall protection level. The location and level of each stage must be coordinated.
+
+**3.5 passive reduction system (PRS):** A passive reduction system uses a step-down transformer to compensate for induced voltages in a telecommunication cable system. It consists of an iron core with a primary winding (the grounded cable sheath or a pilot conductor) and a corresponding number of secondary windings. In general, the secondary windings are shielded telecommunication cables.
+
+**3.6 pilot conductor:** Grounded wire, grounded on both sides of the influenced path to get the steering voltage for the control winding of the active reduction system (ARS) or passive reduction system (PRS).
+
+**3.7 primary protection:** Primary protection is applied using a surge protective device (SPD) to protect an interface or port of an equipment, at the location where it diverts most of the stressful energy from propagation into the equipment. This SPD must be accessible, removable and connected to equipotential bonding.
+
+**3.8 protection coordination:** Protection coordination is the act of ensuring that all the protection elements, internal and external to the equipment, react in such a way so as to limit the amount of energy, voltage or current to levels such that damage does not occur to protection elements or equipment.
+
+**3.9 resistibility:** Resistibility is the ability of telecommunication equipment or installations to withstand, in general, without damage, the effects of overvoltages or overcurrents, up to a certain, specified extent, and in accordance with a specified criterion.
+
+**3.10 secondary protection:** Secondary protection is applied subsequent to the primary protection. It may be provided by inherent protection.
+
+**3.11 surge protective component (SPC):** Constituent part of a surge protective device which cannot be physically divided into smaller parts without losing its protective function.
+
+NOTE 1 – This is a modification to definition of item 151-11-21 (component) in the International Electrotechnical Vocabulary [b-IEC 60050-151].
+
+NOTE 2 – The protective function is non-linear; amplitude restriction effectively begins when the amplitude attempts to exceed the predetermined threshold value of the component.
+
+**3.12 surge protective device (SPD):** Device that restricts the voltage of a designated port or ports, caused by a surge, when it exceeds a predetermined level.
+
+NOTE 1 – An SPD is a combination of a protection circuit and a holder.
+
+NOTE 2 – Secondary functions may be incorporated, such as current limiting to restrict a terminal current.
+
+NOTE 3 – Typically, the protection circuit has at least one non-linear voltage-limiting surge protective component.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|      |                                             |
+|------|---------------------------------------------|
+| ABD  | Avalanche Breakdown Diode                   |
+| ARS  | Active Reduction System                     |
+| BB   | Bonding Bar                                 |
+| DSL  | Digital Subscriber Line                     |
+| EBB  | Equipotential Bonding Bar                   |
+| EMC  | Electromagnetic Compatibility               |
+| GDT  | Gas Discharge Tube                          |
+| ISDN | Integrated Services Digital Network         |
+| ITE  | Information Technology Equipment            |
+| MET  | Main Earth Terminal                         |
+| MDF  | Main Distribution Frame                     |
+| MOV  | Metal Oxide Varistor                        |
+| NT   | Network Termination                         |
+| OCP  | Overcurrent Protector                       |
+| PRS  | Passive Reduction System                    |
+| PTC  | Positive Temperature Coefficient thermistor |
+| RF   | Radio Frequency                             |
+| SOP  | Semiconductor Overcurrent Protector         |
+| SPC  | Surge Protective Component                  |
+| SPD  | Surge Protective Device                     |
+| TSS  | Thyristor Surge Suppressor                  |
+
+# **5 General considerations**
+
+When considering protecting a telecommunication network, it is important to determine the probable overvoltage and overcurrent sources and how energy from these sources is coupled into the network, since there are means for reducing the amount of energy coupled into the telecommunication system, the equipment and its installation.
+
+It is reasonable that the electromagnetic environment should be the major dimensioning factor for protection needs. The electromagnetic environment effect is, on one hand, dependent on the type and probability of the occurrence of the electromagnetic phenomena and, on the other hand, on the physical layout of the system.
+
+The protective measures shall not decrease the electromagnetic compatibility (EMC) of the system and shall not degrade its intended function as described in the product standards for the system.
+
+NOTE – EMC means the ability of equipment or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment.
+
+## **5.1 Effects related to power lines and electric traction systems**
+
+Depending on the physical process, the effects of high voltage power feeding/transforming or traction systems on a telecommunication system can be divided into:
+
+- capacitive coupling which represents the effect of an electric field (electric induction);
+- inductive coupling which represents the effect of a magnetic field (magnetic induction);
+- conductive coupling which represents the effect of a conduction field due to current in the earth.
+
+These effects may contain multiple components, mainly inductive and conductive coupling. Telecommunication systems with dense electrical integration will be more liable to direct damage due to the reduced creepage distances and clearances.
+
+For a broad understanding of telecommunication, power and electrified railway facilities, and their mutual coupling effects, consult [b-Handbook II] and [b-Handbook VI].
+
+### **5.1.1 Induction from fault currents**
+
+Induction from fault currents (earth faults) in power lines, including electric traction systems, causes large unbalanced currents to flow along the power line inducing overvoltages into adjacent telecommunication lines which follow a parallel course. The overvoltages may rise to several kilovolts and have durations of 200 to 1000 ms (occasionally even longer) depending on the fault clearing system used on the power line.
+
+### **5.1.2 Contact with power lines**
+
+Contact between power and telecommunication lines may occur when local disasters, e.g., storms, fires, cause damage to both types of plant or when the normal safeguards of separation and insulation are not followed. Overvoltages from direct contact of overhead lines rarely exceed 230 V a.c. r.m.s. in countries where this is the common distribution voltage, but may continue for an indefinite period until observed. Where higher distribution voltages (e.g., 2 kV) are used, the power line protection arrangements usually ensure that the voltage is removed in a short time if a fault occurs. The overvoltage may cause excessive currents to flow along the line to the exchange earth causing damage to equipment and danger to staff.
+
+### **5.1.3 Rise of earth potential**
+
+Earth faults in power systems cause currents in the soil which raise the potential in the neighbourhood of the fault and of the power supply earth electrode. These earth potentials may affect telecommunication plants in two ways:
+
+- a) For crossbar switches and equipment whose metallic lines take the ground as their loop, telecommunication signalling systems may malfunction if their earth electrodes are in soil whose potential rises by as little as 5 V with respect to true earth. Such voltages may be caused by minor faults on the power system which may remain undetected for long periods. However, for stored program control switches and equipment taking optical fibre cable as their loop, it is not required to consider the interference caused by potential rise due to faults on the power system.
+
+NOTE – Such effects of potential rise on program control switches are different from on the crossbar switches and equipment taking the ground as their loop. Adopting optical fibre cables as the media between program control switches avoids interference due to possible potential difference when the metallic lines take the ground as their loop.
+
+- b) Higher rises of earth potential can cause danger to staff working in the affected area or, in extreme cases, may be sufficient to break down insulation of the telecommunication cable, causing extensive damage.
+
+## **5.2 Effects related to lightning effects**
+
+### **5.2.1 Direct lightning strikes**
+
+Such strikes may cause currents of some thousands of amperes to flow along wires or cables for some microseconds. Physical damage may occur and overvoltage surges of many kilovolts may apply stress to the dielectrics of line plant and terminal equipment.
+
+### **5.2.2 Lightning strikes nearby**
+
+Lightning currents flowing from cloud to earth or cloud to cloud cause overvoltages in overhead or underground lines near to the strike. The area affected may be large in districts of high earth resistivity.
+
+## **5.3 Methods of protection**
+
+The telecommunication network can be endangered by atmospheric discharge, power influence and power cross. Protective measures must be coordinated with the system to be protected. Protection of the telecommunication network and its service is achieved by following fundamental protection methods:
+
+- Earthing: Reliable electrical connection of the system with a conductor that provides a low impedance path to the earth (ground) to prevent hazardous voltages from appearing on equipment. Normally, a grounding conductor does not carry current.
+- Equipotential bonding: Electrical connection putting various exposed conductive parts and extraneous conductive parts at a substantially equal potential. It is orientated to reduce the earth potential difference between different metallic conductors, equipment and circuits in the case of faults or external interference (such as lightning strike).
+- Shielding: Shielding is the process of limiting the flow of electromagnetic fields between two locations, by separating them with a barrier made of conductive material. Typically, it is applied to enclosures, separating the system from the electrical environment. Shielding used to block radio frequency electromagnetic radiation is also known as RF shielding.
+- Improving insulation strength: Improvement of the insulation level of the equipment and lines to prevent overvoltage from damaging insulation so as to ensure equipment and personal safety.
+- Disconnection: Allocation of the line with a fuse, resettable OCP (PTC, SOP) or switch facility to prevent excessive energy from entering sensitive circuits.
+- Current distribution: Installation of an SPD between the lines and/or between lines and earth. SPDs restrict the voltage of a designated port or ports, caused by a surge, when it exceeds a predetermined level. The decision to use surge protective devices (SPDs) is most properly based on an analysis of the risks that are seen by the network or system under consideration.
+- Counter voltages: Counter voltages are used to compensate for induced voltages.
+
+Some of the protective measures for lines which are described in clause 6 have the effect of reducing overvoltages and overcurrents at their source and so reduce the risk of damage to all parts of the system.
+
+Other protective measures which may be applied to specific parts of the system, as indicated in clauses 6, 7 and 8, can be separated into two classes:
+
+- the use of protective devices which prevent excessive energy from reaching vulnerable parts either by diverting it (for example, spark gaps) or by disconnecting the line (for example, fuses);
+- the use of equipment with suitable dielectric strength, current-carrying capacity and impedance so that it can withstand the conditions applied to it.
+
+## **5.4 Surge protective devices and surge protective components**
+
+When considering the application of protective devices and components to a telecommunication system, the probable overvoltage and overcurrent sources, and how energy from these sources is coupled into the network, have to be identified by risk assessment and/or experience.
+
+Primary and secondary protection should always be coordinated correctly. To ensure that two cascaded SPDs or SPCs and a following SPD or the telecommunications system are coordinated, it might be necessary to select primary protection and secondary protection (or multistage protection) to ensure that the inherent protection of the system is not exceeded (see clause 5.7.6).
+
+### **5.4.1 Gas discharge tubes**
+
+Usually, GDTs are used as primary protection connected between each wire of a line and earth or as 3-electrode units between a pair and earth. Their performance may be specified to precise limits to meet system requirements. GDTs operate frequently without degradation if not overloaded.
+
+In case of direct contact between power lines and telecommunication lines, the GDT might be stationary ignited. To prevent this, the GDT might offer a failsafe function whereby heating is detected by a mechanism that is thermally initiated to short-circuit the electrodes of the GDT.
+
+NOTE – Air-gap protectors with carbon or metallic electrodes are usually connected between each wire of a line and earth, they limit the voltage which can appear between their electrodes. They are inexpensive but their insulation resistance can fall appreciably after repeated operation and they may require frequent replacement. For that reason, they are nowadays uncommon.
+
+### **5.4.2 Semi-conductor protective devices**
+
+Semi-conductor protective devices are usually used as secondary protection, but developments in the technology of these devices have produced some units which may be used as primary protection. Semi-conductor protective devices operate frequently without degradation if not overloaded.
+
+### **5.4.3 Varistor**
+
+Usually connected between each wire of a line and earth or across the wires, varistors are nonlinear two-electrode voltage-dependant resistors, whose resistance decrease with increasing voltage. Varistors operate frequently with degradation after repeated transient events.
+
+### **5.4.4 Fuses**
+
+Fuses are connected in series with each wire of a line to disconnect when excessive current flows. Simple fuses have a uniform wire which melts. Slow-acting fuses have a uniform wire which melts quickly when a large current flows, and a spring-loaded fusible element which melts gradually and disconnects when lower currents flow for a prolonged time. High level currents of 2 A and prolonged currents of 250 mA are typical operating levels. Fuses should not sustain an arc after operation. Fuses do not give protection against lightning surges and, in districts where such surges are common, fuses of a high rating (up to 20 A) may be necessary to avoid trouble from fuse failures. Such fuses may not give adequate protection against power line contacts. Fuses can also be a source of noise and disconnection faults. Fuses permanently interrupt a circuit when operated and it is necessary to replace them manually.
+
+### **5.4.5 Heat coils**
+
+Heat coils are connected in series with each wire of a line. Heat coils either disconnect the line, earth it, or do both, with the earth extended to line. Heat coils have some fusible component and operate when currents of, typically, 500 mA flow for some 200 s. Heat coils permanently interrupt a circuit when operated and it is necessary to replace them manually.
+
+### **5.4.6 Fusible links**
+
+Fuseless overvoltage protector assemblies installed on telecommunication lines can be protected against the risk of overheating in the event of a prolonged contact between the telecommunication line and a power distribution line by means of a fusible link.
+
+A fusible link usually consists of insulated conductors in series with the telecommunication line and located between the exposure to the power line and the protector assembly. The conductors are usually at least two wire gauges smaller than the conductors terminated on the protector assembly and are of a suitable length to avoid a sustained arc if the power system does not de-energize promptly and the conductors fuse. If the fusible link, or part of it, is installed in a building or other location where a fire hazard might occur, it is enclosed within a cable sheath, splice enclosure or other suitable enclosure to contain any arcing that may result if the conductors fuse.
+
+### **5.4.7 Overcurrent protectors**
+
+Overcurrent protectors (OCPs) are placed in series with each wire of a line and operate to limit excessive a.c. currents as an open circuit. There are variable impedance devices which, when heated by overload currents, increase their electrical resistance to a very high value. When the overload is removed, the devices will return to their normal condition and permit operation of the line.
+
+## **5.5 Residual effects**
+
+The essential purpose of protective measures is to ensure that the major part of the electrical energy arising from a disturbance is not dissipated in a vulnerable part of the installation and does not reach personnel. However, no device exists which has characteristics for suppressing ideally all voltages or currents connected with disturbances, for the following reasons.
+
+### **5.5.1 Residual overvoltages**
+
+Account should be taken of:
+
+- a) voltages which are unaffected by the protective device because they are below its operating level;
+- b) transients which pass before the device operates;
+- c) residuals which are sustained after the device operates;
+- d) transients produced by the operation of the device.
+
+### **5.5.2 Transverse voltages**
+
+Protective devices on the two wires of a pair may not operate simultaneously and so a transverse pulse may be produced. Under certain conditions, particularly if the equipment to be protected has a low impedance, operation of one protective device may prevent the operation of the other one and a transverse voltage may remain as long as the longitudinal voltages are on the line.
+
+### **5.5.3 Effect on normal circuit operation – Coordinated design**
+
+Sufficient separation should be allowed between the operating voltage of the protective devices and the highest voltage occurring on the line during normal operation.
+
+Likewise, the normal characteristics (internal impedances) of the protective elements must be compatible with the normal functioning of the installations, which must take account of their possible presence.
+
+### **5.5.4 Modifying effects**
+
+SPDs may safeguard one part of a line at the expense of another, e.g., if an MDF fuse operates due to a power line contact, the voltage on the line may rise to full power line voltage when the fuse disconnects the telecommunication's earth.
+
+Likewise, the operation of an SPD may greatly reduce the equivalent internal impedance of a circuit relative to equipment connected to it, thus permitting the circulation of currents which may cause damage.
+
+### **5.5.5 Protection coordination**
+
+For the protection of sensitive equipment, it is sometimes necessary to use more than one protective device, e.g., a fast-operating, low-current device such as a semiconductor and a slower-operating, high-current device such as a gas discharge tube. In such cases, steps must be taken to ensure that, in the event of a sustained overvoltage, the low-current device does not prevent the operation of the high-current device since, if this happens, the smaller device may be damaged, or the interconnecting wiring may conduct excessive current.
+
+### **5.5.6 Temperature rise**
+
+SPCs or SPDs should be designed and positioned in such a way that the rise in temperature which occurs when they operate is unlikely to cause damage to property or danger to people.
+
+### **5.5.7 Circuit availability**
+
+The circuit being protected may be temporarily or permanently put out of service when a protective device operates.
+
+### **5.5.8 Fault liability**
+
+The use of SPDs may cause maintenance problems due to unreliability. They may also prevent some line and equipment testing procedures.
+
+## **5.6 Risk management**
+
+The need for protective measures (e.g., protection with SPDs) should be based on a risk assessment considering the probability of overvoltage and overcurrent. The assessment of all parts of the network shall attain a well-coordinated protection of the whole network. This takes into account the consequences of the loss of service for the customer and the network operator, the importance of the system (e.g., hospitals, traffic control), the electromagnetic environment at the particular site (probability of damages) and the cost related to repair.
+
+### **5.6.1 Assessment of risk**
+
+The performance of a telecommunications system with respect to overvoltages depends on:
+
+- the environment, i.e., the magnitude and probability of overvoltages occurring in the line network associated with the system;
+- the construction methods used in the line network, see clause 6;
+- the resistibility of equipment in the system;
+
+- the provision of protective devices;
+- the quality of the earth system provided for the operation of the protective devices.
+
+The above aspects have to be taken into account to assess the risk.
+
+### **5.6.2 Sources of damage**
+
+In assessing the environment, consideration should be given to the effects mentioned in clauses 5.1 and 5.2.
+
+The severity of overvoltages due to lightning varies widely in different localities. A high keraunic level and a high soil resistivity increase the risk of direct and nearby lightning strokes. Lightning is the cause of a large proportion of power system faults, induction and rise of earth potential effects are also increased. On the other hand, buried metal plant, such as water pipes, armoured cables, etc., screens telephone cables greatly reduces overvoltages due to lightning or induction.
+
+- In city centres and in regions of low keraunic activity, experience shows that overvoltages rarely exceed the residual voltages of protective devices and such environments may be classified as "unexposed". Product Recommendations (listed in the bibliography) specify "basic test levels" to be applied to equipment for use in unexposed environments without protection, and these tests give an indication of the most severe environment which can be regarded as unexposed.
+- All other environments are classified as "exposed" but this, of course, covers a wide range of conditions including exceptionally exposed situations where a satisfactory service can only be achieved by the use of all available protective measures. Product Recommendations (listed in the bibliography) specify "enhanced test levels" applied to equipment for use in exposed environments.
+
+In the case of induced voltages and rise of earth potential, the overvoltages can be calculated with the documents indicated in the bibliography (i.e, those that relate to power supply effects and low frequency interference, and lightning effects) which also recommend the maximum values which may be permitted under various conditions.
+
+### **5.6.3 Fault records**
+
+The risk of overvoltages and overcurrents might be assessed in the light of experience. It is recommended that fault statistics be kept in a form which is convenient for that purpose. Faults due to overvoltages or overcurrents and faults due to failures of protective components should be separated from each other and from other component faults.
+
+## **5.7 Protection principles**
+
+### **5.7.1 Safety principle**
+
+Protection devices should be able to prevent such faults as fire hazards and/or large-scale communication interruption due to extension of the negative effects of the damage to telecommunication equipment, so as to limit the faults within a range acceptable to operators.
+
+When designing, installing and using protective devices, it is required to take it into consideration that the temperature rise due to enabling them should not be high enough to damage their attributes or endanger personal safety.
+
+Radioactive materials or other harmful materials must not be adopted for protective devices.
+
+### **5.7.2 Reliability principle**
+
+Effective protection should be realized within a specified reaction time, and for a specified duration, when the protective devices are exposed to the overvoltage and overcurrent conditions described in this Recommendation. Unreliable protection devices may affect communication as well as maintenance and testing for some lines and equipment.
+
+### **5.7.3 Availability principle**
+
+Designing, installing and using protection devices should not affect normal running of the equipment under protection. The signal loss during transmission and impedance should be limited to a specified range. In addition, convenient installation, maintenance and replacement should be ensured for protective devices, and the effect on other telecommunication lines should be as little as possible.
+
+The non-operating current of second level overcurrent protection should be less than that of first level overcurrent protection.
+
+### **5.7.4 Economy principle**
+
+The appropriate protection level and economic technical scheme should be selected on the basis of safety and reliability.
+
+Since any device itself may be the origin of faults, adopting inappropriate protection devices and circuits for excessive protection is not only very wasteful, but also can attenuate system performance.
+
+### **5.7.5 Principle of hierarchical protection**
+
+Based on safety and economy principles, determine whether to adopt basic protection (second level protection) only or enhanced protection (including both first and second level protection).
+
+### **5.7.6 Coordination principle**
+
+To ensure that two cascaded SPDs, or an SPD and an information technology equipment (ITE) to be protected, are coordinated during overvoltage conditions, the output protective levels from the SPD shall not exceed the input resistibility levels of the followed SPD or the ITE for all known and rated conditions.
+
+For example, the second level SPD adopts small current devices with fast operation (such as semiconductor protective devices), while first level SPD adopts strong current devices with slower operation (such as gas discharge tubes). In this case, coordination is required to prevent the second level SPD from affecting the operation of first level SPD, as well as from being damaged by overcurrent.
+
+For overcurrent protection, the output current upon the operation of first level overvoltage protection should be lower than the non-operating current. Besides, the current-limit operation time for the first level overcurrent protection should be less than that of the second level overcurrent protection.
+
+Normal telecommunication conditions should be appropriately maintained during the implementation of protection circuits or devices.
+
+## **5.8 Decision on protection**
+
+In considering the degree to which a telecommunication network should withstand overvoltages, two classes of failure may be recognized:
+
+- Minor failures affecting only small parts of the system. These may be allowed to occur at a level acceptable to the administration.
+
+- Major breakdowns, fires, exchange failures, etc., which must, so far as possible, be avoided completely.
+
+Examples of conditions which may be permitted to cause minor failures but not major breakdowns are given in the product Recommendations (listed in the bibliography). It is desirable also that failure of a single protective device should not cause a major breakdown. Particular attention should be given to overvoltage and overcurrent protection for new types of exchange or customer equipment to ensure that the benefits of its improved facilities are not lost due to unacceptable failures arising from exposure to overvoltages or overcurrents. Such equipment may be inherently sensitive to these conditions and damage or malfunction may affect large parts of a system. It should be noted that over-protection, by the provision of unnecessary protective devices, is not only uneconomic but may actually worsen system performance since the devices themselves may have some liability to cause failures.
+
+To avoid disturbances in telecommunication circuits caused by activated protective devices, the striking voltage values and the numbers of arresters should be considered.
+
+In the light of the above considerations and the assessment of risks in accordance with clause 5.6.1, a decision should be made on the protection to be provided in all parts of the system. Account should be taken of commercial considerations such as the cost of protective measures, the cost of repairs, relations with customers and the probable frequency of faults due to overvoltage and overcurrent relative to the fault rate due to other causes.
+
+The responsibility for making this decision and for ensuring the provision of any protective devices needed to coordinate lines and equipment should be clearly laid down.
+
+It is necessary for manufacturers of equipment to know the conditions that the equipment will need to resist and for line engineers to know the resistibility of the equipment which will be connected to the lines. The line engineer should also define the constraints which equipment connected to the line will encounter, depending on the standards of line protection provided. Where parts of the network, such as equipment installed in customer premises, lines and telecommunications centres may be under different ownership, this coordination may require formal procedures such as the production of local standards. The Recommendations listed in the bibliography that are related to resistibility of telecommunications equipment give guidance for the preparation of these standards.
+
+# **6 Protection of telecommunication lines**
+
+The general considerations of clauses 5.5 and 5.7 apply to the protection of telecommunication lines. It is highly recommended that the protective measures applied to the line should be decided at the outset of a project and should depend on the environment. It may be difficult and expensive to achieve a satisfactory standard of reliability from a line provided initially with insufficient protection.
+
+Where lines in a telecommunication network are exposed to frequent or severe disturbances from power line faults or lightning, the voltage of these lines relative to local earth potential should be limited either by connecting protective devices between the line conductors and earth or by using appropriate construction methods for the line.
+
+## **6.1 Protective measures external to the conductors themselves**
+
+Telecommunication lines may be shielded from lightning and power induction to some extent by adjacent earthed metal structures, e.g., power lines or electric railway systems. Efficient metallic screens either in the form of cable sheaths, cable ducts or lightning guard wires, reduce the effects of lightning surges and power line induction. It is necessary to point out that these metal structures, like the screen of the cable, shall be continuous and connected across all splices along the length of the cable, and shall be connected to the BB, preferably directly or through an SPD (to avoid corrosion problems), at the ends of the cable.
+
+Induction from power lines may be minimized by coordinating the construction practices for the power and telecommunication lines. The level of induction may be reduced at its source by the installation of earth wires and current limiters in the power system.
+
+The likelihood of contacts occurring between power lines and telecommunications lines is reduced if agreed standards of construction, separation and insulation are followed. Economic considerations arise, but it is often possible to benefit from jointly using trenches, poles and ducts, providing suitable safe practices are adopted.
+
+Installing buried telecommunication lines instead of an aerial will halve the risk of damage due to overvoltages.
+
+## **6.2 Special cables and protective systems**
+
+Standard plastic insulated and sheathed cables have a higher dielectric strength than paper-insulated, lead-sheathed cables and are suitable for most situations where cables with extra thick insulation were formerly used. The use of cables with strengthened insulation may be justified in situations where there is exceptional proximity or length of parallelism to power lines, high rise of earth potential in the immediate neighbourhood of power stations, or extreme exposure to lightning due to high keraunic level and low soil conductivity.
+
+Examples of special cables and protective systems are:
+
+- cables with metal sheaths which provide a good reduction factor to screen circuits within the cable;
+- cables which carry circuits to exposed radio towers and which must be able to carry lightning discharge currents without damage;
+- all-dielectric (i.e., non-metallic) optical fibre cables to affect isolation between conductive lengths of cable;
+- active or passive reduction systems (ARS, PRS).
+
+## **6.3 Use of protective devices**
+
+The use of protective devices may be desirable in the following circumstances.
+
+They may be more economical than the special construction described in clauses 6.1 and 6.2. In this regard, the cost of maintenance should not be overlooked since protective devices inevitably incur some maintenance expenditure whereas special cables, screening, etc., though initially expensive, usually incur no continuing costs.
+
+Cables with extra thick insulation may themselves be undamaged by overvoltages or overcurrents, but they can nevertheless conduct such conditions to other more vulnerable parts of the network. Extra protection is then required for the more vulnerable cables, which is particularly important if these are large underground cables which are expensive to repair and affect service to many customers.
+
+Induced overvoltages from power or traction line faults may still exceed levels permitted by the Directives (see bibliography entries that relate to power supply effects and low frequency interference) even after all practicable avoidance measures have been followed.
+
+## **6.4 Installation of protective devices**
+
+To protect conductor insulation, it is beneficial to bond all metal sheaths, screens, etc., together, and to connect overvoltage protectors between the conductors and this bonded metal which should be connected to earth. This technique is particularly useful in districts of high soil resistivity as it avoids the need for expensive electrode systems for the protector-earth connection.
+
+Where protectors are used to reduce high voltages appearing in telecommunication lines due to induction from power line fault currents, they should be fitted to all wires at suitable intervals and at both ends of the affected length of line, or as near to this as practicable.
+
+To protect underground cables against lightning surges, protective devices may be placed at the points of connection to overhead lines. The protective devices fitted at the MDF and at customers' terminals reduce the risk of damage to lines, but their main function is to protect components having lower dielectric strength than the cables.
+
+Connections for lines and earth to overvoltage protectors used against lightning should be as short as possible to minimize surge voltage levels between lines and the equipotential bond point.
+
+# **7 Protection of exchange and transmission equipment**
+
+## **7.1 Need for protection external to the equipment**
+
+Network operators should take account of the possible need to fit protection external to the equipment, bearing in mind the considerations given below.
+
+A telecommunication line will give some protection to equipment under certain conditions, e.g.:
+
+- a conductor may melt and disconnect an excessive current;
+- conductor insulation may break down and reduce an overvoltage;
+- air-gaps in connection devices may break down and reduce overvoltages.
+
+The robustness of plastic insulated cables has the effect of increasing the levels of overvoltages and overcurrents which can occur in the lines and be applied to equipment. By contrast, the use of miniature electronic components in telecommunication equipment tends to increase its vulnerability to electrical disturbances.
+
+For these reasons, in districts exposed to frequent and serious disturbances (lightning, power lines, soil of low conductivity), it is usually necessary to interpose protective devices of the types described in clause 5.4 between the cable conductors and the equipment to which they are connected, preferably on the MDF. This will prevent cables from the MDF to equipment from having to carry heavy overcurrents.
+
+The protective devices are fitted to the line side of the MDF to avoid the need to carry discharge currents in the MDF jumper field and to expose as little of the MDF wiring and terminal strips as possible to mains voltage in the event that a mains voltage line contact causes a series protective device to disconnect the line.
+
+In less exposed locations, it may be that disturbances (voltages and currents) have statistical characteristics of level and frequency so low that in practice the risks do not exceed those resulting from the residual effects indicated in clause 5.5 for exposed regions. Protective devices then serve no purpose and are an unnecessary expense.
+
+## **7.2 Need for equipment to have a minimum level of electrical robustness**
+
+In locations where lines are exposed and protective devices are provided, the residual effects can cause overvoltages and overcurrents to appear in the equipment. In less exposed environments, the disturbances described in clause 7.1 can cause similar effects. It is necessary for equipment to be designed to withstand these conditions, and detailed Recommendations on the resistibility which telecommunication equipment should possess are listed in the bibliography.
+
+## **7.3 Effect of switching conditions**
+
+Since the configuration and interconnection of equipment connected to a given line is required to vary during the successive stages of connecting a call, it is important not to limit the study of protection solely to individual line equipment. Much equipment is common to all lines and can be exposed to disturbances when connected to a particular line.
+
+The effectiveness of the protection provided can be influenced by the reduction in the probability of exposure if the effective duration of the connection to lines is short. On the other hand, common equipment should be better protected since its failure risks more serious degradation in the performance of the service.
+
+# **8 Protection in access networks**
+
+The increasing use and interconnection of complex electronic telecommunication equipment, such as ISDN terminals, modems and computers, at customers' buildings and xDSL equipment in curbs, requires special care for protecting against overvoltages and overcurrents. Such overvoltages and overcurrents include exposure of the serving telecommunication cable and power line to lightning, and the coupling of a.c. voltages onto the telecommunication cable due to faults on the external power system. Properly configured equipotential bonding within the structure helps to achieve the necessary protection, while also helping to ensure the safety of those using the equipment.
+
+It is reasonable that the electromagnetic environment should be the major dimensioning factor for protection needs, and not its ownership. The electromagnetic environment effect is, on one hand, dependent on the type and probability of the occurrence of the electromagnetic phenomena and, on the other hand, on the physical layout of the equipment installation.
+
+## **8.1 Degree of exposure**
+
+Lines to installations near exchanges in urban or industrial zones are usually little exposed to surges on account of the screening effect of numerous nearby metallic structures as described in clause 6.1.
+
+On the other hand, lines to installations remote from built-up areas can be very exposed on account of their length, the absence of a protective environment, overhead construction at the customer's end and the high resistivity of the soil. The mechanical robustness of the overhead cables at the customer's end makes the effect of surges all the more serious since the line itself can carry higher voltages and currents.
+
+## **8.2 Use of SPDs and SPCs**
+
+### **8.2.1 Use of voltage limiting devices**
+
+Where telecommunication lines are exposed to frequent and severe disturbances from power line faults or lightning, the voltage of the lines relative to local earth potential should be limited by connecting SPDs or SPCs between the line conductors and the earth terminal, see clause 5.4.
+
+The terminal equipment dielectric strength should be chosen taking account of the breakdown voltage of the protective device and the impedance of the protector line to earth connection.
+
+### **8.2.2 Use of high voltage isolation devices**
+
+Where protected telecommunication lines:
+
+- 1) exhibit excessive trouble reports due to lightning activity; or
+- 2) cannot have overvoltage or overcurrent protection installed for whatever reason; or
+- 3) when access to the premises by plant maintenance personnel is difficult;
+
+then high voltage (up to 50 kV) isolation, together with other suitable measures such as protection to be applied at the drop point from the telecommunications cable, may well be considered.
+
+The isolation elements should be installed as close as possible to the customer premises on the outside. They must not be mounted inside buildings.
+
+Isolation techniques may also be helpful at the telecommunication input to high voltage plant (for example, by means of isolation transformers), and in other situations where communications are vital and high plant voltages are probable.
+
+### **8.2.3 Multiservice surge protective devices**
+
+Multiservice surge protective devices consist of a combination of protection circuits in a single enclosure for at least two different services (e.g., telecommunication and power supply), which limits the surge voltages to the equipment and provides equipotential bonding between the different services. The surge voltage protection circuits of combined protective devices shall comply with the requirements of [IEC 61643-1] for the power supply circuit, and with [IEC 61643-21] for the telecommunications/signalling circuits.
+
+## **8.3 Equipotential bonding**
+
+Overvoltage protection has been required for terminal equipment that has been traditionally under the network operators' responsibility. Due to liberalization in telecommunications, the customer may now own this type of equipment. Electrical installations of buildings are a part of the protection for safety and are under the responsibility of the building owner, this includes the existence of EBB to achieve effective protection. The responsibilities for protective measures are now shared between the network operator and the customer. Most of the practices required to achieve effective protection are beyond the control of the network operator. This may be the responsibility of other parties, e.g., the building owner or the customer.
+
+In some countries, connection to the electricity system neutral is governed by national regulations, so that agreement with the electrical authority should be obtained.
+
+In the course of the maintenance of the telecommunication plant, equipotential bonding (connection to the EBB or MET) has to be inspected.
+
+## **8.4 High isolation techniques**
+
+When telecommunication lines are located in areas with a very high level of exposure to lightning (frequent breakdowns on lines and also high probability on the terminal installations) and when lightning protectors cannot be installed on the customer plant owing to earthing and maintenance difficulties and costs, it is recommended to employ a high isolation technique (of a level of at least 20 kV) at the telephone line access by transformer isolator or short fibre links.
+
+This method should be widely introduced at the input to high-voltage plant and is strongly recommended.
+
+## **8.5 National regulations**
+
+Many countries have national standards covering the protection of users of telecommunication equipment not only from the risks associated with connection to the electricity mains but also from conditions which may appear on the telecommunication line.
+
+## **8.6 Maintenance of installations**
+
+The maintenance requirements of customer installations may be high by reason of the distance from the maintenance centre, transport delays and, possibly, the seriousness of the damage. Moreover, insufficient protection is the cause of repeated interruptions of service which are particularly damaging to the quality of service and to the satisfaction of the customer. This justifies the granting of special attention to the maintenance of the protective measures that might become necessary in the following cases:
+
+- repeated appearance of damage caused by electrical sources;
+- later erection of exposed structures;
+- later erection or changes of electric power plants/traction systems;
+- change of the operating currents in existing power plants/traction systems;
+- customer or authority request.
+
+The maintenance of the interconnection of cable screens and the earthing of the screen at both ends, including equipotentialization of the system together with remote steerable protective systems, is seen as the most effective measure to reduce maintenance costs.
+
+# Bibliography
+
+- [b-ITU-T Guide] ITU-T Reference Document (2008), *Guide to the use of ITU-T publications produced by Study Group 5 aimed at achieving electromagnetic compatibility and safety.*
+
+## **ITU-T Recommendations related to power supply effects and low frequency interference**
+
+- [b-ITU-T K.5] Recommendation ITU-T K.5 (1988), *Joint use of poles for electricity distribution and for telecommunications.*
+- [b-ITU-T K.6] Recommendation ITU-T K.6 (1988), *Precautions at crossings.*
+- [b-ITU-T K.8] Recommendation ITU-T K.8 (1988), *Separation in the soil between telecommunication cables and earthing system of power facilities.*
+- [b-ITU-T K.9] Recommendation ITU-T K.9 (1988), *Protection of telecommunication staff and plant against a large earth potential due to a neighbouring electric traction line.*
+- [b-ITU-T K.13] Recommendation ITU-T K.13 (1988), *Induced voltages in cables with plastic-insulated conductors.*
+- [b-ITU-T K.14] Recommendation ITU-T K.14 (1988), *Provision of a metallic screen in plastic-sheathed cables.*
+- [b-ITU-T K.19] Recommendation ITU-T K.19 (1988), *Joint use of trenches and tunnels for telecommunication and power cables.*
+- [b-ITU-T K.26] Recommendation ITU-T K.26 (1988), *Protection of telecommunication lines against harmful effects from electric power and electrified railway lines.*
+- [b-ITU-T K.29] Recommendation ITU-T K.29 (1992), *Coordinated protection schemes for telecommunication cables below ground.*
+- [b-ITU-T K.50] Recommendation ITU-T K.50 (2000), *Safe limits of operation voltages and currents for telecommunication systems powered over the network.*
+- [b-ITU-T K.54] Recommendation ITU-T K.54 (2004), *Conducted immunity test method and level at fundamental power frequencies.*
+- [b-Handbook II] ITU-T Handbook (1999), *Directives concerning the protection of telecommunication lines against harmful effects from electric power and electrified railway lines; Volume II: Calculating induced voltages and currents in practical cases.*
+- [b-Handbook VI] ITU-T Handbook (2008), *Directives concerning the protection of telecommunication lines against harmful effects from electric power and electrified railway lines; Volume VI: Danger, damage and disturbance.*
+- [b-Handbook VII] ITU-T Handbook (1989), *Directives concerning the protection of telecommunication lines against harmful effects from electric power and electrified railway lines; Volume VII: Protective measures and safety precautions.*
+
+## ITU-T Recommendations related to lightning effects
+
+- [b-ITU-T K.25] Recommendation ITU-T K.25 (2000), *Protection of optical fibre cables.*
+- [b-ITU-T K.29] Recommendation ITU-T K.29 (1992), *Coordinated protection schemes for telecommunication cables below ground.*
+- [b-ITU-T K.39] Recommendation ITU-T K.39 (1996), *Risk assessment of damages to telecommunication sites due to lightning discharges.*
+- [b-ITU-T K.40] Recommendation ITU-T K.40 (1996), *Protection against LEMP in telecommunications centres.*
+- [b-ITU-T K.46] Recommendation ITU-T K.46 (2008), *Protection of telecommunication lines using metallic symmetric conductors against lightning-induced surges.*
+- [b-ITU-T K.47] Recommendation ITU-T K.47 (2008), *Protection of telecommunication lines using metallic conductors against direct lightning discharges.*
+- [b-ITU-T K.56] Recommendation ITU-T K.56 (2003), *Protection of radio base stations against lightning discharges.*
+- [b-ITU-T K.57] Recommendation ITU-T K.57 (2003), *Protection measures for radio base stations sited on power line towers.*
+- [b-ITU-T K.67] Recommendation ITU-T K.67 (2006), *Expected surges on telecommunications and signalling networks due to lightning.*
+- [b-ITU-T Lightning] ITU-T Handbook (1994), *The Protection of Telecommunication Lines and Equipment Against Lightning Discharges.*
+
+## ITU-T Recommendations related to surge protective devices and components
+
+- [b-ITU-T K.12] Recommendation ITU-T K.12 (2006), *Characteristics of gas discharge tubes for the protection of telecommunications installations.*
+- [b-ITU-T K.28] Recommendation ITU-T K.28 (1993), *Characteristics of semi-conductor arrester assemblies for the protection of telecommunications installations.*
+- [b-ITU-T K.30] Recommendation ITU-T K.30 (2004), *Self-restoring overcurrent protectors.*
+- [b-ITU-T K.36] Recommendation ITU-T K.36 (1996), *Selection of protective devices.*
+- [b-ITU-T K.55] Recommendation ITU-T K.55 (2002), *Overvoltage and overcurrent requirements for insulation displacement connectors (IDC) terminations.*
+- [b-ITU-T K.65] Recommendation ITU-T K.65 (2004), *Overvoltage and overcurrent requirements for termination modules with contacts for test ports or SPDs.*
+- [b-ITU-T K.69] Recommendation ITU-T K.69 (2006), *Maintenance of protective measures.*
+- [b-Handbook VIII] ITU-T Handbook (1989), *Directives concerning the protection of telecommunication lines against harmful effects from electric power and electrified railway lines; Volume VIII: Protective devices.*
+
+NOTE – ITU-T is considering the publication of guidance on the application of protective devices and/or components in telecommunication installations.
+
+### **Other documents related to surge protective devices and components**
+
+- [b-IEC 61643-311] IEC 61643-311 (2001), *Components for low-voltage protective devices – Part 311: Specification for gas discharge tubes (GDT)*.
+- [b-IEC 61643-321] IEC 61643-321 (2001), *Components for low-voltage protective devices – Part 321: Specification for avalanche breakdown diode (ABD)*.
+- [b-IEC 61643-331] IEC 61643-331 (2003), *Components for low-voltage surge protective devices – Part 331: Specification for metal oxide varistors (MOV)*.
+- [b-IEC 61643-341] IEC 61643-341 (2001), *Components for low-voltage surge protective devices – Part 341: Specification for thyristor surge suppressors (TSS)*.
+
+## **ITU-T Product Recommendations related to resistibility of telecommunications equipment**
+
+- [b-ITU-T K.20] Recommendation ITU-T K.20 (2003), *Resistibility of telecommunication equipment installed in a telecommunications centre to overvoltages and overcurrents*.
+- [b-ITU-T K.21] Recommendation ITU-T K.21 (2003), *Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents*.
+- [b-ITU-T K.44] Recommendation ITU-T K.44 (2003), *Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents – Basic Recommendation*.
+- [b-ITU-T K.45] Recommendation ITU-T K.45 (2003), *Resistibility of telecommunication equipment installed in the access and trunk networks to overvoltages and overcurrents*.
+
+### **Other documents on general topics**
+
+- [b-IEC 60050-151] IEC 60050-151 (2001), *International Electrotechnical Vocabulary – Part 151: Electrical and magnetic devices*.
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                             |
+|-----------------|---------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                           |
+| Series D        | General tariff principles                                                                   |
+| Series E        | Overall network operation, telephone service, service operation and human factors           |
+| Series F        | Non-telephone telecommunication services                                                    |
+| Series G        | Transmission systems and media, digital systems and networks                                |
+| Series H        | Audiovisual and multimedia systems                                                          |
+| Series I        | Integrated services digital network                                                         |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals |
+| <b>Series K</b> | <b>Protection against interference</b>                                                      |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant     |
+| Series M        | Telecommunication management, including TMN and network maintenance                         |
+| Series N        | Maintenance: international sound programme and television transmission circuits             |
+| Series O        | Specifications of measuring equipment                                                       |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                |
+| Series Q        | Switching and signalling                                                                    |
+| Series R        | Telegraph transmission                                                                      |
+| Series S        | Telegraph services terminal equipment                                                       |
+| Series T        | Terminals for telematic services                                                            |
+| Series U        | Telegraph switching                                                                         |
+| Series V        | Data communication over the telephone network                                               |
+| Series X        | Data networks, open system communications and security                                      |
+| Series Y        | Global information infrastructure, Internet protocol aspects and next-generation networks   |
+| Series Z        | Languages and general software aspects for telecommunication systems                        |

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+
+
+International Telecommunication Union
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**K.117**
+
+(12/2016)
+
+SERIES K: PROTECTION AGAINST INTERFERENCE
+
+# --- **Primary protector parameters for the surge protection of equipment Ethernet ports**
+
+Recommendation ITU-T K.117
+
+![ITU logo](6ed175c791b5e156d9c98a8dbcc3318c_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a globe with a red lightning bolt striking it, symbolizing telecommunications and protection against interference. To the right of the globe, the text "International Telecommunication Union" is written in a blue sans-serif font, with "ITU" in a larger, bold font above it.
+
+ITU logo
+
+International  
+Telecommunication  
+Union
+
+
+
+## Recommendation ITU-T K.117
+
+## Primary protector parameters for the surge protection of equipment Ethernet ports
+
+## Summary
+
+Recommendation ITU-T K.117 specifies the common-mode, differential mode and common mode to differential mode conversion surge parameter and test circuit requirements of an Ethernet port primary protector. The preferred surge generator voltage levels are 2.5 kV, 6 kV and 12 kV, but the test circuits can be used for any surge voltage environmental. Power over Ethernet (PoE) feed requirements are also given. Ethernet signal performance parameters are not covered and standards such as [b-IEC 60603-7-7] may be used for this purpose.
+
+This Recommendation should be used for the harmonization of existing or future specifications issued by Ethernet surge protective device (SPD) manufacturers, telecommunication equipment manufacturers, administrations or network operators.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T K.117    | 2016-12-14 | 5           | <a href="http://handle.itu.int/11.1002/1000/13133">11.1002/1000/13133</a> |
+
+## Keywords
+
+Ethernet, in-line SPD, insulation resistance, overvoltage protector, Power over Ethernet (PoE), primary protector, surge protective device (SPD).
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2017
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+|                                                            | Page |
+|------------------------------------------------------------|------|
+| 1 Scope.....                                               | 1    |
+| 2 References.....                                          | 1    |
+| 3 Definitions .....                                        | 1    |
+| 3.1 Terms defined elsewhere .....                          | 1    |
+| 3.2 Terms defined in this Recommendation.....              | 3    |
+| 4 Abbreviations and acronyms .....                         | 3    |
+| 5 Conventions .....                                        | 3    |
+| 5.1 Connections .....                                      | 3    |
+| 5.2 Protective function.....                               | 4    |
+| 6 Electrical parameters .....                              | 4    |
+| 6.1 Common-mode surge .....                                | 5    |
+| 6.2 Differential-mode surge.....                           | 6    |
+| 6.3 Common-mode to differential-mode surge conversion..... | 9    |
+| 6.4 Surge durability (optional) .....                      | 11   |
+| 6.5 Cable screen terminal .....                            | 11   |
+| 7 DC tests.....                                            | 12   |
+| 7.1 Insulation resistance .....                            | 12   |
+| 7.2 DC voltage drop .....                                  | 13   |
+| 8 Identification.....                                      | 14   |
+| 8.1 Marking .....                                          | 14   |
+| 8.2 Documentation .....                                    | 14   |
+| 9 Ordering information .....                               | 14   |
+| Bibliography.....                                          | 15   |
+
+
+
+## Recommendation ITU-T K.117
+
+## Primary protector parameters for the surge protection of equipment Ethernet ports
+
+# 1 Scope
+
+This Recommendation applies to surge protective devices (SPDs) to be used for Ethernet primary protection in surge voltage environments with a peak value of 2.5 kV and above. It covers the following device parameters:
+
+- a) electrical surge
+- b) electrical d.c.
+- c) identification and marking.
+
+This Recommendation does not deal with:
+
+- a) mountings for SPDs and their effect on characteristics;
+- b) mechanical dimensions;
+- c) quality assurance requirements;
+- d) units containing current limiters;
+- e) signal performance parameters, standards such as [b-IEC 60603-7-7] may be used for this purpose;
+- f) diagnostic properties such as indicators and status monitor outputs.
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+[ITU-T K.44] Recommendation ITU-T K.44 (2016), *Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents – Basic Recommendation*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 common-mode conversion** [b-ITU-T K.96]: Process by which a differential mode electrical signal is produced in response to a common mode electrical signal.
+
+NOTE – This definition is based on the definition provided in [b-IEC 60050-161].
+
+**3.1.2 common-mode surge** [b-ITU-T K.96]: Surge appearing equally on all conductors of a group at a given location.
+
+NOTE 1 – The reference point for common-mode surge voltage measurement can be a chassis terminal, or a local earth/ground point.
+
+NOTE 2 – Also known as longitudinal surge or asymmetrical surge.
+
+- 3.1.3 connector** [b-IEC 14776-153]: Electro-mechanical components consisting of a receptacle and a plug that provide a separable interface between two transmission segments.
+- 3.1.4 differential-mode surge** [b-ITU-T K.96]: Surge occurring between any two conductors or two groups of conductors at a given location.
+- NOTE 1 – The surge source maybe be floating, without a reference point or connected to reference point, such as a chassis terminal, or a local earth/ground point.
+- NOTE 2 – Also known as metallic surge or transverse surge or symmetrical surge or normal surge.
+- 3.1.5 hard-wired** [b-IEC 60601-2-1]: Term used where the features of a system can be modified only by physically removing and re-routing wires.
+- 3.1.6 insulation** [b-IEC 60664-2-1]: That part of an electrotechnical product which separates the conducting parts at different electrical potentials.
+- 3.1.7 isolating transformer** [b-IEC 60065]: Transformer with protective separation between the input and output windings.
+- NOTE – Isolating transformers can be divided into three groups; mains, switched mode and signal (e.g., Ethernet data).
+- 3.1.8 impulse limiting voltage,  $V_P$**  [b-ITU-T K.28]: Highest value of voltage across the terminals of the SPD during the application of a specified impulse.
+- NOTE – Also called voltage protection level or measured limiting voltage.
+- 3.1.9 in-line SPD** [b-ITU-T K.28]: A two-port SPD connected in series with the service feed.
+- 3.1.10 insulation resistance (effective)** [b-ITU-T K.28]: Quotient of the voltage applied to a designated terminal pair,  $V_{IR}$ , by the current,  $I_{IR}$ , drawn from the applied voltage.
+- 3.1.11 impulse generator charge voltage,  $V_C$**  [b-ITU-T K.82]: Value of impulse generator charging voltage.
+- 3.1.12 impulse withstand voltage** [b-IEC 60664-2-1]: Highest peak value of impulse voltage of prescribed form and polarity applied to a circuit or equipment, which does not cause degradation or result in breakdown or flashover.
+- 3.1.13 let-through current** [b-ITU-T K.28]: In-line SPD peak short-circuit output current when a specified impulse is applied to the SPD input.
+- 3.1.14 overvoltage** [b-IEC 60664-2-1]: Any voltage having a peak value exceeding the corresponding peak value of maximum steady-state voltage at normal operating conditions.
+- 3.1.15 parameter** [b-IEC 61643-341]: Device descriptor that is measurable or quantifiable, such as a characteristic or rating.
+- 3.1.16 port** [b-IEC 60050-131]: Access to a device or network where electromagnetic energy or signals may be supplied or received or where the device or network variables may be observed or measured.
+- NOTE – An example of a port is a terminal pair.
+- 3.1.17 primary protection** [ITU-T K.44]: Means by which the majority of the surge stress is prevented from propagating beyond a designated location (preferably the building entrance point).
+- 3.1.18 rated peak impulse current** [b-ITU-T K.28]: Maximum value of peak impulse current of specified amplitude and waveshape that may be applied without causing degradation.
+- 3.1.19 sparkover** [b-IEC 60050-212]: Disruptive discharge in a gaseous or liquid insulating material.
+- 3.1.20 surge** [b-ITU-T K.96]: Temporary disturbance on the conductors of an electrical service caused by an electrical event not related to the service.
+
+NOTE – For non-linear SPCs a surge event is defined as an overvoltage or overcurrent or both.
+
+**3.1.21 surge protective component (SPC)** [b-ITU-T K.96]: Component specifically included in a device or equipment for the mitigation of the onward propagation of overvoltages or overcurrents or both.
+
+**3.1.22 surge protective device (SPD)** [b-ITU-T K.96]: Device that mitigates the onward propagation of overvoltages or overcurrents or both.
+
+**3.1.23 two-port** [b-IEC 60050-131]: Device or network with two separate ports.
+
+## **3.2 Terms defined in this Recommendation**
+
+None.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|      |                            |
+|------|----------------------------|
+| GDT  | Gas Discharge Tube         |
+| IR   | Insulation Resistance      |
+| PD   | Powered Device/equipment   |
+| PE   | Protective Earth           |
+| PoE  | Power over Ethernet        |
+| PSE  | Power Sourcing Equipment   |
+| RJ45 | Registered Jack #45        |
+| SPC  | Surge Protective Component |
+| SPD  | Surge Protective Device    |
+
+# **5 Conventions**
+
+## **5.1 Connections**
+
+The connection designation used in this Recommendation corresponds to the normal Ethernet cable RJ45 contacts. Figure 1 shows the RJ45 contact numbers that are associated with signal connections and the PoE power feed modes. When an SPD does not use a RJ45 receptacle but uses, for example, a hard-wired cable connection, the terminal notations may be different. A hard-wire connector may be required when the RJ45 contact currents exceed 1 kA or voltages between adjacent contacts will exceed 4 kV. The SPD configuration is assumed as in-line (2 port) with the test being applied to one port and the let-through surge measured on the other terminated port.
+
+![Diagram of Ethernet RJ45 contact connections. On the left, four twisted-pair signals are labeled: (1, 2), (3, 6), (4, 5), and (7, 8). These connect to pins 1 through 8. Pins 1, 2, 3, and 6 are grouped together on the right as '1, 2 and 3, 6 PoE mode A powering feed pair'. Pins 4, 5, 7, and 8 are grouped as '4, 5 and 7, 8 PoE mode B powering feed pair'. At the bottom, a 'Cable screen if present' connects to a 'Screen' terminal, which is then connected to 'Protective earth /common'. The diagram is labeled K.117(16)_F01.](a5ee5c23b6dc52ec1d724b76d5a5f58f_img.jpg)
+
+Diagram of Ethernet RJ45 contact connections. On the left, four twisted-pair signals are labeled: (1, 2), (3, 6), (4, 5), and (7, 8). These connect to pins 1 through 8. Pins 1, 2, 3, and 6 are grouped together on the right as '1, 2 and 3, 6 PoE mode A powering feed pair'. Pins 4, 5, 7, and 8 are grouped as '4, 5 and 7, 8 PoE mode B powering feed pair'. At the bottom, a 'Cable screen if present' connects to a 'Screen' terminal, which is then connected to 'Protective earth /common'. The diagram is labeled K.117(16)\_F01.
+
+**Figure 1 – Ethernet RJ45 contact connections**
+
+## 5.2 Protective function
+
+This Recommendation tries to be technology neutral on the surge protective components (SPCs) used in the SPD. SPDs using voltage limiting components or isolating components, or both are tested with the SPD terminated. Figures 2 and 3 show examples of a voltage limiting gas discharge tube (GDT) and isolating transformer in a common-mode surge test with the termination connected.
+
+![Circuit diagram for GDT common-mode voltage limiting. A surge pulse is applied to the input of an SPD block containing a GDT symbol. The output of the SPD connects to a termination circuit. The termination circuit consists of two 1 Ω resistors in series with a 10 nF capacitor connected between the lines. Additionally, there is a 75 Ω resistor in parallel with a 1 nF capacitor connected to ground. The diagram is labeled K.117(16)_F02.](daa4a6fa7e2ba1954258f86b4928eb32_img.jpg)
+
+Circuit diagram for GDT common-mode voltage limiting. A surge pulse is applied to the input of an SPD block containing a GDT symbol. The output of the SPD connects to a termination circuit. The termination circuit consists of two 1 Ω resistors in series with a 10 nF capacitor connected between the lines. Additionally, there is a 75 Ω resistor in parallel with a 1 nF capacitor connected to ground. The diagram is labeled K.117(16)\_F02.
+
+**Figure 2 – GDT common-mode voltage limiting  
+(partial circuit for only one twisted pair)**
+
+![Circuit diagram for isolating transformer common-mode voltage blocking. A surge pulse is applied to the input of an SPD block containing an isolating transformer symbol. The output of the SPD connects to the same termination circuit as in Figure 2: two 1 Ω resistors, a 10 nF capacitor, a 75 Ω resistor, and a 1 nF capacitor. The diagram is labeled K.117(16)_F03.](053f1077d592e6622cd21dc4bb4cb366_img.jpg)
+
+Circuit diagram for isolating transformer common-mode voltage blocking. A surge pulse is applied to the input of an SPD block containing an isolating transformer symbol. The output of the SPD connects to the same termination circuit as in Figure 2: two 1 Ω resistors, a 10 nF capacitor, a 75 Ω resistor, and a 1 nF capacitor. The diagram is labeled K.117(16)\_F03.
+
+**Figure 3 – Isolating transformer common-mode voltage blocking  
+(partial circuit for only one twisted pair)**
+
+# 6 Electrical parameters
+
+The objective of an Ethernet SPD is to mitigate the cable surge levels down to levels that the equipment port can withstand. Cable surges can be common mode or differential mode. In addition
+
+the SPD must not generate an excessive differential surge in common-mode surge operation; see Tables 2 and 3 for preferred maximum differential surge values.
+
+Three [b-IEC 60664-2-1] preferred values of generator charging voltage are used: 2.5 kV, 6 kV and 12 kV. Manufacturers may also define levels to suit specific applications. SPDs rated for 2.5 kV are intended to protect equipment ports that do not meet a basic port withstand voltage of 2.5 kV. SPDs rated for 6 kV are intended to protect equipment ports that have a basic port withstand voltage of 2.5 kV but the equipment has been installed in an environment that requires an enhanced 6 kV capability. SPDs rated for 12 kV are intended for severe installation environments to protect equipment ports that only have the basic (2.5 kV) or enhanced (6 kV) withstand voltages.
+
+The testing assumes all 8 Ethernet conductors are protected. Where the SPD is designed to protect a lesser number of conductors and surge mode requirements (e.g. non-PoE) only the appropriate SPD equipment terminals are tested and measured.
+
+## 6.1 Common-mode surge
+
+The purpose of this test is to measure the impulse limiting voltage at the SPD port connecting to the equipment Ethernet port. The test circuit is shown in Figure 4. To test this, set the generator charge voltage to the required level from Table 1 and surge the SPD while recording an SPD equipment port terminal voltage. Record the terminal peak voltage measured. Repeat this test with the generator voltage polarity reversed. Repeat this procedure until all the port terminals have been measured for positive and negative surges and their peak voltage values have been recorded. For each configuration a minimum of three surges must be applied and the recorded value is the highest measured value. Finally, measure the d.c. insulation resistance for terminals 1 to 8 of the SPD cable port, as described in clause 7.1.
+
+![Figure 4 – Impulse limiting voltage under common-mode surge conditions. The diagram shows a test circuit for measuring impulse limiting voltage. On the left, a 1.2/50-8/20 combination wave generator is connected to the SPD's cable port (terminals 1, 2, 3, 4, 5, 6, 7, 8) through a resistor R9 = 5 Ω. The generator's return/earth is connected to a reference bar (point 'a'). The SPD has an equipment port (terminals 1, 2, 3, 4, 5, 6, 7, 8) connected to a termination circuit. The termination circuit consists of eight resistors (R1 to R8 = 1 Ω) in series with capacitors (C1 to C4 = 10 nF, 300 V) and resistors (R11 to R14 = 75 Ω). The termination circuit is connected to a reference bar (point 'c') and a 1 nF 3 kV capacitor (C5) connected to ground (point 'd'). The SPD's screen is connected to the reference bar (point 'b').](7e670a2b556b53ea9002dfff3a420e08_img.jpg)
+
+Figure 4 shows the test circuit for measuring impulse limiting voltage under common-mode surge conditions. The circuit includes a 1.2/50-8/20 combination wave generator connected to the SPD's cable port (terminals 1, 2, 3, 4, 5, 6, 7, 8) through a resistor  $R9 = 5 \Omega$ . The generator's return/earth is connected to a reference bar (point 'a'). The SPD has an equipment port (terminals 1, 2, 3, 4, 5, 6, 7, 8) connected to a termination circuit. The termination circuit consists of eight resistors ( $R1$  to  $R8 = 1 \Omega$ ) in series with capacitors ( $C1$  to  $C4 = 10 \text{ nF}$ , 300 V) and resistors ( $R11$  to  $R14 = 75 \Omega$ ). The termination circuit is connected to a reference bar (point 'c') and a 1 nF 3 kV capacitor ( $C5$ ) connected to ground (point 'd'). The SPD's screen is connected to the reference bar (point 'b').
+
+Component values:  
+ $R1$  to  $R8 = 1 \Omega$   
+ $C1$  to  $C4 = 10 \text{ nF}$ , 300 V  
+ $R11$  to  $R14 = 75 \Omega$
+
+Termination circuit: 1 nF 3 kV
+
+Labels: a, b, c, d
+
+Reference bar
+
+Screen
+
+PE
+
+SPD
+
+Cable port
+
+Equipment port
+
+Generator return/Earth
+
+$R9 = 5 \Omega$
+
+1.2/50-8/20 combination wave generator
+
+K.117(16)\_F04
+
+Figure 4 – Impulse limiting voltage under common-mode surge conditions. The diagram shows a test circuit for measuring impulse limiting voltage. On the left, a 1.2/50-8/20 combination wave generator is connected to the SPD's cable port (terminals 1, 2, 3, 4, 5, 6, 7, 8) through a resistor R9 = 5 Ω. The generator's return/earth is connected to a reference bar (point 'a'). The SPD has an equipment port (terminals 1, 2, 3, 4, 5, 6, 7, 8) connected to a termination circuit. The termination circuit consists of eight resistors (R1 to R8 = 1 Ω) in series with capacitors (C1 to C4 = 10 nF, 300 V) and resistors (R11 to R14 = 75 Ω). The termination circuit is connected to a reference bar (point 'c') and a 1 nF 3 kV capacitor (C5) connected to ground (point 'd'). The SPD's screen is connected to the reference bar (point 'b').
+
+Figure 4 – Impulse limiting voltage under common-mode surge conditions
+
+**Table 1 – Preferred values of common-mode impulse limiting voltage**
+
+| <b>Generator charge voltage</b> | <b>Maximum impulse limiting voltage on any SPD equipment port terminal (excluding the screen connection)</b> |
+|---------------------------------|--------------------------------------------------------------------------------------------------------------|
+| <b>kV</b>                       | <b>kV</b>                                                                                                    |
+| 2.5                             | 1.0                                                                                                          |
+| 6                               | 1.5                                                                                                          |
+| 12                              | 2.0                                                                                                          |
+| Manufacturer defined            | Manufacturer defined                                                                                         |
+
+The recorded peak voltages shall not exceed the impulse limiting voltage corresponding to the selected generator charge voltage. After the surge testing, the 500 V insulation resistance values shall not be less than 2 M $\Omega$ .
+
+## **6.2 Differential-mode surge**
+
+The most critical factor for a twisted pair differential surge is the current waveform as the port termination is a low value resistance, usually below 5  $\Omega$ . Conversely, the most critical factor for a PoE power feed pair is peak voltage as the need is to protect some form of integrated circuit, which usually is rated at about 100 V. Common-mode surge operation of an SPD can generate differential-mode surges and these self-generated differential-mode surges at the SPD cable connection should not exceed the specified differential-mode surge voltage levels for a single twisted pair and power feed pairs.
+
+### **6.2.1 Single twisted pair**
+
+The purpose of this test is to measure the termination differential-mode surge levels of a single twisted pair. The test circuit is shown in Figure 5. In Figure 5 all four switches, SW(1-2) to SW(7-8), are single-pole change-over break before make ones. The switch contact arm is shown in red to clearly indicate the arm position. Figure 5 shows the test configuration for port terminal pair 1-2 with the generator output connected to terminal 1 via switch SW(1-2). The test configuration for a given terminal pair is with that terminal pair switch connecting the switched terminal to the generator series resistor R9, while all the other three terminal pair switches connect their terminals to the reference bar.
+
+To test this, set the generator charge voltage to the required level from Table 2 and surge the SPD while recording the selected SPD equipment port termination peak voltage and current. Record the termination peak voltage and current. Repeat this test with the generator voltage polarity reversed. Repeat this procedure until all the appropriate port terminals have been measured and their peak voltage and current values recorded. Finally, measure the d.c. insulation resistance for terminals 1 to 8 of the SPD cable port, as described in clause 7.1.
+
+![Figure 5 – Single twisted-pair differential-mode surge test circuit. The diagram shows a 1.2/50-8/20 generator connected to a cable port (1-8) through a switch (SW) and resistors R9 (10 Ω) and R10 (10 Ω). The cable port is connected to an equipment port (1-8) through an SPD. The equipment port is connected to a termination circuit containing resistors R1 to R8 (1 Ω), capacitors C1 to C4 (10 nF, 300 V), and resistors R11 to R14 (75 Ω). The termination circuit is connected to a reference bar (a, b, c, d) and a PE (Screen) connection. The diagram also includes a 'Differential voltage' measurement point and a 'Termination circuit' label with '1 nF 3 kV'.](af7916c89a458fdab6c3f443217388ae_img.jpg)
+
+Figure 5 – Single twisted-pair differential-mode surge test circuit. The diagram shows a 1.2/50-8/20 generator connected to a cable port (1-8) through a switch (SW) and resistors R9 (10 Ω) and R10 (10 Ω). The cable port is connected to an equipment port (1-8) through an SPD. The equipment port is connected to a termination circuit containing resistors R1 to R8 (1 Ω), capacitors C1 to C4 (10 nF, 300 V), and resistors R11 to R14 (75 Ω). The termination circuit is connected to a reference bar (a, b, c, d) and a PE (Screen) connection. The diagram also includes a 'Differential voltage' measurement point and a 'Termination circuit' label with '1 nF 3 kV'.
+
+**Figure 5 – Single twisted-pair differential-mode surge test circuit**
+
+**Table 2 – Preferred values of termination peak voltage and current**
+
+| Generator charge voltage<br>kV | Measured values for 1-2, 3-6, 4-5 and 7-8 |                               |
+|--------------------------------|-------------------------------------------|-------------------------------|
+|                                | Termination peak voltage<br>V             | Termination peak current<br>A |
+| 2.5                            | 100                                       | 50                            |
+| 6                              | 200                                       | 100                           |
+| 12                             | 300                                       | 150                           |
+| Manufacturer defined           | Manufacturer defined                      | Manufacturer defined          |
+
+The recorded peak levels shall not exceed the termination peak values corresponding to the selected generator charge voltage. After the surge testing, the 500 V insulation resistance values shall not be less than 2 MΩ.
+
+### 6.2.2 PoE power feed pairs
+
+PoE power can be delivered in either mode A or mode B, or both modes (A + B). In powered equipment (PD) the power feed is extracted from the twisted pairs, sent to a multiphase diode bridge, decoupled and overvoltage protected before being applied to a d.c./d.c. converter. Power sourcing equipment (PSE) usually has some form of power regulator with overvoltage protection which feeds the power to the twisted pairs. The Figure 6 test circuit uses a powered equipment type termination as it works for both surge polarities and is often the equipment with the lowest surge resistibility. The components and their values correspond to the established components used in [b-IEEE 802.3] designs. Diodes D1 to D4 and D6 to D9 form polarity correction bridges that feed the avalanche breakdown diodes D5 and D10 and capacitors C1 and C2. Typical emulation components used are Schottky rectifier bridge diodes type B1100/B, avalanche breakdown diode type SMAJ58A and decoupling capacitor 100 nF, 100 V.
+
+In Figure 6, switch SW selects test mode A or test mode B. The peak surge voltage in these modes is measured at the SPD equipment port termination.
+
+To test this, set the generator charge voltage to the required level from Table 3, set switch SW for a mode and surge the SPD while measuring the SPD equipment port termination peak voltage for that mode. Record the termination peak voltage. Repeat this test with the generator voltage polarity reversed. Repeat this procedure for the other mode. Finally, measure the d.c. insulation resistance for terminals 1 to 8 of the SPD cable port, as described in clause 7.1.
+
+![Figure 6 – Power feed differential mode surge test circuit. The diagram shows a 1.2/50-8/20 Generator connected to a switch (SW) via resistors R9 and R10 (both 10 Ω). The switch selects between test mode A and test mode B. The SPD (Surge Protection Device) has a cable port with terminals 1, 2, 3, 4, 5, 6, 7, and 8, and an equipment port with terminals 1, 2, 3, 4, 5, 6, 7, and 8. The equipment port is connected to a PoE port termination box containing diodes D1 through D10, capacitors C1 and C2, and a reference bar. The generator return/earth is connected to a reference bar (a, b, c) which is also connected to the SPD screen and PE (Protective Earth).](4ee27dbf5ef12e7b58b0ef0937bc5a5e_img.jpg)
+
+Figure 6 – Power feed differential mode surge test circuit. The diagram shows a 1.2/50-8/20 Generator connected to a switch (SW) via resistors R9 and R10 (both 10 Ω). The switch selects between test mode A and test mode B. The SPD (Surge Protection Device) has a cable port with terminals 1, 2, 3, 4, 5, 6, 7, and 8, and an equipment port with terminals 1, 2, 3, 4, 5, 6, 7, and 8. The equipment port is connected to a PoE port termination box containing diodes D1 through D10, capacitors C1 and C2, and a reference bar. The generator return/earth is connected to a reference bar (a, b, c) which is also connected to the SPD screen and PE (Protective Earth).
+
+K.117(16)\_F06
+
+##### Key
+
+SW = Double pole, two position selector switch
+
+R9, R10 = 10 Ω
+
+C1, C2 = 100 nF, 100 V
+
+D5, D10 = SMAJ58A or equivalent 400 W avalanche breakdown diodes
+
+D1 to D4, D6 to D9 = B1100/B Schottky rectifier diodes or equivalent 1 A, 100 V diodes
+
+**Figure 6 – Power feed differential mode surge test circuit**
+
+**Table 3 – Preferred mode A or mode B peak voltage**
+
+| Generator charge voltage<br>kV | Peak mode A or mode B<br>termination voltage<br>V |
+|--------------------------------|---------------------------------------------------|
+| 2.5                            | 90                                                |
+| 6                              | 95                                                |
+| 12                             | 100                                               |
+| Manufacturer defined           | Manufacturer defined                              |
+
+The recorded peak voltages shall not exceed the peak mode A and peak mode B voltages corresponding to the selected generator charge voltage. After the surge testing, the 500 V insulation resistance values shall not be less than 2 MΩ.
+
+## 6.3 Common-mode to differential-mode surge conversion
+
+The purpose of this test is to measure the SPD common-mode to differential-mode surge conversion for the twisted-pair and power-feed situations of clause 6.2.
+
+In both Figure 7 and Figure 8 the generator output connects to each cable contact via a high value  $40\ \Omega$  feed resistor to reduce the interactions. In Figure 7, the twisted pair is terminated in a high value resistance of  $150\ \Omega$  to maximise the measured twisted-pair differential voltage. In Figure 8 the twisted pair termination is low in value ( $1\ \Omega+1\ \Omega$ ) as the measurement is being made pair to pair.
+
+![Figure 7 – Twisted-pair common-mode to differential mode voltage surge conversion test circuit. The diagram shows a 1.2/50-8/20 generator connected to a 'Generator current sharing network' containing resistors R1 through R8, each 40 Ω. These resistors connect to 'Cable port' terminals 1 through 8. These terminals are connected to 'Equipment port' terminals 1 through 8 of an SPD. The SPD has a 'Screen' and 'PE' connection to a 'Reference bar' at points 'a', 'b', and 'c'. The 'Generator return/Earth' is also connected to the reference bar. On the equipment side, twisted pairs are terminated in a 'Termination circuit' containing resistors R12, R36, R45, and R78, each 150 Ω. Vertical double-headed arrows between the equipment ports indicate the 'Twisted pair differential voltage' being measured.](7efae06af3af43ffe5d4b956a679cf54_img.jpg)
+
+The diagram illustrates the test circuit for twisted-pair common-mode to differential mode voltage surge conversion. A 1.2/50-8/20 generator is connected to a 'Generator current sharing network' which includes eight resistors, R1 through R8, each with a value of  $40\ \Omega$ . These resistors are connected to 'Cable port' terminals 1 through 8. These terminals are then connected to 'Equipment port' terminals 1 through 8 of an SPD. The SPD has a 'Screen' and 'PE' connection to a 'Reference bar' at points 'a', 'b', and 'c'. The 'Generator return/Earth' is also connected to the reference bar. On the equipment side, twisted pairs are terminated in a 'Termination circuit' which includes resistors R12, R36, R45, and R78, each with a value of  $150\ \Omega$ . Vertical double-headed arrows between the equipment ports indicate the 'Twisted pair differential voltage' being measured.
+
+Figure 7 – Twisted-pair common-mode to differential mode voltage surge conversion test circuit. The diagram shows a 1.2/50-8/20 generator connected to a 'Generator current sharing network' containing resistors R1 through R8, each 40 Ω. These resistors connect to 'Cable port' terminals 1 through 8. These terminals are connected to 'Equipment port' terminals 1 through 8 of an SPD. The SPD has a 'Screen' and 'PE' connection to a 'Reference bar' at points 'a', 'b', and 'c'. The 'Generator return/Earth' is also connected to the reference bar. On the equipment side, twisted pairs are terminated in a 'Termination circuit' containing resistors R12, R36, R45, and R78, each 150 Ω. Vertical double-headed arrows between the equipment ports indicate the 'Twisted pair differential voltage' being measured.
+
+Figure 7 – Twisted-pair common-mode to differential mode voltage surge conversion test circuit
+
+![Circuit diagram for Figure 8 showing a power feed pair common-mode to differential mode surge conversion test circuit. It includes a 1.2/50-8/20 Generator connected to a Generator current sharing network with resistors R1-R8 (40 Ω each). This is connected to the Cable port (1-8) of an SPD. The SPD's Equipment port (10-8) is connected to a Termination circuit with resistors R11-R18 (1 Ω each). The diagram also shows PoE differential voltage, Mode A and Mode B differential voltages, a PE reference bar, and a screen connection. The diagram is labeled K.117(16)_F08.](fa859e4e468bfb2710a94527f2c504af_img.jpg)
+
+Circuit diagram for Figure 8 showing a power feed pair common-mode to differential mode surge conversion test circuit. It includes a 1.2/50-8/20 Generator connected to a Generator current sharing network with resistors R1-R8 (40 Ω each). This is connected to the Cable port (1-8) of an SPD. The SPD's Equipment port (10-8) is connected to a Termination circuit with resistors R11-R18 (1 Ω each). The diagram also shows PoE differential voltage, Mode A and Mode B differential voltages, a PE reference bar, and a screen connection. The diagram is labeled K.117(16)\_F08.
+
+**Figure 8 – Power feed pair common-mode to differential mode surge conversion test circuit**
+
+For Figure 7, set the generator charge voltage to the level used in clause 6.2.1 and surge the SPD while measuring the SPD equipment port pair 1-2 termination peak voltage. Record the termination peak voltage. Repeat this test with the generator voltage polarity reversed. Repeat this procedure for the port pairs of 3-6, 4-5 and 7-8. Finally, measure the d.c. insulation resistance for terminals 1 to 8 of the SPD cable port, as described in clauses 7.1 and 6.2.2 from Table 3.
+
+For Figure 8, set the generator charge voltage to the level used in clause 6.2.2 and surge the SPD while measuring the SPD equipment port mode A peak voltage. Record the termination peak voltage. Repeat this test with the generator voltage polarity reversed. Repeat this procedure for the port mode B peak voltage. Finally, measure the d.c. insulation resistance for terminals 1 to 8 of the SPD cable port, as described in clause 7.1.
+
+**Table 4 – Preferred maximum values common-mode to differential mode surge voltage**
+
+| Generator charge voltage<br>kV | Peak twisted-pair<br>differential termination<br>voltage<br>V | Peak mode A or mode B<br>differential termination<br>voltage<br>V |
+|--------------------------------|---------------------------------------------------------------|-------------------------------------------------------------------|
+| 2.5                            | 100                                                           | 90                                                                |
+| 6                              | 200                                                           | 95                                                                |
+| 12                             | 300                                                           | 100                                                               |
+| Manufacturer defined           | Manufacturer defined                                          | Manufacturer defined                                              |
+
+The recorded peak voltages shall not exceed the peak differential voltage values corresponding to the selected generator charge voltage. After the surge testing, the 500 V insulation resistance values shall not be less than 2 MΩ.
+
+## 6.4 Surge durability (optional)
+
+This test verifies the surge durability of the SPD.
+
+For each of the selected test levels and configurations of clauses 6.1, 6.2.1 and 6.2.2 apply 50 surges in one polarity followed by 50 surges in the opposite polarity. Finally, measure the d.c. insulation resistance for terminals 1 to 8 as appropriate of the SPD cable port, as described in clause 7.1.
+
+NOTE – Applying the surges first in one polarity, then in the opposite polarity maximises the electrode erosion of Figure 2 type technologies; see [b-ITU-T K.99].
+
+After the surge durability testing, the SPD shall be tested as described in clauses 6.1, 6.2.1 and 6.2.2 at the selected surge levels. The SPD shall still comply with the requirements of these three tests.
+
+## 6.5 Cable screen terminal
+
+This test verifies the bonding of the cable port screen terminal to protective earth (PE) terminal, the equipment port screen terminal to PE terminal and the cable port screen terminal to the equipment port screen terminal. In the test circuit Figure 9, these test configurations are switch SW positions 1, 2 and 3. SPDs using the Figure 3 type protection may not have a PE terminal.
+
+To test this, set the generator charge voltage to the required level from Table 5, set switch SW for the appropriate test configuration and surge the SPD while measuring the SPD screen voltage of that configuration. Record the measured peak voltage. Repeat this test with the generator voltage polarity reversed. Repeat this procedure for the other appropriate configurations. Finally, measure the d.c. insulation resistance for terminals 1 to 8 of the SPD cable port, as described in clause 7.1.
+
+![Circuit diagram for screen bonding test (Figure 9).](43837b056625d3d6ce615e4c02f163bb_img.jpg)
+
+The diagram illustrates the test circuit for screen bonding. On the left, a '1.2/50-8/20 Generator' is shown. Its output is connected to a resistor labeled 'R9 = 5Ω'. This resistor is connected to a 'Double pole, three position selector switch' (SW). The switch has three positions labeled 1, 2, and 3. Position 1 connects the generator circuit to the 'Cable port' terminals (1, 2, 3, 6, 4, 5, 7, 8) of the SPD. Position 2 connects it to the 'Equipment port' terminals (1, 2, 3, 6, 4, 5, 7, 8). Position 3 connects it to the 'Screen' terminal of the SPD. The 'Generator return/Earth' is connected to a 'Reference bar'. The 'PE' (Protective Earth) terminal of the SPD is also connected to this 'Reference bar'. The 'Equipment port' is connected to a 'Reference bar' as well. The diagram is labeled 'b' and 'K.117(16)\_F09'.
+
+Key  
+SW = Double pole, three position selector switch      R9 = 5Ω
+
+Circuit diagram for screen bonding test (Figure 9).
+
+**Figure 9 – Screen bonding test**
+
+**Table 5 – Preferred maximum values of screen surge voltage based on [b-IEC 60603-7-7] screen contact resistance limits**
+
+| Generator charge voltage<br>kV | Maximum screen to PE voltage,<br>Figure 9 SW positions 1 and 2<br>V | Maximum screen to screen voltage,<br>Figure 9 SW position 3<br>V |
+|--------------------------------|---------------------------------------------------------------------|------------------------------------------------------------------|
+| 2.5                            | 40                                                                  | 80                                                               |
+| 6                              | 90                                                                  | 180                                                              |
+| 12                             | 180                                                                 | 360                                                              |
+| Manufacturer defined           | Manufacturer defined                                                | Manufacturer defined                                             |
+
+# 7 DC tests
+
+## 7.1 Insulation resistance
+
+Insulation resistance (IR) meters can produce voltages of up to 1 kV d.c. or more. To avoid possible electric shock or personal injury, the safety guidelines issued by the IR meter manufacturer should be followed.
+
+Figure 10 shows the test circuit to measure the insulation resistance of an SPD with a PE terminal or screen terminals, or both connections (protection function corresponding to Figure 2). The insulation resistance is measured between each twisted pair cable port contacts and the PE/screen terminals. [b-IEEE 802.3] requires that "the isolation resistance measured at 500 V d.c. shall be at least 2 M $\Omega$ ".
+
+![Figure 10: Test circuit to measure the insulation resistance of an SPD with a PE terminal or screen terminals, or both. The diagram shows an SPD with 8 cable ports (1-8) and 8 equipment ports (10-17). A four-position selector switch (SW) is connected to an IR meter (Ω) and a DC voltage source. The switch can connect the IR meter to the cable ports (positions 1.2, 3.6, 4.5, 7.8) or to the PE/screen terminals. The PE and Screen terminals are connected to a reference bar. The diagram is labeled 'b K.117(16)_F10'.](8592a32c2fdf17c1e562f0ba6b7e8e1a_img.jpg)
+
+Key  
+SW = Four position selector switch    Ω = IR meter with defined d.c. bias
+
+Figure 10: Test circuit to measure the insulation resistance of an SPD with a PE terminal or screen terminals, or both. The diagram shows an SPD with 8 cable ports (1-8) and 8 equipment ports (10-17). A four-position selector switch (SW) is connected to an IR meter (Ω) and a DC voltage source. The switch can connect the IR meter to the cable ports (positions 1.2, 3.6, 4.5, 7.8) or to the PE/screen terminals. The PE and Screen terminals are connected to a reference bar. The diagram is labeled 'b K.117(16)\_F10'.
+
+**Figure 10 – Test circuit to measure the insulation resistance of an SPD with a PE terminal or screen terminals, or both**
+
+Figure 11 shows the test circuit to measure the insulation resistance of an SPD without a PE terminal (protection function corresponding to Figure 3). The insulation resistance is measured between each twisted pair cable port contacts and the equipment port twisted pair contacts.
+
+![Figure 11: Test circuit to measure the insulation resistance of an isolating transformer SPD without a PE terminal. The diagram shows an SPD with 'Cable port' terminals 1, 2, 3, 4, 5, 6, 7, 8 and 'Equipment port' terminals 10, 20, 30, 40, 50, 60, 70, 80. A four-position selector switch (SW) is connected to an IR meter (Ω) with defined d.c. bias. The switch has positions for 1.2, 3.6, 7.8, and 4.5. The switch is connected to the cable port terminals. The equipment port terminals are connected to a reference bar. The screen of the SPD is also connected to the reference bar. The reference bar is connected to the IR meter. The diagram is labeled K.117(16)_F11. A key indicates SW = Four position selector switch and Ω = IR meter with defined d.c. bias.](7f25db95ce3916c0e09803b861a2f7bc_img.jpg)
+
+Figure 11: Test circuit to measure the insulation resistance of an isolating transformer SPD without a PE terminal. The diagram shows an SPD with 'Cable port' terminals 1, 2, 3, 4, 5, 6, 7, 8 and 'Equipment port' terminals 10, 20, 30, 40, 50, 60, 70, 80. A four-position selector switch (SW) is connected to an IR meter (Ω) with defined d.c. bias. The switch has positions for 1.2, 3.6, 7.8, and 4.5. The switch is connected to the cable port terminals. The equipment port terminals are connected to a reference bar. The screen of the SPD is also connected to the reference bar. The reference bar is connected to the IR meter. The diagram is labeled K.117(16)\_F11. A key indicates SW = Four position selector switch and Ω = IR meter with defined d.c. bias.
+
+**Figure 11 – Test circuit to measure the insulation resistance of an isolating transformer SPD without a PE terminal**
+
+This test measures the resistance of the insulation at a defined d.c. voltage. The insulation resistance meter shall be set for a d.c. test voltage of 500 V. The test voltage shall be applied for at least 60 s before the insulation resistance value is taken. The tested SPD must not be modified in any way for this test, for example removing any internal components.
+
+To test this, set switch SW, to select terminals 1, 2. Measure and record the 500 V insulation resistance value. Repeat this procedure with terminals 3, 6 selected, then for terminals 4, 5 selected and finally for terminals 7, 8 selected.
+
+The measured insulation resistance values shall be 2 M $\Omega$  or more, measured at 500 V d.c.
+
+## 7.2 DC voltage drop
+
+An Ethernet SPD intended for PoE will be able to transfer d.c. power in mode A, mode B or both (see clause 6.2.1). It is important that the SPD does not cause a significant power loss and the d.c. voltage drop test verifies the SPD power loss is less than the typical equipment Ethernet PoE transformer.
+
+The test circuit of Figure 12 passes 0.5 A through all the input/output contacts. The individual measured voltages  $V_{12}$ ,  $V_{36}$ ,  $V_{45}$  and  $V_{78}$  shall not exceed 0.5 V. This will guarantee the total d.c. power feed mode A or B series resistance of the SPD will not exceed 0.5  $\Omega$ .
+
+NOTE – This test approach cannot be used for SPDs that isolate the cable side PoE feed from the equipment side PoE feed by means of a d.c./d.c. converter.
+
+![Figure 12 – Test circuit to measure the PoE SPD d.c. input/output voltage drop. The diagram shows a PoE SPD device with 'Cable port' terminals 1, 2, 3, 4, 5, 6, 7, 8 and 'Equipment port' terminals 10, 20, 30, 40, 50, 60, 70, 80. A 0.5 A current source is connected between the Cable port terminals. Voltage drops are indicated: V12 between terminals 1 and 2, V36 between 3 and 6, V45 between 4 and 5, and V78 between 7 and 8. The SPD also has 'Screen' and 'PE' terminals at the bottom. The diagram is labeled K.117(16)_F12.](b6671cfafda3820aafe9a24fa7a4d8c7_img.jpg)
+
+Figure 12 – Test circuit to measure the PoE SPD d.c. input/output voltage drop. The diagram shows a PoE SPD device with 'Cable port' terminals 1, 2, 3, 4, 5, 6, 7, 8 and 'Equipment port' terminals 10, 20, 30, 40, 50, 60, 70, 80. A 0.5 A current source is connected between the Cable port terminals. Voltage drops are indicated: V12 between terminals 1 and 2, V36 between 3 and 6, V45 between 4 and 5, and V78 between 7 and 8. The SPD also has 'Screen' and 'PE' terminals at the bottom. The diagram is labeled K.117(16)\_F12.
+
+**Figure 12 – Test circuit to measure the PoE SPD d.c. input/output voltage drop**
+
+# **8 Identification**
+
+## **8.1 Marking**
+
+Legible and permanent marking shall be applied to the SPD, as necessary, to ensure that the user can determine the following information by inspection:
+
+- manufacturer
+- year of manufacture
+- device number or code
+- port designation (cable or equipment) if the SPD requires specific installation.
+
+If requested and agreed, the customer's identification should be marked on each device.
+
+## **8.2 Documentation**
+
+Documents shall be provided to the user so that from the information in clause 8.1 the user can determine the following additional information:
+
+- appropriate device parameters as set out in this Recommendation
+- component mounting requirements and processes.
+
+# **9 Ordering information**
+
+The following information should be supplied by the user:
+
+- drawing giving all dimensions, finishes and termination details
+- type or model
+- quantity
+- quality assurance requirements.
+
+## Bibliography
+
+- [b-ITU-T K.28] Recommendation ITU-T K.28 (2012), *Parameters of thyristor-based surge protective devices for the protection of telecommunication installations.*
+- [b-ITU-T K.82] Recommendation ITU-T K.82 (2010), *Characteristics and ratings of solid-state, self-restoring overcurrent protectors for the protection of telecommunications installations.*
+- [b-ITU-T K.96] Recommendation ITU-T K.96 (2014), *Surge protective components: Overview of surge mitigation functions and technologies.*
+- [b-ITU-T K.99] Recommendation ITU-T K.99 (2014), *Surge protective component application guide – Gas discharge tubes.*
+- [b-IEC 14776-153] ISO/IEC 14776-153:2015, *Information technology – Small computer system interface (SCSI) – Part 153: Serial attached SCSI – 2.1 (SAS-2.1).*
+- [b-IEC 60050-131] IEC 60050-131:2002, *International Electrotechnical Vocabulary – Part 131: Circuit theory.*
+- [b-IEC 60050-161] IEC 60050-161:1990, *International Electrotechnical Vocabulary. Chapter 161: Electromagnetic compatibility.*
+- [b-IEC 60050-212] IEC 60050-212:2010, *International Electrotechnical Vocabulary – Part 212: Electrical insulating solids, liquids and gases.*
+- [b-IEC 60065] IEC 60065:2014, *Audio, video and similar electronic apparatus – Safety requirements.*
+- [b-IEC 60601-2-1] IEC 60601-2-1:2009, *Medical electrical equipment – Part 2-1: Particular requirements for the basic safety and essential performance of electron accelerators in the range 1 MeV to 50 MeV.*
+- [b-IEC 60603-7-7] IEC 60603-7-7:2010, *Connectors for electronic equipment – Part 7-7: Detail specification for 8-way, shielded, free and fixed connectors for data transmission with frequencies up to 600 MHz.*
+- [b-IEC TR 60664-2-1] IEC TR 60664-2-1 (2011), *Insulation coordination for equipment within low voltage systems – Part 2-1: Application guide – Explanation of the application of the IEC 60664 series, dimensioning examples and dielectric testing.*
+- [b-IEC 61643-341] IEC 61643-341:2001, *Components for low-voltage surge protective devices – Part 341: Specification for thyristor surge suppressors (TSS).*
+- [b-IEEE 802.3] 802.3-2015, *IEEE Standard for Ethernet.*
+
+
+
+
+
+## **SERIES OF ITU-T RECOMMENDATIONS**
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| Series E        | Overall network operation, telephone service, service operation and human factors                                                                         |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| <b>Series K</b> | <b>Protection against interference</b>                                                                                                                    |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/K/T-REC-K.118-201612-I_PDF-E/raw.md

@@ -0,0 +1,421 @@
+
+
+International Telecommunication Union
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**K.118**
+
+(12/2016)
+
+SERIES K: PROTECTION AGAINST INTERFERENCE
+
+---
+
+**Requirements for lightning protection of fibre to  
+the distribution point equipment**
+
+Recommendation ITU-T K.118
+
+![ITU logo](6ed175c791b5e156d9c98a8dbcc3318c_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a globe with a red lightning bolt striking it, symbolizing telecommunications. The text "ITU" is prominently displayed in blue, with "International Telecommunication Union" written in smaller blue text to the right.
+
+ITU logo
+
+
+
+# Recommendation ITU-T K.118
+
+# Requirements for lightning protection of fibre to the distribution point equipment
+
+## Summary
+
+Recommendation ITU-T G.9701 specifies a gigabit broadband access technology that exploits the existing infrastructure of wire pairs that were originally deployed for plain old telephone service (POTS) services. Equipment implementing this Recommendation can be deployed from fibre to the distribution point (FTTdp) located very near the customers' premises.
+
+Recommendation ITU-T K.118 contains the necessary information to enable the protection of a distribution point (DP) node in the access network and the associated equipment in the customers' premises. It includes information on the resistibility requirements of the equipment, the rating of the lightning protection, when the installation of protection is necessary and on how to install this protection.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T K.118    | 2016-12-14 | 5           | <a href="http://handle.itu.int/11.1002/1000/13134">11.1002/1000/13134</a> |
+
+## Keywords
+
+EPR, GDT, lightning protection, MOVs, MSPDs, power contact and SPDs.
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2017
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+|                                                                                                                                     | Page |
+|-------------------------------------------------------------------------------------------------------------------------------------|------|
+| 1 Scope.....                                                                                                                        | 1    |
+| 2 References.....                                                                                                                   | 1    |
+| 3 Definitions .....                                                                                                                 | 2    |
+| 3.1 Terms defined elsewhere .....                                                                                                   | 2    |
+| 3.2 Terms defined in this Recommendation.....                                                                                       | 2    |
+| 4 Abbreviations and acronyms .....                                                                                                  | 2    |
+| 5 Conventions .....                                                                                                                 | 3    |
+| 6 Elements of protection.....                                                                                                       | 3    |
+| 6.1 Correct classification and use of ports.....                                                                                    | 4    |
+| 6.2 Equipment design considerations .....                                                                                           | 4    |
+| 6.3 Equipment resistibility.....                                                                                                    | 6    |
+| 6.4 Primary protection and MSPDs.....                                                                                               | 6    |
+| 6.5 Requirements for earthing and bonding .....                                                                                     | 7    |
+| 6.6 Risk assessment .....                                                                                                           | 7    |
+| 6.7 Responsibility .....                                                                                                            | 8    |
+| 6.8 A.C. earth potential rise (EPR).....                                                                                            | 8    |
+| Appendix I – Level of protection.....                                                                                               | 9    |
+| I.1 Protection against surges induced into external cables .....                                                                    | 9    |
+| I.2 Protection against direct strikes to the power or telecommunications<br>cables or lines more than 100 m away from the DPU ..... | 9    |
+| I.3 Protection against direct strikes.....                                                                                          | 9    |
+| Bibliography.....                                                                                                                   | 10   |
+
+# **Introduction**
+
+Fibre to the distribution point (FTTdp) supports one or more high-speed copper drops into customer premises and uses a gigabit (or faster) fibre link to backhaul user data to a high order node (HON). A key aspect of the new node type is the ability for it to be reverse power fed from one or more copper drop pairs. To reverse power feed (RPF), there needs to be power supply functionality at the customer's premises. To this end a new node type, the distribution point unit (DPU), is defined. This node is typically positioned at the distribution point (DP).
+
+To maintain the reliability of the network it is necessary to ensure that this equipment has the required level of resistibility and that the necessary lightning protection is installed when needed.
+
+# Recommendation ITU-T K.118
+
+## Requirements for lightning protection of fibre to the distribution point (FTTdp) equipment
+
+# 1 Scope
+
+This Recommendation applies to the equipment installed at the distribution point (DP) node and the associated equipment installed at the customers' premises.
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [ITU-T K.12] Recommendation ITU-T K.12 (2010), *Characteristics of gas discharge tubes for the protection of telecommunications installations.*
+- [ITU-T K.21] Recommendation ITU-T K.21 (2016), *Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents.*
+- [ITU-T K.35] Recommendation ITU-T K.35 (1996), *Bonding configurations and earthing at remote electronic sites.*
+- [ITU-T K.44] Recommendation ITU-T K.44 (2016), *Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents – Basic Recommendation.*
+- [ITU-T K.45] Recommendation ITU-T K.45 (2016), *Resistibility of telecommunication equipment installed in the access and trunk networks to overvoltages and overcurrents.*
+- [ITU-T K.65] Recommendation ITU-T K.65 (2011), *Overvoltage and overcurrent requirements for termination modules with contacts for test ports or surge protective devices.*
+- [ITU-T K.66] Recommendation ITU-T K.66 (2011), *Protection of customer premises from overvoltages.*
+- [ITU-T K.75] Recommendation ITU-T K.75 (2016), *Classification of interface for application of standards on resistibility and safety of telecommunication equipment.*
+- [ITU-T K.85] Recommendation ITU-T K.85 (2011), *Requirements for the mitigation of lightning effects on home networks installed in customer premises.*
+- [ITU-T K.98] Recommendation ITU-T K.98 (2014), *Overvoltage protection guide for telecommunication equipment installed in customer premises.*
+- [ITU-T K.108] Recommendation ITU-T K.108 (2015), *Joint use of poles by telecommunication and solidly earthed power lines.*
+- [ITU-T K.109] Recommendation ITU-T K.109 (2015), *Installation of telecommunication equipment on utility poles.*
+- [IEC 60950-1] IEC 60950-1:2005+AMD1:2009+AMD2:2013 CSV, *Information technology equipment – Safety – Part 1: General requirements.*
+
+- [IEC 61643-311] IEC 61643-331:2013, *Components for low-voltage surge protective devices – Part 311: Performance requirements and test circuits for gas discharge tubes (GDT)*.
+- [IEC 61643-331] IEC 61643-331:2003, *Components for low-voltage surge protective devices – Part 331: Specification for metal oxide varistors (MOV)*.
+- [IEC 62305-2] IEC 62305-2 Ed. 2.0 (2010), *Protection against lightning – Part 2: Risk management*.
+- [IEC 62368-1] IEC 62368-1 Ed. 2.0 (2014), *Audio/video, information and communication technology equipment – Part 1: Safety requirements*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 high current carrying protection components** [ITU-T K.44]: A high current carrying protection component is an SPD which, when activated by the surge, conducts/diverts the majority of the surge away from the circuit it is protecting. High current carrying protection components are mainly used as primary protection components, but in some cases may be integrated into the equipment as inherent protection.
+
+**3.1.2 inherent protection** [ITU-T K.44]: Inherent protection is protection that is provided within the equipment either by virtue of its intrinsic characteristics, by specific design, or by suitable protection components.
+
+**3.1.3 primary protection** [ITU-T K.44]: Means by which the majority of the surge stress is prevented from propagating beyond a designated location (preferably the building entrance point).
+
+**3.1.4 spark-overvoltage** [ITU-T K.12]: The voltage which causes spark-over when applied across the terminals of a gas discharge tube.
+
+## 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following term:
+
+**3.2.1 thermal protection:** integral switch function of a surge protective component (SPC) that operates when the component temperature exceeds a pre-set value.
+
+NOTE 1 – A thermally protected gas discharge tube (GDT) has a normally open thermal switch connected in parallel with the electrodes, which shorts out the GDT when the component temperature exceeds a pre-set value.
+
+NOTE 2 – A thermally protected metal oxide varistor (MOV) has a normally closed thermal switch connected in series with MOV element, which disconnects the MOV when the component temperature exceeds a pre-set value.
+
+# 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|      |                         |
+|------|-------------------------|
+| a.c. | alternating current     |
+| d.c. | direct current          |
+| DP   | Distribution Point      |
+| DPU  | Distribution Point Unit |
+| EPR  | Earth Potential Rise    |
+
+|       |                                       |
+|-------|---------------------------------------|
+| ES1   | Electrical Energy Source class 1      |
+| ES2   | Electrical Energy Source class 2      |
+| FTTdp | Fibre To The distribution point       |
+| GDT   | Gas Discharge Tube                    |
+| HON   | High Order Node                       |
+| MEB   | Main Electrical Board                 |
+| MOV   | Metal Oxide Varistor                  |
+| MSPD  | Multi-service Surge Protective Device |
+| PE    | Protective Earth                      |
+| RPF   | Reverse Power Feeding                 |
+| SELV  | Safety Extra Low Voltage              |
+| SPC   | Surge Protective Component            |
+| SPD   | Surge Protective Device               |
+| VoIP  | Voice over Internet Protocol          |
+
+# 5 Conventions
+
+None.
+
+# 6 Elements of protection
+
+Fibre to the distribution point (FTTdp) supports one or more high-speed copper drops into customer premises and uses a gigabit (or faster) fibre link to backhaul user data to a high order node (HON). A key aspect of the new node type is the ability for it to be reverse power fed from one or more copper drop pairs. To reverse power feed (RPF), there needs to be power supply functionality at the customer premises. To this end a new node type, the distribution point unit (DPU), is defined. This node is typically positioned at the distribution point (DP).
+
+![Diagram of Fibre to the distribution point (FTTdp) showing two customer premises connected to a central FTTdp equipment. Each customer premise contains a Modem and an RPF. The Modem is connected to the RPF, and the RPF is connected to the FTTdp equipment. The FTTdp equipment is also connected to an existing copper cable from the exchange node and an optic fibre. The diagram is labeled K.118(16)_F01.](a5ee5c23b6dc52ec1d724b76d5a5f58f_img.jpg)
+
+The diagram illustrates the FTTdp architecture. On the left, two 'Customer premises' are shown, each containing a 'Modem' and an 'RPF'. The Modem is connected to the RPF, and the RPF is connected to the 'FTTdp equipment' on the right. The FTTdp equipment is connected to an 'Existing copper to exchange node' and an 'Optic fibre'. A dashed line connects the two customer premises, indicating they are separate units. The diagram is labeled 'K.118(16)\_F01'.
+
+Diagram of Fibre to the distribution point (FTTdp) showing two customer premises connected to a central FTTdp equipment. Each customer premise contains a Modem and an RPF. The Modem is connected to the RPF, and the RPF is connected to the FTTdp equipment. The FTTdp equipment is also connected to an existing copper cable from the exchange node and an optic fibre. The diagram is labeled K.118(16)\_F01.
+
+In some implementations the FTTdp equipment may be connected to the existing copper cable from the exchange node until all customers are converted to VoIP.
+
+**Figure 1 – Fibre to the distribution point (FTTdp)**
+
+There are many different methods of supplying the RPF to the FTTdp equipment at the DP. In some applications the modem signal will share the copper pair and in other applications separate pairs will be used. These options are described in [b-ETSI TS 101 548].
+
+To ensure that adequate lightning protection is installed, or can be installed, it is necessary to consider a number of issues. These are:
+
+- 1 correct classification and use of ports
+- 2 equipment design considerations
+- 3 equipment resistibility
+- 4 primary protection
+- 5 requirements for earthing and bonding
+- 6 risk assessment
+- 7 responsibility
+- 8 A.C. earth potential rise (EPR).
+
+## 6.1 Correct classification and use of ports
+
+Correct classification and use of ports: It is necessary that the equipment ports have been correctly classified, designed and used in accordance with [ITU-T K.75].
+
+For the RPF equipment installed in the customer premises both the mains and the power feed ports need to be "external ports".
+
+For the DP equipment all ports need to be "external ports".
+
+## 6.2 Equipment design considerations
+
+Where lightning protection above the inherent resistibility level of 1.5 kV is required, there are two options:
+
+- Add primary protection outside the equipment when a risk assessment indicates that protection should be installed.
+
+- Design the equipment with integral high current carrying protection components (e.g., gas discharge tubes (GDTs)) as part of the inherent protection. Typically, this is only implemented for access network equipment.
+
+In both cases the protection could be used as bypass protection or the protection could be earthed. Bypass and earthed protection is shown pictorially in Figure 2.
+
+![Figure 2 – Pictorial illustration of bypass and earthed protection. The diagram shows two configurations for FTTdp equipment protection. The top configuration, labeled 'Bypass protection', shows the equipment connected to two GDTs (Cust 1 GDT and Cust 2 GDT) which are then connected to a common bypass line. The bottom configuration, labeled 'Earthed protection', shows the equipment connected to two GDTs (Cust 1 GDT and Cust 2 GDT) which are then connected to a common 'Network earth' point. Both diagrams include a 'Fibre' input and output, and lightning strike symbols on the input lines.](e9314c83043183351ed74908e9bf2f90_img.jpg)
+
+The diagram consists of two parts. The upper part illustrates 'Bypass protection'. It shows a central box labeled 'FTTdp equipment'. To its left, two lines enter from 'Cust 1 GDT', and to its right, two lines exit to 'Cust 2 GDT'. Red lightning bolts indicate surges on the input lines. A red line bypasses the equipment, connecting the GDTs directly. A blue line labeled 'Fibre' also enters and exits the equipment. The lower part illustrates 'Earthed protection'. It is similar to the upper part but instead of a bypass line, the GDTs and the equipment are connected to a common point labeled 'Network earth', which is connected to a ground symbol labeled 'Earthed protection'. The reference code 'K.118(16)\_F02' is in the bottom right.
+
+Figure 2 – Pictorial illustration of bypass and earthed protection. The diagram shows two configurations for FTTdp equipment protection. The top configuration, labeled 'Bypass protection', shows the equipment connected to two GDTs (Cust 1 GDT and Cust 2 GDT) which are then connected to a common bypass line. The bottom configuration, labeled 'Earthed protection', shows the equipment connected to two GDTs (Cust 1 GDT and Cust 2 GDT) which are then connected to a common 'Network earth' point. Both diagrams include a 'Fibre' input and output, and lightning strike symbols on the input lines.
+
+**Figure 2 – Pictorial illustration of bypass and earthed protection**
+
+### 6.2.1 Floating equipment
+
+This is equipment that does not require a protective earth (PE) and it is powered from an SELV, ES1 or ES2 circuit, or has a double insulated power supply.
+
+If the DPU will not be earthed it is a good idea to ensure that a flashover to earth is unlikely. A figure of 20 kV of isolation is probably a good figure to achieve. While it is possible for a telecommunications cable to conduct 100 kV surges, joints will break down at lower voltages. At the breakdown point of the joint an EPR will occur and the voltage on the cable can still be more than the breakdown voltage of the joint. The more joints that break down the lower the cable voltage will be. Further information on the surge voltage in a cable is provided in [ITU-T K.98].
+
+[ITU-T K.109] has additional requirements for installations on power poles.
+
+### 6.2.2 Earthed equipment
+
+This equipment requires a PE connection.
+
+[ITU-T K.109] has additional requirements for installations on power poles.
+
+### 6.2.3 Equipment with integral high current carrying protection components
+
+This is equipment with integral high current carrying protection components. The "enhanced requirement" in [ITU-T K.21] and [ITU-T K.45] requires that the current carrying capacity of the printed circuit tracks needs to be 5 kA 8/20  $\mu\text{s}$  per conductor and 30 kA 8/20  $\mu\text{s}$  for the conductors carrying the sum of the single conductor currents.
+
+NOTE – Printed circuit tracks, particularly the track conducting the sum of the currents, will need to be thicker and wider than normal tracks. This ensures compatibility with good quality filled cable connectors (grease or gel filled) which can safely conduct 5 kA 8/20  $\mu$ s currents.
+
+## **6.3 Equipment resistibility**
+
+### **6.3.1 Network equipment installed in the network**
+
+For **network equipment installed in the network** the requirements should be as recommended in [ITU-T K.45]. The "Enhanced" test levels are suggested to ensure reliable equipment, particularly for equipment which contains high current carrying protection components within the equipment to eliminate the need for primary protection.
+
+### **6.3.2 Network equipment installed in customer premises**
+
+For **network equipment installed in customer premises** the requirements should be as recommended in [ITU-T K.21]. The "Enhanced" test levels are suggested to ensure reliable equipment.
+
+NOTE – For "floating equipment", with no connection to PE, the line to earth resistibility requirement is 6 kV for the "Enhanced" test level and this ensures a far more robust product.
+
+## **6.4 Primary protection and MSPDs**
+
+Refer to clause 6.6 on performing a risk assessment to determine when primary protection is necessary. Refer to clause 6.7 regarding the responsibility for installing lighting protection.
+
+#### **6.4.1 Requirements of the SPDs**
+
+#### **6.4.1.1 Multi-service surge protective devices (MSPDs)**
+
+MSPDs shall comply with [IEC 60950-1] or [IEC 62368-1]. The protection components shall comply with [IEC 61643-331] for MOVs and [IEC 61643-311] for GDTs. Ideally, the MOVs should have a minimum of a 5kA rating and the GDTs should have a minimum of a 5 kA rating per side, (i.e., 10 kA in the centre electrode for a 3 electrode type).
+
+#### **6.4.1.2 GDTs at the DPU**
+
+This applies to GDTs within the equipment or those installed in a protection frame. The GDTs should have a minimum of a 5 kA rating per side (i.e., 10 kA in the centre electrode for a 3 electrode type). The spark-over voltage will be as agreed by the equipment manufacturer and the network operator. Guidance is provided in [ITU-T K.12]. Refer to clause 6.4.1.5 for power contact and fire considerations.
+
+#### **6.4.1.3 GDTs at customer premises**
+
+The GDTs should have a minimum of a 5 kA rating per side, (i.e., 10 kA in the centre electrode for a 3 electrode type). The spark-over voltage will be as agreed by the equipment manufacturer and the network operator. Guidance is provided in [ITU-T K.12]. National regulations of the country may have specific requirements. Refer to clause 6.4.1.5 for power contact and fire considerations.
+
+#### **6.4.1.4 Mains SPDs at customer premises**
+
+Ideally, the SPD should have a minimum of a 40 kA 8/20  $\mu$ s rating. In extreme situations, e.g., long rural power lines, an SPD with a 100 kA 8/20  $\mu$ s rating should be considered.
+
+#### **6.4.1.5 Fire consideration**
+
+Consideration should be given to the possibility of a power contact to the telecommunications line causing the GDT to overheat and resulting in a fire. A fire can be prevented by selecting the voltage limiter threshold voltage to be above the mains voltage or by the use of thermal protection to prevent the GDT from overheating.
+
+Where the GDT is an integral part of the equipment the requirements are contained in [ITU-T K.21] and [ITU-T K.45] as applicable and in [IEC 62368-1]. Where the GDT is installed in a protection frame the requirements are given in [ITU-T K.65].
+
+#### **6.4.2 Installation**
+
+#### **6.4.2.1 DPU**
+
+When needed, GDTs could be installed outside the equipment or the equivalent of primary protection included in the equipment design as inherent protection. The GDT requirements are provided in [ITU-T K.12]. The protection holder requirements are provided in [ITU-T K.65].
+
+NOTE – When the equivalent of primary protection is included in the equipment design as inherent protection, primary protection is not required.
+
+#### **6.4.2.2 Customer premises**
+
+Overvoltage protection, when required, should be installed according to [ITU-T K.66]. This includes the use of both MSPDs and primary protectors for both the mains and telecommunications services.
+
+An MSPD should be the first level of protection for equipment installed in the customers' premises to protect the RPF equipment. The requirements for installing MSPDs are provided in [ITU-T K.66].
+
+To prevent possible problems both the RPF equipment, the modem and any nearby equipment such as a computer or mains powered telephone plugged into the modem, need to be powered from this MSPD. Ideally, if mains powered telephones are used remotely from the modem the "internal" port of the modem needs to be protected to prevent both damage to the modem and possible damage to the RPF equipment. This is described in [ITU-T K.66]. However, as an MSPD with the necessary internal port protection does not exist, this protection cannot be easily provided. Responsibility for the decision to install, or when to install, an MSPD needs to be allocated.
+
+In lightning-prone areas primary protection may also need to be installed. This would include an SPD in the main electrical board (MEB) and GDTs on the cable from the DP. This is to protect the MSPD.
+
+## **6.5 Requirements for earthing and bonding**
+
+For customer premises the earthing and bonding practices should comply with [ITU-T K.66]. Earthing is the connection of the earth bar to earth, usually via an installed earth electrode. Bonding is the interconnection of earth electrodes and metallic parts to minimise potential differences.
+
+For the DPU the earthing and bonding practices should comply with [ITU-T K.35] if earthing is provided. The value of the resistance of the earthing electrode depends on its function. If required for functional reasons a single earth electrode is all that is required. If the earth is required to protect against a direct strike to the pole a 10 Ω earth is a nominal requirement. As this may be difficult to achieve, a higher value may need to be accepted. [ITU-T K.109] has additional requirements for installations on power poles.
+
+## **6.6 Risk assessment**
+
+To determine the risk of lightning damage for different installations [IEC 62305-2] can be used to perform a risk assessment. This would determine when MSPDs and primary protection are required. Examples of such risk assessments are provided in [ITU-T K.85].
+
+### **6.6.1 DPU**
+
+If the DPU equipment has integral high current carrying protection components (e.g., GDTs) as part of the inherent protection, the equivalent of primary protection is effectively always provided.
+
+If primary protection is added to a protection frame when necessary, either the equipment provider, installer or network operator has to decide when primary protection is required and take the necessary steps to ensure that it is installed.
+
+### **6.6.2 Customer premises**
+
+At the customer's premises, it is necessary to decide when to:
+
+- 1 install an MSPD to protect the RPF equipment and associated equipment;
+- 2 install primary protection on both the telecommunications and power services. Note, some services may already have an SPD for the power service to protect computer-controlled equipment such as washing machines, etc.
+
+## **6.7 Responsibility**
+
+To ensure that the required level of protection is provided it is necessary that the parties involved agree on the breakdown of responsibility. Proposals for the sharing of this responsibility are provided in [ITU-T K.66] and [ITU-T K.85].
+
+## **6.8 A.C. earth potential rise (EPR)**
+
+Avoiding an a.c. EPR in the network is outside the scope of this document but it is an issue which needs consideration when installing DPUs. [ITU-T K.109] has requirements for installations on power poles.
+
+# Appendix I
+
+## Level of protection
+
+(This appendix does not form an integral part of this Recommendation.)
+
+Three levels of protection can nominally be provided.
+
+### **I.1 Protection against surges induced into external cables**
+
+The equipment inherent resistibly level of 1.5 kV is meant to provide protection against approximately 95% of induced surges. However, this is not an indication of how often damage may occur. [IEC 62305-2] can be used to determine the frequency of damage. [IEC 62305-2] nominally calculates loss but without understanding the implications that it can result in an incorrect conclusion.
+
+### **I.2 Protection against direct strikes to the power or telecommunications cables or lines more than 100 m away from the DPU**
+
+The installation of an MSPD at customers' premises will protect the equipment in the majority of cases. The use of MSPDs in suburban areas would ensure that overvoltage damage is kept to a low level. The installation of primary protection in the main electrical switchboard and in the telecommunications termination box will enhance this protection particularly against surges entering on the mains conductors. Primary protection is probably unnecessary for most installations except in known lightning-prone areas.
+
+The use of primary protection at the DPU or the use of a DPU with inherent protection equivalent to primary protection will protect the equipment in the majority of cases.
+
+Both of the above statements are based on the data in [ITU-T K.98].
+
+### **I.3 Protection against direct strikes**
+
+This would mean protection against direct strikes to the houses, to the pole and even the cable in high lightning-prone areas. It would require direct strike protection of the building and a 10 ohm earth for each structure. Protection to this level would incur significant expense and is not practical.
+
+# Bibliography
+
+- [b-ITU-T G.9701] Recommendation ITU-T G.9701 (2014), *Fast access to subscriber terminals (G.fast) – Physical layer specification.*
+- [b-ETSI TS 101 548] ETSI TS 101 548 V2.1.1 (2016), *Access, Terminals, Transmission and Multiplexing (ATTM); European Requirements for Reverse Powering of Remote Access Equipment.*
+
+
+
+## **SERIES OF ITU-T RECOMMENDATIONS**
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| Series E        | Overall network operation, telephone service, service operation and human factors                                                                         |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| <b>Series K</b> | <b>Protection against interference</b>                                                                                                                    |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/K/T-REC-K.119-201612-I_PDF-E/raw.md

@@ -0,0 +1,642 @@
+
+
+International Telecommunication Union
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**K.119**
+
+(12/2016)
+
+SERIES K: PROTECTION AGAINST INTERFERENCE
+
+---
+
+**Conformance assessment of radio base stations  
+regarding lightning protection and earthing**
+
+Recommendation ITU-T K.119
+
+![ITU logo](6ed175c791b5e156d9c98a8dbcc3318c_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a globe with a red lightning bolt striking it, symbolizing telecommunications and protection against interference. To the right of the globe, the text "International Telecommunication Union" is written in a blue sans-serif font, with "ITU" in a larger, bold font above it.
+
+ITU logo
+
+
+
+# Recommendation ITU-T K.119
+
+# Conformance assessment of radio base stations regarding lightning protection and earthing
+
+## Summary
+
+Recommendation ITU-T K.119 provides the technical requirements and measurement methods to assess the validity and reliability of the lightning protection and earthing system of radio base stations (RBSs). It focuses on the quality control in the process of construction, acceptance, inspection and maintenance.
+
+Normally, the conformance assessment is carried out during and immediately after the construction period and it results in the commissioning of the installation to start its operation. Routine inspections are scheduled in order to assure the maintenance of the lightning protection and earthing characteristics, during the operation life of the installation.
+
+Depending on the function and installation location, the lightning protection system of an RBS can be partitioned into 4 parts which consist of an air-termination and down conductor system, earthing system, equipotential bonding network and surge protective devices (SPDs). The conformance assessment is directed to these parts, and may consist in visual inspection, measurement, analysis and other applicable methods.
+
+The assessment requirements of each part for commissioning and routine inspections are presented in clauses 8 to 11 separately. In addition, management rules are introduced in clause 12, which are effective for conformance maintenance during the operation life of the RBS.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T K.119    | 2016-12-14 | 5           | <a href="http://handle.itu.int/11.1002/1000/13135">11.1002/1000/13135</a> |
+
+## Keywords
+
+Assessment, conformance, earthing, lightning protection, radio base station.
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2017
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+###### Page
+
+|      |                                                                            |    |
+|------|----------------------------------------------------------------------------|----|
+| 1    | Scope.....                                                                 | 1  |
+| 2    | References.....                                                            | 1  |
+| 3    | Definitions .....                                                          | 1  |
+| 3.1  | Terms defined elsewhere .....                                              | 1  |
+| 3.2  | Terms defined in this Recommendation.....                                  | 2  |
+| 4    | Abbreviations and acronyms .....                                           | 2  |
+| 5    | Conventions .....                                                          | 2  |
+| 6    | General.....                                                               | 2  |
+| 6.1  | Commissioning.....                                                         | 3  |
+| 6.2  | Routine inspection .....                                                   | 3  |
+| 7    | Constitution of the lightning protection and earthing system of RBSs ..... | 4  |
+| 8    | Air-termination and down conductor system .....                            | 5  |
+| 8.1  | Requirements for commissioning.....                                        | 6  |
+| 8.2  | Requirements for routine inspections .....                                 | 6  |
+| 9    | Earthing system .....                                                      | 6  |
+| 9.1  | Requirements for commissioning.....                                        | 7  |
+| 9.2  | Requirements for routine inspections.....                                  | 8  |
+| 10   | Equipotential bonding network.....                                         | 9  |
+| 10.1 | Requirements for commissioning.....                                        | 9  |
+| 10.2 | Requirements for routine inspections.....                                  | 11 |
+| 11   | Requirements for surge protective devices (SPDs) .....                     | 12 |
+| 11.1 | Requirements for commissioning.....                                        | 12 |
+| 11.2 | Requirements for routine inspections.....                                  | 12 |
+| 12   | Management of the conformance assessment.....                              | 13 |
+| 12.1 | File management .....                                                      | 13 |
+| 12.2 | Interval of routine inspections .....                                      | 13 |
+|      | Appendix I – Test of the DC parameters of MOV SPDs.....                    | 14 |
+| I.1  | Test apparatus .....                                                       | 14 |
+| I.2  | Test method .....                                                          | 14 |
+| I.3  | Evaluation criteria .....                                                  | 15 |
+|      | Bibliography.....                                                          | 17 |
+
+
+
+# Recommendation ITU-T K.119
+
+## Conformance assessment of radio base stations regarding lightning protection and earthing
+
+# 1 Scope
+
+This Recommendation provides the technical requirements and measurement methods to assess the validity and reliability of the lightning protection and earthing system of radio base stations (RBS). It focuses on the quality control of the processes of construction, acceptance, inspection and maintenance.
+
+The detailed requirements for the lightning protection of RBSs are provided by [ITU-T K.56], [ITU-T K.112] and their references.
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [ITU-T K.56] Recommendation ITU-T K.56 (2010), *Protection of radio base stations against lightning discharges*.
+- [ITU-T K.111] Recommendation ITU-T K.111 (2015), *Protection of surrounding structures of telecommunication towers against lightning*.
+- [ITU-T K.112] Recommendation ITU-T K.112 (2015), *Lightning protection, earthing and bonding: practical procedures for radio base stations*.
+- [IEC 61643-11] IEC 61643-11 (2010), *Low-voltage surge protective devices – Part 11: Surge protective devices connected to low-voltage power systems – Requirements and test methods*.
+- [IEC 61643-21] IEC 61643-21 (2012), *Low voltage surge protective devices – Part 21: Surge protective devices connected to telecommunications and signalling networks – Performance requirements and testing methods*.
+- [IEC 62305-3] IEC 62305-3 (2010), *Protection against lightning – Part 3: Physical damage to structures and life hazard*.
+
+# 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+The definitions contained in the references apply to this Recommendation. Some of them are reproduced here for convenience.
+
+**3.1.1 earth conductor** [b-ITU-T Handbook]: A conductor or group of conductors connecting the earth electrode to the earth collector. In the case of partly buried connections, this definition is valid only for the sections which are electrically insulated from the ground, the sections in contact with the ground forming part of the earth electrode.
+
+**3.1.2 earthing network** [ITU-T K.112]: The part of an earthing installation that is restricted to the earth electrodes and their interconnections.
+
+**3.1.3 one-port SPD** [b-IEC 61643-11]: SPD having no intended series impedance.
+
+NOTE – A one port SPD may have separate input and output connections.
+
+**3.1.4 two-port SPD** [b-IEC 61643-11]: SPD having a specific series impedance connected between separate input and output connections.
+
+### **3.2 Terms defined in this Recommendation**
+
+This Recommendation defines the following terms:
+
+**3.2.1 commissioning:** Acceptance of the whole installation that is carried out when all the work has been finished and the installation complies with the design criteria.
+
+**3.2.2 final inspection:** Inspection that is carried out when all the work has been finished.
+
+**3.2.3 follow-up inspection:** Inspection performed during the construction work in order to verify the compliance of the installation with the design criteria.
+
+NOTE – Follow-up inspection is normally required for parts of the installation that are not accessible afterwards (e.g., earthing network).
+
+**3.2.4 routine inspection:** Inspection that is carried out at regular intervals during the operational life of the installation.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+AC      Alternating Current
+
+DC      Direct Current
+
+LPL    Lightning Protection Level
+
+MET    Main Earthing Terminal
+
+MOV    Metal Oxide Varistor
+
+RBS    Radio Base Station
+
+SPD    Surge Protective Device
+
+# **5 Conventions**
+
+None.
+
+# **6 General**
+
+In order to ensure the validity and reliability of the lightning protection and earthing system, its assessment and maintenance should be carried out throughout the entire lifetime of the radio base station. According to the different requirements during the construction period and the operation period, the assessment can be divided into two categories: commissioning and routine inspections.
+
+Effective management procedures also have to be implemented for conformance assessment, such as documentation management and a periodic inspection schedule. Moreover, the conformance assessment shall be implemented by skilled professionals and the measuring equipment (e.g., earthing resistance meter) shall have a valid calibration.
+
+### 6.1 Commissioning
+
+During the construction period, a systemic assessment should be performed to ensure that the lightning protection and earthing system satisfies the requirements of design, which is regarded as the acceptance of the project. The follow-up inspection shall be applied to the concealed works (e.g., embedded electrodes). After the installation, a final inspection shall be exerted for all the components.
+
+The primary aspects needed to be considered for commissioning an RBS include:
+
+- the installation shall conform to the project requirements;
+- the applied materials and devices are in good condition and capable of performing their designed functions;
+- the construction technology and quality of the supplies are adequate for environmental suitability and service life.
+
+The RBS shall be commissioned to start its operation only if both the results of the follow-up and final inspections comply with the requirements.
+
+## 6.2 Routine inspection
+
+During the operating period, regular and periodic inspections are fundamental for the reliable maintenance of all the components in the lightning protection and earthing system, which is regarded as routine inspection. The interval between consecutive routine inspections needs to consider the nature of RBS and environmental factors. An unordered inspection may need to be performed at some emergency conditions. The property owner shall be informed of all observed faults and they shall be repaired without delay.
+
+The primary aspects that need to be considered in routine inspections include:
+
+- all components of the lightning protection and earthing system are in good condition and capable of performing their designed functions, and that there is no corrosion;
+- any recently installed equipment or constructions are incorporated into the lightning protection and earthing system;
+- any remaining effect caused by lightning flashes or natural calamities (e.g., flood, earthquake) or nearby constructions shall be assessed and removed.
+
+Any problem detected during the routine inspections must be corrected in order to make sure that the installation complies with the requirements of the inspection.
+
+Figure 1 shows a flowchart of the conformance assessment process according to this Recommendation.
+
+![Flowchart of the conformance assessment process. The process starts with 'START', followed by 'Follow-up inspection', a decision 'OK?'. If 'N' (No), it goes to 'Fix the problems' and loops back to 'Follow-up inspection'. If 'Y' (Yes), it goes to 'Final inspection', another decision 'OK?'. If 'N', it goes to 'Fix the problems' and loops back to 'Final inspection'. If 'Y', it goes to 'RBS commissioned', then 'Wait for the next inspection', then 'Routine inspection', and finally a decision 'OK?'. If 'N', it goes to 'Fix the problems' and loops back to 'Routine inspection'. If 'Y', it loops back to 'Wait for the next inspection'. The diagram is labeled K.119(16)_F01.](a5ee5c23b6dc52ec1d724b76d5a5f58f_img.jpg)
+
+```
+
+graph TD
+    START([START]) --> FUI[Follow-up inspection]
+    FUI --> OK1{OK?}
+    OK1 -- N --> FP1[Fix the problems]
+    FP1 --> FUI
+    OK1 -- Y --> FI[Final inspection]
+    FI --> OK2{OK?}
+    OK2 -- N --> FP2[Fix the problems]
+    FP2 --> FI
+    OK2 -- Y --> RC[RBS commissioned]
+    RC --> WNI[Wait for the next inspection]
+    WNI --> RI[Routine inspection]
+    RI --> OK3{OK?}
+    OK3 -- N --> FP3[Fix the problems]
+    FP3 --> RI
+    OK3 -- Y --> WNI
+  
+```
+
+K.119(16)\_F01
+
+Flowchart of the conformance assessment process. The process starts with 'START', followed by 'Follow-up inspection', a decision 'OK?'. If 'N' (No), it goes to 'Fix the problems' and loops back to 'Follow-up inspection'. If 'Y' (Yes), it goes to 'Final inspection', another decision 'OK?'. If 'N', it goes to 'Fix the problems' and loops back to 'Final inspection'. If 'Y', it goes to 'RBS commissioned', then 'Wait for the next inspection', then 'Routine inspection', and finally a decision 'OK?'. If 'N', it goes to 'Fix the problems' and loops back to 'Routine inspection'. If 'Y', it loops back to 'Wait for the next inspection'. The diagram is labeled K.119(16)\_F01.
+
+**Figure 1 – Flowchart of the conformance assessment process**
+
+# 7 Constitution of the lightning protection and earthing system of RBSs
+
+Depending on the function and installation location, the lightning protection and earthing system of an RBS can be partitioned as follows:
+
+- air-termination and down conductor system;
+- earthing system;
+- equipotential bonding network;
+- surge protective devices (SPDs).
+
+Figure 2 shows the parts of an RBS where it can be seen that each part has its main function and need to coordinate with the other parts. The malfunction or degradation of any part can affect the overall performance and even lead to a hazardous result. The common important components belonging to each part are listed in Table 1.
+
+NOTE – The lightning protection and earthing system of roof-top RBSs can also be partitioned into the above 4 parts, although the layout of an external system may have some differences.
+
+Correspondingly, the assessment of conformance can be partitioned into the itemized evaluation for each part through visual inspection, measurement, analysis and other applicable methods.
+
+![Figure 2: Typical layout of RBS consisting of all the important constituent parts. The diagram shows a cross-section of a radio base station (RBS) structure. On the left, a building contains two 'Equipment' units. Above the building is an 'Air-termination conductor (if needed)'. A 'Bonding ring' is connected to the building's structure, with a 'Bonding conductor' leading to the equipment. A 'Feeder SPD (if needed)' is shown on the power line. To the right of the building is a tower with an 'Antenna' and an 'Air-termination rod'. A 'Down conductor (if needed)' runs down the tower. 'Feeder cable bonding' is indicated on the tower. Inside the building, there's a 'Bonding bar' connected to the 'Earth conductor', which leads to the 'Earthing network'. Another 'SPD' is shown on the signal line. Outside the building, a 'Power meter' is connected to an 'SPD'. The diagram is labeled with numbers ① to ④ corresponding to the legend below. The code 'K.119(16)_F02' is in the bottom right corner.](cfef993dcc8fb513de79eb1f93cf26ae_img.jpg)
+
+K.119(16)\_F02
+
+① air-termination and down conductor system      ② earthing system  
+ ③ equipotential bonding network                      ④ SPDs
+
+Figure 2: Typical layout of RBS consisting of all the important constituent parts. The diagram shows a cross-section of a radio base station (RBS) structure. On the left, a building contains two 'Equipment' units. Above the building is an 'Air-termination conductor (if needed)'. A 'Bonding ring' is connected to the building's structure, with a 'Bonding conductor' leading to the equipment. A 'Feeder SPD (if needed)' is shown on the power line. To the right of the building is a tower with an 'Antenna' and an 'Air-termination rod'. A 'Down conductor (if needed)' runs down the tower. 'Feeder cable bonding' is indicated on the tower. Inside the building, there's a 'Bonding bar' connected to the 'Earth conductor', which leads to the 'Earthing network'. Another 'SPD' is shown on the signal line. Outside the building, a 'Power meter' is connected to an 'SPD'. The diagram is labeled with numbers ① to ④ corresponding to the legend below. The code 'K.119(16)\_F02' is in the bottom right corner.
+
+**Figure 2 – Typical layout of RBS consisting of all the important constituent parts**
+
+**Table 1 – The constituent parts and the corresponding components**
+
+| Parts                                     | Components                                                                                                                                                                                    |
+|-------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Air-termination and Down conductor system | Air-termination rod or mesh<br>Down conductors                                                                                                                                                |
+| Earthing system                           | Earthing network<br>Earth conductor                                                                                                                                                           |
+| Equipotential bonding network             | Internal equipotential bonding (e.g., bonding conductor for equipment and devices)<br>External equipotential bonding (e.g., bonding of the tower and feeder cable outside the equipment room) |
+| Surge protective devices (SPDs)           | Electric power SPDs<br>Signal and communication SPDs                                                                                                                                          |
+
+# 8 Air-termination and down conductor system
+
+The air-termination and down conductor system is intended to intercept direct lightning flashes to the antennae or structure and conduct the lightning current from the point of strike to earth.
+
+## 8.1 Requirements for commissioning
+
+The following items shall be verified for commissioning:
+
+- The height, position, size and materials of an air-termination and down conductor system should conform to the design and the corresponding requirements regulated in [ITU-T K.112].
+- Inspect and ensure that the antennae, the structure and other outdoor installations are protected by an air-termination rod (mesh). If needed, after the installation of antennae, a height indicator is used to determine the actual height of the air-termination rod and antennae to estimate the validity of protection for direct strikes. The estimation method shall refer to [ITU-T K.112].
+- The down conductors should be away from sewage tubes and drains when they are installed below the earth surface. The down-conductor section that is above the earth surface shall be protected against mechanical damage.
+- Inspect the reliability of welding and anticorrosion for all welding points or connecting points. For the welding of flat steel conductors, the minimum overlap length should be not less than twice the width of the flat steel conductor. For the welding of round steel conductors, the minimum overlap length should be not less than 10 times the diameter of the round steel conductor. The anticorrosion protection of the connecting points or welding points can be achieved by wrapping these connections with waterproof tape or coating them with anticorrosion paint, silica gel or asphalt. If they are buried in concrete, the follow-up acceptance should apply and the anticorrosion can be ignored. If a down conductor is partially inserted into the earth, anticorrosion and anti-rust measures must be taken for the part 50 cm above the earth surface and the part 50 cm below the earth surface.
+- If the down conductors of the building can be shared for a roof-top RBS, the validity of down conductors should conform in accordance with [ITU-T K.112] through consulting the design documentation of the building.
+
+## 8.2 Requirements for routine inspections
+
+The routine inspections are recommended to be performed before lightning season. The following items shall be verified:
+
+- The connection conditions of the air-termination and down conductor system should be inspected periodically, especially for the points of welding or bonding. If there is evidence of breaks, looseness, mechanical damage or corrosion, corrective measures should be implemented as soon as possible. When the corroded part is greater than one third of the cross-section area of the down conductor, the down conductor shall be replaced.
+- If the down conductors are concealed, the measurement of the bonding resistance shall be performed and the measured value shall be below 0.2 Ω. More detailed information about the measurement method is provided in [IEC 62305-3; Annex E].
+- Any extraneous installation (e.g., TV antenna, metal lines) must not be hanged or connected to the tower, which should be inspected by maintainers frequently.
+
+# 9 Earthing system
+
+The earthing system is intended to disperse the lightning current into the earth and provides a basic equipotential platform for the interconnected structures and installations in an RBS.
+
+### 9.1 Requirements for commissioning
+
+#### 9.1.1 General
+
+When a building and an earthing network is to be constructed for an RBS, the follow-up inspection shall be carried out in order to assure that the earthing network and its connections comply with the project requirements. This is important as because of the configuration of the earthing electrodes these are no more accessible once they are buried in the soil.
+
+When the RBS is installed in a rented building, the validity of building foundation should conform to [ITU-T K.112] through consulting the documentation of the building. Moreover, prior to connecting earth conductors to the building steelwork, the overall electrical continuity of the steelwork shall be verified. The measured resistance between parts of the steelwork used as a part of the earthing system shall be below  $0.2\ \Omega$ .
+
+When earthing resistances need to be measured, the measuring method should refer to Annex A of [ITU-T K.112].
+
+#### 9.1.2 Requirements for follow-up inspections
+
+The actual implementation of an earthing system shall be plotted as one of the acceptance files which can give an important reference for the subsequent maintenance. After the construction phase, it is nearly impossible to determine the layout and construction of the earthing system. Therefore, the layout should be well documented. This can be done utilizing drawings, descriptions and photographs taken during construction.
+
+The following items should be considered during the period of construction:
+
+- The shape, dimensions and materials of the earthing network should conform to the requirements of design and the corresponding requirements regulated in [ITU-T K.112].
+- Inspect the depth of electrodes. The embedded depth and the type of earth electrodes shall be such as to minimize the effects of corrosion, soil drying and freezing and thereby stabilize the conventional earth resistance. The depth of the conductor shall be at least 0.5 m. On bare solid rock or thin soil district, the depth requirement can be relaxed but the electrodes are not permitted to be exposed on the surface of the ground due to rain erosion. On freezing regions, it is recommended that the upper part of a vertical earth electrode within the freezing soil should not be regarded as effective under frost conditions.
+- Inspect the separation from other installations. The embedded electrodes shall have a safe separation with other buried installations, such as buried telecommunication cables, power cables, pipes, etc. Table 2 gives the recommended safe distances from common installations. The distance of the buried electrode from the associated structure shall be approximately 1.0 m.
+- Inspect the reliability of welding and anticorrosion. For the welding of flat steel conductors, the minimum overlap length should be not less than twice the width of the flat steel. For the welding of round steel conductors, the minimum overlap length should be not less than 10 times the diameter of the round steel. The anticorrosion protection of the connecting points or welding points can be achieved by wrapping these connections with waterproof tape or coating them with anticorrosion paint, silica gel or asphalt.
+- Inspect the backfill of ditches. The soil is permitted to backfill only if the electrodes have been accepted by an inspector. The bigger rocks need be screened out from the backfilled soil. The soil shall be tamped down to avoid the sedimentation of the surface. On the district with a large slope or severe soil loss, it is required to cover concrete or grass on the surface of the earthing network to avoid the exposure of electrodes due to rain erosion.
+
+**Table 2 – Recommended safe distances from buried installations for earthing electrodes (cm)**
+
+| Type of installation                                                           | Crossover              | Horizontal |
+|--------------------------------------------------------------------------------|------------------------|------------|
+| Low-voltage cable, fibre cable, telecommunication cable serving the RBS (Note) | 20                     | 20         |
+| High-voltage cable serving the RBS (Note)                                      | 50                     | 100        |
+| Other metallic installations                                                   | Refer to [ITU-T K.111] |            |
+
+NOTE – All the installations serving the RBS shall be connected to the earthing network through hard wires or SPDs at the entrance; if the installations are placed in pipes, the distance can be disregarded.
+
+#### 9.1.3 Requirements for the final inspection
+
+- The resistance of the earthing network shall be measured after the installation. The measured value shall satisfy the designed requirement or the regulated value in national regulations, if any.
+- The earth conductors shall be installed in a manner that they provide the shortest and most direct path to earth. They shall not be installed in gutters or water spouts, even if they are covered by insulating material.
+- The welding and bonding point of earth conductors shall be inspected to ensure the reliability of welding and anticorrosion.
+- The section that is above the earth surface shall be protected against mechanical damage.
+
+### 9.2 Requirements for routine inspections
+
+The earthing system should be inspected and measured periodically. The normal methods are visual inspection and resistance measurement which are described in the following clauses. The inspection is recommended to be performed before lightning season. In normal conditions, the routine inspection should be implemented according to Table 3. The frequency of routine inspections may increase, depending on the following factors:
+
+- the earthing electrodes are made of two or more types of materials;
+- the surrounding soil includes chemical components, such as acid, alkali, salt, etc.;
+- there are highly corrosive installations, such as strengthening a sewage tank, drainage ditch, industrial plant;
+- resistance reducing backfill is used in the earthing system.
+
+#### 9.2.1 Visual inspection
+
+The visual inspection shall include:
+
+- Check whether the surface soil is lost due to rain erosion. When there is the collapse, crack or down punching of soil in the ditches or hollow under the concrete surface, the corresponding preventive and remedial measures should be taken in time.
+- Check whether the earth conductors are firm and complete. When there are cases related to broken, looseness, mechanical damage and corrosion, the remedy measures should be implemented as soon as possible. When the corrosion part is beyond one third of the cross-section area, the conductor should be replaced in time.
+- When the life of electrodes made of galvanized steel is beyond 15 years, it is recommended to dig out some typical points as samples to estimate the corrosion and reliability condition. The selected points are distributed in different directions and the number shall be not less than 4. According to the inspection results, the efficiency of an earthing network can be estimated. When the corrosion part is beyond one third of the cross-section area of the electrode, the affected earthing electrodes shall be replaced.
+
+#### 9.2.2 Measurement and estimation
+
+- The resistance of the earthing network shall be measured annually. The measured value shall satisfy the designed requirement or the regulated value in national regulations, if any. The test should not be performed on rainy days. The information including apparatus, test layout and weather shall be recorded for subsequent estimations.
+- When the measured resistance values show larger changes than anticipated in the design, especially when the resistance increases steadily between inspections, additional investigations should be made to determine the reason for the changes.
+- If the reason for unexpected changes in the earthing resistance cannot be found, it is recommended to dig out some typical points as samples, in order to estimate the corrosion and reliability condition. If there is evidence of breaks, looseness, mechanical damage or corrosion, the remedy measures should be implemented as soon as possible.
+
+NOTE – The judgement of "large changes" shall consider the circumstance and weather factors (e.g., rainy or dry season), which may influence the measured value.
+
+#### 9.2.3 Assessment for outside threat
+
+When there are the constructions of underground pipelines or foundations in the vicinity of electrodes, the owner of the earthing network needs to determine whether these constructions affect the mechanical reliability and anticorrosion properties. If this risk exists, the appropriate precautions shall be taken through negotiation with the parts involved.
+
+When a natural calamity (e.g., flood, earthquake) occurs nearby, the reassessment should be implemented according to clauses 9.2.1 and 9.2.2.
+
+# 10 Equipotential bonding network
+
+The equipotential bonding network is intended to provide an optimized equipotential platform for the different metal parts on the basis of the earthing network.
+
+According to its position in the installation, it can be divided into internal and external equipotential bonding networks. The former includes the bonding bar (ring) and bonding conductor for equipment and devices in the machine room. The latter includes the bonding for the tower and feeder cable outside the equipment room.
+
+### 10.1 Requirements for commissioning
+
+#### 10.1.1 Internal equipotential bonding network
+
+For the first assessment, the following requirements for the internal equipotential bonding network should be considered:
+
+- The configuration, dimensions and materials of internal equipotential bonding network should conform to the requirements of design and related recommendations.
+- The cross-section of bonding conductors shall be determined according to the mechanical strength of materials and the maximum expected fault current, if any. Generally, the minimum size for bonding conductors should be  $16\text{ mm}^2$  for mechanical robustness. Smaller size conductors may be used where the conductors are protected against mechanical damage and a coarser size is normally not needed for current-carrying capacity.
+- Bonding conductors shall be connected to a bonding bar (ring) constructed and installed in such a way that it allows easy access for inspection. For the parts that are not visible for inspection, the measurement of electrical continuity should be performed.
+
+- Both ends of the bonding conductor should be labelled to indicate the connected equipment or bonding bar. For labelling, use stencilled labels or other permanent labelling methods. The laying of bonding conductors shall be firmly bandaged, neat and straight.
+- The size of the wiring terminals shall match with the diameter of bonding conductors. The place where wiring terminals and equipment contact with bonding bars shall be smooth and fastened, without rusting or oxidation. The copper wiring terminals must be mounted and pressed (welded) tightly. When bonding bars are interconnected with bonding conductors via different metal materials, electrochemical corrosion shall be prevented.
+- Bare surfaces should be coated with an appropriate antioxidant compound before crimp connections are made. All unplated connectors, braided straps and bus bars should be brought to a bright finish and then coated with an antioxidant before they are connected. Tinned, solder-plated or silver-plated connectors and other plated connection surfaces do not have to be prepared in this manner, but they should be clean and free of contaminants.
+- All raceway fittings should be tightened to provide a permanent low-impedance path.
+- The same bolt assemblies should not secure multiple connectors.
+- Non-conductive coatings (such as paint, lacquer and enamel) on equipment to be bonded or grounded should be removed from threads and other contact surfaces to assure electrical continuity.
+- The fibre splice tray should be connected to the main earthing terminal (MET) directly. If an optical fibre has metal strength members, the metal strength members must be bonded to the fibre splice tray. The fibre splice tray should be insulated from other metallic parts in the equipment room.
+- The metallic shield of shielded cables shall be connected to equipment metallic frames at both ends. The external conductor of feeder cables shall be connected to the equipment frames.
+- The metallic ducts or trays that carry the cabling shall be connected to the equipment metallic frame (or structure) at both ends, as shown in Figure 3.
+
+![Figure 3: Lateral view of the RBS showing the bonding between the internal tray and equipment frame. The diagram illustrates a cross-section of a building wall with an internal tray and external tray. Two equipment frames are shown inside the building. Bonding conductors connect the internal tray to the equipment frames. A feeder cable enters from the external tray, passing through the building wall. The external tray is connected to an external earthing bar, which is further connected to a ring electrode. The diagram is labeled with 'Building wall', 'Internal tray', 'Feeder', 'External tray', 'Bonding', 'Equipment frame', 'MEB', 'External earthing bar', and 'To the ring electrode'. The code 'K.119(16)_F03' is visible in the bottom right corner.](5cab96b2d23174c25919840ecd50aa48_img.jpg)
+
+Figure 3: Lateral view of the RBS showing the bonding between the internal tray and equipment frame. The diagram illustrates a cross-section of a building wall with an internal tray and external tray. Two equipment frames are shown inside the building. Bonding conductors connect the internal tray to the equipment frames. A feeder cable enters from the external tray, passing through the building wall. The external tray is connected to an external earthing bar, which is further connected to a ring electrode. The diagram is labeled with 'Building wall', 'Internal tray', 'Feeder', 'External tray', 'Bonding', 'Equipment frame', 'MEB', 'External earthing bar', and 'To the ring electrode'. The code 'K.119(16)\_F03' is visible in the bottom right corner.
+
+**Figure 3 – Lateral view of the RBS showing the bonding between the internal tray and equipment frame**
+
+- The metallic ducts and trays shall be electrically continuous for their entire length. The continuity at joints shall be achieved at least in two symmetrically spaced points (e.g., by the use of two bonding clamps on the sides of the tray), as shown in Figure 4.
+
+![Diagram showing the details of electrical continuity in trays and equipment frame. It illustrates a cable tray connected to an equipment frame via joints. The cable tray is shown in two sections, with joints indicated by arrows pointing to the connection points. The equipment frame is shown as a solid base. The diagram is labeled 'K.119(16)_F04'.](ac852a162572ca8a8c8478c49b571af5_img.jpg)
+
+Diagram showing the details of electrical continuity in trays and equipment frame. It illustrates a cable tray connected to an equipment frame via joints. The cable tray is shown in two sections, with joints indicated by arrows pointing to the connection points. The equipment frame is shown as a solid base. The diagram is labeled 'K.119(16)\_F04'.
+
+**Figure 4 – Details of the electrical continuity in trays and equipment frame**
+
+- Two-hole compression-type connectors are preferred for making connections to flat surfaces (such as bus bars, frames, racks or cabinets). The reason for this is to prevent the loosening of connections. Torque and bolt assembly requirements for securing the connector should be as specified by the connector supplier. Nuts, bolts, washers and lock washers should be of high quality bronze or stainless steel alloy or equivalent.
+- Connection devices or fittings that depend solely on solder should be avoided. A soldering lug, a screwless (push-in) connector or a quick-connect or other friction-fit connector shall not be used to terminate a bonding or earthing conductor.
+
+#### 10.1.2 External equipotential bonding network
+
+The following requirements for external equipotential bonding networks should be considered for commissioning:
+
+- The facilities and equipment within a metallic shell installed on the tower shall be bonded to the tower directly. If the conductor terminal cannot be connected to the tower directly, it shall be bonded to a bonding bar first and the bonding bar shall be bonded to the tower.
+- The feeder cable should be bonded at the top of the tower and at the bonding bar near the feeder window. The connection at the point where they leave the tower (bending point) depends on the length of the horizontal section of the feeder tray, according to [ITU-T K.56].
+- The feeder tray shall be continuous and bonded to the tower and to the earthing bar located near the feed-through window of the building.
+- All the connections must be mounted and pressed (welded) tightly and the electrochemical corrosion shall be prevented.
+- If the conductors supplying power to the tower lights (lighting cable) are installed inside a metallic duct or if they are shielded, the metallic duct or the shield shall be bonded to the bonding bar located near the feed-through window. In both cases, the bonding shall be made by means of a conductor as short as possible.
+
+### 10.2 Requirements for routine inspections
+
+Visual inspection shall be carried out to verify that:
+
+- there are no loose connections or any accidental breaks in conductors and joints;
+- no part of the system has been weakened due to corrosion;
+- bonding conductors and cable shields are intact and interconnected;
+- appropriate line routings are maintained.
+
+If there are cases related to breaks, looseness, mechanical damage or corrosion, the remedy measures should be implemented as soon as possible.
+
+When there are additions or alterations, it shall be checked that the scheme of the bonding configuration is modified by these additions or alterations. More detailed information about the requirements for bonding configurations are provided by [ITU-T K.112].
+
+# **11 Requirements for surge protective devices (SPDs)**
+
+The SPDs are intended to provide an equipotential bonding between the live parts of incoming wires and local earth, in order to ensure that the residual overvoltages are less than the inherent resistibility of the equipment.
+
+### **11.1 Requirements for commissioning**
+
+The following items should be verified for commissioning:
+
+- The capacity, installation position and other parameters of the coordinated SPDs should conform to the requirements of design. The requirements of power and signal SPDs should refer to [IEC 61643-11] and [IEC 61643-21] respectively.
+- Inspect the alarm unit or status indicator of SPDs and ensure the validity of the operating state. If the SPDs have no indicators, the protected equipment and circuits shall be inspected for any evidence of equipment malfunction. Special attention should be paid to the effect of SPDs on the transmission performance due to its installation in series with signal or telecommunication circuits.
+- The lead and bonding conductor of SPDs shall be made as direct and straight as possible. For power SPDs, the length of lead conductors shall be less than 0.5 m and the length of bonding conductors shall be less than 1.5 m. For Class I and Class II power SPDs, the minimum cross-sectional area of the lead and bonding conductor is 16 mm<sup>2</sup>.
+- The coaxial SPDs for a feeder cable and other signal SPDs, if they are needed according to [ITU-T K.56], shall be installed near the protected equipment. Their bonding conductors shall be directly connected to the bonding bar of the equipment.
+
+NOTE – In some countries, the bonding conductors of coaxial SPDs are required to be connected to the outdoor bonding bar.
+
+- The lead and bonding conductors shall be connected and fastened via wiring terminals or copper pigtails. When copper pigtails are connected with cable cores, they shall be secured by hydraulic clamps or treated by dip soldering. These conductors shall be laid in order and fixed at racks. The routing shall be short and straight, without loops.
+
+### **11.2 Requirements for routine inspections**
+
+The periodic assessment for SPDs should be implemented at least once per year. For the RBSs with a high risk of lightning strikes, it is recommended that the visual inspection of the coordinated SPDs is integrated into the scope of the routine inspection and maintenance for the equipment.
+
+The following items shall be verified:
+
+- Inspect the alarm unit or status indicator of SPDs. When a failure is displayed, the SPD should be replaced without delay. If an SPD does not have a visual indicator, measurements shall be performed in accordance with the manufacturer's instructions to confirm its operating status, when so required.
+- Inspect the operation state of the external disconnectors of SPDs if they exist. When the disconnector is found operated or broken, it should be switched on or replaced immediately. If the disconnector cannot be switched on, the problem shall be fixed or the SPD / disconnector shall be replaced.
+- Inspect the connection reliability of the lead and bonding conductors of SPDs. If the conductors are found loose or twisted, the problem shall be fixed.
+
+- It is recommended to implement a periodical test on the DC parameters of SPDs for the voltage-limited SPDs using metal oxide varistors (MOV). The inconformity of test results means that the performance of the SPDs has been compromised and that the SPD should be replaced in time. Appendix I gives the test method and the evaluation criteria.
+- When the system is expanded or the equipment is changed, it should be ensured that these alterations would not affect the coordination performance of SPDs.
+- For the two-port SPD or one port-SPD with separate input / output terminals, it should be ensured that the current consumption of the downstream equipment does not exceed the rated current capacity of the SPD.
+
+# 12 Management of the conformance assessment
+
+### 12.1 File management
+
+When the lightning protection and earthing system of an RBS is put into service, the relevant documentation shall be constructed at the same time. The complete documents about the lightning protection and earthing system shall include:
+
+- design files and acceptance reports
+- previous inspection reports
+- previous maintenance records
+- damage records of equipment, if they exist.
+
+### 12.2 Interval of routine inspections
+
+The interval between successive routine inspections needs to consider the protection level of the RBS, the nature of its parts and the environmental factors. Where no specific requirements are identified by the authority having jurisdiction, the values of Table 3 are recommended.
+
+**Table 3 – Recommended interval of routine inspections (years)**
+
+| Component<br>LPL (Note 1) | Air-termination and down conductor system (Note 2) | Earthing system (Note 3) | Equipotential bonding system |                   | SPDs |
+|---------------------------|----------------------------------------------------|--------------------------|------------------------------|-------------------|------|
+|                           |                                                    |                          | Internal                     | External (Note 2) |      |
+| I and II                  | 2                                                  | 2                        | 2                            | 2                 | 1    |
+| III and IV                | 4                                                  | 4                        | 4                            | 4                 | 1    |
+
+NOTE 1 – Normally, the LPL for an RBS is determined during the design period and the relative information can refer to [ITU-T K.56].
+
+NOTE 2 – Considering the difficulty in inspecting high towers, the inspection of external equipotential bonding networks can be integrated into the scope of the routine maintenance for antennae and feeder cables.
+
+NOTE 3 – When there are the special factors described in clause 9.2, the frequency may be increased.
+
+In addition, an extraordinary inspection needs to be performed under the following conditions:
+
+- when a significant alteration or repair is made to the components of lightning protection and earthing system;
+- when an altered equipment or system may affect the whole performance of the lightning protection and earthing system;
+- when the natural calamities (e.g., flood, earthquake) or nearby constructions may affect the whole performance of the lightning protection and earthing system;
+- when damage due to lightning strikes occurs.
+
+## Appendix I
+
+## Test of the DC parameters of MOV SPDs
+
+(This appendix does not form an integral part of this Recommendation.)
+
+This test is only suited for voltage-limiting SPDs using metal oxide varistors (MOV) without filtration or current limiting elements. When the voltage-limited SPDs are installed in the low-voltage power distribution system, there is a leakage current in the order of microamperes flowing through SPDs. If the value of the current is relatively high, it means that the SPD performance has degraded and that the SPD should be replaced in time. The comparison of varistor voltages (at 1 mA) can be a supplementary method used for this evaluation.
+
+### I.1 Test apparatus
+
+The selected test apparatus could be a lightning protection element tester or other similar apparatus with corresponding functions. Figure I.1 gives a typical example of a lightning protection element tester.
+
+NOTE – Some manufacturers of SPDs provided a dedicated test apparatus for this test.
+
+![Figure I.1: A typical example of apparatus for the test of the DC parameters of MOV SPDs. The image shows a grey rectangular test unit with a digital display and several buttons. Two red and black test leads with alligator clips are connected to the front panel and coiled in front of the unit.](1fd4fda95d22e337df091dfa8fa80f90_img.jpg)
+
+Figure I.1: A typical example of apparatus for the test of the DC parameters of MOV SPDs. The image shows a grey rectangular test unit with a digital display and several buttons. Two red and black test leads with alligator clips are connected to the front panel and coiled in front of the unit.
+
+Figure I.1 – A typical example of apparatus for the test of the DC parameters of MOV SPDs
+
+### I.2 Test method
+
+If the SPDs are pluggable, these SPDs can be plugged out for test. If not, disconnect the lead conductors and test each line in order, as showed in Figure I.2.
+
+![Figure I.2: Layout for SPD testing. This is a circuit diagram showing a 'Test apparatus' connected to an SPD. The SPD is represented by a dashed box containing four varistor symbols. The input lines are labeled L1, L2, L3, and N. The L1 line is connected to the test apparatus. The other three lines (L2, L3, and N) are connected to a common ground symbol. The test apparatus is also connected to this common ground. The diagram is labeled K.119(16)_FI.2 at the bottom right.](d79d33da852cb7bca3e87b400a15c3e8_img.jpg)
+
+Figure I.2: Layout for SPD testing. This is a circuit diagram showing a 'Test apparatus' connected to an SPD. The SPD is represented by a dashed box containing four varistor symbols. The input lines are labeled L1, L2, L3, and N. The L1 line is connected to the test apparatus. The other three lines (L2, L3, and N) are connected to a common ground symbol. The test apparatus is also connected to this common ground. The diagram is labeled K.119(16)\_FI.2 at the bottom right.
+
+Figure I.2 – Layout for SPD testing
+
+The measured values shall be recorded, in order to assess its evolution in time (from one inspection to the next one) and the performance of the SPDs. Table I.1 gives an example of the form for this measurement.
+
+**Table I.1 – Example of form for SPD data**
+
+| <b>Date</b> | <b>Measured varistor voltage<br/>(V)</b> | <b>Measured leakage current<br/>(mA)</b> |
+|-------------|------------------------------------------|------------------------------------------|
+|             |                                          |                                          |
+|             |                                          |                                          |
+|             |                                          |                                          |
+
+### I.3 Evaluation criteria
+
+For the evaluation criteria described in this clause, varistor voltage  $U_V$  is the voltage across the varistor when it conducts a current equal to 1 mA. This value is usually provided by the manufacturer.
+
+The SPD is considered as degraded when at least one of the following conditions is met:
+
+- leakage current.
+
+The leakage current value measured at 75%  $U_V$  drifts upward progressively:
+
+- varistor voltages.
+
+The measured varistor voltage ( $U_V$ ) is not within the permitted range specified by the manufacturer or the measured value drifts downward progressively. If specific information is not provided, the deviation of the measured value should be less than 10% comparing with the initial test value and the corresponding rated varistor voltage. Table I.2 gives typical values of the rated varistor voltages and the corresponding maximum continued operation voltage for usual voltage-limiting SPDs.
+
+**Table I.2 – Typical values of varistor voltage and the corresponding maximum continue operation voltage for usual voltage-limiting SPDs (values in Volts)**
+
+| <b>Rated varistor voltage<br/>(<math>U_V</math>)</b> | <b>Maximum AC continue<br/>operation voltage<br/>(<math>U_C</math>)</b> | <b>Maximum DC continue<br/>operation voltage<br/>(<math>U_{DC}</math>)</b> |
+|------------------------------------------------------|-------------------------------------------------------------------------|----------------------------------------------------------------------------|
+| 82                                                   | 50                                                                      | 65                                                                         |
+| 100                                                  | 60                                                                      | 85                                                                         |
+| 120                                                  | 75                                                                      | 100                                                                        |
+| 150                                                  | 95                                                                      | 125                                                                        |
+| 200                                                  | 130                                                                     | 170                                                                        |
+| 220                                                  | 140                                                                     | 180                                                                        |
+| 240                                                  | 150                                                                     | 200                                                                        |
+| 270                                                  | 175                                                                     | 225                                                                        |
+| 360                                                  | 230                                                                     | 300                                                                        |
+| 390                                                  | 250                                                                     | 320                                                                        |
+| 430                                                  | 275                                                                     | 350                                                                        |
+| 470                                                  | 300                                                                     | 385                                                                        |
+| 500                                                  | 320                                                                     | 410                                                                        |
+
+**Table I.2 – Typical values of varistor voltage and the corresponding maximum continue operation voltage for usual voltage-limiting SPDs (values in Volts)**
+
+| <b>Rated varistor voltage<br/>(<math>U_V</math>)</b> | <b>Maximum AC continue<br/>operation voltage<br/>(<math>U_C</math>)</b> | <b>Maximum DC continue<br/>operation voltage<br/>(<math>U_{DC}</math>)</b> |
+|------------------------------------------------------|-------------------------------------------------------------------------|----------------------------------------------------------------------------|
+| 620                                                  | 385                                                                     | 505                                                                        |
+| 680                                                  | 420                                                                     | 560                                                                        |
+| 750                                                  | 460                                                                     | 615                                                                        |
+| 780                                                  | 485                                                                     | 640                                                                        |
+| 820                                                  | 510                                                                     | 670                                                                        |
+| 910                                                  | 550                                                                     | 745                                                                        |
+
+## Bibliography
+
+- [b-ITU-Handbook] ITU-T Handbook (2003), *Handbook on earthing and bonding*.
+- [b-IEC 61643-11] IEC 61643-11:2008, *Low-voltage surge protective devices. Part 11: Surge protective devices connected to low-voltage power distribution systems – Performance requirements and testing methods*.
+
+
+
+
+
+## **SERIES OF ITU-T RECOMMENDATIONS**
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| Series E        | Overall network operation, telephone service, service operation and human factors                                                                         |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| <b>Series K</b> | <b>Protection against interference</b>                                                                                                                    |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

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+
+
+# Recommendation **ITU-T K.12 (08/2024)**
+
+SERIES K: Protection against interference
+
+---
+
+# **Characteristics of gas discharge tubes for the protection of telecommunication installations**
+
+![ITU logo](390120de4fe440c42fea8154fcaad334_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with white lines representing latitude and longitude, and the letters 'ITU' in a bold, blue, sans-serif font superimposed on the globe.
+
+ITU logo
+
+
+
+# Recommendation ITU-T K.12
+
+# Characteristics of gas discharge tubes for the protection of telecommunication installations
+
+# Summary
+
+Recommendation ITU-T K.12 defines the basic characteristics to be met by gas discharge tubes for the protection of exchange and outdoor equipment, subscriber or customer equipment and telecommunication lines from surges. It is intended to be used for the harmonization of existing or future specifications issued by gas discharge tube manufacturers, telecommunication equipment manufacturers, administrations or network operators.
+
+## History \*
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID          |
+|---------|----------------|------------|-------------|--------------------|
+| 1.0     | ITU-T K.12     | 1976-10-08 |             | 11.1002/1000/10056 |
+| 2.0     | ITU-T K.12     | 1980-11-21 |             | 11.1002/1000/7842  |
+| 3.0     | ITU-T K.12     | 1981-07-21 | 5           | 11.1002/1000/10750 |
+| 4.0     | ITU-T K.12     | 1984-10-19 |             | 11.1002/1000/6956  |
+| 5.0     | ITU-T K.12     | 1988-11-25 |             | 11.1002/1000/1376  |
+| 6.0     | ITU-T K.12     | 1995-05-31 | 5           | 11.1002/1000/1377  |
+| 7.0     | ITU-T K.12     | 2000-02-25 | 5           | 11.1002/1000/4903  |
+| 8.0     | ITU-T K.12     | 2006-02-13 | 5           | 11.1002/1000/8739  |
+| 9.0     | ITU-T K.12     | 2010-05-29 | 5           | 11.1002/1000/10838 |
+| 10.0    | ITU-T K.12     | 2024-08-13 | 5           | 11.1002/1000/16002 |
+
+## Keywords
+
+Electrical characteristics and test methods, gas discharge tube (GDT).
+
+---
+
+\* To access the Recommendation, type the URL <https://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, and information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2024
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+###### Page
+
+|      |                                                                      |    |
+|------|----------------------------------------------------------------------|----|
+| 1    | Scope.....                                                           | 1  |
+| 2    | References.....                                                      | 1  |
+| 3    | Definitions .....                                                    | 2  |
+| 3.1  | Terms defined elsewhere .....                                        | 2  |
+| 3.2  | Terms defined in this Recommendation.....                            | 2  |
+| 4    | Abbreviations and acronyms .....                                     | 3  |
+| 5    | Conventions .....                                                    | 3  |
+| 6    | Storage conditions .....                                             | 3  |
+| 7    | Electrical requirements .....                                        | 4  |
+| 7.1  | Sparkover voltages (see clause 8.1).....                             | 4  |
+| 7.2  | Insulation resistance (see clause 8.2).....                          | 6  |
+| 7.3  | Capacitance.....                                                     | 6  |
+| 7.4  | Transverse voltage.....                                              | 6  |
+| 7.5  | d.c. holdover voltages (see clause 8.5 and Figures 4 and 5) .....    | 6  |
+| 7.6  | Life tests (see clause 8.6).....                                     | 7  |
+| 7.7  | Short-circuit behaviour .....                                        | 8  |
+| 8    | Test methods .....                                                   | 8  |
+| 8.1  | Sparkover voltage .....                                              | 8  |
+| 8.2  | Insulation resistance .....                                          | 9  |
+| 8.3  | Capacitance.....                                                     | 10 |
+| 8.4  | Impulse transverse voltage for 3-electrode gas discharge tubes ..... | 10 |
+| 8.5  | Holdover test .....                                                  | 10 |
+| 8.6  | Life tests .....                                                     | 12 |
+| 8.7  | Short-circuit test .....                                             | 13 |
+| 9    | Environment tests .....                                              | 14 |
+| 9.1  | Radiation.....                                                       | 14 |
+| 9.2  | Robustness of terminations.....                                      | 14 |
+| 9.3  | Solderability .....                                                  | 14 |
+| 9.4  | Resistance to soldering heat .....                                   | 14 |
+| 9.5  | Vibration.....                                                       | 14 |
+| 9.6  | Damp heat cyclic .....                                               | 14 |
+| 9.7  | Sealing .....                                                        | 14 |
+| 9.8  | Low temperature.....                                                 | 14 |
+| 10   | Informative characteristics.....                                     | 15 |
+| 11   | Identification.....                                                  | 15 |
+| 11.1 | Marking .....                                                        | 15 |
+| 11.2 | Documentation .....                                                  | 15 |
+
+|                                                             | Page |
+|-------------------------------------------------------------|------|
+| 12    Ordering information .....                            | 15   |
+| Annex A – Test circuit for GDT used in ISDN circuits.....   | 17   |
+| Annex B – Sparkover test waveform .....                     | 18   |
+| Annex C – Determining the special test protector (STP)..... | 19   |
+
+# Recommendation ITU-T K.12
+
+# Characteristics of gas discharge tubes for the protection of telecommunication installations
+
+# 1 Scope
+
+This Recommendation:
+
+- a) gives the characteristics of gas discharge tubes used in accordance with [b-ITU-T K.11] and [b-ITU-T K.46] for the protection of exchange and outdoor equipment, subscriber or customer equipment and telecommunication lines against overvoltages;
+- b) deals with gas discharge tubes which have two or three electrodes;
+- c) does not deal with mountings and their effect on tube characteristics (see [ITU-T K.65]); characteristics apply to gas discharge tubes as a component, mounted only in the ways described for the tests;
+- d) does not deal with mechanical dimensions;
+- e) does not deal with quality assurance requirements; and
+- f) does not deal with gas discharge tubes which are connected to electrical power systems.
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [ITU-T K.65] Recommendation ITU-T K.65 (2011), *Overvoltage and overcurrent requirements for termination modules with contacts for test ports or surge protective devices*.
+- [IEC 60060] IEC 60060-1:2010 and IEC 60060-2:2010, *High-voltage test techniques – Part 1: General definitions and test requirements and Part 2: Measuring systems*.
+- [IEC 60068-2-1] IEC 60068-2-1:2007, *Environmental testing – Part 2-1: Tests – Test A: Cold*.
+- [IEC 60068-2-6] IEC 60068-2-6:2007, *Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)*.
+- [IEC 60068-2-17] IEC 60068-2-17:2023, *Environmental testing – Part 2-17: Tests – Test Q: Sealing*.
+- [IEC 60068-2-20] IEC 60068-2-20:2021, *Environmental testing – Part 2-20: Tests – Test Ta and Tb: Test methods for solderability and resistance to soldering heat of devices with leads*.
+- [IEC 60068-2-21] IEC 60068-2-21:2021, *Environmental testing – Part 2-21: Tests – Test U: Robustness of terminations and integral mounting devices*.
+- [IEC 60068-2-30] IEC 60068-2-30:2005, *Environmental testing – Part 2-30: Tests – Test Db: Damp heat, cyclic (12 h + 12 h cycle)*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+None.
+
+## 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following terms:
+
+**3.2.1 arc mode:** The lowest impedance or on-state of a gas discharge tube during normal operation (Figure 6).
+
+**3.2.2 arc voltage:** The voltage measured across the tube while in the lowest impedance state or arc mode (Figure 6).
+
+**3.2.3 breakdown:** See "sparkover".
+
+**3.2.4 current turn-off time:** The time required for the gas discharge tube to return itself to a non-conducting state following a period of conduction.
+
+**3.2.5 d.c. holdover voltage:** The maximum d.c. voltage across the terminals of a gas discharge tube under which it may be expected to clear and to return to the high impedance state after the passage of a surge, under specified circuit conditions.
+
+**3.2.6 destruction characteristic:** The relationship between the value of the discharge current and the time of flow until the gas discharge tube is mechanically destroyed (break, electrode short-circuit). For periods of time between 1 µs and some ms, it is based on impulse discharge currents, and for periods of time of 0.1 s and greater, it is based on alternating discharge currents.
+
+**3.2.7 discharge current:** The current that passes through a gas discharge tube when sparkover occurs.
+
+- **discharge current, alternating:** The r.m.s. value of an approximately sinusoidal alternating current passing through the gas discharge tube.
+- **discharge current, impulse:** The peak value of the impulse current passing through the gas discharge tube.
+
+**3.2.8 discharge voltage:** The voltage that appears across the terminals of a gas discharge tube during the passage of discharge current. Note that residual voltage is also equivalent to discharge voltage.
+
+**3.2.9 gas discharge tube (GDT):** A gap, or several gaps, in an enclosed discharge medium, other than air at atmospheric pressure, designed to protect apparatus or personnel, or both, from high transient voltages; see clause 10 for the electrical characteristics of GDT also referred to as "gas tube surge arrester".
+
+**3.2.10 glow current:** The current which flows after sparkover when circuit impedance limits the discharge current to a value less than the glow-to-arc transition current.
+
+**3.2.11 glow mode:** This is a semi on-state in the area of the V/I curve where only a limited glow-current flows and the device has not yet turned on or reached the lowest impedance arc-mode (Figure 6).
+
+**3.2.12 glow voltage:** The peak value of the voltage drop across the GDT when a glow current is flowing. It is sometimes called the glow-mode voltage (Figure 6).
+
+- 3.2.13 glow-to-arc (transition) current:** The current required for the gas discharge tube to pass from the glow-mode into the arc mode.
+- 3.2.14 impulse waveshape:** An impulse waveform designated as  $x/y$  has a rise time of  $x$   $\mu\text{s}$  and a decay time to half value of  $y$   $\mu\text{s}$  as standardized in [IEC 60060].
+- 3.2.15 nominal alternating discharge current:** For currents with a frequency of 15 Hz to 62 Hz, the alternating discharge current which the gas discharge tube is designed to carry for a defined time.
+- 3.2.16 nominal d.c. sparkover voltage:** The voltage specified by the manufacturer to designate the gas discharge tube (type designation) and to indicate its application with respect to the service conditions of the installation to be protected. Tolerance limits of the d.c. sparkover voltage are also referred to the nominal d.c. sparkover voltage.
+- 3.2.17 nominal impulse discharge current:** The peak value of the impulse current with a defined waveshape with respect to time for which the gas discharge tube is rated.
+- 3.2.18 residual voltage:** See "discharge voltage".
+- 3.2.19 sparkover:** An electrical breakdown of the discharge gap of a gas discharge tube. Also referred to as "breakdown".
+- 3.2.20 sparkover voltage:** The voltage which causes sparkover when applied across the terminals of a gas discharge tube (Figure 6).
+- **sparkover voltage, d.c.:** The voltage at which the gas discharge tube sparks over when a slowly rising d.c. voltage up to 2 kV/s is applied.
+  - **sparkover voltage, impulse:** The highest voltage which appears across the terminals of a gas discharge tube in the period between the application of an impulse of a given waveshape and the time when current begins to flow.
+- 3.2.21 transverse voltage:** For a gas discharge tube with several gaps, the difference of the discharge voltages of the gaps assigned to the two conductors of a telecommunication circuit during the passage of discharge current.
+
+# 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|      |                                     |
+|------|-------------------------------------|
+| GDT  | Gas Discharge Tube                  |
+| ISDN | Integrated Services Digital Network |
+| xDSL | Digital Subscriber Line             |
+
+# 5 Conventions
+
+None.
+
+# 6 Storage conditions
+
+Gas discharge tubes shall be capable of withstanding the following conditions without damage:
+
+- Temperature:  $-40$  to  $+70^{\circ}\text{C}$ ;
+- Relative humidity: up to 95%.
+
+See also clauses 9.6 and 9.8 for environmental conditions.
+
+# 7 Electrical requirements
+
+Gas discharge tubes should have the following characteristics when tested in accordance with clause 8. Clauses 7.1 to 7.5 apply to virgin gas discharge tubes and also, where quoted in clause 7.6, to tubes subjected to life tests.
+
+NOTE – Using GDTs in circuits protecting certain systems can cause secondary effects like oscillations. This behaviour is dependent on certain circuit combinations like impedance and inductance in connection with certain GDT parameters like glow-to-arc transition current, etc.
+
+This phenomenon has not been studied adequately at this time and will be added to future work of ITU-T.
+
+## 7.1 Sparkover voltages (see clause 8.1)
+
+Sparkover voltages between the electrodes of a 2-electrode tube or between either line electrode and the earth electrode of a 3-electrode tube shall be within the limits in either Table 1a or Table 1b.
+
+NOTE 1 – For the definition of sparkover waveforms, see Annex B.
+
+Two types of GDT may be differentiated by their voltage nominal values. By employing special design techniques on either type, the disadvantages of the different technologies, to a certain extent, could be compensated for.
+
+The values for these types are given in tables 1a and 1b. Type 1 (Table 1a) represents the common type with a technology well suited for high current protection accomplished by a low glow voltage and arc voltage. Type 2 (Table 1b) represents the low impulse sparkover voltage type which has a faster response time, thus achieving lower impulse sparkover voltages with higher glow voltage and arc voltage, but offer lower current carrying capabilities.
+
+For 3-electrode tubes, the sparkover voltage between the line electrodes shall not be less than the minimum d.c. sparkover voltage in either Table 1a or Table 1b. It is recommended to achieve at least 1.2 times the minimum d.c. sparkover voltage given in either Table 1a or Table 1b.
+
+NOTE 2 – For 3-electrode GDTs, the maximum d.c. sparkover voltage a-b (line-line) may be restricted; a reasonable value is about 1.8-2.0 times the voltage a/b-c.
+
+### 7.1.1 Sparkover voltage values for type 1 GDT (common type)
+
+This type represents a technology well suited for high current protection accomplished by a low glow-voltage and arc-voltage (Table 1a).
+
+**Table 1a – Sparkover voltage values for common types of GDT**
+
+| Sparkover voltage  |             |          |                      |          |                 |                          |                 |                          |
+|--------------------|-------------|----------|----------------------|----------|-----------------|--------------------------|-----------------|--------------------------|
+| d.c.               |             |          |                      |          | Impulse         |                          |                 |                          |
+|                    | Initial (1) |          | After life tests (2) |          | at 100 V/μs     |                          | at 1 000 V/μs   |                          |
+|                    | Min. (V)    | Max. (V) | Min. (V)             | Max. (V) | Initial (3) (V) | After life tests (4) (V) | Initial (5) (V) | After life tests (6) (V) |
+| <b>Nominal (V)</b> |             |          |                      |          |                 |                          |                 |                          |
+| 90                 | 72          | 108      | 65                   | 120      | 450             | 550                      | 500             | 600                      |
+| 150                | 120         | 180      | 110                  | 195      | 500             | 600                      | 600             | 700                      |
+| 200                | 160         | 240      | 150                  | 250      | 600             | 700                      | 700             | 800                      |
+| 230                | 184         | 280      | 170                  | 300      | 600             | 700                      | 700             | 800                      |
+| 250                | 200         | 300      | 180                  | 325      | 600             | 700                      | 700             | 800                      |
+
+**Table 1a – Sparkover voltage values for common types of GDT**
+
+| Sparkover voltage |     |     |     |     |         |       |       |       |
+|-------------------|-----|-----|-----|-----|---------|-------|-------|-------|
+| d.c.              |     |     |     |     | Impulse |       |       |       |
+| 350               | 280 | 420 | 260 | 455 | 900     | 1 000 | 1 000 | 1 100 |
+| 420               | 360 | 520 | 360 | 550 | 1 000   | 1 100 | 1 100 | 1 200 |
+| 500               | 400 | 600 | 400 | 650 | 1 100   | 1 200 | 1 200 | 1 300 |
+| 600               | 480 | 720 | 450 | 780 | 1 300   | 1 400 | 1 400 | 1 500 |
+
+### **7.1.2 Sparkover voltage values for type 2 GDT (low impulse sparkover type)**
+
+This type (Table 1b) has a faster response time, thus achieving lower impulse sparkover voltages with higher glow-voltages and arc-voltages. Due to the design of this alternative type, the current capability according to Table 5 is, in general, much lower than for the comparable size of a common type GDT.
+
+Higher glow-voltage and arc-voltage in the gas discharge tube means higher power dissipation and thus reduction in class capability.
+
+It should be noted that there might be some restrictions on the availability of certain higher classes of Table 5 for some of the enhanced impulse voltage limits listed in Table 1b.
+
+**Table 1b – Sparkover voltage values for type 2 GDT (low impulse sparkover type)**
+
+| Sparkover voltage  |                 |                 |                      |                 |                 |                          |                 |                          |
+|--------------------|-----------------|-----------------|----------------------|-----------------|-----------------|--------------------------|-----------------|--------------------------|
+| d.c.               |                 |                 |                      |                 | Impulse         |                          |                 |                          |
+|                    | Initial (1)     |                 | After life tests (2) |                 | at 100 V/μs     |                          | at 1 000 V/μs   |                          |
+|                    | Min. (V)        | Max. (V)        | Min. (V)             | Max. (V)        | Initial (3) (V) | After life tests (4) (V) | Initial (5) (V) | After life tests (6) (V) |
+| <b>Nominal (V)</b> | <b>Min. (V)</b> | <b>Max. (V)</b> | <b>Min. (V)</b>      | <b>Max. (V)</b> | <b>(V)</b>      | <b>(V)</b>               | <b>(V)</b>      | <b>(V)</b>               |
+| 200                | 160             | 240             | 150                  | 250             | 350             | 450                      | 450             | 550                      |
+| 230                | 184             | 280             | 170                  | 300             | 400             | 500                      | 450             | 550                      |
+| 350                | 265             | 455             | 265                  | 600             | 700             | 800                      | 800             | 900                      |
+| 420                | 360             | 520             | 360                  | 650             | 750             | 900                      | 850             | 1 000                    |
+| 500                | 400             | 600             | 400                  | 700             | 800             | 950                      | 900             | 1 050                    |
+| 600                | 480             | 720             | 420                  | 800             | 900             | 1 100                    | 1 000           | 1 200                    |
+
+### **7.1.3 Sparkover voltage assessment**
+
+The sparkover voltages are characterized by a normal distribution assuming that a sufficient number of samples are tested.
+
+The sparkover voltages should be assessed with the criteria specified in Table 2, using the test methods specified in clause 8.1.
+
+**Table 2 – Sparkover voltage assessment method**
+
+|                           | Measured values initial                                       |                                                              |
+|---------------------------|---------------------------------------------------------------|--------------------------------------------------------------|
+|                           | Probability of the measured values to be within the tolerance | Assessment expression                                        |
+| d.c. sparkover voltage    | 99.7%                                                         | $U + 3S \leq \text{Maximum}$<br>$U - 3S \geq \text{Minimum}$ |
+| Impulse sparkover voltage | 99.7%                                                         | $U + 3S \leq \text{Maximum}$<br>$U - 3S \geq \text{Minimum}$ |
+
+NOTE – U is the statistical average value of sparkover voltages. S is the standard deviation.
+
+## **7.2 Insulation resistance** (see clause 8.2)
+
+Not less than 1 G $\Omega$  initially.
+
+## **7.3 Capacitance**
+
+Typically, GDTs have a capacitance value of few pF, but not greater than 20 pF.
+
+## **7.4 Transverse voltage**
+
+The transverse voltage for a 3-electrode gas discharge tube is the difference in the discharge voltages between terminals a and b of the gaps assigned to the two conductors of the circuit during the passage of discharge current. For a 3-electrode gas discharge tube, the difference in time between the sparkover of the first and second gap shall not exceed 200 ns.
+
+## **7.5 d.c. holdover voltages** (see clause 8.5 and Figures 4 and 5)
+
+All types of tube shall have a current turn-off time less than 150 ms when subjected to one or more of the following tests according to the projected use.
+
+### **7.5.1 d.c. holdover test values for 2-electrode tubes**
+
+2-electrode tubes are tested in a circuit equivalent to that of Figure 4, where the test circuit components have the values given in Table 3. Gas discharge tubes with a nominal d.c. voltage of 230 V or higher shall be tested according to the test circuit shown in Annex A.
+
+**Table 3 – Holdover test values for 2-electrode tubes**
+
+| Component | Test 1       | Test 2       | Test 3         |
+|-----------|--------------|--------------|----------------|
+| PS1       | 52 V         | 80 V         | 135 V          |
+| R3        | 200 $\Omega$ | 330 $\Omega$ | 1 300 $\Omega$ |
+| R2        | (Note)       | 150 $\Omega$ | 150 $\Omega$   |
+| C1        | (Note)       | 100 nF       | 100 nF         |
+
+NOTE – Components omitted in this test.
+
+### **7.5.2 d.c. holdover test values for 3-electrode tubes**
+
+3-electrode tubes are tested in a circuit equivalent to that of Figure 5, where components have the values given in Table 4.
+
+**Table 4 – Holdover test values for 3-electrode tubes**
+
+| Component   | Test 1   | Test 2 |                | Test 3  |                |
+|-------------|----------|--------|----------------|---------|----------------|
+| PS1         | 52 V     | 80 V   |                | 135 V   |                |
+| PS2         | 0 V      | 0 V    |                | 52 V    |                |
+| R3          | 200 Ω    | 330 Ω  |                | 1 300 Ω |                |
+| R2          | (Note 1) | 150 Ω  | 272 Ω (Note 2) | 150 Ω   | 272 Ω (Note 2) |
+| C1          | (Note 1) | 100 nF | 43 nF (Note 2) | 100 nF  | 43 nF (Note 2) |
+| R4 (Note 3) | 136 Ω    | 136 Ω  |                | 136 Ω   |                |
+| C2 (Note 3) | 83 nF    | 83 nF  |                | 83 nF   |                |
+
+NOTE 1 – Components omitted in this test.  
+NOTE 2 – Optional alternative.  
+NOTE 3 – Optional.
+
+## 7.6 Life tests (see clause 8.6)
+
+The currents specified in clause 7.6.1 for the appropriate nominal current rating of the tube shall be applied. After each current application, the gas discharge tube shall be capable of meeting the requirements of clause 7.6.2. On completion of the number of current applications specified, the tube shall be capable of meeting the requirements of clause 7.6.3.
+
+### 7.6.1 Test currents
+
+Gas discharge tubes shall be subjected to the currents of columns 1 to 5 of Table 5. For each life test new gas discharge tubes shall be used.
+
+**Table 5 – Life test current values**
+
+| Test number  | Nominal alternating discharge current | Nominal impulse discharge current |                         |             |             |
+|--------------|---------------------------------------|-----------------------------------|-------------------------|-------------|-------------|
+|              | 1                                     | 2                                 | 3                       | 4           | 5           |
+| Waveform     | a.c. 50-60 Hz                         | 8/20 μs                           | 10/350 μs <sup>a)</sup> | 10/1 000 μs | 10/1 000 μs |
+| Applications | 10                                    | 10                                | 1                       | 300         | 1 500       |
+| Dimension    | A rms                                 | kA peak                           | kA peak                 | A peak      | A peak      |
+| Class        |                                       |                                   |                         |             |             |
+| 1            | 2.5                                   | 2.5                               | 0.5                     | 50          | 10          |
+| 2            | 5                                     | 5                                 | 1                       | 100         | 10          |
+| 3            | 10                                    | 10                                | 2.5                     | 100         | 10          |
+| 4            | 20                                    | 10                                | 4                       | 100         | 10          |
+| 5            | 20                                    | 20                                | 4                       | 200         | 10          |
+
+<sup>a)</sup> Different high-energy test waveforms exist in some countries and regions, for example, see [IEC 61643-21].
+
+### 7.6.2 Requirements during life test
+
+Insulation resistance: not less than 100 MΩ.
+
+d.c. and impulse sparkover voltage: not more than the relevant value in columns 2, 4 and 6 of either Table 1a or Table 1b.
+
+### 7.6.3 Requirements after completion of life test
+
+Insulation resistance: not less than 100 M $\Omega$ .
+
+d.c. and impulse sparkover voltage: not more than the relevant value in columns 2, 4 and 6 of either Table 1a or Table 1b.
+
+NOTE – After the passage of an alternating or impulse current of a value much higher than that shown in Table 5, the electrical characteristics of the GDT may be severely altered or the GDT may be even destroyed.
+
+Two extreme situations may occur:
+
+- 1) The gas discharge tube vents and acts like an insulator and presents a higher dielectric strength than it had initially.
+- 2) The gas discharge tube turns to a low resistance or even becomes a short circuit which does not allow normal operation of the telecommunication service. (This situation may be preferable from the point of view of fault detection, fault signalling, protection and maintenance.)
+
+Test methods and the relations between the value and duration of the destructive current are not detailed in this Recommendation, nor is the state of the element after destruction. Operators should cover their requirements in these respects in their own documentation.
+
+Holdover voltage: as in clause 7.5.
+
+## 7.7 Short-circuit behaviour
+
+A short-circuit mechanism is necessary for gas discharge tubes intended for use in telecommunication applications where an a.c. current can occur, flowing for an unpredictable time.
+
+Depending on the a.c. current flow, the short-circuit mechanism shall operate in sufficient time to prevent the gas discharge tube from being overheated.
+
+# 8 Test methods
+
+Gas discharge tubes shall be tested according to the methods described in clauses 8.1 to 8.7 and, in given cases, according to Figure A.1 (Test circuit for GDT for integrated services digital network (ISDN) or other telecommunication equipment using higher voltages or bitrates (xDSL)).
+
+## 8.1 Sparkover voltage
+
+For testing the initial values of a gas discharge tube, the gas discharge tube shall be placed in darkness for at least 24 hours immediately prior to testing and shall be tested in darkness.
+
+### 8.1.1 d.c. sparkover voltage
+
+The gas discharge tube shall be tested with a voltage which increases so slowly that the sparkover voltage is independent of the rate of rise of the applied voltage. Typically, a rate of rise of 100 V/s is used, but higher rates may be used if it can be shown that the sparkover voltage is thereby not significantly changed. The tolerances on the waveshape of the rising test voltage are indicated in Annex B. The voltage is measured across the open-circuited terminals of the generator.  $U_{max}$  of Figure B.1 is any voltage greater than the maximum permitted d.c. sparkover voltage of the gas discharge tube.
+
+The test shall employ a suitable circuit such as that shown in Figure 1. A minimum of 3 seconds shall elapse between repetitions of the test, with either polarity, on the same gas discharge tube.
+
+![Circuit diagram for d.c. sparkover test. A variable voltage power supply (PS) is connected in series with a 51 kΩ resistor. This series combination is connected in parallel with a voltmeter (V) and a gas discharge tube (E). The voltmeter measures the voltage across the gas discharge tube. The reference label K.12(10)_F01 is shown below the circuit.](33ed1f9b27c7c21c797aa928b0f06851_img.jpg)
+
+Circuit diagram for d.c. sparkover test. A variable voltage power supply (PS) is connected in series with a 51 kΩ resistor. This series combination is connected in parallel with a voltmeter (V) and a gas discharge tube (E). The voltmeter measures the voltage across the gas discharge tube. The reference label K.12(10)\_F01 is shown below the circuit.
+
+PS Variable voltage power supply
+
+NOTE – Means shall be included to ensure that the gas discharge tube sparks over once only.
+
+**Figure 1 – Circuit for d.c. sparkover test**
+
+For 3-electrode tubes, the sparkover voltage between the line electrodes shall not be less than the minimum d.c. sparkover voltage in either Table 1a or Table 1b.
+
+Each pair of terminals of a 3-electrode gas discharge tube shall be tested separately with the other terminal unterminated.
+
+### 8.1.2 Impulse sparkover voltage
+
+The voltage waveform measured across the open circuit test terminals shall have a nominal rate of rise selected from Table 1a or Table 1b and shall be within the enclosed limits indicated in Figure B.1. Figure 2 shows a suggested arrangement for testing with a voltage impulse which has a nominal rate of rise of 1.0 kV/μs.
+
+A minimum of 3 seconds shall elapse between repetitions of the test, with either polarity, on the same gas discharge tube.
+
+Each pair of terminals of a 3-electrode gas discharge tube shall be tested separately with the other terminal unterminated.
+
+![Circuit diagram for impulse sparkover test. A 5 kV impulse source (represented by a battery symbol and 0.1 μF capacitor) is connected in series with a 1 kΩ resistor. This is followed by a parallel combination of a 10 MΩ resistor and a 5 nF capacitor. The output of this network is connected in series with a 50 Ω resistor, which is then connected to a gas discharge tube (E) and an oscilloscope. The reference label K.12(10)_F02 is shown below the circuit.](70de8885bd7de15723aaad5eb5c5febf_img.jpg)
+
+Circuit diagram for impulse sparkover test. A 5 kV impulse source (represented by a battery symbol and 0.1 μF capacitor) is connected in series with a 1 kΩ resistor. This is followed by a parallel combination of a 10 MΩ resistor and a 5 nF capacitor. The output of this network is connected in series with a 50 Ω resistor, which is then connected to a gas discharge tube (E) and an oscilloscope. The reference label K.12(10)\_F02 is shown below the circuit.
+
+**Figure 2 – Testing arrangement producing a voltage impulse which has a wavefront with a virtual steepness of 1 kV/μs (see clauses 7.1 and 8.3)**
+
+## 8.2 Insulation resistance
+
+The insulation resistance shall be measured from each terminal to every other terminal of the gas discharge tube (see clause 7.2). The measurement shall be made at an applied potential of at least 100 V or not more than 90% of the minimum permitted d.c. sparkover voltage. The measuring source shall be limited to a short-circuit current of less than 10 mA. Terminals of 3-electrode gas discharge tubes not involved in the measurement shall be left unterminated.
+
+## 8.3 Capacitance
+
+The capacitance shall be measured between each terminal and every other terminal of the gas discharge tube (see clause 7.3). In measurements involving 3-electrode gas discharge tubes, the terminal not being tested shall be connected to a ground plane in the measuring instrument.
+
+## 8.4 Impulse transverse voltage for 3-electrode gas discharge tubes
+
+The duration of the transverse voltage shall be measured while an impulse voltage that has a virtual steepness of an impulse wavefront of 1 kV/μs is applied simultaneously to both discharge gaps. Measurement may be made with an arrangement as indicated in Figure 3 (also see clause 7.4). The difference in time between the sparkover of the first gap and that of the second is specified in clause 7.4.
+
+![Circuit diagram for impulse transverse voltage test. A surge generator (SG) is connected to two resistors (R) in series. The first resistor is connected to the anode (A) of a gas discharge tube (GDT). The second resistor is connected to the cathode (C) of the GDT. The GDT is connected to an oscilloscope (OSC). The circuit is labeled K.12(24).](16152cf1d84aea10848758f51a91ff6a_img.jpg)
+
+OSC Oscilloscope  
+R Line impedance  
+SG Surge generator (see Figure 2)
+
+Circuit diagram for impulse transverse voltage test. A surge generator (SG) is connected to two resistors (R) in series. The first resistor is connected to the anode (A) of a gas discharge tube (GDT). The second resistor is connected to the cathode (C) of the GDT. The GDT is connected to an oscilloscope (OSC). The circuit is labeled K.12(24).
+
+Figure 3 – Circuit for impulse transverse voltage test (see clause 7.4)
+
+## 8.5 Holdover test
+
+### 8.5.1 2-electrode gas discharge tube
+
+Tests shall be conducted using the circuit of Figure 4 (see also clause 7.5). Values of PS1, R2, R3 and C1 shall be selected for each test condition from Table 3. The current from the surge generator shall have an impulse waveform of 100 A, 10/1000 μs measured through a short circuit replacing the gas discharge tube under test. The polarity of the impulse current through the gas discharge tube shall be the same as the current from PS1. The time for current turn-off shall be measured for each direction of current passage through the gas discharge tube. Three impulses shall be applied at not greater than 1-minute intervals and the current turn-off time measured for each impulse.
+
+![Circuit diagram for holdover test of a 2-electrode gas discharge tube. A surge generator (SG) is connected to an isolation gap (E1). The circuit includes a resistor R1 in series with the gap, followed by a parallel combination of a resistor R2 and a capacitor C1. This is followed by an isolation diode D1 and a resistor R3. A gas discharge tube (GDT) with electrodes A and C is connected in parallel across the output. An oscilloscope (OSC) and a constant voltage d.c. supply (PS1) are also connected across the output. The diagram is labeled K.12(24).](8fbdfc3d17fb1dae7b2d8f5a287fa9fc_img.jpg)
+
+Circuit diagram for holdover test of a 2-electrode gas discharge tube. A surge generator (SG) is connected to an isolation gap (E1). The circuit includes a resistor R1 in series with the gap, followed by a parallel combination of a resistor R2 and a capacitor C1. This is followed by an isolation diode D1 and a resistor R3. A gas discharge tube (GDT) with electrodes A and C is connected in parallel across the output. An oscilloscope (OSC) and a constant voltage d.c. supply (PS1) are also connected across the output. The diagram is labeled K.12(24).
+
+- D1 Isolation diode or other isolation device  
+ E1 Isolation gap or equivalent device  
+ OSC Oscilloscope  
+ PS1 Constant voltage d.c. supply or battery  
+ R1 Impulse current-limiting resistor or waveshaping network  
+ R2, R3 See Table 3  
+ SG Surge generator, 100 A, 10/1 000 μs
+
+**Figure 4 – Circuit for holdover test of 2-electrode gas discharge tube (see clause 7.5.1)**
+
+### 8.5.2 3-electrode gas discharge tube
+
+Tests shall be conducted using the circuit of Figure 5. Values of circuit components shall be selected from Table 4. The simultaneous currents that are applied to the gaps of the gas discharge tube shall have impulse waveforms of 100 A /10/1000 μs per side or chamber, measured through a short circuit replacing the gas discharge tube under test. The polarity of the impulse current through the gas discharge tube shall be the same as the current from PS1 and PS2.
+
+![Circuit diagram for holdover test of a 3-electrode gas discharge tube. A surge generator (SG) is connected to an isolation gap (E1). The circuit features two symmetrical branches. The left branch contains a resistor R1, diodes D1 and D3, a capacitor C2, a power supply PS1, and a resistor R3. The right branch contains a resistor R1, diodes D2 and D4, a capacitor C2, a power supply PS2, and a resistor R3. A central gas discharge tube (GDT) with electrodes A, B, and C is connected. Electrode A is connected to a network of capacitors C1, C2 and resistors R2, R4. Electrode B is connected to a network of capacitors C1, C2 and resistors R2, R4. Electrode C is connected to a network of resistors R3, R4. A dual channel oscilloscope (OSC) is connected across the output. The diagram is labeled K.12(24).](33a8f3f01dfa8bce75d23017855a13c5_img.jpg)
+
+Circuit diagram for holdover test of a 3-electrode gas discharge tube. A surge generator (SG) is connected to an isolation gap (E1). The circuit features two symmetrical branches. The left branch contains a resistor R1, diodes D1 and D3, a capacitor C2, a power supply PS1, and a resistor R3. The right branch contains a resistor R1, diodes D2 and D4, a capacitor C2, a power supply PS2, and a resistor R3. A central gas discharge tube (GDT) with electrodes A, B, and C is connected. Electrode A is connected to a network of capacitors C1, C2 and resistors R2, R4. Electrode B is connected to a network of capacitors C1, C2 and resistors R2, R4. Electrode C is connected to a network of resistors R3, R4. A dual channel oscilloscope (OSC) is connected across the output. The diagram is labeled K.12(24).
+
+- C1, C2 See Table 4  
+ E1 Isolation gap or equivalent device  
+ OSC Dual channel oscilloscope  
+ PS1, PS2 Batteries or d.c. power supplies  
+ R1 Impulse current-limiting resistors or wave-shaping networks  
+ R2, R3, R4 See Table 4
+
+NOTE 1 – The polarity of diodes D1 to D4 must be reversed when the polarity of the d.c. power supplies and surge generators is reversed.
+
+**Figure 5 – Circuit for holdover test of 3-electrode gas discharge tube (see clause 7.5.2)**
+
+For each test condition, measurement of the time to current turn-off shall be made for both polarities of the impulse current. Three impulses in each direction shall be applied at intervals not greater than 1 minute and the time to current turn-off measured for each impulse.
+
+## 8.6 Life tests
+
+New gas discharge tubes shall be used for each of the tests.
+
+A proposed type test procedure is given in Table 6.
+
+**Table 6 – Recommended sample sizes to be used for a.c. and impulse life tests**
+
+| Test         | Sample size | Test performed in accordance with clause 7.6.1, Table 5, column |
+|--------------|-------------|-----------------------------------------------------------------|
+| a.c. life    | 20          | 1                                                               |
+| Impulse life | 20          | 2                                                               |
+| Impulse life | 20          | 3                                                               |
+| Impulse life | 20          | 4                                                               |
+| Impulse life | 20          | 5                                                               |
+
+Alternating respectively impulse currents shall be applied as specified in Table 5 for the relevant class of the tube.
+
+The time between applications should be such as to prevent thermal accumulation in the tube.
+
+DC and impulse sparkover tests shall be performed on gas discharge tubes which are subject to the life conditions specified in clause 7.6.1. In order to achieve a test procedure as close to real practice as possible, the test has to be carried out under daylight conditions. All other test details should comply according to clause 8.1.
+
+It is recommended that a minimum of four sparkover voltage measurements are performed on each sample, two in each polarity.
+
+Measured values after life test under consideration (5% failure rate accepted), compare either Table 1a or Table 1b values after life.
+
+### 8.6.1 a.c. life (see clause 7.6)
+
+The alternating currents shall be applied as specified in Table 5, column 1, for a duration of 1 second.
+
+The r.m.s. a.c. voltage of the current source shall exceed the maximum d.c. sparkover voltage of the gas discharge tube by not less than 50%.
+
+The specified a.c. discharge current and duration shall be measured with the gas discharge tube replaced with a short circuit. For 3-electrode gas discharge tubes, a.c. discharge currents each with the value specified in Table 5, column 1, shall be discharged simultaneously from each electrode to the common electrode.
+
+The gas discharge tube shall be tested after each passage of a.c. discharge current to determine its ability to satisfy the requirements of clause 7.6.2.
+
+On completion of the specified number of current applications, the tube shall be allowed to cool to an ambient temperature and tested for compliance with clause 7.6.3.
+
+### 8.6.2 Impulse discharge current 8/20 µs
+
+Half the specified number of tests shall be carried out with one polarity followed by half with the opposite polarity. Alternatively, half the tubes in a sample may be tested with one polarity and the other half with the opposite polarity.
+
+For 3-electrode gas discharge tubes, independent impulse currents each with the value specified in Table 5, column 2, shall be discharged simultaneously from each electrode to the common electrode.
+
+### 8.6.3 Impulse discharge current 10/350 μs
+
+This test shall be applied only one time.
+
+For 3-electrode gas discharge tubes, independent impulse currents each with the value specified in Table 5, column 3, shall be discharged simultaneously from each electrode to the common electrode.
+
+### 8.6.4 Impulse discharge current 10/1000 μs
+
+To carry out this test, one of the methods listed in Table 7, shall be applied. Methods 1 and 2 must be used together for testing 3-electrode gas discharge tubes by testing 50% of the sample lot with method 1 and the remaining 50% with method 2.
+
+Although these four methods apply the same number of discharges, their end results may not be the same.
+
+**Table 7 – Impulse discharge current test method**
+
+| Method                                                                                                                                                                    | Number of applications<br>10/1 000 μs (50..200 A);<br>(see column 4 of Table 5) | Number of applications<br>10/1 000 μs (10 A);<br>(see column 5 of Table 5) | Polarity |
+|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------|----------------------------------------------------------------------------|----------|
+| 1                                                                                                                                                                         | 300 times                                                                       | 1 500 times                                                                |          |
+| 2                                                                                                                                                                         | 300 times                                                                       | 1 500 times                                                                |          |
+| 3                                                                                                                                                                         | 150 times + and 150 times –                                                     | 750 times + and 750 times –                                                |          |
+| 4                                                                                                                                                                         | 300 times +/–                                                                   | 1 500 times +/–                                                            |          |
+| NOTE – The test results can vary depending on the test methods 1-4. It should be stated which test method was used or tested as agreed upon by the user and manufacturer. |                                                                                 |                                                                            |          |
+
+The voltage of the source shall exceed the maximum impulse sparkover voltage of the gas discharge tube by not less than 50%. The specified impulse discharge current and waveform shall be measured with the gas discharge tube replaced with a short circuit. For 3-electrode gas discharge tubes, independent impulse currents, each with the value specified in Table 5, columns 4 and 5, shall be discharged simultaneously from each electrode to the common electrode.
+
+The gas discharge tube shall be tested after each passage of an impulse discharge current or at less frequent intervals if agreed between the manufacturer and the user to determine its ability to satisfy the requirements of clause 7.6.2.
+
+On completion of the specified number of impulse currents, the tube shall be allowed to cool to an ambient temperature and tested for compliance with clause 7.6.3.
+
+### 8.7 Short-circuit test
+
+New tubes shall be used and an a.c. current capable of activating the thermal overload shall be applied to the gas discharge tube. The short-circuit mechanism shall be operated after it is subjected to a given a.c. current and time. The proposed sample size to be used for short-circuit tests is five for each test condition.
+
+The values and duration should be specified by the manufacturer of the gas discharge tubes.
+
+The behaviour of the short-circuit mechanism is particularly influenced by the environmental conditions and the termination module. Therefore, it is necessary that the test procedure and the requirements be in detail arranged between the manufacturer and the user of gas discharge tubes.
+
+Rec. ITU-T K.12 (08/2024) 13
+
+# **9 Environment tests**
+
+## **9.1 Radiation**
+
+Gas discharge tubes shall not contain radioactive material.
+
+## **9.2 Robustness of terminations**
+
+The user shall specify a suitable test from [IEC 60068-2-21], if applicable.
+
+## **9.3 Solderability**
+
+Soldering terminations shall meet the requirements of [IEC 60068-2-20], test Ta method 1.
+
+## **9.4 Resistance to soldering heat**
+
+Gas discharge tubes with soldering terminations shall be capable of withstanding [IEC 60068-2-20], test Tb method 1b. After recovery, the gas discharge tube shall be visually checked and show no signs of damage, and its d.c. sparkover shall be within the limits for that tube.
+
+## **9.5 Vibration**
+
+A gas discharge tube shall be capable of withstanding [IEC 60068-2-6], Environmental testing, Test Fc: Vibration (sinusoidal) 10-500 Hz, 0.15 mm displacement for 90 minutes without damage. The user may select a more severe test from this reference. At the end of the test, the tube shall show no signs of damage and shall meet the d.c. sparkover and insulation resistance requirements specified in clauses 7.1 and 7.2.
+
+## **9.6 Damp heat cyclic**
+
+A gas discharge tube shall be capable of withstanding [IEC 60068-2-30]. At the end of the test, the tube shall meet the insulation resistance requirement specified in clause 7.2.
+
+## **9.7 Sealing**
+
+A gas discharge tube shall be capable of passing [IEC 60068-2-17] Test Qk, severity 600 hours, for fine leaks. The fine leak rate shall be less than  $10^{-7}$  bar cm<sup>3</sup> s<sup>-1</sup>. Helium shall be used as the test gas.
+
+The tube shall then be capable of passing the coarse leak test Qc method 1.
+
+## **9.8 Low temperature**
+
+A gas discharge tube shall be capable of withstanding [IEC 60068-2-1] Test Aa.  $-40^{\circ}\text{C}$ , duration 2 hours, without damage. At the end of the test, the tube must meet the d.c. and impulse sparkover requirements of clause 7.1.
+
+# 10 Informative characteristics
+
+![Figure 6: Electrical characteristics of GDT. The figure contains three graphs: 6a shows voltage (V) vs. time (t) with a dashed sinusoidal surge and a solid limiting curve; 6b shows current (i) vs. time (t) with a dashed sinusoidal surge and a solid limiting curve; 6c shows voltage (V) vs. current (i) with a solid hysteresis loop. Key voltage levels V_s, V_gl, V_a, and V_e are marked on the y-axis of 6c. Regions G (glow mode) and A (arc mode) are labeled on the curves in 6a and 6b.](f8630b0582d6e5b1d81f877880ef0dda_img.jpg)
+
+$V_s$  Spark-over voltage  
+ $V_{gl}$  Glow voltage  
+ $V_a$  Arc voltage  
+ $V_e$  Extinction voltage  
+ G Glow mode range  
+ A Arc mode range
+
+Figure 6: Electrical characteristics of GDT. The figure contains three graphs: 6a shows voltage (V) vs. time (t) with a dashed sinusoidal surge and a solid limiting curve; 6b shows current (i) vs. time (t) with a dashed sinusoidal surge and a solid limiting curve; 6c shows voltage (V) vs. current (i) with a solid hysteresis loop. Key voltage levels V\_s, V\_gl, V\_a, and V\_e are marked on the y-axis of 6c. Regions G (glow mode) and A (arc mode) are labeled on the curves in 6a and 6b.
+
+NOTE 1 – Graph 6a shows voltage at the GDT as a function of time when limiting a sinusoidal voltage surge.
+
+NOTE 2 – Graph 6b shows current at the GDT as a function of time when limiting a sinusoidal voltage surge.
+
+NOTE 3 – Graph 6c shows the voltage/current characteristic of the GDT obtained by combining the graphs of voltage and current.
+
+K.12(10)\_F6
+
+6a – Voltage at the GDT as a function of time when limiting a sinusoidal voltage surge
+
+6b – Current at the GDT as a function of time when limiting a sinusoidal voltage surge
+
+6c – V/I characteristic of the GDT obtained by combining the graphs of voltage and current
+
+**Figure 6 – Electrical characteristics of GDT**
+
+# 11 Identification
+
+## 11.1 Marking
+
+Legible and permanent marking shall be applied to the tube, as necessary, to ensure that the user can determine the following information by inspection:
+
+- manufacturer;
+- year of manufacture;
+- code.
+
+The user may specify the codes to be used for this marking.
+
+## 11.2 Documentation
+
+Documents shall be provided to the user so that from the information in clause 11.1 he or she can determine the following further information:
+
+- full characteristics as set out in this Recommendation;
+- statement that no radioactive material has been used.
+
+# 12 Ordering information
+
+The following information should be supplied by the user:
+
+- a) drawing giving all dimensions, finishes and termination details (including numbers of electrodes and identifying the earth electrode);
+- b) nominal d.c. sparkover voltage, chosen from clause 7.1.1;
+- c) nominal current rating chosen from clause 7.6.1;
+- d) holdover voltage tests required in clause 7.5;
+- e) marking codes required for clause 11.1;
+- f) robustness of terminations – test required for clause 9.2;
+- g) destruction characteristic, if required, including failure mode (see Note in clause 7.6.3);
+- h) short-circuit mechanism;
+- i) quality assurance requirements.
+
+# Annex A
+
+## Test circuit for GDT used in ISDN circuits
+
+(This annex forms an integral part of this Recommendation.)
+
+![Circuit diagram and graph for GDT testing in ISDN circuits. The circuit includes a surge generator, resistors R1 and R2, a diode, a capacitor, and a 135 V power supply. The graph shows voltage (U) vs current (I) with various test curves.](a289b64f80c6df506c0c55d553fc4496_img.jpg)
+
+The figure illustrates the test circuit and operating conditions for a GDT in ISDN circuits. The circuit diagram shows a surge generator connected to a series combination of a resistor  $R_1$  and a diode. This is followed by a parallel combination of a resistor  $R_2$  (150  $\Omega$ ) and a capacitor (100 nF). A second diode and resistor  $R_2$  (450  $\Omega$ ) are connected in series with a 135 V power supply that has an automatic current limiter of 80 mA. A variable current source is also shown in parallel with the capacitor.
+
+The graph plots voltage  $U$  (V) on the y-axis (0 to 200) against current  $I$  (mA) on the x-axis (0 to 300). Key features include:
+ 
+
+- A shaded region labeled "ISDN" between 0 and 70 mA, with a top boundary at 100 V.
+- A dashed line labeled "Test curve for ISDN" starting at 135 V, 0 mA, and ending at 97 V, 80 mA.
+- A solid line labeled "Test 2 according to Table 3" starting at 80 V, 0 mA and ending at 240 V, 0 mA.
+- A solid line labeled "Test 3 according to Table 3" starting at 135 V, 0 mA and ending at 100 V, 0 mA.
+
+Reference: K.12(10)\_FA.1
+
+Circuit diagram and graph for GDT testing in ISDN circuits. The circuit includes a surge generator, resistors R1 and R2, a diode, a capacitor, and a 135 V power supply. The graph shows voltage (U) vs current (I) with various test curves.
+
+Figure A.1 – Test circuit for GDT used in ISDN circuits
+
+# Annex B
+
+## Sparkover test waveform
+
+(This annex forms an integral part of this Recommendation.)
+
+The use of Figure B.1:
+
+A single mask will do for all values of  $U_{max}$  and the nominal rate of rise, provided that it is a suitable size for the display of the waveform and that the scales of  $U$  and  $T$  of the waveform can be adjusted. This follows because the Y-axis has arbitrary points marked 0 and  $U_{max}$  with  $0.2 U_{max}$  at the appropriate point between them, while the X-axis has arbitrary points marked 0 and  $T_2$  with  $T_1 (= 0.2 T_2)$ ,  $0.9 T_1$ ,  $1.1 T_1$ ,  $0.9 T_2$ ,  $1.1 T_2$  marked at the appropriate points. The X and Y zeros need not coincide and, in fact, need not be shown at all.
+
+![Figure B.1: Sparkover test waveform graph showing voltage V vs time T with a shaded limit region defined by nominal rate of rise lines.](b6bd6d8ee5821226bc79251ca5937e07_img.jpg)
+
+The figure is a graph with Voltage (V) on the vertical axis and Time (T) on the horizontal axis. The vertical axis has markings for  $0$ ,  $0.2 U_{max}$ , and  $U_{max}$ . The horizontal axis has markings for  $0$ ,  $0.9 T_1$ ,  $T_1$ ,  $1.1 T_1$ ,  $0.9 T_2$ ,  $T_2$ , and  $1.1 T_2$ . A shaded region labeled 'Limit' is bounded by two parallel lines representing the 'Nominal rate of rise'. One boundary line passes through  $(T_1, 0.2 U_{max})$  and  $(T_2, U_{max})$ . The other boundary line is shifted horizontally, passing through  $(0.9 T_1, 0.2 U_{max})$  and  $(1.1 T_2, U_{max})$ .
+
+Figure B.1: Sparkover test waveform graph showing voltage V vs time T with a shaded limit region defined by nominal rate of rise lines.
+
+NOTE – Sparkover test waveform (non-conducting) must be within enclosed limits.
+
+K.12(24)
+
+**Figure B.1 – Sparkover test waveform**
+
+To compare a waveform trace with the mask, it is necessary to know the values of  $U_{max}$  and the nominal rate of rise for the waveform in question. As an example, consider a waveform with  $U_{max} = 750$  V and nominal rate of rise = 100 V/s:
+
+Then  $0.2 U_{max} = 150$  V,  $T_2 = 7.5$  s,  $T_1 = 1.5$  s.
+
+Hold the mask against the trace and adjust the vertical scale so that the 150 V calibration is against  $0.2 U_{max}$  and the 750 V point against  $U_{max}$ . Adjust the horizontal scale similarly for 1.5 s =  $T_1$  and 7.5 s =  $T_2$ . Slide the mask so that the 150 V point on the trace is within the bottom boundary of the test window; the remainder of the trace up to 750 V must be within the test window.
+
+# Annex C
+
+## Determining the special test protector (STP)
+
+(This annex forms an integral part of this Recommendation.)
+
+### Selection of the primary protector
+
+A test house or laboratory needs to be given the characteristics of the "agreed" primary protector, for the equipment under test, so that they can select the special test protector. It is important that the "agreed" primary protector and special test protector characteristics determined and used at resistibility testing, be recorded in the test report\*. This may prevent an additional compliance test from having to be performed.
+
+The characteristics of the special test protector are determined by the "agreed" primary protector. Unfortunately, there are many types of primary protector available. This Recommendation lists the many nominal d.c. firing voltages and other characteristics for GDTs. Furthermore, the network operator may require a change of one of the characteristics in this Recommendation because of an agreement with a manufacturer. There are at least four reasons for the range of primary protectors used, and some of these are:
+
+- The network operator has a specific requirement, e.g., minimum d.c. firing voltage to prevent ring trip or the use of a specific termination module. [ITU-T K.65] may limit the range of GDTs which can be used.
+- The manufacturer may specify a maximum d.c. and a maximum impulse firing voltage to coordinate with their equipment.
+- The administration may specify a minimum d.c. firing voltage to prevent operation due to 230 V a.c. for safety reasons.
+- The environment, predominantly a.c. or lightning surges, may also limit the characteristics of the GDT.
+
+The end result is an agreed primary protector. The characteristics of the agreed primary protector must be known to determine the characteristics of the special test protector. An equipment manufacturer needs to balance market opportunities (design the equipment to coordinate with the worst-case GDT) with design costs (design for the best case GDT). It should be noted that the term "worst case" does not indicate a poor quality GDT. GDTs may have a high firing voltage for many reasons, e.g., the GDT has to operate in an environment where a.c. surges predominate or the operator requires a high minimum d.c. firing voltage. A list of typical protection points and likely GDT used is given in Table C.1.
+
+NOTE – The specification of an agreed primary protector and special test protector used in resistibility test for products sold on the general market shall be determined based on complying to the rule or regulation for the networks to be connected. The manufacturer of equipment shall provide the specification of the agreed primary protector and special test protector to the user or installer of the equipment.
+
+**Table C.1 – Typical GDT application for equipment connected to external cables and for plant**
+
+| <b>Application</b>                                | <b>Standard GDTs (Type 1)<br/>Table 1a</b><br><br>(Characteristics are better suited for withstanding a.c. currents) |                                  | <b>Low impulse voltage GDTs (Type 2)<br/>Table 1b</b><br><br>(May not be suitable when a.c. surges predominate) |                                  |
+|---------------------------------------------------|----------------------------------------------------------------------------------------------------------------------|----------------------------------|-----------------------------------------------------------------------------------------------------------------|----------------------------------|
+|                                                   | <b>d.c.<br/>(V)</b>                                                                                                  | <b>Impulse at 1kV/μs<br/>(V)</b> | <b>d.c.<br/>(V)</b>                                                                                             | <b>Impulse at 1kV/μs<br/>(V)</b> |
+| Line cards, data circuits (nominally a 230 V GDT) | max. 300                                                                                                             | max. 800                         | max. 300                                                                                                        | max. 550                         |
+| RFT circuits (nominally a 350 V GDT)              | max. 455                                                                                                             | max. 1 100                       | max. 600                                                                                                        | max. 900                         |
+| Customer premises (nominally a 600 V GDT)         | max. 780                                                                                                             | max. 1 500                       | max. 800                                                                                                        | max. 1 200                       |
+| Cable protection (nominally a 600 V GDT)          | max. 780                                                                                                             | max. 1 500                       | max. 800                                                                                                        | max. 1 200                       |
+
+To assist those manufacturers who wish to design for, or test for, a worst-case GDT, a table of protection purposes and a typical worst-case GDT is provided in Table C.2. These values are based on this Recommendation.
+
+**Table C.2 – Worst-case GDT voltages**
+
+| <b>Application</b>                                | <b>Worst-case GDT firing<br/>(voltages taken from tables 1a and 1b)</b> |                                   |
+|---------------------------------------------------|-------------------------------------------------------------------------|-----------------------------------|
+|                                                   | <b>d.c.<br/>(V)</b>                                                     | <b>Impulse at 1 kV/μs<br/>(V)</b> |
+| Line cards, data circuits (nominally a 230 V GDT) | max. 300                                                                | max. 800                          |
+| RFT circuits (nominally a 350 V GDT)              | max. 600                                                                | max. 1 100                        |
+| Customer premises (nominally a 600 V GDT)         | max. 800                                                                | max. 1 500                        |
+| Cable protection (nominally a 600 V GDT)          | max. 800                                                                | max. 1 500                        |
+
+NOTE – The values in this table are given to assist manufacturers to determine a worst-case "agreed" primary protector for design and testing purposes. Use of these values does not guarantee compliance with the product recommendations for every application in every country. ITU-T will update these values when feedback is received.
+
+
+
+# SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| Series E        | Overall network operation, telephone service, service operation and human factors                                                                         |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| <b>Series K</b> | <b>Protection against interference</b>                                                                                                                    |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/K/T-REC-K.129-201801-I_PDF-E/raw.md

@@ -0,0 +1,999 @@
+
+
+International Telecommunication Union
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**K.129**
+
+(01/2018)
+
+SERIES K: PROTECTION AGAINST INTERFERENCE
+
+---
+
+**Characteristics and ratings of silicon PN  
+junction voltage clamping components used for  
+the protection of telecommunication  
+installations**
+
+Recommendation ITU-T K.129
+
+ITU-T
+
+![ITU logo: A globe with a red lightning bolt striking it, next to the text 'ITU International Telecommunication Union'.](84a1d09fb489061482111515543b60dc_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with a red lightning bolt striking it from the top right. To the right of the globe, the text "ITU" is written in a bold, blue, sans-serif font. Below "ITU", the words "International Telecommunication Union" are written in a smaller, blue, sans-serif font.
+
+ITU logo: A globe with a red lightning bolt striking it, next to the text 'ITU International Telecommunication Union'.
+
+
+
+# Recommendation ITU-T K.129
+
+# Characteristics and ratings of silicon PN junction voltage clamping components used for the protection of telecommunication installations
+
+## Summary
+
+Recommendation ITU-T K.129 defines the basic electrical parameters to be met by silicon PN junction voltage clamping components used for the protection of telecommunication equipment or lines from surges. Examples of equipment include those located within a telecommunication centre, customer premise, access or trunk network. It is intended that this Recommendation be used for the harmonization of existing or future specifications issued by PN diode surge protective component manufacturers, telecommunication equipment manufacturers, administrators or network operators.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T K.129    | 2018-01-13 | 5           | <a href="http://handle.itu.int/11.1002/1000/13452">11.1002/1000/13452</a> |
+
+## Keywords
+
+Avalanche breakdown, electrical characteristics, electrical ratings, fold-back, forward conduction, overvoltage protection, punch-through, surge protective component (SPC), test methods, Zener breakdown.
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2018
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+###### Page
+
+|     |                                                                             |    |
+|-----|-----------------------------------------------------------------------------|----|
+| 1   | Scope.....                                                                  | 1  |
+| 2   | References.....                                                             | 1  |
+| 3   | Definitions .....                                                           | 1  |
+| 3.1 | Terms defined elsewhere .....                                               | 1  |
+| 3.2 | Terms defined in this Recommendation.....                                   | 4  |
+| 4   | Abbreviations and acronyms .....                                            | 5  |
+| 5   | Conventions .....                                                           | 5  |
+| 5.1 | Letter symbols .....                                                        | 5  |
+| 5.2 | Component graphical symbols .....                                           | 6  |
+| 6   | Environments.....                                                           | 7  |
+| 6.1 | Normal service conditions .....                                             | 7  |
+| 6.2 | Storage temperature range, $T_{\text{stgmin}}$ to $T_{\text{stgmax}}$ ..... | 8  |
+| 6.3 | Lead soldering temperature, $T_{\text{lmax}}$ .....                         | 8  |
+| 7   | Essential characteristics and ratings .....                                 | 8  |
+| 7.1 | General .....                                                               | 8  |
+| 7.2 | Electrical characteristics .....                                            | 8  |
+| 7.3 | Thermal ratings.....                                                        | 10 |
+| 7.4 | Electrical ratings .....                                                    | 11 |
+| 8   | Measuring and test methods .....                                            | 11 |
+| 8.1 | Mounting and ambient conditions .....                                       | 11 |
+| 8.2 | Test circuits .....                                                         | 11 |
+| 8.3 | Measuring methods for electrical characteristics .....                      | 12 |
+| 8.4 | Measuring methods for thermal characteristics.....                          | 16 |
+| 8.5 | Verification test methods for ratings (limiting values).....                | 17 |
+| 9   | Mechanical requirements and identification.....                             | 18 |
+| 9.1 | Robustness of terminations.....                                             | 18 |
+| 9.2 | Solderability .....                                                         | 18 |
+| 9.3 | Marking .....                                                               | 18 |
+| 9.4 | Documentation .....                                                         | 19 |
+|     | Bibliography.....                                                           | 20 |
+
+
+
+# Recommendation ITU-T K.129
+
+# Characteristics and ratings of silicon PN junction voltage clamping components used for the protection of telecommunication installations
+
+# 1 Scope
+
+Silicon PN-junction surge protective components (SPCs) are special silicon diodes designed to limit overvoltages and divert surge currents by a voltage clamping action. This Recommendation applies to silicon PN-junction SPCs used in surge protective devices (SPDs) and telecommunication equipment ports to provide overvoltage protection for installations during lightning surges and alternating current (AC) power faults, in accordance with [b-ITU-T K.11]. Telecommunication equipment port test levels and criteria are defined by [b-ITU-T K.20], [b-ITU-T K.21] and [b-ITU-T K.45], as appropriate and are supported by [b-ITU-T K.44] with test circuit details and application guidance. In conjunction, [ITU-T K.103] should be read as it explains the parameters measured or verified in this Recommendation.
+
+The following PN-junction component technologies are covered:
+
+- Zener breakdown;
+- avalanche breakdown;
+- fold-back;
+- punch-through;
+- forward conduction.
+
+This Recommendation contains information on:
+
+- a) terminology;
+- b) letter and circuit symbols;
+- c) essential electrical ratings and characteristics;
+- d) rating verification and characteristic measurement;
+- f) mechanical requirements and identification.
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+[ITU-T K.103] Recommendation ITU-T K.103 (2015), *Surge protective component application guide – Silicon PN junction components*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 acceptor** [b-IEC IEV], definition 521-02-39: Imperfection in a crystal lattice which, when it is predominant, permits hole conduction by the acceptance of electrons.
+
+- 3.1.2 ambient temperature** [b-IEC TR 62240-1]: Temperature of the environment in which a semiconductor component is operating.
+- 3.1.3 avalanche breakdown (of a PN junction)** [b-IEC IEV], definition 521-05-07: Breakdown that is caused by the cumulative multiplication of charge carriers in a semi-conductor under the action of a strong electric field which causes some carriers to gain enough energy to liberate new hole-electron pairs by ionization.
+- 3.1.4 avalanche voltage** [b-IEC IEV], definition 521-05-08: Applied voltage at which avalanche breakdown occurs.
+- 3.1.5 bidirectional transistor** [b-IEC IEV], definition 521-04-49: Transistor which has substantially the same electrical characteristics when the terminals normally designated as emitter and collector are interchanged.
+- 3.1.6 bipolar junction transistor** [b-IEC IEV], definition 521-04-47: Transistor having at least two junctions and whose functioning depends on both majority carriers and minority carriers.
+- 3.1.7 breakdown (of a reverse-biased PN junction)** [b-IEC IEV], definition 521-05-06: Phenomenon, the initiation of which is observed as a transition from a state of high dynamic resistance to a state of substantially lower dynamic resistance for increasing magnitude of reverse current.
+- 3.1.8 breakdown voltage,  $V_{(BR)}$**  [b-IEC 60747-2]: Voltage in the region where breakdown occurs.
+- 3.1.9 case temperature** [b-IEC 60747-1]: Temperature of a reference point, on or near the surface of the case.
+- 3.1.10 conduction electron** [b-IEC IEV], definition 521-02-14: Electron in the conduction band of a semiconductor, which is free to flow under the action of an electric field.
+- 3.1.11 donor** [b-IEC IEV], definition 521-02-38: Imperfection in a crystal lattice which, when it is predominant, permits electron conduction by the donation of electrons.
+- 3.1.12 extrinsic semiconductor** [b-IEC IEV], definition 521-02-08: Semiconductor in which charge carrier concentration depends upon impurities or other imperfections.
+- 3.1.13 forward current,  $I_F$**  [b-IEC 60747-2]: Current flowing through the diode in forward direction.
+- 3.1.14 forward direction (of a PN junction)** [b-IEC IEV], definition 521-05-03: Direction of current that results when the P-type semiconductor region is at a positive voltage relative to the N-type region.
+- 3.1.15 forward recovery voltage,  $V_{FR}$**  [b-IEC 60747-2]: Varying voltage occurring during the forward recovery time after instantaneous switching from zero or a specified reverse voltage to a specified forward current.
+- 3.1.16 forward voltage,  $V_F$**  [b-IEC 60747-2]: Voltage across the terminals which results from the flow of current in the forward direction.
+- 3.1.17 hole conduction** [b-IEC IEV], definition 521-02-18: Conduction in a semiconductor, in which holes in a crystal lattice are propagated through the lattice under the influence of an electric field.
+- 3.1.18 Kelvin measurement** [b-IEC 62624]: Four-wire electrical resistance technique that uses separate contacts for measuring voltage across a device from that used to apply a known current through the device.
+
+NOTE 1 – This separation minimizes current flow through the voltage probes, which minimizes errors due to contact or lead resistance.
+
+NOTE 2 – Used for characterization of materials with electrical resistances comparable to or lower than the leads and contacts.
+
+**3.1.19 lead temperature** [b-IEC 60747-1]: Temperature of a reference point, on or near the surface of a specified component lead.
+
+**3.1.20 N-type semiconductor** [b-IEC IEV], definition 521-02-09: Extrinsic semiconductor in which the conduction electron density exceeds the hole density.
+
+**3.1.21 peak pulse current (impulse discharge current)** [b-IEC 61000-5-5]: Peak value of a specified current waveform.
+
+**3.1.22 PN junction** [b-IEC IEV], definition 521-02-78: Junction between P and N type semiconductor materials.
+
+**3.1.23 P-type semiconductor** [b-IEC IEV], definition 521-02-10: Extrinsic semiconductor in which the hole density exceeds the conduction electron density.
+
+**3.1.24 punch-through (between two PN junctions)** [b-IEC IEV], definition 521-05-12: Contact between the space charge regions of two PN junctions as a result of widening of one or both of them.
+
+**3.1.25 reverse current,  $I_R$**  [b-IEC 60747-2]: Current flowing through the diode when reverse voltage is applied.
+
+**3.1.26 reverse direction (of a PN junction)** [b-IEC IEV], definition 521-05-04: Direction of current that results when the N-type semiconductor region is at a positive voltage relative to the P-type region.
+
+**3.1.27 reverse voltage,  $V_R$**  [b-IEC 60747-2]: Constant voltage applied to a diode in the reverse direction.
+
+NOTE – This term normally applies to the portion of the reverse characteristic before breakdown occurs.
+
+**3.1.28 space-charge region** [b-IEC IEV], definition 521-02-79: Region in which the net charge density is not zero.
+
+NOTE – The net charge is caused by electrons, holes, ionized acceptors and donors.
+
+**3.1.29 storage temperature** [b-IEC 60747-1]: Temperature at which the device may be stored without any voltage being applied.
+
+**3.1.30 temperature coefficient of breakdown voltage  $\alpha V_{BR}$**  [b-IEC 61643-321]: Ratio of the change in breakdown voltage  $V_{BR}$  to changes in temperature.
+
+NOTE – Expressed as either millivolts per degree Kelvin or per cent per degree Kelvin (mV/K or %/K).
+
+**3.1.31 thermal resistance** [b-IEC IEV], definition 521-05-13: Quotient of the difference between the virtual temperature of the device and the temperature of a stated external reference point, by the steady-state power dissipation in the device.
+
+**3.1.32 total capacitance** [b-IEC 60747-3]: Capacitance at the diode terminals, measured under specified bias conditions.
+
+**3.1.33 transient thermal impedance** [b-IEC 60747-1]: Quotient of:
+
+- a) the change in temperature difference between two specified points or regions at the end of a time interval, and
+- b) the step-function change in power dissipation beginning at that time interval which causes the change in temperature difference.
+
+NOTE – The term used in practice must indicate the two specified points or regions, for example, as in "junction-case transient thermal impedance". The use of the shortened term "transient thermal impedance" is permitted only if no ambiguity is likely to occur.
+
+**3.1.34 Zener breakdown (of a PN junction)** [b-IEC IEV], definition 521-05-09: Breakdown caused by the transition of electrons from the valence band to the conduction band due to tunnel action under the influence of a strong electric field in a PN junction.
+
+**3.1.35 Zener voltage** [b-IEC IEV], definition 521-05-10: Minimum voltage across a PN junction at which Zener breakdown occurs.
+
+## **3.2 Terms defined in this Recommendation**
+
+This Recommendation defines the following terms:
+
+**3.2.1 clamping (limiting) voltage:** Breakdown voltage developed across the diode at a specified impulse current.
+
+NOTE – Normally the maximum value of clamping voltage is reported for the rated value of peak pulse current.
+
+**3.2.2 discrete (semiconductor) component:** Semiconductor component that is specified to perform an elementary function and that is not divisible into separate components functional in themselves. (modified version of [b-IEC IEV], definition 521-04-02)
+
+NOTE – There is no clear delimitation possible between discrete components and integrated circuits. In principle, a discrete component consists of a single circuit element only. However, a component sold and specified as a discrete component may internally consist of more than one circuit element.
+
+**3.2.3 fold-back breakdown (of a bidirectional bipolar junction transistor diode):** Re-entrant breakdown characteristic caused by transistor action after the initiation of breakdown producing a region of negative dynamic resistance before reverting back to a low positive dynamic resistance condition.
+
+NOTE – The negative resistance region and its voltage range is only pronounced for breakdown voltages in excess of about 20 V.
+
+**3.2.4 fold-back diode:** Bidirectional bipolar junction transistor packaged with only the collector and emitter terminals made available.
+
+**3.2.5 punch-through voltage:** Low-current peak voltage marking the start of the diode clamping characteristic.
+
+NOTE – This punch-through diode term may also be applied to fold-back diodes.
+
+**3.2.6 semiconductor component:** Component whose essential characteristics are due to the flow of charge carriers within a semi-conductor. (modified version of [b-IEC IEV], definition 521-04-01)
+
+NOTE – The definition includes components whose essential characteristics are only in part due to the flow of charge carriers in a semiconductor but that are considered as semiconductor components for the purpose of specification.
+
+**3.2.7 (semiconductor) diode:** Two-terminal semiconductor component having an asymmetrical voltage-current characteristic. (modified version of [b-IEC IEV], definition 521-04-03)
+
+NOTE 1 – Unless otherwise qualified, this term usually means a device with the voltage-current characteristic typical of a single PN junction.
+
+NOTE 2 – Voltage clamping diodes are normally classified by clamping phenomenon; Zener, avalanche, fold-back, punch-through and forward conduction. Acronyms such as ABD (avalanche breakdown diode), TVS (transient voltage suppressor) and SAD (silicon avalanche diode) may also be used.
+
+**3.2.8 snap-back voltage:** Lowest voltage in the clamping characteristic after the punch-through voltage occurs.
+
+NOTE – This punch-through diode term may also be applied to fold-back diodes.
+
+**3.2.9 terminal (of a semiconductor component):** Conductive element provided for external connection. (modified version of [b-IEC IEV], definition 521-05-02)
+
+**3.2.10 total power dissipation:** Rated (maximum) value of the power that can be continuously dissipation by the diode at a specified ambient, case or lead temperature without exceeding the maximum rated junction temperature.
+
+**3.2.11 virtual junction temperature, internal equivalent temperature (of a semiconductor component):** Theoretical temperature which is based on a simplified representation of the thermal and electrical behaviour of the semiconductor device. (modified version of [b-IEC IEV], definition 521-05-14)
+
+# 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|      |                                           |
+|------|-------------------------------------------|
+| ABD  | Avalanche Breakdown Device                |
+| AC   | Alternating Current                       |
+| DC   | Direct Current                            |
+| ICT  | Information and Communication Technology  |
+| SAD  | Silicon Avalanche Diode                   |
+| SPC  | Surge Protective Component                |
+| TVS  | Transient Voltage Suppressor              |
+| WEEE | Waste Electrical and Electronic Equipment |
+
+# 5 Conventions
+
+## 5.1 Letter symbols
+
+The general rules and letter symbols of clause 4 of [b-IEC 60747-1] apply to this Recommendation. To indicate a limit or rated value, the letter symbol subscript appends <sub>M</sub> or <sub>max</sub> to indicate maximum and <sub>min</sub> to indicate a minimum.
+
+|                      |                                                               |
+|----------------------|---------------------------------------------------------------|
+| $C_{\text{tot}}$     | Total capacitance                                             |
+| $dI_F/dt$            | Rate of forward current rise                                  |
+| $I_{(\text{BR})}$    | Breakdown current                                             |
+| $I_F$                | Forward current                                               |
+| $I_{\text{PP}}$      | Peak pulse current                                            |
+| $I_{\text{PP}}$      | Peak pulse current                                            |
+| $I_R$                | Reverse current                                               |
+| $P_{\text{PP}}$      | Maximum peak pulse power                                      |
+| $P_{\text{tot}}$     | Total power dissipation                                       |
+| $R_{\text{th(j-a)}}$ | Thermal resistance junction to ambient                        |
+| $R_{\text{th(j-c)}}$ | Thermal resistance junction to case                           |
+| $R_{\text{th(j-l)}}$ | Thermal resistance junction to lead                           |
+| $T_a$                | Operating ambient temperature                                 |
+| $T_c$                | Case temperature                                              |
+| $T_j$                | Virtual junction temperature, internal equivalent temperature |
+
+|                          |                                                                |
+|--------------------------|----------------------------------------------------------------|
+| $T_1$                    | Lead temperature                                               |
+| $T_{\text{stg}}$         | Storage temperature                                            |
+| $V_{(\text{BR})}$        | Breakdown voltage                                              |
+| $V_{(\text{PT})}$        | Punch-through voltage                                          |
+| $V_{(\text{SB})}$        | Snap-back voltage                                              |
+| $V_C$                    | Clamping voltage                                               |
+| $V_F$                    | Forward biased PN junction voltage                             |
+| $V_{\text{FRM}}$         | Peak forward recovery voltage                                  |
+| $V_R$                    | Reverse working voltage                                        |
+| $V_{\text{RWM}}$         | Stand-off or maximum reverse working voltage                   |
+| $Z_{\text{th(j-a)(t)}}$  | Transient thermal impedance, junction to ambient               |
+| $Z_{\text{th(j-c)(t)}}$  | Transient thermal impedance, junction to case                  |
+| $Z_{\text{th(j-l)(t)}}$  | Transient thermal impedance, junction to lead                  |
+| $\alpha V_{(\text{BR})}$ | Temperature coefficient of breakdown voltage $V_{(\text{BR})}$ |
+
+## 5.2 Component graphical symbols
+
+### 5.2.1 General
+
+This Recommendation uses the following SPC graphical symbols from [b-IEC 60617]:
+
+### 5.2.2 Single PN-junction symbols
+
+![General symbol for a semiconductor diode, consisting of a triangle pointing to a vertical line, with leads extending from both sides.](e159e9f78612406820a4d40e26e01413_img.jpg)
+
+K.129(18)\_F5-1
+
+General symbol for a semiconductor diode, consisting of a triangle pointing to a vertical line, with leads extending from both sides.
+
+Figure 5-1 – Semiconductor diode, general symbol (symbol S00641)
+
+![Symbol for a unidirectional breakdown diode, which is the general diode symbol with an additional L-shaped line at the cathode end.](53298644c66fa3fca81d6eec654afec5_img.jpg)
+
+K.129(18)\_F5-2
+
+Symbol for a unidirectional breakdown diode, which is the general diode symbol with an additional L-shaped line at the cathode end.
+
+Figure 5-2 – Breakdown diode, unidirectional (symbol S00646)
+
+### 5.2.3 Multiple PN-junction symbols
+
+![Symbol for a bidirectional breakdown diode, which is the general diode symbol with an additional L-shaped line at the anode end.](10d19f166f9b7f5961f09f8041896943_img.jpg)
+
+K.129(18)\_F5-3
+
+Symbol for a bidirectional breakdown diode, which is the general diode symbol with an additional L-shaped line at the anode end.
+
+Figure 5-3 – Breakdown diode, bidirectional (symbol S00647)
+
+![Figure 5-4: Examples of diode arrays. The diagram shows three different diode array configurations. The first is a single diode. The second is a bridge rectifier consisting of four diodes. The third is a more complex array with two vertical columns of four diodes each, connected in a bridge-like configuration with multiple input and output terminals.](af7916c89a458fdab6c3f443217388ae_img.jpg)
+
+Figure 5-4: Examples of diode arrays. The diagram shows three different diode array configurations. The first is a single diode. The second is a bridge rectifier consisting of four diodes. The third is a more complex array with two vertical columns of four diodes each, connected in a bridge-like configuration with multiple input and output terminals.
+
+K.129(18)\_F5-4
+
+**Figure 5-4 – Examples of diode arrays**
+
+![Figure 5-5: Examples of breakdown diodes combined with diodes and diode arrays. The diagram shows five different configurations. The top row shows three individual breakdown diode symbols. The bottom row shows two more complex arrays: the first consists of three vertical branches, each with a breakdown diode and a regular diode in series; the second is a larger array with five vertical branches, each containing a breakdown diode and a regular diode.](ff0952ef692c9d960ce5f6708bcc9711_img.jpg)
+
+Figure 5-5: Examples of breakdown diodes combined with diodes and diode arrays. The diagram shows five different configurations. The top row shows three individual breakdown diode symbols. The bottom row shows two more complex arrays: the first consists of three vertical branches, each with a breakdown diode and a regular diode in series; the second is a larger array with five vertical branches, each containing a breakdown diode and a regular diode.
+
+K.129(18)\_F5-5
+
+**Figure 5-5 – Examples of breakdown diodes combined with diodes and diode arrays**
+
+# 6 Environments
+
+The preferred climatic conditions are taken from the IEC classification of environmental conditions standards and the storage temperature ranges are taken from the IEC semiconductor devices standards.
+
+## 6.1 Normal service conditions
+
+This standard is for components mounted in stationary equipment and device installations that are weather-protected, see [b-IEC 60721-3-3]. The two preferred microclimates within the products are selected from [b-IEC 60721-3-9].
+
+### 6.1.1 Normal microclimate
+
+- ambient air temperature within the range of 0°C to 70°C;
+- air pressure within the range of 80 kPa to 106 kPa;
+- relative humidity within the range of 25% to 75%.
+
+### 6.1.2 Extended microclimate
+
+- ambient air temperature within the range of –40°C to 85°C;
+
+- air pressure within the range of 70 kPa to 106 kPa;
+- relative humidity 10% to 95%.
+
+## 6.2 Storage temperature range, $T_{\text{stgmin}}$ to $T_{\text{stgmax}}$
+
+The temperatures over which a component can be stored without any voltage applied has the following preferred temperature ranges (selected from [b-IEC 60747-1] and [b-IEC 60749-1]):
+
+- a) 0°C to 125°C;
+- b) –55°C to 125°C;
+- c) –65°C to 150°C.
+
+NOTE – In some cases the storage temperature range may be limited by the component shipping containers and not by the component itself.
+
+## 6.3 Lead soldering temperature, $T_{\text{Imax}}$
+
+Legislation, such as the waste electrical and electronic equipment (WEEE) directive and restriction of hazardous substances (RoHS) directive in the European Union, has accelerated the use of lead-free soldering. Removing the lead from solder results in increased soldering temperatures and component manufactures now routinely specify maximum soldering conditions in terms of component lead temperature,  $T_{\text{Imax}}$ , and temperature duration time,  $t_{\text{Imax}}$ , see [b-IEC 60068-2-20]. Examples are 260°C for 10 s and 260°C for 40 s.
+
+# 7 Essential characteristics and ratings
+
+## 7.1 General
+
+For compatibility with general purpose breakdown diodes, the format of this clause follows that of [b-IEC 60747-3]. Many of the ratings and characteristics are required to be quoted at a temperature of 25°C and at one other specified temperature.
+
+## 7.2 Electrical characteristics
+
+### 7.2.1 PN-junction structure electrical characteristics
+
+#### 7.2.1.1 Single PN-junction
+
+This classification covers forward biased diodes, reverse biased diodes, Zener breakdown diodes and avalanche breakdown diodes. Symmetrical breakdown diodes are made by the series connection of a PN-junction and a NP-junction giving a limiting voltage of  $V_{(\text{BR})} + V_{\text{F}}$ . Such arrangements can be made in a single chip. The electrical characteristics and symbol identification for a forward conducting diode and a breakdown diode are shown in Figure 7-1 and Figure 7-2, respectively.
+
+![Figure 7-1: Diode characteristic graph showing forward and reverse blocking characteristics.](71ab4df17511d75261da8d462d643b1a_img.jpg)
+
+This graph shows the current ( $i$ ) versus voltage ( $v$ ) characteristic of a diode. The vertical axis represents current, with positive values labeled  $I_{PP}$  and  $I_F$ , and negative values labeled  $I_R$  and  $-i$ . The horizontal axis represents voltage, with a break in the scale. The forward characteristic curve starts at the origin and rises steeply, passing through a point marked  $V_F$  and  $I_F$ , and continuing towards  $I_{PP}$ . The reverse blocking characteristic curve is shown in the third quadrant, starting from a voltage  $V_R$  and current  $I_R$ , and remaining very close to the voltage axis. The label 'Forward characteristic' is placed near the first curve, and 'Reverse blocking characteristic' is placed near the second curve. The code 'K.129(18)\_F7-1' is at the bottom right.
+
+Figure 7-1: Diode characteristic graph showing forward and reverse blocking characteristics.
+
+Figure 7-1 – Diode characteristic
+
+![Figure 7-2: Breakdown diode characteristic graph showing current versus voltage with breakdown region.](177e8bc1c595b7fe3461d9919f87e044_img.jpg)
+
+This graph shows the current versus voltage characteristic of a breakdown diode. The vertical axis is labeled 'Current' and has markings for  $I_{PP}$ ,  $I_{(BR)}$ , and  $I_R$ . The horizontal axis is labeled 'Voltage' and has markings for  $V_{RWM}$ ,  $V_{(BR)}$ , and  $V_C$ . The curve shows a very low current  $I_R$  until it reaches the breakdown voltage  $V_{(BR)}$ , where it rises sharply. A horizontal line at  $I_{(BR)}$  indicates the start of the breakdown region. The current continues to rise towards  $I_{PP}$  as voltage increases towards  $V_C$ . The code 'K.129(18)\_F7-2' is at the bottom right.
+
+Figure 7-2: Breakdown diode characteristic graph showing current versus voltage with breakdown region.
+
+Figure 7-2 – Breakdown diode characteristic
+
+#### 7.2.1.2 Multiple PN-junction
+
+This classification for transistor-like structures covers punch-through diodes and fold-back diodes. The voltage limiting characteristic for these types is strongly re-entrant. The electrical characteristic and symbol identification is shown in Figure 7-3.
+
+![Figure 7-3: Punch-through diode and fold-back diode characteristic graph. The vertical axis is labeled 'Current' and the horizontal axis is labeled 'Voltage'. The graph shows a curve that starts at a low current $I_R$ and remains nearly constant until it reaches a voltage $V_{RWM}$. At $V_{RWM}$, the current begins to increase. It reaches a peak current $I_{PP}$ at a voltage $V_{PT}$. Beyond $V_{PT}$, the current decreases as voltage increases, reaching a minimum current at $V_{SB}$. From $V_{SB}$, the current increases again, reaching $I_{PP}$ at $V_C$. The curve then continues to rise. The label 'K.129(18)_F7-3' is at the bottom right.](ad29805cd4f64ad2828e14feb66de664_img.jpg)
+
+Figure 7-3: Punch-through diode and fold-back diode characteristic graph. The vertical axis is labeled 'Current' and the horizontal axis is labeled 'Voltage'. The graph shows a curve that starts at a low current \$I\_R\$ and remains nearly constant until it reaches a voltage \$V\_{RWM}\$. At \$V\_{RWM}\$, the current begins to increase. It reaches a peak current \$I\_{PP}\$ at a voltage \$V\_{PT}\$. Beyond \$V\_{PT}\$, the current decreases as voltage increases, reaching a minimum current at \$V\_{SB}\$. From \$V\_{SB}\$, the current increases again, reaching \$I\_{PP}\$ at \$V\_C\$. The curve then continues to rise. The label 'K.129(18)\_F7-3' is at the bottom right.
+
+Figure 7-3 – Punch-through diode and fold-back diode characteristic
+
+### 7.2.2 Reverse current, $I_R$
+
+Maximum value at a specified reverse voltage.
+
+### 7.2.3 Breakdown voltage, $V_{(BR)}$
+
+Minimum value for a specified current.
+
+### 7.2.4 Clamping voltage, $V_C$
+
+Maximum value for specified current.
+
+### 7.2.5 Punch-through voltage, $V_{(PT)}$
+
+Maximum value.
+
+### 7.2.6 Snap-back voltage, $V_{(SB)}$
+
+Minimum value.
+
+### 7.2.7 Forward biased PN junction voltage, $V_F$
+
+Maximum value at specified forward current.
+
+### 7.2.8 Total capacitance, $C_{tot}$
+
+Maximum value for specified terminal and electrical conditions.
+
+### 7.2.9 Thermal resistance ( $R_{th}$ )
+
+Maximum value or a graph of maximum total power dissipation as a function of temperature over the range of operating temperatures.
+
+### 7.2.10 Thermal impedance ( $Z_{th}$ )
+
+A graph of thermal impedance as a function of time up to the thermal resistance value.
+
+## 7.3 Thermal ratings
+
+### 7.3.1 Storage temperature ( $T_{stg}$ )
+
+Minimum and maximum values.
+
+### 7.3.2 Operating ambient temperature ( $T_a$ )
+
+Minimum and maximum values.
+
+### 7.3.3 Lead soldering temperature, $T_l$
+
+$T_{lmax}$ , and temperature duration time,  $t_{lmax}$ .
+
+### 7.3.4 Virtual junction temperature, internal equivalent temperature, $T_J$
+
+Maximum value.
+
+## 7.4 Electrical ratings
+
+### 7.4.1 Peak pulse current, $I_{PP}$
+
+Maximum value at a specified ambient or sink or case and virtual junction temperature.
+
+### 7.4.2 Maximum peak pulse power, $P_{PP}$
+
+Maximum value at specified current waveform.
+
+### 7.4.3 Total power dissipation, $P_{tot}$
+
+Where thermal resistance is not given in the characteristics, maximum total power dissipation as a function of temperature over the range of operating temperatures shall be given.
+
+# 8 Measuring and test methods
+
+## 8.1 Mounting and ambient conditions
+
+For these tests, the component should be mounted as detailed in the product documentation. All room temperature electrical measurements, as well as recoveries followed by measurements, shall be carried out under the following conditions as recommended in clause 4, chapter 1 of [b-IEC 60749-1]:
+
+- temperature: 20°C to 30°C;
+- relative humidity: 25% to 75%, where appropriate;
+- air pressure: 80 kPa to 106 kPa.
+
+Referee tests shall be carried out under the following standard atmospheric conditions (see clause 4, chapter 1 of [b-IEC 60749-1]):
+
+- temperature: 24°C to 26°C;
+- relative humidity: 25% to 75%;
+- air pressure: 80 kPa to 106 kPa.
+
+## 8.2 Test circuits
+
+### 8.2.1 Pulsed current
+
+This circuit, shown in Figure 8-1, forces a current of defined polarity, amplitude and duration through the SPC under test. The SPC conduction voltage is digitally recorded at a defined time during the current pulse duration.
+
+![Circuit diagram for Figure 8-1: Current pulse, voltage measurement circuit. A current source labeled 'G' with a pulse waveform icon is connected in series with a voltmeter labeled 'V' and a component labeled 'SPC'. The current 'I' is shown entering the SPC. The diagram is labeled K.129(18)_F8-1.](7ec4ba01d21d0840c67e18d51aeb1415_img.jpg)
+
+The diagram shows a series circuit. On the left, a current source labeled 'G' is shown with a rectangular pulse waveform icon. A current 'I' is indicated entering the circuit. In the center, a voltmeter labeled 'V' is connected in parallel across the component on the right. The component on the right is labeled 'SPC'. The entire circuit is connected between two horizontal bus lines. Below the diagram, the text 'K.129(18)\_F8-1' is present.
+
+Circuit diagram for Figure 8-1: Current pulse, voltage measurement circuit. A current source labeled 'G' with a pulse waveform icon is connected in series with a voltmeter labeled 'V' and a component labeled 'SPC'. The current 'I' is shown entering the SPC. The diagram is labeled K.129(18)\_F8-1.
+
+Figure 8-1 – Current pulse, voltage measurement circuit
+
+### 8.2.2 Pulsed voltage
+
+This circuit, shown in Figure 8-2, applies a voltage of defined polarity, amplitude and duration to the SPC under test. The SPC current is digitally recorded at a defined time during the voltage pulse duration.
+
+![Figure 8-2: Voltage pulse, current measurement circuit. A generator (G) with a voltage pulse waveform (V) is connected in series with an ammeter (A) and a Semiconductor Power Component (SPC). The circuit is labeled K.129(18)_F8-2.](76b0cd79baaedd942af4dc42f2e764b8_img.jpg)
+
+Figure 8-2: Voltage pulse, current measurement circuit. A generator (G) with a voltage pulse waveform (V) is connected in series with an ammeter (A) and a Semiconductor Power Component (SPC). The circuit is labeled K.129(18)\_F8-2.
+
+**Figure 8-2 – Voltage pulse, current measurement circuit**
+
+### 8.2.3 Current ramp
+
+This circuit, shown in Figure 8-3, forces a current of defined polarity, amplitude and duration through the SPC under test. The SPC conduction voltage is digitally recorded at a defined time during the current pulse duration.
+
+![Figure 8-3: Current ramp, voltage measurement circuit. A generator (G) with a current ramp waveform (I) is connected in parallel with a voltmeter (V) and a Semiconductor Power Component (SPC). The circuit is labeled K.129(18)_F8-3.](9b9d2abd741ed4bafe7f78f89961c663_img.jpg)
+
+Figure 8-3: Current ramp, voltage measurement circuit. A generator (G) with a current ramp waveform (I) is connected in parallel with a voltmeter (V) and a Semiconductor Power Component (SPC). The circuit is labeled K.129(18)\_F8-3.
+
+**Figure 8-3 – Current ramp, voltage measurement circuit**
+
+### 8.2.4 Surge
+
+This circuit, shown in Figure 8-4, forces a surge impulse current of defined polarity, amplitude and waveshape through the SPC under test. The SPC conduction voltage is digitally recorded at a defined event during the current impulse duration.
+
+![Figure 8-4: Surge verification and voltage measurement circuit. A generator (G) with a surge impulse current waveform is connected in parallel with a voltmeter (V) and a Semiconductor Power Component (SPC). The circuit is labeled K.129(18)_F8-4.](51db757d054ce1ce83c436a3578b56ca_img.jpg)
+
+Figure 8-4: Surge verification and voltage measurement circuit. A generator (G) with a surge impulse current waveform is connected in parallel with a voltmeter (V) and a Semiconductor Power Component (SPC). The circuit is labeled K.129(18)\_F8-4.
+
+**Figure 8-4 – Surge verification and voltage measurement circuit**
+
+### 8.2.5 Capacitance
+
+![Figure 8-5: Kelvin connected capacitance measurement. A capacitance measuring equipment with terminals H_I, H_V, L_V, and L_I is connected to a Semiconductor Power Component (SPC). The equipment is labeled with V_D, f, V_d. The circuit is labeled K.129(18)_F8-5.](e928f4874ed492d3ad4c6fa2d29aedbc_img.jpg)
+
+Figure 8-5: Kelvin connected capacitance measurement. A capacitance measuring equipment with terminals H\_I, H\_V, L\_V, and L\_I is connected to a Semiconductor Power Component (SPC). The equipment is labeled with V\_D, f, V\_d. The circuit is labeled K.129(18)\_F8-5.
+
+**Figure 8-5 – Kelvin connected capacitance measurement**
+
+## 8.3 Measuring methods for electrical characteristics
+
+### 8.3.1 Stand-off or maximum reverse working voltage, $V_{RWM}$
+
+#### a) Purpose
+
+To measure the reverse current of a diode under specified reverse voltage.
+
+- b) *Circuit diagram*
+
+Figure 8-2.
+
+- c) *Circuit description and requirements*
+
+Main elements are a voltage pulse generator of sufficient voltage and duration, a time or event programmable digital ammeter of sufficient sensitivity and the SPC under test.
+
+- d) *Measurement procedure*
+
+Using the circuit of Figure 8-2, a voltage pulse of  $V_{RWM}$  is applied to the SPC, the current  $I_R$  is measured after the initial capacitive charging current component is negligible. The same technique can be used for a diode to measure  $I_R$  for a voltage pulse of  $V_R$ , see Figure 7-1.
+
+- e) *Specified conditions*
+
+- ambient or case temperature ( $T_a$ ,  $T_c$ );
+- reverse voltage ( $V_{RWM}$  or  $V_R$ ).
+
+### 8.3.2 Breakdown voltage, $V_{(BR)}$
+
+- a) *Purpose*
+
+To measure the breakdown voltage of a diode at a specified current.
+
+- b) *Circuit diagram*
+
+Figure 8-1.
+
+- c) *Circuit description and requirements*
+
+Main elements are a current pulse generator of sufficient current and duration, a time or event programmable digital voltmeter of sufficient sensitivity and the SPC under test.
+
+- d) *Measurement procedure*
+
+Using the circuit of Figure 8-1 a current pulse of  $I_{(BR)}$  is applied to the SPC, the voltage  $V_{(BR)}$  is measured before any heating effects cause a change in the  $V_{(BR)}$  value.
+
+- e) *Specified conditions*
+
+- ambient or case temperature ( $T_a$ ,  $T_c$ );
+- breakdown current ( $I_{(BR)}$ ).
+
+### 8.3.3 Clamping voltage $V_C$
+
+- a) *Purpose*
+
+To measure the clamping voltage of a diode at a specified current.
+
+- b) *Circuit diagram*
+
+Figure 8-1 or Figure 8-4.
+
+- c) *Circuit description and requirements*
+
+Main elements are a current pulse generator of sufficient current and duration (Figure 8-1) or a defined surge impulse generator (Figure 8-4), a time or event programmable digital voltmeter of sufficient sensitivity and the SPC under test.
+
+- d) *Measurement procedure*
+
+Using the circuit of Figure 8-1 or Figure 8-4, a current pulse or impulse of  $I_{PP}$  is applied to the SPC, the maximum voltage  $V_C$  is measured after any transient effects have died out.
+
+- e) *Specified conditions*
+
+- ambient or case temperature ( $T_a$ ,  $T_c$ );
+- peak pulse current ( $I_{PP}$ );
+
+- pulse duration used if appropriate;
+- surge impulse used if appropriate.
+
+### 8.3.4 Punch-through voltage $V_{(PT)}$
+
+#### a) Purpose
+
+To measure the peak low-current voltage of a diode. This applies to punch-through or fold-back diodes.
+
+#### b) Circuit diagram
+
+Figure 8-3.
+
+#### c) Circuit description and requirements
+
+Main elements are a current ramp generator of sufficient current and duration (Figure 8-3), a time or event programmable digital voltmeter of sufficient sensitivity and the SPC under test.
+
+#### d) Measurement procedure
+
+Using the circuit of Figure 8-3, a current ramp of sufficient amplitude to reach the  $V_{(PT)}$  region is applied to the SPC. The voltage  $V_{(PT)}$  is measured by programming the digital voltage recorder to measure the maximum voltage that occurs.
+
+#### e) Specified conditions
+
+- ambient or case temperature ( $T_a$ ,  $T_c$ ).
+
+### 8.3.5 Snap-back voltage $V_{(SB)}$
+
+#### a) Purpose
+
+To measure the peak low-current voltage of a diode. This applies to punch-through or fold-back diodes.
+
+#### b) Circuit diagram
+
+Figure 8-3.
+
+#### c) Circuit description and requirements
+
+Main elements are a current ramp generator of sufficient current and duration (Figure 8-3), a time or event programmable digital voltmeter of sufficient sensitivity and the SPC under test.
+
+#### d) Measurement procedure
+
+Using the circuit of Figure 8-3, a current ramp of sufficient amplitude to reach the  $V_{(SB)}$  region is applied to the SPC. The voltage  $V_{(SB)}$  is measured by programming the digital voltage recorder to measure the minimum voltage that occurs after  $V_{(PT)}$ . The current ramp speed should be selected to avoid possible transient effects, if too fast, or heating effects, if too slow.
+
+#### e) Specified conditions
+
+- ambient or case temperature ( $T_a$ ,  $T_c$ ).
+
+### 8.3.6 Forward biased PN junction voltage, $V_F$
+
+#### a) Purpose
+
+To measure the forward voltage of a diode at a specified current.
+
+#### b) Circuit diagram
+
+Figure 8-1 or Figure 8-4.
+
+#### c) Circuit description and requirements
+
+Main elements are a current pulse generator of sufficient current and duration (Figure 8-1) or a defined surge impulse generator (Figure 8-4), a time or event programmable digital voltmeter of sufficient sensitivity and the SPC under test.
+
+#### d) *Measurement procedure*
+
+Using the circuit of Figure 8-1 or Figure 8-4, a current pulse or impulse of  $I_{PP}$  is applied to the SPC, the forward voltage  $V_F$  is measured after any transient effects have died out and before any pulse heating effects cause a change in the  $V_F$  value.
+
+#### e) *Specified conditions*
+
+- ambient or case temperature ( $T_a$ ,  $T_c$ );
+- peak pulse current ( $I_{PP}$ );
+- pulse duration used if appropriate;
+- surge impulse used if appropriate.
+
+### 8.3.7 Peak forward recovery voltage, $V_{FRM}$
+
+#### a) *Purpose*
+
+To measure the peak forward recovery voltage of a diode at a specified rate of forward current rise ( $di_F/dt$ ).
+
+#### b) *Circuit diagram*
+
+Figure 8-1.
+
+#### c) *Circuit description and requirements*
+
+Main elements are a current pulse generator of sufficient current ( $I_F$ ) and specified rate of current rise ( $di_F/dt$ ) (Figure 8-1), a time or event programmable digital voltmeter of sufficient sensitivity and the SPC under test.
+
+#### d) *Measurement procedure*
+
+Using the circuit of Figure 8-1, a current pulse is applied to the SPC, the maximum forward voltage  $V_{FRM}$  is measured after any transient effects have died out, see Figure 8-6.
+
+#### e) *Specified conditions*
+
+- ambient or case temperature ( $T_a$ ,  $T_c$ );
+- forward current ( $I_F$ );
+- rate of forward current rise ( $di_F/dt$ ).
+
+![Figure 8-6 shows two waveforms versus time (t in μs). The top graph shows the forward voltage (V) rising to a peak value V_FRM and then settling to a steady-state value V_F. The bottom graph shows the forward current (i) rising with a specified rate di_F/dt to a steady-state value I_F.](2aec26453a9ccef03f76f0a531a01a1a_img.jpg)
+
+The figure contains two vertically aligned graphs sharing a common horizontal time axis labeled  $t$  ( $\mu\text{s}$ ).
+
+The top graph plots forward voltage  $V$  on the vertical axis. The curve starts at the origin, rises sharply to a peak labeled  $V_{FRM}$ , and then decays towards a steady-state value labeled  $V_F$ . A vertical double-headed arrow indicates the magnitude of  $V_F$ .
+
+The bottom graph plots forward current  $i$  on the vertical axis. The curve starts at the origin and rises with a constant slope, indicated by a double-headed arrow and labeled  $di_F/dt$ , until it reaches a steady-state value labeled  $I_F$ . A vertical double-headed arrow indicates the magnitude of  $I_F$ .
+
+Figure 8-6 shows two waveforms versus time (t in μs). The top graph shows the forward voltage (V) rising to a peak value V\_FRM and then settling to a steady-state value V\_F. The bottom graph shows the forward current (i) rising with a specified rate di\_F/dt to a steady-state value I\_F.
+
+K.129(18)\_F8-6
+
+Figure 8-6 – Diode forward voltage and current waveforms versus time
+
+### 8.3.8 Total capacitance $C_{tot}$
+
+#### a) Purpose
+
+To measure the capacitance of a diode at a specified direct current (DC) voltage ( $V_D$ ), AC voltage ( $V_a$ ) and frequency ( $f$ ).
+
+#### b) Circuit diagram
+
+Figure 8-5.
+
+#### c) Circuit description and requirements
+
+Main elements are a Kevin connection capacitance measurement meter, the Kelvin voltage ( $H_v, L_v$ ) and current ( $H_i, L_i$ ) leads and the SPC under test.
+
+#### d) Measurement procedure
+
+Set the capacitance meter for the specified DC bias voltage ( $V_D$ ), AC test voltage ( $V_a$ ) and frequency ( $f$ ). Measure the SPC capacitance. There may be a requirement to measure the capacitance at more than one value of DC bias voltage ( $V_D$ ).
+
+#### e) Specified conditions
+
+- ambient or case temperature ( $T_a, T_c$ );
+- DC bias voltage ( $V_D$ );
+- AC test voltage ( $V_a$ );
+- frequency ( $f$ ).
+
+## 8.4 Measuring methods for thermal characteristics
+
+### 8.4.1 Introduction
+
+The measurement of thermal resistance and transient thermal impedance is based on the use of a temperature-sensitive parameter of the semiconductor as an indicator of virtual junction temperature ( $T_j$ ). The forward voltage ( $V_F$ ) of a diode, at a small percentage of rated current, can be used as the temperature-sensitive parameter or the breakdown voltage ( $V_{BR}$ ).
+
+### 8.4.2 Transient thermal impedance $Z_{th(j-a)(t)}$ or $Z_{th(j-c)(t)}$ or $Z_{th(j-l)(t)}$
+
+#### a) Purpose
+
+To measure the transient thermal impedance ( $Z_{th(j-a)(t)}$  or  $Z_{th(j-c)(t)}$  or  $Z_{th(j-l)(t)}$ ) of a SPC at a specified ambient ( $T_a$ ), case ( $T_c$ ), or lead ( $T_l$ ) temperature.
+
+#### b) Circuit diagram
+
+Figure 8-7.
+
+![Circuit diagram for transient thermal impedance test. It shows a generator (G) connected to a diode. The diode is connected to a reference current source (I_REF) and a voltmeter (V) in parallel. The voltmeter is connected to the SPC (Semiconductor Package) under test. The generator (G) is shown with a pulse waveform labeled I. The diagram is labeled K.129(18)_F8-7.](bf10cf36bba7b1d1f5ba30447da6905f_img.jpg)
+
+```
+
+graph LR
+    G[Generator G] -- Pulse I --> D{Diode}
+    D --> Node1
+    Node1 --> IREF((I_REF))
+    Node1 --> V[Voltmeter V]
+    Node1 --> SPC[SPC under test]
+    IREF --> Rail
+    V --> Rail
+    SPC --> Rail
+  
+```
+
+The diagram shows a circuit for measuring transient thermal impedance. On the left, a generator (G) is connected to a diode. The diode's anode is connected to the generator's output, and its cathode is connected to a node. From this node, three parallel branches extend to the right: a reference current source labeled  $I_{REF}$ , a voltmeter labeled V, and the semiconductor package (SPC) under test. All three branches rejoin at a common bottom rail. The generator (G) is shown with a pulse waveform labeled I. The diagram is labeled K.129(18)\_F8-7.
+
+Circuit diagram for transient thermal impedance test. It shows a generator (G) connected to a diode. The diode is connected to a reference current source (I\_REF) and a voltmeter (V) in parallel. The voltmeter is connected to the SPC (Semiconductor Package) under test. The generator (G) is shown with a pulse waveform labeled I. The diagram is labeled K.129(18)\_F8-7.
+
+**Figure 8-7 – Transient thermal impedance test circuit**
+
+#### c) Circuit description and requirements
+
+Main elements are a reference current source ( $I_{REF}$ ) for the temperature sensitive parameter, a high current pulsed source ( $I \gg I_{REF}$ ) for applying the power pulse to the SPC, a time or event programmable digital voltmeter of sufficient sensitivity and the SPC under test.
+
+#### d) *Measurement procedure*
+
+The  $I_{REF}$  current flows continuously. The current pulse  $I$  should be of sufficient amplitude that it causes a temperature rise of at least 50 K at the end of the pulse duration ( $t$ ). The temperature rise is calculated from the difference in the reference parameter immediately before and immediately after the pulse divided by the reference parameter temperature coefficient. The transient thermal impedance is calculated from the calculated temperature rise divided by the product of the pulsed current and the average voltage measured during the pulse duration.
+
+#### e) *Specified conditions*
+
+- ambient or case or lead temperature ( $T_a$ ,  $T_c$ ,  $T_l$ );
+- pulse duration ( $t$ ).
+
+### 8.4.3 Thermal resistance $R_{th(j-a)}$ or $R_{th(j-c)}$ or $R_{th(j-l)}$
+
+The technique for thermal resistance ( $R_{th(j-a)}$  or  $R_{th(j-c)}$  or  $R_{th(j-l)}$ ) is the same as transient thermal impedance, see clause 8.4.2, except the pulse duration must be long enough for the temperature rise to have stabilised at a constant value. Typically, the pulse duration to achieve thermal equilibrium is in the region of 100 s.
+
+### 8.4.4 Temperature coefficient of breakdown voltage $V_{(BR)}$ , $\alpha V_{(BR)}$
+
+#### a) *Purpose*
+
+To measure the temperature coefficient of breakdown voltage ( $\alpha V_{(BR)}$ ) of a diode at a specified current. This approach can also be used for determining the temperature coefficient of forward voltage ( $\alpha V_F$ ).
+
+#### b) *Circuit diagram*
+
+Figure 8-1.
+
+#### c) *Circuit description and requirements*
+
+Main elements are a current pulse generator of sufficient current and duration, a time or event programmable digital voltmeter of sufficient sensitivity and the SPC under test. The SPC is mounted in a temperatures control oven
+
+#### d) *Measurement procedure*
+
+Using the circuit of Figure 8-1, a current pulse of  $I_{(BR)}$  is applied to the SPC, the voltage  $V_{(BR)}$  is measured before any heating effects cause a change in the  $V_{(BR)}$  value. This measurement is repeated at several temperatures within the specified operating temperature range. The temperature coefficient between successive temperatures is the change in  $V_{(BR)}$  divided by the change in temperature. Often  $\alpha_{V(BR)}$  is quoted as a %/K obtained by multiplying the calculated  $V/K$  value by 100 and dividing by the average value of  $V_{(BR)}$  between the two temperatures.
+
+#### e) *Specified conditions*
+
+- temperature range;
+- breakdown current ( $I_{(BR)}$ ).
+
+## 8.5 Verification test methods for ratings (limiting values)
+
+### 8.5.1 Peak pulse current, $I_{PP}$
+
+#### a) *Purpose*
+
+To verify the peak pulse current ( $I_{PP}$ ) of a diode at a specified ambient temperature ( $T_a$ ).
+
+#### b) *Circuit diagram*
+
+Figure 8-2 and Figure 8--4.
+
+#### c) *Circuit description and requirements*
+
+The Figure 8-2 circuit has a voltage pulse generator to apply the specified  $V_{\text{RMW}}$  or  $V_{\text{R}}$  to the SPC. A time or event programmable digital ammeter of sufficient sensitivity measures the  $I_{\text{R}}$  value. The Figure 8-4 circuit applies a specified surge impulse of  $I_{\text{PP}}$  to the SPC for a specified number of times and polarities.
+
+#### d) *Measurement procedure*
+
+Using the circuit of Figure 8-2, measure the selected SPC  $I_{\text{R}}$  value, see clause 8.3.1. Using the circuit of Figure 8-4 apply the specified surge impulse of  $I_{\text{PP}}$  to the SPC for the specified number of times and polarities. After the surge impulse testing is completed re-measure the selected SPC  $I_{\text{R}}$  value. The final value of  $I_{\text{R}}$  shall not have degraded to exceed the specified maximum limit  $I_{\text{R}}$  value.
+
+#### e) *Specified conditions*
+
+- ambient or case temperature ( $T_{\text{a}}$ ,  $T_{\text{c}}$ );
+- peak pulse current ( $I_{\text{PP}}$ );
+- surge impulse waveshape;
+- surge impulse repetitions and polarities;
+- maximum data sheet value of  $I_{\text{R}}$ .
+
+### 8.5.2 Maximum peak pulse power $P_{\text{PP}}$
+
+This parameter is fictive in that it is the product of two values that do not necessarily occur at the same instant of time. The maximum peak pulse power value ( $P_{\text{PP}}$ ) is the product of the peak pulse current ( $I_{\text{PP}}$ ) and the maximum value of clamping voltage ( $V_{\text{C}}$ ).
+
+### 8.5.3 Power dissipation, $P_{\text{tot}}$
+
+The maximum power dissipation at a specified ambient temperature is the quotient of the difference between the maximum junction temperature ( $T_{\text{JMAX}}$ ) and the specified ambient ( $T_{\text{a}}$ ) and the thermal resistance value ( $R_{\text{th(j-a)}}$ ).
+
+# 9 Mechanical requirements and identification
+
+## 9.1 Robustness of terminations
+
+If applicable, the user shall specify a suitable test from [b-IEC 60068-2-21].
+
+## 9.2 Solderability
+
+Solder terminations shall meet the requirements of [b-IEC 60068-2-20].
+
+## 9.3 Marking
+
+Legible and permanent marking shall be applied to the surge protective component, as necessary, to ensure that the user can determine the following information by inspection:
+
+- a) manufacturer;
+- b) year of manufacture;
+- c) component number or code.
+
+If requested and agreed, the customer's identification should be marked on each component.
+
+NOTE 1 – The necessary information can also be coded.
+
+NOTE 2 – When space is not sufficient for printing these data, it should be provided in the technical documentation after agreement between the manufacturer and purchaser.
+
+## **9.4 Documentation**
+
+Documents shall be provided to the user so that from the information in clause 9.3, the user can determine the following additional information:
+
+- a) appropriate component parameters as set out in this standard;
+- b) component mounting requirements and processes;
+- c) ordering information.
+
+The following information should be supplied by the user:
+
+- a) drawing giving all dimensions, finishes and termination details;
+- b) type or model;
+- c) quantity;
+- d) quality assurance requirements.
+
+# Bibliography
+
+- [b-ITU-T K.11] Recommendation ITU-T K.11 (2009), *Principles of protection against overvoltages and over currents*.
+- [b-ITU-T K.20] Recommendation ITU-T K.20 (2017), *Resistibility of telecommunication equipment installed in a telecommunication centre to overvoltages and overcurrents*.
+- [b-ITU-T K.21] Recommendation ITU-T K.21 (2017), *Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents*.
+- [b-ITU-T K.44] Recommendation ITU-T K.44 (2017), *Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents – Basic Recommendation*.
+- [b-ITU-T K.45] Recommendation ITU-T K.45 (2017), *Resistibility of telecommunication equipment installed in the access and trunk networks to overvoltages and overcurrents*.
+- [b-IEC IEV] IEC 60050, *International Electrotechnical Vocabulary (IEV)*.
+- [b-IEC 60068-2-20] IEC 60068-2-20 (2008), *Environmental testing – Part 2-20: Tests – Test T: Test methods for solderability and resistance to soldering heat of devices with leads*.
+- [b-IEC 60068-2-21] IEC 60068-2-21 (2008) *Environmental testing – Part 2-21: Tests – Test U: Robustness of terminations and integral mounting devices*.
+- [b-IEC 60617] IEC 60617 (2012), *Graphical symbols for diagrams*.
+- [b-IEC 60721-3-3] IEC 60721-3-3:1994+AMD1:1995+AMD2 (1996), *Classification of environmental conditions – Part 3-3: Classification of groups of environmental parameters and their severities – Stationary use at weather protected locations*.
+- [b-IEC 60721-3-9] IEC 60721-3-9 (1993), *Classification of environmental conditions - Part 3: Classification of groups of environmental parameters and their severities – Section 9: Microclimates inside products*.
+- [b-IEC 60747-1] IEC 60747-1:2006+AMD1 (2010), *Semiconductor devices – Part 1: General*.
+- [b-IEC 60747-2] IEC 60747-2 (2016), *Semiconductor devices – Part 2: Discrete devices – Rectifier diodes*.
+- [b-IEC 60747-3] IEC 60747-3 (2013), *Semiconductor devices – Part 3: Discrete devices: Signal, switching and regulator diodes*.
+- [b-IEC 60749-1] IEC 60749-1 (2002), *Semiconductor devices – Mechanical and climatic test methods – Part 1: General*.
+- [b-IEC 61000-5-5] IEC 61000-5-5 (1996), *Electromagnetic compatibility (EMC) – Part 5: Installation and mitigation guidelines – Section 5: Specification of protective devices for HEMP conducted disturbance. Basic EMC Publication*.
+- [b-IEC 61643-321] IEC 61643-321 (2001), *Components for low-voltage surge protective devices – Part 321: Specifications for avalanche breakdown diode (ABD)*.
+
+- [b-IEC 62624] IEC 62624 (2009), *Test methods for measurement of electrical properties of carbon nanotubes.*
+- [b-IEC TR 62240-1] IEC TR 62240-1 (2018), *Process management for avionics - Electronic components capability in operation – Part 1: Temperature uprating.*
+
+
+
+
+
+# SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| Series E        | Overall network operation, telephone service, service operation and human factors                                                                         |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| <b>Series K</b> | <b>Protection against interference</b>                                                                                                                    |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/K/T-REC-K.132-201801-I_PDF-E/raw.md

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+
+
+I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
+
+# **ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+# **K.132**
+
+(01/2018)
+
+### SERIES K: PROTECTION AGAINST INTERFERENCE
+
+---
+
+**Electromagnetic compatibility requirements of  
+electromagnetic disturbances from lighting  
+equipment located in telecommunication  
+facilities**
+
+Recommendation ITU-T K.132
+
+**ITU-T**
+
+![ITU logo](84a1d09fb489061482111515543b60dc_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a blue globe with a red lightning bolt striking it. To the right of the globe, the text "International Telecommunication Union" is written in blue.
+
+ITU logo
+
+**International  
+Telecommunication  
+Union**
+
+
+
+# Recommendation ITU-T K.132
+
+# Electromagnetic compatibility requirements of electromagnetic disturbances from lighting equipment located in telecommunication facilities
+
+## Summary
+
+Recommendation ITU-T K.132 specifies limits and measurement methods of electromagnetic disturbances from lighting equipment for installation in telecommunication facilities. The requirements in Recommendation ITU-T K.132 are based on CISPR 15 and CISPR 32 for continuous electromagnetic disturbances. Furthermore, Recommendation ITU-T K.132 specifies the limit of transient conducted current and measurement methods.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T K.132    | 2018-01-13 | 5           | <a href="http://handle.itu.int/11.1002/1000/13455">11.1002/1000/13455</a> |
+
+## Keywords
+
+Disturbance, lighting equipment, transient.
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2018
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+###### Page
+
+|                   |                                                                                                          |    |
+|-------------------|----------------------------------------------------------------------------------------------------------|----|
+| 1                 | Scope.....                                                                                               | 1  |
+| 2                 | References.....                                                                                          | 1  |
+| 3                 | Definitions .....                                                                                        | 1  |
+| 3.1               | Terms defined elsewhere .....                                                                            | 1  |
+| 3.2               | Terms defined in this Recommendation.....                                                                | 2  |
+| 4                 | Abbreviations and acronyms .....                                                                         | 2  |
+| 5                 | Conventions .....                                                                                        | 2  |
+| 6                 | Limits.....                                                                                              | 2  |
+| 6.1               | Limits for conducted disturbances at mains ports .....                                                   | 3  |
+| 6.2               | Limits for radiated disturbances .....                                                                   | 3  |
+| 6.3               | Limits for transient currents at mains port .....                                                        | 4  |
+| 7                 | Measurement methods .....                                                                                | 4  |
+| 7.1               | Conducted disturbance at mains ports .....                                                               | 4  |
+| 7.2               | Radiated disturbances .....                                                                              | 4  |
+| 7.3               | Transient currents at mains port .....                                                                   | 4  |
+| Annex A           | Transient current measurement method at a mains port.....                                                | 5  |
+| A.1               | General .....                                                                                            | 5  |
+| A.2               | Measurement system layout .....                                                                          | 5  |
+| A.3               | Measurement instruments.....                                                                             | 6  |
+| A.4               | Test site.....                                                                                           | 7  |
+| A.5               | Measurement procedure .....                                                                              | 7  |
+| Appendix I        | – The measurement example of radiated disturbance over 300 MHz from<br>lighting equipment.....           | 9  |
+| I.1               | Measurement method .....                                                                                 | 9  |
+| I.2               | Measurement results.....                                                                                 | 9  |
+| Appendix II       | An example of a malfunction caused by a transient disturbance on switching<br>on lighting equipment..... | 10 |
+| II.1              | An example of actual condition.....                                                                      | 10 |
+| II.2              | An example of measurement in a laboratory.....                                                           | 11 |
+| Bibliography..... |                                                                                                          | 13 |
+
+
+
+# Recommendation ITU-T K.132
+
+## Electromagnetic compatibility requirements of electromagnetic disturbances from lighting equipment located in telecommunication facilities
+
+# 1 Scope
+
+This Recommendation specifies limits and measurement methods for electromagnetic disturbances from lighting equipment for installation in telecommunication facilities.
+
+The electromagnetic disturbances specified in this Recommendation are continuous conducted and radiated disturbances emitted when lighting equipment is operating, and conducted transient disturbances generated when it is switched on and off. The frequency range of continuous conducted disturbances, from 9 kHz to 30 MHz, and continuous radiated disturbances, in the frequency range 30 MHz to 1 GHz, lie within the scope of this Recommendation.
+
+Additionally, this Recommendation specifies the limit of conducted transient disturbances to prevent malfunctions in telecommunication equipment that transmits signals below 30 MHz, such as the integrated service digital network (ISDN), asymmetric digital subscriber line (ADSL) and very high bit rate digital subscriber line (VDSL).
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+[ITU-T K.48] Recommendation ITU-T K.48 (2006), *EMC requirements for telecommunication equipment – Product family Recommendation*.
+
+[CISPR 15] CISPR 15:2015, *Limits and methods of measurement of radio disturbance characteristics of electrical lighting and similar equipment*.
+
+[CISPR 16-1-2] CISPR 16-1-2:2017, *Specification for radio disturbance and immunity measuring apparatus and methods – Part 1-2: Radio disturbance and immunity measuring apparatus – Coupling devices for conducted disturbance measurements*.
+
+[CISPR 32] CISPR 32:2015, *Electromagnetic compatibility of multimedia equipment – Emission requirements*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 conducted disturbance** [b-IEC 60050], 161-03-27: Electromagnetic disturbance for which the energy is transferred via one or more conductors.
+
+**3.1.2 electromagnetic disturbance** [b-IEC 60050], 161-01-05: Any electromagnetic phenomenon which can degrade the performance of a device, equipment or system, or adversely affect living or inert matter.
+
+**3.1.3 port** [b-IEC 60050], 161-01-27: Particular interface of an equipment which couples this equipment with the external electromagnetic environment and through which the equipment is influenced by this environment.
+
+**3.1.4 radiated disturbance** [b-IEC 60050], 161-03-28: Electromagnetic disturbance for which the energy is transferred through space in the form of electromagnetic waves.
+
+**3.1.5 transient** [b-IEC 60050], 161-02-01: Pertaining to or designating a phenomenon or a quantity which varies between two consecutive steady states during a time interval short compared with the timescale of interest.
+
+## **3.2 Terms defined in this Recommendation**
+
+This Recommendation defines the following term:
+
+**3.2.1 telecommunication facility:** A facility that mainly houses telecommunication equipment, such as telecommunication equipment rooms or remotely located telecommunication sites.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|      |                                            |
+|------|--------------------------------------------|
+| ADSL | Asymmetric Digital Subscriber Line         |
+| CDN  | Coupling and Decoupling Network            |
+| CRC  | Cyclic Redundancy Check                    |
+| EUT  | Equipment Under Test                       |
+| ISDN | Integrated Service Digital Network         |
+| LED  | Light-Emitting Diode                       |
+| OATS | Open-Air Test Site                         |
+| PC   | Personal Computer                          |
+| RBW  | Resolution Bandwidth                       |
+| SAC  | Semi-Anechoic Chamber                      |
+| VDSL | Very high bit rate Digital Subscriber Line |
+
+# **5 Conventions**
+
+None.
+
+# **6 Limits**
+
+The limits of disturbance from telecommunication equipment are specified in [ITU-T K.48] and [CISPR 32]. In order to harmonize the levels of disturbances from telecommunication equipment and lighting equipment that are installed in a telecommunication equipment room, the disturbance from lighting equipment should be the same or lower than that from telecommunication equipment.
+
+In this Recommendation, the limits of continuous conducted and radiated disturbances in the frequency range 9 kHz to 300 MHz from lighting equipment are specified with reference to [CISPR 15]. The limits of radiated continuous disturbance above 300 MHz to 1 GHz are specified with reference to [CISPR 32]. The limit is set also between 300 MHz and 1 GHz, since radiated disturbance in this frequency range is observed in commercially available light sources, as shown in Appendix I. Moreover, a limit for transient disturbance is required in this Recommendation, since malfunctions in transmission systems have been reported caused by transient disturbance generated
+
+by lighting equipment switching operations in telecommunication equipment rooms, as shown in Appendix II.
+
+## 6.1 Limits for conducted disturbances at mains ports
+
+Disturbances measured by a quasi-peak and average detector at the mains ports shall not be greater than the values in Table 1.
+
+**Table 1 – Test methods and limits for conducted disturbance voltage at main ports  
+(from [CISPR 15])**
+
+| Frequency range    | Test methods       | Limits (dB $\mu$ V) |          |
+|--------------------|--------------------|---------------------|----------|
+|                    | Reference standard | Quasi-peak          | Average  |
+| 9 kHz to 50 kHz    | [CISPR 15]         | 110                 | –        |
+| 50 kHz to 150 kHz  |                    | 90 to 80            | –        |
+| 150 kHz to 0.5 MHz |                    | 66 to 56            | 56 to 46 |
+| 0.5 MHz to 5.0 MHz |                    | 56                  | 46       |
+| 5 MHz to 30 MHz    |                    | 60                  | 50       |
+
+NOTE 1 – 1  $\mu$ V is taken to be 0 dB $\mu$ V.
+
+NOTE 2 – If the quasi-peak value of measurement is less than the limit specified for average value detection, the equipment shall be deemed to meet both limits and there is no need to measure the average value.
+
+NOTE 3 – The lower limit shall apply at transition frequency.
+
+NOTE 4 – The limit shall decrease linearly with the logarithm of frequency.
+
+NOTE 5 – For electrode-less lamps and luminaires, the limit in the frequency range 2.51 to 3.00 MHz is not applied in this Recommendation.
+
+## 6.2 Limits for radiated disturbances
+
+The limit values of radiated disturbances shall not be greater than the values at the specified distance given in Table 2.
+
+**Table 2 – Test methods and limits for radiated disturbances (10 m)**
+
+| Frequency range (MHz) | Test methods                                                           |                    | Quasi-peak limit (dB $\mu$ V/m) |
+|-----------------------|------------------------------------------------------------------------|--------------------|---------------------------------|
+|                       | Measurement facility                                                   | Reference standard |                                 |
+| 30-230                | Semi-anechoic chamber (SAC) or open-air test site (OATS) 10 m distance | [CISPR 15]         | 30                              |
+| 230-300               |                                                                        |                    | 37                              |
+| 300-1000              |                                                                        | [CISPR 32]         | 37                              |
+
+NOTE 1 – 1  $\mu$ V/m is taken to be 0 dB $\mu$ V/m.
+
+NOTE 2 – The lower limit shall apply at the transition frequency.
+
+NOTE 3 – Add 10 dB to the limit when measurement distance is 3 m. Subtract 10 dB from the limit when the measurement distance is 30 m.
+
+NOTE 4 –The coupling and decoupling network (CDN) measurement method described in Annex B of [CISPR 15] is not applied in this Recommendation, because the measurement method has not yet been established.
+
+## 6.3 Limits for transient currents at mains port
+
+The limit for transient currents that arise at a mains port when a piece of lighting equipment is turned on and off is shown in Table 3.
+
+**Table 3 – Test method and limit for transient current**
+
+| Test methods | Limit              |
+|--------------|--------------------|
+| Annex A      | 5 A <sub>p-p</sub> |
+
+# 7 Measurement methods
+
+This clause describes the measurement methods for electromagnetic disturbances emitted from lighting equipment.
+
+## 7.1 Conducted disturbance at mains ports
+
+- 1) Measurement arrangement and procedures
+
+Measurement arrangement and procedure shall comply with [CISPR 15].
+
+- 2) Components of lighting equipment and operating conditions
+
+The equipment under test (EUT) for the emission test shall consist of all components based on the manufacturer's specification for the equipment. If the lighting equipment is of the twin tube type, measurement shall be carried out with the two tubes attached.
+
+Operating conditions of the lighting equipment shall comply with clause 6 of [CISPR 15].
+
+- 3) Measurement instruments and test site
+
+Measurement instruments and test site shall comply with [CISPR 32].
+
+## 7.2 Radiated disturbances
+
+- 1) Measurement arrangement and procedures
+
+Measurement arrangement and procedure shall comply with [CISPR 32]. General measurement arrangements and test procedures are given in [CISPR 15].
+
+- 2) Components of lighting equipment and operating conditions
+
+The EUT for the emission test shall consist of all components based on the manufacturer's specification for the equipment. If the lighting equipment is of the twin tube type, measurement shall be carried out with the two tubes attached. Operating conditions shall comply with clause 6 of [CISPR 15].
+
+- 3) Measurement instruments and test site
+
+Measurement instruments and test site shall comply with [CISPR 32].
+
+## 7.3 Transient currents at mains port
+
+- 1) Measurement arrangement and procedures
+
+Measurement arrangement and procedure shall comply with Annex A.
+
+- 2) Components of lighting equipment and operating conditions
+
+Components of lighting equipment shall be based on normal conditions provided by the manufacturer. If the lighting equipment is of the twin tube type, measurement shall be carried out with the two tubes attached.
+
+Operating conditions shall comply with clause 6 of [CISPR 15].
+
+- 3) Measurement instruments and locations
+
+Measurement instruments and locations shall comply with Annex A.
+
+# Annex A
+
+## Transient current measurement method at a mains port
+
+(This annex forms an integral part of this Recommendation.)
+
+### A.1 General
+
+This clause specifies the measurement method for transient currents at mains ports that arise when lighting equipment is switched on or off in an environment in which the lighting equipment is connected to the mains network and the supply is switched electronically or mechanically.
+
+### A.2 Measurement system layout
+
+The measurement system is shown in Figure A.1. One of the phase lines of the power supply to the EUT is clamped by a current probe. The transient current on the phase line is measured when the switch is turned on and off using an oscilloscope. In addition, a differential voltage probe is connected between the lines of the power supply to the EUT. The power switch is turned on or off using a switch that can operate at a specific phase of the power supply voltage. A circuit that simulates the power impedance is inserted between the EUT and the programmable switch. The length of the line between the EUT and the power impedance simulation circuit shall be 0.8 m. The current probe should be set to the phase line of the power supply to the EUT at a distance of 0.1 m from the EUT. The mains power outlet at the measuring site can be used, but a correction capacitor shall be inserted between the power line and the mains port of the switch. The external trigger port of the oscilloscope shall be connected to the synchronization signal output port of the switch. If the programmable switch does not have a trigger signal output, the output of the differential voltage probe can be used as a triggering signal.
+
+The EUT, the programmable switch, the correction capacity and the power impedance simulation circuit shall be placed on a table of an insulating material at a height of 0.4 m above the reference ground plane. The reference ground plane shall be made of metal extending more than 0.5 m from the edge of the EUT and 2 m × 2 m in size or larger. If the EUT has an earthing port, it shall be connected to the reference ground plane with as short a conducting wire as possible. An artificial mains network, which is used to measure the continuous conducted disturbances, and the load except for the EUT shall not be connected to the transient current measurement system.
+
+![Figure A.1 – Transient current measurement system. The diagram shows a series of components connected in a circuit: a Power Supply (PS) connected to a Capacitor (C), which is connected to a Programmable Switch (SW) with a Voltage detector, which is connected to an Artificial Network (AN). A Differential Voltage Probe (DVP) is connected across the AN. A Current Probe (CP) is connected to the AN. The AN is connected to the Equipment Under Test (EUT). The EUT is connected to a Ground plane. The PS is connected to the Ground plane. The SW is connected to the Ground plane. The AN is connected to the Ground plane. The EUT is connected to the Ground plane. The DVP is connected to the Ground plane. The CP is connected to the Ground plane. The OS (Oscilloscope) is connected to the DVP and the CP. The SYN (Signal synchronized with switching) is connected to the OS. The IS (Insulating support) is shown below the components, with dimensions 0.1 m, 0.8 m, and 0.4 m. The Ground plane is shown at the bottom.](d4af765160d04ecef538e5066006dc77_img.jpg)
+
+EUT: Equipment under test                      CO: Current probe  
+ OS: Oscilloscope                                      DVP: Differential voltage probe  
+ SW: Programmable switch                      SYN: Signal synchronized with switching  
+ C: Capacitor                                            PS: Power supply  
+ AN: Artificial network                            IS: Insulating support
+
+K.132(18)\_FA.1
+
+Figure A.1 – Transient current measurement system. The diagram shows a series of components connected in a circuit: a Power Supply (PS) connected to a Capacitor (C), which is connected to a Programmable Switch (SW) with a Voltage detector, which is connected to an Artificial Network (AN). A Differential Voltage Probe (DVP) is connected across the AN. A Current Probe (CP) is connected to the AN. The AN is connected to the Equipment Under Test (EUT). The EUT is connected to a Ground plane. The PS is connected to the Ground plane. The SW is connected to the Ground plane. The AN is connected to the Ground plane. The EUT is connected to the Ground plane. The DVP is connected to the Ground plane. The CP is connected to the Ground plane. The OS (Oscilloscope) is connected to the DVP and the CP. The SYN (Signal synchronized with switching) is connected to the OS. The IS (Insulating support) is shown below the components, with dimensions 0.1 m, 0.8 m, and 0.4 m. The Ground plane is shown at the bottom.
+
+**Figure A.1 – Transient current measurement system**
+
+### A.3 Measurement instruments
+
+The basic configuration of the system for transient current measurement is shown in Figure A.1. Measurement instruments used for the system are specified in clauses A.3.1 to A.3.6.
+
+#### A.3.1 Oscilloscope
+
+An oscilloscope that can take more than 250 million samples per second and can start sampling with an external trigger shall be used. There shall be at least two input channels for waveform monitoring and another channel for trigger input. A peak detection mode may be selected in order to record the true peak value.
+
+#### A.3.2 Programmable switch (electronic switch for the on/off control of the power supply)
+
+An electronic switch that can detect the phase of the power supply voltage and can switch the power on or off when the phase is  $90^\circ$  or  $270^\circ$  shall be used. An electronic switch shall be able to output a signal to the external trigger input of an oscilloscope at an instant when the power is switched on or off in order to measure the current waveform in synchronization with the power switching operation. However, if a programmable switch cannot be acquired, the peak level of the transient current may be obtained by turning a hand-operated switch on and off 30 times.
+
+#### A.3.3 Current probe
+
+The current probe for measurement shall conform to [CISPR 16-1-2], and the measurement frequency shall cover the range 30 Hz to 100 MHz, and shall measure a peak current of around 30 A.
+
+#### A.3.4 Differential voltage probe
+
+A differential voltage probe shall be able to measure the supply voltage of the mains. This probe is mainly used to verify that the timing of switching is at the maximum and minimum of the power supply voltage.
+
+If the programmable switch does not have a function to output the trigger signal, the probe can be used as trigger detection.
+
+#### A.3.5 Compensation capacitor
+
+In this test, the commercial mains are also used to supply power to the lighting equipment. However, the impedance of commercial mains changes depending on the measurement site. A capacitor (with a capacitance of 10  $\mu\text{F}$ ) shall be inserted between the mains port of the programmable switch and the power cable to eliminate the effect of the mains' impedance at the measurement site. The capacitors may be connected in parallel to obtain the necessary capacitance and a withstand voltage of 440 V or higher is desirable.
+
+#### A.3.6 Power impedance simulation circuit
+
+The power impedance simulation circuit shall have the impedance characteristics shown in Figure A.2 in the frequency range 1 kHz to 10 MHz. The impedance of the circuit shall be measured at the port of the EUT when the port on the programmable switch side is shorted.
+
+The allowable deviation of the impedance shall be  $\pm 20\%$ , and that of the impedance phase angle  $\pm 10^\circ$ .
+
+![Figure A.2: Impedance characteristics of a power impedance simulation circuit. It includes a circuit diagram, a component value table, an impedance formula, and a graph of magnitude and phase angle vs. frequency.](8791f79b259a7463279c1aeb14c31580_img.jpg)
+
+The figure illustrates the impedance characteristics of a power impedance simulation circuit. It consists of a circuit diagram, a table of component values, an impedance formula, and a graph of magnitude and phase angle versus frequency.
+
+**Circuit Diagram:** The diagram shows an equivalent circuit with three components: R1, R2, and R3. R1 and R2 are connected in parallel, and this combination is connected in series with R3. The input terminals are labeled 'Equivalent circuit'.
+
+**Component Values:**
+
+| R1 [ $\Omega$ ] | R2 [ $\Omega$ ] | L1 [ $\mu\text{H}$ ] |
+|-----------------|-----------------|----------------------|
+| 85              | 0.5             | 10                   |
+
+**Impedance Formula:**
+
+$$Z = \frac{R1 (R2 + j\omega L1)}{R1 + R2 + j\omega L1}$$
+
+**Graph:** The graph plots Magnitude [ $\Omega$ ] on the left y-axis (0 to 100) and Phase angle [ $^\circ$ ] on the right y-axis (0 to 90) against Frequency [MHz] on a logarithmic x-axis (0.001 to 10). The 'Magnitude' curve (solid line) starts at approximately 10  $\Omega$  at 0.001 MHz, peaks at about 80  $\Omega$  at 0.1 MHz, and then decreases to about 10  $\Omega$  at 10 MHz. The 'Phase angle' curve (dashed line) starts at 0  $^\circ$  at 0.001 MHz, rises to about 80  $^\circ$  at 0.1 MHz, and then decreases to about 10  $^\circ$  at 10 MHz.
+
+Figure A.2: Impedance characteristics of a power impedance simulation circuit. It includes a circuit diagram, a component value table, an impedance formula, and a graph of magnitude and phase angle vs. frequency.
+
+Figure A.2 – Impedance characteristics of a power impedance simulation circuit
+
+## A.4 Test site
+
+A shielded room shall be used for the measurement of transient currents so that transient currents from the EUT can be isolated from ambient noise. The ambient noise measured at the site while the power switch is off (i.e., when no disturbances are emitted by the EUT) shall be small enough not to influence the measurement.
+
+## A.5 Measurement procedure
+
+The transient voltage shall be measured at both lines of power supply to the EUT. It is necessary to measure transient currents of each of the two power wires at the time of switching on and switching off when the phase of the mains voltage is  $90^\circ$  and  $270^\circ$  as shown in Figure A.3. In other words, transient currents shall be measured under a total of eight conditions. The timing of the switch operation shall be verified by measuring the waveform of the mains with the differential voltage probe.
+
+The peak levels of the transient current can be observed several microseconds or several seconds after the switching on or off of the power. An appropriate time span or triggering delay time shall be determined by checking the transient current waveforms so that the peak value of the current shall be overlooked. The recording length of the oscilloscope shall be 50 thousand samples or greater.
+
+![A graph showing a sinusoidal voltage waveform over time. The y-axis is labeled 'Voltage [V]' and ranges from -150 to 150. The bottom x-axis is labeled 'Time [ms]' and ranges from -5 to 30. The top x-axis is labeled 'Phase [degree]' and ranges from -90 to 540. The waveform starts at -150 V at -5 ms, crosses zero at 0 ms, reaches a peak of approximately 140 V at 5 ms, crosses zero at 10 ms, reaches a trough of approximately -140 V at 15 ms, crosses zero at 20 ms, reaches a peak of approximately 140 V at 25 ms, and crosses zero at 30 ms. A vertical dashed line at 5 ms indicates the timing at which the programmable switch turns the power on or off. An arrow points from the text 'Voltage waveform of commercial power supply in the case of 100 V/50 Hz' to the peak at 5 ms. Another arrow points from the text 'The timing at which the programmable switch turns the power on or off' to the vertical dashed line at 5 ms.](0b8b087a7baa471015d3ffeaa43d9a6c_img.jpg)
+
+Voltage waveform of commercial power supply  
+in the case of 100 V/50 Hz
+
+Phase [degree]
+
+Voltage [V]
+
+Time [ms]
+
+The timing at which the programmable switch turns the power on or off
+
+K.132(18)\_FA.3
+
+A graph showing a sinusoidal voltage waveform over time. The y-axis is labeled 'Voltage [V]' and ranges from -150 to 150. The bottom x-axis is labeled 'Time [ms]' and ranges from -5 to 30. The top x-axis is labeled 'Phase [degree]' and ranges from -90 to 540. The waveform starts at -150 V at -5 ms, crosses zero at 0 ms, reaches a peak of approximately 140 V at 5 ms, crosses zero at 10 ms, reaches a trough of approximately -140 V at 15 ms, crosses zero at 20 ms, reaches a peak of approximately 140 V at 25 ms, and crosses zero at 30 ms. A vertical dashed line at 5 ms indicates the timing at which the programmable switch turns the power on or off. An arrow points from the text 'Voltage waveform of commercial power supply in the case of 100 V/50 Hz' to the peak at 5 ms. Another arrow points from the text 'The timing at which the programmable switch turns the power on or off' to the vertical dashed line at 5 ms.
+
+**Figure A.3 – Example of a voltage waveform**
+
+# Appendix I
+
+## The measurement example of radiated disturbance over 300 MHz from lighting equipment
+
+(This appendix does not form an integral part of this Recommendation.)
+
+This appendix provides an example of measurement of a radiated disturbance from lighting equipment with a frequency over 300 MHz.
+
+### I.1 Measurement method
+
+Since [CISPR 15] specifies the measurement method for radiated disturbances below 300 MHz from the lighting equipment, the radiated disturbance is measured with reference to [CISPR 32] [test distance: 10 m; detection: quasi peak; resolution bandwidth (RBW): 120 kHz]. In this measurement, the EUT (power source: single phase AC 100 V, power consumption: 7 W) was selected from commercially available light-emitting diode (LED) sources. A biconical antenna was used for measurement in the frequency range 30 MHz to 300 MHz and log-periodic antenna was used for frequencies over 300 MHz.
+
+### I.2 Measurement results
+
+Figure I.1 shows radiated disturbance measurement results, in which the red line represents the vertically polarized wave and the blue line represents the horizontally polarized wave. The result for the vertically polarized wave exceeds the quasi-peak limit in the frequency range lower than 300 MHz. Although radiated disturbance is higher, the limit was observed even at a frequencies higher than 300 MHz; no limit is currently specified in [CISPR 15]. Therefore, radiated disturbances in the frequency range 300 MHz to 1 GHz from lighting equipment located in a telecommunication equipment room is specified in this Recommendation.
+
+![Figure I.1: Measured continuous radiated disturbance using a light-emitting diode source as an example. The graph shows Electric field strength (dBμV/m) on the Y-axis (0 to 60) versus Frequency (MHz) on the X-axis (10.00 to 1000.00). The red line represents the Vertically polarized wave, and the blue line represents the Horizontally polarized wave. The vertically polarized wave shows higher field strength, peaking around 55 dBμV/m at 100 MHz, while the horizontally polarized wave peaks around 35 dBμV/m at 100 MHz.](4a8166688ed7276efb173f550ba47eb4_img.jpg)
+
+The figure is a line graph showing the measured continuous radiated disturbance from a light-emitting diode (LED) source. The Y-axis represents the Electric field strength in dBμV/m, ranging from 0 to 60. The X-axis represents the Frequency in MHz, ranging from 10.00 to 1000.00 on a logarithmic scale. Two data series are plotted: a red line for the vertically polarized wave and a blue line for the horizontally polarized wave. The red line shows higher field strength, with peaks around 55 dBμV/m at 100 MHz and 500 MHz. The blue line shows lower field strength, with peaks around 35 dBμV/m at 100 MHz and 300 MHz. The graph is labeled 'K.132(18)\_FI.1' in the bottom right corner.
+
+Figure I.1: Measured continuous radiated disturbance using a light-emitting diode source as an example. The graph shows Electric field strength (dBμV/m) on the Y-axis (0 to 60) versus Frequency (MHz) on the X-axis (10.00 to 1000.00). The red line represents the Vertically polarized wave, and the blue line represents the Horizontally polarized wave. The vertically polarized wave shows higher field strength, peaking around 55 dBμV/m at 100 MHz, while the horizontally polarized wave peaks around 35 dBμV/m at 100 MHz.
+
+Figure I.1 – Measured continuous radiated disturbance using a light-emitting diode source as an example
+
+# Appendix II
+
+## An example of a malfunction caused by a transient disturbance on switching on lighting equipment
+
+### II.1 An example of actual condition
+
+When a fluorescent lamp was turned on at an office in which an ADSL communication environment had been installed, a session time-out of the telecommunication system occurred.
+
+Figure II.1 shows the connection configuration of the communication system at the office. Some personal computers (PCs) are connected to an ADSL modem through router and hub.
+
+Figure II.2 illustrates the unsymmetrical voltages of the communication line and the power line of the ADSL modem measured with an oscilloscope when a fluorescent lamp is turned on. The disturbances in the communication line and the power line of the ADSL modem appear at the time of switching on the fluorescent lamp. The unsymmetrical voltage when the fluorescent lamp of the glow starter type was turned on was larger than that of other types and was about 10 V<sub>p-p</sub> on the communication line, about 20 V<sub>p-p</sub> on the power line. The ping test to head office system from the PC of the office connected to the ADSL was not confirmed, and session time-out occurred.
+
+![Figure II.1: Connection architecture of the office communication system. A block diagram showing the interconnection of a terminal board, ADSL modem, router, hub, and multiple PCs, along with power supply and fluorescent lamps.](41a438d7e4adc17c3a4005e7c9500091_img.jpg)
+
+```
+graph LR
+    TB[Terminal board] -- Communication line --- ADSL[ADSL modem]
+    TB -- Power line --- PS[Power supply AC100V]
+    ADSL -- Communication line Ethernet --- R[Router]
+    R --- H[HUB]
+    H --- PC1[PC]
+    H --- PC2[PC]
+    H --- PC3[...] 
+    H --- PC4[PC]
+    PS --- FL1[Fluorescent lamp]
+    PS --- FL2[Fluorescent lamp]
+    PS --- FL3[Fluorescent lamp]
+    PS --- FL4[Fluorescent lamp]
+    FL1 --- ADSL
+    FL2 --- R
+    FL3 --- PS
+    FL4 --- PS
+```
+
+The diagram illustrates the office communication system architecture. A 'Terminal board' is connected to a 'Communication line' and a 'Power line'. The 'Communication line' connects to an 'ADSL modem', which is connected to a 'Router' via a 'Communication line (Ethernet)'. The 'Router' is connected to a 'HUB', which is connected to multiple 'PC' units. The 'Power line' connects to a 'Power supply (AC100V)', which is connected to four 'Fluorescent lamp' units. The diagram is labeled K.132(18)\_FII.1.
+
+Figure II.1: Connection architecture of the office communication system. A block diagram showing the interconnection of a terminal board, ADSL modem, router, hub, and multiple PCs, along with power supply and fluorescent lamps.
+
+**Figure II.1 – Connection architecture of the office communication system**
+
+![Figure II.2: Measurement result of ADSL modem at the office. Oscilloscope traces showing transient disturbances on the communication line and power line.](0bd23f00e0632855cfef9274f1ab93d8_img.jpg)
+
+The figure displays two oscilloscope traces. The top trace, labeled 'Communication line', shows a transient disturbance with a peak-to-peak voltage labeled as  $20\text{V}_{\text{p-p}}$ . The bottom trace, labeled 'Power line', shows a transient disturbance with a peak-to-peak voltage labeled as  $10\text{V}_{\text{p-p}}$ . The time scale is indicated as [2 μs/div]. The figure is labeled K.132(18)\_FII.2.
+
+Figure II.2: Measurement result of ADSL modem at the office. Oscilloscope traces showing transient disturbances on the communication line and power line.
+
+**Figure II.2 – Measurement result of ADSL modem at the office**
+
+### II.2 An example of measurement in a laboratory
+
+An experimental configuration using the VDSL system and an inverter-type fluorescent lamp in the laboratory is shown in Figure II.3. The power line of the lighting equipment runs side by side with the communication line of the VDSL system for approximately 10 m.
+
+Figure II.4 depicts a differential mode voltage on the communication line and a common mode current on the power line of the fluorescent lamp when it was turned on. The observed conducted disturbance was about  $28\text{ V}_{\text{p-p}}$  on the communication line and about  $9\text{ A}_{\text{p-p}}$  in the power line of the fluorescent lamp. A cyclic redundancy check (CRC) error was observed at the timing of turning on the fluorescent lamp by a line monitor function of the VDSL system with the PC.
+
+![Block diagram of the experiment system showing a VDSL system connected to a PC and a Modem, with a fluorescent lamp and power line running alongside the communication line. Measurement probes are connected to an Oscilloscope.](8307f6b04df072c9332f9987e034272c_img.jpg)
+
+The diagram illustrates the experimental setup. A vertical loop represents the 'Power line' and 'Communication line', with a height of 4 m and a width of 2 m. At the top of the loop, a 'Fluorescent lamp' is connected. At the bottom, a 'Modem' is connected to the communication line. The Modem is connected to a 'VDSL' unit, which is in turn connected to a 'PC'. The PC is connected to a 'Switch', which is connected to an 'Oscilloscope'. The Oscilloscope is also connected to a 'Trans.' (Transformer) unit. A 'Differential voltage probe' is connected to the communication line, and a 'Current probe' is connected to the power line. Both probes are connected to the Oscilloscope. A 'Power supply (AC100V)' is connected to the bottom of the loop. The diagram is labeled 'K.132(18)\_FII.3' in the bottom right corner.
+
+Block diagram of the experiment system showing a VDSL system connected to a PC and a Modem, with a fluorescent lamp and power line running alongside the communication line. Measurement probes are connected to an Oscilloscope.
+
+Figure II.3 – Experiment system
+
+![Two stacked plots showing Voltage [V] and Current [A] over Time [μs]. The top plot shows a voltage spike reaching approximately 15 V at 0 μs, followed by a noisy signal around 0 V. The bottom plot shows a current spike reaching approximately 5 A at 0 μs, followed by a noisy signal around 0 A. Both plots have a time axis from 0 to 10 μs.](b53846f262c6904a1b45abef2e95fbd8_img.jpg)
+
+The figure consists of two vertically stacked plots sharing a common time axis. The top plot shows Voltage [V] on the y-axis, ranging from -20 to 20, with major ticks at -20, -10, 0, 10, and 20. The bottom plot shows Current [A] on the y-axis, ranging from -10 to 10, with major ticks at -10, 0, 5, and 10. Both plots have a time axis labeled 'Time [μs]' with major ticks at 0, 5, and 10. The top plot shows a sharp positive spike reaching about 15 V at 0 μs, followed by a noisy signal fluctuating around 0 V. The bottom plot shows a sharp negative spike reaching about -5 A at 0 μs, followed by a noisy signal fluctuating around 0 A. A small label 'K.132(18)\_FII.4' is visible in the bottom right corner of the figure area.
+
+Two stacked plots showing Voltage [V] and Current [A] over Time [μs]. The top plot shows a voltage spike reaching approximately 15 V at 0 μs, followed by a noisy signal around 0 V. The bottom plot shows a current spike reaching approximately 5 A at 0 μs, followed by a noisy signal around 0 A. Both plots have a time axis from 0 to 10 μs.
+
+**Figure II.4 - Experimental result**
+
+# Bibliography
+
+[b-IEC 60050] IEC 60050, *International Electrotechnical Vocabulary*.  
+<http://www.electropedia.org/>
+
+
+
+
+
+# SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| Series E        | Overall network operation, telephone service, service operation and human factors                                                                         |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| <b>Series K</b> | <b>Protection against interference</b>                                                                                                                    |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/K/T-REC-K.133-201801-I_PDF-E/raw.md

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+
+
+International Telecommunication Union
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**K.133**
+
+(01/2018)
+
+SERIES K: PROTECTION AGAINST INTERFERENCE
+
+---
+
+**Electromagnetic environment of body-worn  
+equipment in the 2.4 GHz and 13.56 MHz  
+industrial, scientific and medical band**
+
+Recommendation ITU-T K.133
+
+ITU-T
+
+![ITU logo](84a1d09fb489061482111515543b60dc_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a globe with a red lightning bolt striking it, symbolizing telecommunications. To the right of the globe, the text "International Telecommunication Union" is written in blue, with the acronym "ITU" in a larger, bold blue font.
+
+ITU logo
+
+International  
+Telecommunication  
+Union
+
+
+
+# Recommendation ITU-T K.133
+
+# Electromagnetic environment of body-worn equipment in the 2.4 GHz and 13.56 MHz industrial, scientific and medical band
+
+## Summary
+
+Recommendation ITU-T K.133 specifies electromagnetic characterization of the radiation and conduction environment for body-worn electronic devices.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T K.133    | 2018-01-13 | 5           | <a href="http://handle.itu.int/11.1002/1000/13456">11.1002/1000/13456</a> |
+
+## Keywords
+
+Body-worn equipment, electromagnetic environment, EM environment, body-worn device.
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2018
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+###### Page
+
+|     |                                                                                                                                                    |    |
+|-----|----------------------------------------------------------------------------------------------------------------------------------------------------|----|
+| 1   | Scope.....                                                                                                                                         | 1  |
+| 2   | References.....                                                                                                                                    | 1  |
+| 3   | Definitions .....                                                                                                                                  | 1  |
+| 3.1 | Terms defined elsewhere .....                                                                                                                      | 1  |
+| 3.2 | Terms defined in this Recommendation.....                                                                                                          | 1  |
+| 4   | Abbreviations and acronyms .....                                                                                                                   | 2  |
+| 5   | Conventions .....                                                                                                                                  | 2  |
+| 6   | Description of the body-worn device environment .....                                                                                              | 2  |
+| 6.1 | Typical configuration of the body-worn device environment.....                                                                                     | 2  |
+| 6.2 | Powering and ports .....                                                                                                                           | 3  |
+| 6.3 | Mobility .....                                                                                                                                     | 4  |
+| 6.4 | Possibility of interference.....                                                                                                                   | 4  |
+| 7   | Typical phenomena in the electromagnetic environment of body-worn equipment ....                                                                   | 4  |
+| 8   | Disturbance characteristics and levels in the 2.4GHz and 13.56MHz bands .....                                                                      | 4  |
+| 8.1 | Attributes of environment.....                                                                                                                     | 4  |
+| 8.2 | Specification of disturbance characteristics and levels .....                                                                                      | 5  |
+| 9   | Interference management.....                                                                                                                       | 8  |
+|     | Appendix I – Study roadmap of the electromagnetic environment and electromagnetic compatibility issues of body-worn devices and Bluetooth v4 ..... | 9  |
+| I.1 | Bluetooth v4 and the body-worn device electromagnetic environment.....                                                                             | 9  |
+| I.2 | Cases of electromagnetic compatibility failure in body-worn devices .....                                                                          | 9  |
+| I.3 | Proposed procedure for the study of electromagnetic compatibility of body-worn devices.....                                                        | 9  |
+|     | Bibliography.....                                                                                                                                  | 10 |
+
+# **Introduction**
+
+In recent years, many body-worn communication devices, such as those for medical use, smart watches and smart bracelets, have been produced and are widely used by the public. Most of them have a wireless fidelity (Wi-Fi) or Bluetooth module that uses the 2.4 GHz industrial, scientific and medical (ISM) band for communication or implement near field communication technology in the 13.56 MHz ISM band. This Recommendation is applicable to the environment in which body-worn equipment operates.
+
+## Recommendation ITU-T K.133
+
+## Electromagnetic environment of body-worn equipment in the 2.4 GHz and 13.56 MHz industrial, scientific and medical band
+
+# 1 Scope
+
+This Recommendation specifies electromagnetic characterization of the radiation and conduction environment for body-worn electronic devices. Body-worn equipment includes that for electronic glasses, electronic bracelets, smartphone-supported watches and health supervision.
+
+This Recommendation aims to provide an effective and exercisable method to improve understanding of the electromagnetic (EM) environment of body-worn devices.
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [ITU-T K.34] Recommendation ITU-T K.34 (2003), *Classification of electromagnetic environmental conditions for telecommunication equipment – Basic EMC Recommendation*.
+- [ITU-T K.79] Recommendation ITU-T K.79 (2015), *Electromagnetic characterization of the radiated environment in the 2.4 GHz ISM band*.
+- [IEC TR 61000-2-5] IEC TR 61000-2-5:2017, *Electromagnetic compatibility (EMC) – Part 2-5: Environment – Description and classification of electromagnetic environments*.
+- [ISO/IEC 18000-3] ISO/IEC 18000-3:2010, *Information technology – Radio frequency identification for item management – Part 3: Parameters for air interface communications at 13.56 MHz*.
+- [ISO/IEC 18000-4] ISO/IEC 18000-4:2015, *Information technology – Radio frequency identification for item management – Part 4: Parameters for air interface communications at 2.45 GHz*.
+
+# 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following term defined elsewhere:
+
+**3.1.1 body-worn device** [b-ITU-T K.91]: A portable device containing a wireless transmitter or transceiver which may be located close to a person's torso except the head during its intended use or operation of its radio functions (e.g., on a belt clip, holster, pouch, or on a lanyard when worn as necklace).
+
+### 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following terms:
+
+**3.2.1 electronic glasses equipment:** A type of body-worn device that is similar to glasses in shape and that has an information record module, as well as a signal-processing unit, incorporated within it.
+
+**3.2.2 electronic bracelet equipment:** A type of body-worn device that is similar to a bracelet in shape and that has an information record module, as well as a signal-processing unit, incorporated within it.
+
+**3.2.3 smart watch:** A type of body-worn device that is similar in shape to a watch and that has an information record module, as well as a signal-processing unit, incorporated within it.
+
+**3.2.4 wireless body area communication (WBAN):** A short-range communication technique within, on and in the immediate proximity of a human body.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|          |                                           |
+|----------|-------------------------------------------|
+| AC       | Alternating Current                       |
+| AM       | Amplitude Modulation                      |
+| DC       | Direct Current                            |
+| EM       | Electromagnetic                           |
+| EMC      | Electromagnetic Compatibility             |
+| ERP      | Effective Radiated Power                  |
+| ESD      | Electrostatic Discharge                   |
+| HIPERLAN | High Performance Radio Local Area Network |
+| ISM      | Industrial, Scientific and Medical        |
+| LAN      | Local Area Network                        |
+| PLT      | Power Line Telecommunication              |
+| RF       | Radio Frequency                           |
+| RFID     | Radio Frequency Identification            |
+| r.m.s.   | root mean square                          |
+| WBAN     | Wireless Body Area Communication          |
+| Wi-Fi    | Wireless Fidelity                         |
+
+# **5 Conventions**
+
+None.
+
+# **6 Description of the body-worn device environment**
+
+### **6.1 Typical configuration of the body-worn device environment**
+
+Many people use body-worn devices to monitor human health and exercise. The wireless network around the human body connects to the Internet and other networks to exchange information with other nodes or the remote centre.
+
+If several body-worn devices are located in a person's body area, a high deployment density of wireless equipment results and produces a complex radiated EM environment.
+
+Figure 1 shows a typical layout scenario consisting of body-worn devices and the surrounding body area environment. In Figure 1, affected objects can be classified by wearable centre node or body-worn device according to coupling mechanism.
+
+The body-worn device environment usually has the following features.
+
+- 1) Typical dimensions of the body-worn device environment is usually defined as  $2\text{ m} \times 2\text{ m} \times 2\text{ m}$ .
+- 2) The number of body-worn devices on one person is typically in the range 1-10.
+- 3) Most person have at least one mobile phone and possibly several body-worn devices.
+- 4) There is typically one ISM band body-worn device in each body-worn device node.
+- 5) Depending on the number of body-worn device nodes, there may be two or three ISM band devices for everybody.
+- 6) It is common to find two personal node clusters within a 3 m separation distance in a crowded area.
+
+![Figure 1: Typical body-worn device environment. A silhouette of a person is shown within a 3D rectangular prism representing a 2m x 2m x 2m volume. The prism's dimensions are labeled 'a' (width), 'b' (depth), and 'c' (height). Four numbered callouts point to specific body-worn devices: 1) glasses on the head, 2) a mobile phone at the waist, 3) a shoe on the foot, and 4) a watch on the wrist. The label 'K.133(18)_F01' is at the bottom right of the diagram.](c37fe03d7cad74ad675a0eb16aa43821_img.jpg)
+
+Figure 1: Typical body-worn device environment. A silhouette of a person is shown within a 3D rectangular prism representing a 2m x 2m x 2m volume. The prism's dimensions are labeled 'a' (width), 'b' (depth), and 'c' (height). Four numbered callouts point to specific body-worn devices: 1) glasses on the head, 2) a mobile phone at the waist, 3) a shoe on the foot, and 4) a watch on the wrist. The label 'K.133(18)\_F01' is at the bottom right of the diagram.
+
+**Figure 1 – Typical body-worn device environment [b-electfans.com]**
+
+The body-worn devices layout is shown in Figure 1. The volume,  $abc$ , is  $2\text{ m} \times 2\text{ m} \times 2\text{ m}$  [one wearable centre node (labelled 2), such as a handset with an ISM band communication module, is installed at waist height of about 1 m]. Three body-worn devices (labelled 1, 4 and 3) are located at heights of about 1.7 m, 1.0 m and 0.0 m around the head, the wrist and the foot as glasses, watch and shoe, respectively. Other body-worn devices can be used, such as an intelligent waistband or intelligent walking stick.
+
+### 6.2 Powering and ports
+
+There are at least two kinds of powering mechanism for body-worn devices:
+
+- 1) powered by battery only – this kind of device has an enclosure port only;
+- 2) powered by battery, and can be powered or charged through a direct current (DC) power input port (barrel port or USB port etc.) or alternating current (AC) power input port.
+
+### 6.3 Mobility
+
+With movement, body-worn devices can work in several typical EM environments – commercial, residential, industrial and so on. This Recommendation takes this feature into account. However, consideration of the speed of mobility to the EM environment is under study.
+
+### 6.4 Possibility of interference
+
+Interference can occur because the operating frequency of the devices is in the 2.4 GHz, 13.56 MHz or other frequency band.
+
+Considering that telecommunication equipment density is very high in some areas and that a metal frame of a cabin reflects electromagnetic waves, the problem of electromagnetic compatibility (EMC) can be severe. The transmission rate of a wireless local area network (LAN) system can be greatly affected in this situation.
+
+Refer to [ITU-T K.79] to analyse the possibility of interference in the 2.4 GHz ISM band.
+
+When body-worn devices operate on commercial or industrial premises, such as a hospital or factory, interference from ISM devices can affect body-worn devices.
+
+# 7 Typical phenomena in the electromagnetic environment of body-worn equipment
+
+In the 2.4 GHz and 13.56 MHz bands, typical phenomena in the EM environment of body-worn equipment are as follows.
+
+- a) Conducted high-frequency phenomena:
+  - direct-conducted continuous wave;
+  - transients.
+- b) Radiated high frequency phenomena:
+  - radiated (continuous wave) oscillatory disturbances;
+  - radiated (modulated) signal disturbances;
+  - radiated (transient) pulsed disturbances.
+- c) Electrostatic discharge (ESD) phenomena in the 13.56 MHz or 2.4 GHz band.
+
+The details of these phenomena are described in the basic EMC Recommendation [ITU-T K.34] and in [IEC TR 61000-2-5]. In the context of this Recommendation and in accordance with the IEC EMC approach, the term "high frequency" applies to frequencies above 9 kHz.
+
+# 8 Disturbance characteristics and levels in the 2.4GHz and 13.56MHz bands
+
+### 8.1 Attributes of environment
+
+Enclosure:
+
+- radiated signal from ISM services in the 13.56 MHz band;
+- radiated signal from portable communication devices in the 2.4 GHz band [e.g., wireless phones, Bluetooth and wireless fidelity (Wi-Fi)];
+- high concentration of multimedia and household equipment (e.g., microwave oven);
+- amateur radio in the 2.4 GHz band.
+
+Alternating current power:
+
+- high concentration of switched mode power supplies;
+- existence of power line telecommunication (PLT) equipment.
+
+## 8.2 Specification of disturbance characteristics and levels
+
+According to [ITU-T K.34] and [IEC TR 61000-2-5], the disturbance characteristics and levels in the 13.553-13.567 MHz and 2.400 0-2.483 5 GHz bands are as listed in Tables 1 to 6.
+
+**Table 1 – Disturbance degrees, levels (in volts per metre, r.m.s.) and distance to source – Radiated continuous oscillatory disturbances**
+
+| <b>Disturbance degree and corresponding field strength</b> | Phenomena (sources)                                  |
+|------------------------------------------------------------|------------------------------------------------------|
+|                                                            | ISM Group 2 equipment                                |
+|                                                            | Transmitter frequencies [MHz]                        |
+|                                                            | 13.553 to 13.567<br>2 400 to 2 500                   |
+|                                                            | Distance to source [m]                               |
+| A (Controlled)                                             | Case-by-case according to the equipment requirements |
+| 1 0.3 V/m                                                  | $d$ (Note)                                           |
+| 2 1 V/m                                                    | $d$ (Note)                                           |
+| 3 3 V/m                                                    | $d$ (Note)                                           |
+| 4 10 V/m                                                   | $d$ (Note)                                           |
+| 5 30 V/m                                                   | $d$ (Note)                                           |
+| X (harsh)                                                  | Case-by-case according to the situation              |
+
+NOTE – ISM group 2 equipment (according to [b-CISPR 11]) is not limited in the power used for operation and therefore there are no limits to be observed for radiated disturbances with regard to EMC. Hence it is not possible to generally calculate distance,  $d$ .
+
+(Source: Table 16 of [IEC TR 61000-2-5].)
+
+**Table 2 – Disturbance degrees, levels (in volts per metre, r.m.s.) and distance to source – Analogue communication services below 30 MHz**
+
+| <b>Disturbance degree and corresponding field strength</b> | Phenomena (sources)                                    |
+|------------------------------------------------------------|--------------------------------------------------------|
+|                                                            | Amplitude modulation (AM) broadcasting<br>$P = 500$ kW |
+|                                                            | Transmitter frequencies [MHz]                          |
+|                                                            | 0.150 – 30                                             |
+|                                                            | Distance to source [m]                                 |
+| A (Controlled)                                             | Case-by-case according to the equipment requirements   |
+| 1 0.3 V/m                                                  | 16 500                                                 |
+| 2 1 V/m                                                    | 4 959                                                  |
+| 3 3 V/m                                                    | 1 650                                                  |
+| 4 10 V/m                                                   | 430                                                    |
+| 5 30 V/m                                                   | 378.5                                                  |
+| X (harsh)                                                  | Case-by-case according to the situation                |
+
+NOTE 1 – No AM broadcasting transmitter is expected in the ISM bands, but spurious emissions of radio frequency (RF) sources may be present in ISM bands if RF filters are not properly implemented.  
+NOTE 2 – The distances are derived assuming an antenna gain of 2.15 dBi of a half-wavelength dipole antenna and at the lowest frequency. This table provides data for the frequency range 0.150 MHz to 30 MHz for a 500 kW transmitter. Other power levels (50 kW to 2 500 kW) and antenna types (and resulting antenna gains) are also possible.
+
+(Source: Table 19 of [IEC TR 61000-2-5].)
+
+**Table 3 – Disturbance degrees, levels (in volts per metre, r.m.s.) and distance to source – Amateur radio bands in the 2.4 GHz band**
+
+| Disturbance degree and corresponding field strength | Amateur radio station                                                                                         |
+|-----------------------------------------------------|---------------------------------------------------------------------------------------------------------------|
+|                                                     | $P = 1\,500\text{ W}$<br>$P_{\text{EIRP}} \approx 2\,500\text{ W}$<br>Transmitter frequencies 2 300-2 450 MHz |
+|                                                     | Distance to source [m]                                                                                        |
+| A (Controlled)                                      | Case-by-case according to the equipment requirements                                                          |
+| 1 0.3 V/m                                           | 905                                                                                                           |
+| 2 1 V/m                                             | 271                                                                                                           |
+| 3 3 V/m                                             | 90.5                                                                                                          |
+| 4 10 V/m                                            | 27.1                                                                                                          |
+| 5 30 V/m                                            | 9.05                                                                                                          |
+| X (harsh)                                           | Case-by-case according to the situation                                                                       |
+
+NOTE 1 – The distances are derived assuming a power of 1 500 W and an antenna gain of 2.15 dBi of a half-wavelength dipole antenna. Practical limitations restrict antenna gain for lower frequency bands and amplifier power for higher frequency bands.
+
+NOTE 2 – The above-mentioned power and frequency bands are a summary of all three ITU Regions. The power  $P$  is (if not otherwise mentioned) the maximum allowed output power of the amplifier. The power arriving at the antenna and radiated by it is  $P_{\text{ANT}}$  and is  $P$  reduced by the losses of the feeding cable. For easy calculation of  $E$  and  $d$ , the effective isotropic power  $P_{\text{EIRP}}$  is useful. Most antennas have a direction with maximum radiation, i.e., in that direction they have a significant antenna gain  $G_{\text{ISO}}$  compared to an isotropic radiator.  $E$  and  $d$  of this maximum radiation can be easily calculated by means of  $P_{\text{EIRP}}$ , which is obtained by multiplying  $P_{\text{ANT}}$  by the isotropic antenna gain  $G_{\text{ISO}}$ .  $d$  Is the spatial distance from the antenna. A power  $P = 1\,500\text{ W}$  fed into a dipole results in an isotropic effective radiated power of  $P_{\text{EIRP}} \approx 2\,500\text{ W}$ . In the case of an amateur radio station operating at VHF, UHF, SHF and EHF, many antenna types are possible. Typical resulting antenna gains  $G_{\text{ISO}}$  are between about 10 dBi and >30 dBi. These (mostly rotatable) antennas are normally mounted on antenna towers 10 m to 30 m above ground or on a roof. In this case, full field strength will occur only in the direction of the main beam of the antenna. Even for slight deviations from the direction of maximum beam strength, significant reductions of antenna gain are observed.
+
+The same values for  $P_{\text{EIRP}}$  and therefore for  $E$  and  $d$  in the beam direction for the amateur station in this example could also be obtained with  $P = 100\text{ W}$ , a feeding cable attenuation of 2 dB and a directional antenna with an isotropic antenna gain  $G_{\text{ISO}}$  of 16 dBi. However, with the same  $P_{\text{EIRP}}$ , the probability of disturbance of such an antenna is much lower than that of an omnidirectional antenna, because the beam width is limited in the horizontal and vertical plane.
+
+(Source: Table 31 of [IEC TR 61000-2-5].)
+
+**Table 4 – Disturbance degrees, levels (in volts per metre, r.m.s.) and distance to source – Other RF items in 2.4 GHz band**
+
+| Disturbance degree and corresponding field strength | Wideband data transmission systems and high performance radio local area network (HIPERLAN; Note 1) | Wideband data transmission systems and HIPERLAN terminal (Note 2)        |
+|-----------------------------------------------------|-----------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------|
+|                                                     | $P = 0.1 \text{ WERP}$<br>Transmitter frequencies<br>2.400 0-2.483 5 GHz                            | $P = 0.1 \text{ WERP}$<br>Transmitter frequencies<br>2.400 0-2.483 5 GHz |
+|                                                     | Distance to source [m]                                                                              |                                                                          |
+| A (Controlled)                                      | Case-by-case according to the equipment requirements                                                |                                                                          |
+| 1 0.3 V/m                                           | 58                                                                                                  | 7.4                                                                      |
+| 2 1 V/m                                             | 17                                                                                                  | 2.2                                                                      |
+| 3 3 V/m                                             | 5.8                                                                                                 | 0.74                                                                     |
+| 4 10 V/m                                            | 1.7                                                                                                 | 0.22                                                                     |
+| 5 30 V/m                                            | 0.58                                                                                                | 0.074                                                                    |
+| X (harsh)                                           | Case-by-case according to the situation                                                             |                                                                          |
+
+NOTE 1 – The absolute gain of wideband data transmission systems/HIPERLAN is assumed to be 20 dBi maximum (for fixed wireless access service).  
+NOTE 2 – The absolute gain of wideband data transmission systems/HIPERLAN is assumed to be 2.14 dBi (for terminals).  
+NOTE 3 – ERP: effective radiated power.
+
+(Source: Table 33 and Table 34 of [IEC TR 61000-2-5].)
+
+**Table 5 – Disturbance degrees, levels (in volts per metre, r.m.s.) and distance to source – Radio frequency identification systems**
+
+| Disturbance degree and corresponding field strength (Note 1) | Radio frequency identification (RFID) (Note 2)           | RFID ( Note 3)                                               |
+|--------------------------------------------------------------|----------------------------------------------------------|--------------------------------------------------------------|
+|                                                              | $P = 4 \text{ W}$<br>Transmitter frequencies<br>13.56MHz | $P = 4 \text{ WEIRP}$<br>Transmitter frequencies<br>2450 MHz |
+|                                                              | Distance to source [m]                                   |                                                              |
+| A (Controlled)                                               | Case-by-case according to the equipment requirements     |                                                              |
+| 1 0.3 V/m                                                    | 3.3                                                      | 36.55                                                        |
+| 2 1 V/m                                                      | 1.6                                                      | 11                                                           |
+| 3 3 V/m                                                      | 0.9                                                      | 3.7                                                          |
+| 4 10 V/m                                                     | 0.49                                                     | 1.1                                                          |
+| 5 30 V/m                                                     | 0.28                                                     | 0.37                                                         |
+| X (harsh)                                                    | Case-by-case according to the situation                  |                                                              |
+
+NOTE 1 – The fields are calculated from Formula B.6 for 13.56 MHz RFID and Formula B.4 for 2 450 MHz RFID in Annex B of [IEC TR 61000-2-5].  
+NOTE 2 – See [ISO/IEC 18000-3].  
+NOTE 3 – See [ISO/IEC 18000-4], the power level is specified by EIRP, an antenna gain of 0 dBi is assumed.
+
+(Source: Table 39 of [IEC TR 61000-2-5].)
+
+**Table 6 – Disturbance degrees, levels (in microamperes per metre, r.m.s.) and distance to source – Radio frequency identification systems**
+
+| Disturbance degree and corresponding field strength | RFID (Note 2)<br>$P = 4 \text{ W}$<br>Transmitter frequencies<br>13.56 MHz |
+|-----------------------------------------------------|----------------------------------------------------------------------------|
+|                                                     | Distance to source [m]                                                     |
+| A (Controlled)                                      | Case-by-case according to the equipment requirements                       |
+| 1 3 $\mu\text{A/m}$                                 | 600                                                                        |
+| 2 10 $\mu\text{A/m}$                                | 180                                                                        |
+| 3 30 $\mu\text{A/m}$                                | 60                                                                         |
+| 4 100 $\mu\text{A/m}$                               | 17                                                                         |
+| 5 300 $\mu\text{A/m}$                               | 5.2                                                                        |
+| 6 1000 $\mu\text{A/m}$                              | 2.7                                                                        |
+| X (harsh)                                           | Case-by-case according to the situation                                    |
+
+NOTE 1 – The fields are calculated from Formula B.7 in Annex B of [IEC TR 61000-2-5].  
+NOTE 2 – See [ISO/IEC 18000-3].
+
+(Source: Table 40 of [IEC TR 61000-2-5].)
+
+# 9 Interference management
+
+No significant interference source has yet been identified. This is under study.
+
+If interference occurs on body-worn equipment, Table 7 may be used by the wearer, the manufacturer or other interested stakeholder to collect information about the case. Information about cases of interference sent to ITU-T SG5 for further study is welcome. See Table 7.
+
+**Table 7 – Template for submission of information about cases of interference**
+
+|                                                                                   |                                                                                                                                                   |                                      |                  |       |        |  |  |  |  |  |
+|-----------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------|------------------|-------|--------|--|--|--|--|--|
+| Title                                                                             |                                                                                                                                                   |                                      |                  |       |        |  |  |  |  |  |
+| Nature of trouble                                                                 | malfunction, disturbance, other ( )                                                                                                               |                                      |                  |       |        |  |  |  |  |  |
+|                                                                                   | More detail:                                                                                                                                      |                                      |                  |       |        |  |  |  |  |  |
+| Environment                                                                       | 1. Residence                      2. Office                      3. Outdoor<br>4. Industrial area              5. Telecom centre<br>6. Others ( ) |                                      |                  |       |        |  |  |  |  |  |
+| Situation, configuration, measured data, etc. (Please add figures, if necessary.) |                                                                                                                                                   |                                      |                  |       |        |  |  |  |  |  |
+|                                                                                   |                                                                                                                                                   |                                      |                  |       |        |  |  |  |  |  |
+| Source of EM interference                                                         |                                                                                                                                                   |                                      |                  |       |        |  |  |  |  |  |
+| Type of interference                                                              |                                                                                                                                                   | Characteristics of the interferences |                  |       |        |  |  |  |  |  |
+|                                                                                   |                                                                                                                                                   | Type                                 | Frequency (band) | Level | Others |  |  |  |  |  |
+| Conducted                                                                         | Voltage or current                                                                                                                                | Continuous                           | Hz               | [ ]   |        |  |  |  |  |  |
+|                                                                                   |                                                                                                                                                   | Transient                            | Hz               | [ ]   |        |  |  |  |  |  |
+| Radiated                                                                          | Electromagnetic wave (field)                                                                                                                      | Continuous                           | Hz               | [ ]   |        |  |  |  |  |  |
+|                                                                                   |                                                                                                                                                   | Transient                            | Hz               | [ ]   |        |  |  |  |  |  |
+
+# Appendix I
+
+## **Study roadmap of the electromagnetic environment and electromagnetic compatibility issues of body-worn devices and Bluetooth v4**
+
+(This appendix does not form an integral part of this Recommendation.)
+
+The number of body-worn devices sold annually exceeded 100 million in 2016. There are more developers working on applications for body-worn devices [b-WTST]. The EMC of body-worn devices needs study. Furthermore, the EM environment and EMC failure cases and problems require collection and study.
+
+### **I.1 Bluetooth v4 and the body-worn device electromagnetic environment**
+
+Most body-worn devices use Bluetooth v4 for data exchange, as it features very low power consumption and high data rates. The EM environment when using Bluetooth v4 in the 2.4 GHz band needs study; to optimize power consumption, devices could switch between sleep and working mode. The EM environment characteristics of wake-up and sleep modes require collection and study.
+
+### **I.2 Cases of electromagnetic compatibility failure in body-worn devices**
+
+A few EMC failure cases have been reported. Big EMC problems are not found now with body-worn devices. However, body-worn device applications increase year on year; there are some healthcare and medical body-worn devices that may be interfaced with other normal use body-worn devices. Any EMC interference cases need continuous collection and study.
+
+## **I.3 Proposed procedure for the study of electromagnetic compatibility of body-worn devices**
+
+The following steps are proposed:
+
+- 1) collection of EMC failure cases of body-worn devices;
+- 2) study of EMC failure cases;
+- 3) collection of EMC test data and results of body-worn devices;
+- 4) comparison and study of test data and results;
+- 5) drafting of EMC requirements and test conditions.
+
+# Bibliography
+
+- [b-ITU-T K.91] Recommendation ITU-T K.91 (2018), *Guidance for assessment, evaluation and monitoring of human exposure to radio frequency electromagnetic fields.*
+- [b-elecfans] [http://www.elecfans.com/consume/wearable\\_devices.html](http://www.elecfans.com/consume/wearable_devices.html)
+- [b-CISPR 11] CISPR 11:2016, *Industrial, scientific and medical equipment – Radio-frequency disturbance characteristics – Limits and methods of measurement.*
+- [b-WTST] Wade J (2017). *Wearable technology statistics and trends 2018*. Leeds: Smart Insights (Marketing Intelligence).  
+<https://www.smartinsights.com/digital-marketing-strategy/wearables-statistics-2017/>
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| Series E        | Overall network operation, telephone service, service operation and human factors                                                                         |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| <b>Series K</b> | <b>Protection against interference</b>                                                                                                                    |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/K/T-REC-K.134-201811-I_PDF-E/raw.md

@@ -0,0 +1,733 @@
+
+
+International Telecommunication Union
+
+# **ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+# **K.134**
+
+(11/2018)
+
+### SERIES K: PROTECTION AGAINST INTERFERENCE
+
+---
+
+**Protection of small-size telecommunication  
+installations with poor earthing conditions**
+
+Recommendation ITU-T K.134
+
+**ITU-T**
+
+![ITU logo](84a1d09fb489061482111515543b60dc_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a blue globe with a red lightning bolt striking it. To the right of the globe, the text "International Telecommunication Union" is written in blue.
+
+ITU logo
+
+International  
+Telecommunication  
+Union
+
+
+
+# Recommendation ITU-T K.134
+
+# Protection of small-size telecommunication installations with poor earthing conditions
+
+## Summary
+
+Recommendation ITU-T K.134 provides engineering solutions for lightning protection and safety of small-size telecommunication installations under poor earthing conditions. These protection measures compromise alternatives due to restrictions of circumstance or expense. These protection measures are not common requirements for most circumstances and have defined conditions for certain applications. The selection of appropriate and feasible solutions is helpful to acquire the best technology to cost ratio.
+
+Accompanying the miniaturization development trends of network termination units, more and more telecommunication installations, e.g., wire or wireless access units, are being installed in customer premises or other uncontrolled places. Compared with dedicated telecommunication buildings, these installation environments may be more complex and severe. Recommendations ITU-T K.66 and ITU-T K.120 provide bonding and earthing requirements for customer premises and miniature base stations, respectively. However, in some scenarios, it may be very difficult or expensive to satisfy these requirements. If ignored, there is a risk of equipment damage or human safety due to lightning strikes or electric shock.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T K.134    | 2018-11-13 | 5           | <a href="http://handle.itu.int/11.1002/1000/13713">11.1002/1000/13713</a> |
+
+## Keywords
+
+Earthing, lightning protection, safety, small-size telecommunication installation.
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2019
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+|                                                                                                    | Page |
+|----------------------------------------------------------------------------------------------------|------|
+| 1 Scope.....                                                                                       | 1    |
+| 2 References.....                                                                                  | 1    |
+| 3 Definitions .....                                                                                | 2    |
+| 3.1 Terms defined elsewhere .....                                                                  | 2    |
+| 3.2 Terms defined in this Recommendation.....                                                      | 3    |
+| 5 Conventions .....                                                                                | 4    |
+| 6 General consideration .....                                                                      | 4    |
+| 7 Protection under no earthing connection .....                                                    | 5    |
+| 7.1 Protection for electric safety.....                                                            | 5    |
+| 7.2 Lightning protection .....                                                                     | 8    |
+| 8 Protection under long earthing conductor.....                                                    | 11   |
+| 8.1 Consideration of hazards .....                                                                 | 11   |
+| 8.2 Protection measures.....                                                                       | 12   |
+| 9 Protection under high earth resistance .....                                                     | 13   |
+| Annex A – Enclosure live voltage detection.....                                                    | 14   |
+| Appendix I – Possible hazards of electric shock for SSIs in a.c. TN system .....                   | 16   |
+| Appendix II – Possible hazards of electric shock for SSIs in a.c. TT or IT system .....            | 18   |
+| Appendix III – Possible hazards of electric shock for SSIs powered by up to 400VDC IT system ..... | 19   |
+| Bibliography.....                                                                                  | 20   |
+
+
+
+# Protection of small-size telecommunication installations with poor earthing conditions
+
+# 1 Scope
+
+This Recommendation:
+
+- provides engineering solutions for lightning protection and safety for small-size telecommunication installations under poor earthing conditions. These protection measures are not common requirements for most circumstances and have defined conditions for certain applications. If these installations have equivalent inherent capacity and function, the same results can be acquired;
+- is not intended to replace traditional rules on bonding configurations and earthing. These protection measures compromise alternatives under poor earthing conditions due to restrictions of circumstance or expense;
+- is intended to apply to installations powered by a.c. mains and comply with [IEC 60364 series] or national standards bodies on a.c. power installations;
+- is intended to apply to installations powered by remote power output up to 400 VDC IT system and comply with [ETSI EN 302 099] and [ETSI EN 301 605].
+
+The applied objects in this Recommendation are small-size telecommunication installations which are owned by network operators and controlled by skilled or trained personnel.
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [ITU-T K.21] Recommendation ITU-T K.21 (2018), *Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents.*
+- [ITU-T K.66] Recommendation ITU-T K.66 (2011), *Protection of customer premises from overvoltages.*
+- [ITU-T K.75] Recommendation ITU-T K.75 (2016), *Classification of interface for application of standards on resistibility and safety of telecommunication equipment.*
+- [ITU-T K.85] Recommendation ITU-T K.85 (2011), *Requirements for the mitigation of lightning effects on home networks installed in customer premises.*
+- [ITU-T K.95] Recommendation ITU-T K.95 (2016), *Surge parameters of isolating transformers used in telecommunication devices and equipment.*
+- [ITU-T K.98] Recommendation ITU-T K.98 (2014), *Overvoltage protection guide for telecommunication equipment installed in customer premises.*
+- [ITU-T K.120] Recommendation ITU-T K.120 (2016), *Lightning protection and earthing of a miniature base station.*
+
+|                    |                                                                                                                                                  |
+|--------------------|--------------------------------------------------------------------------------------------------------------------------------------------------|
+| [IEC 60364 series] | IEC 60364-series, <i>Low-voltage electrical installations.</i>                                                                                   |
+| [IEC 60364-4-41]   | IEC 60364-4-41 (2005), <i>Low-voltage electrical installations – Part 4-41: Protection for safety – Protection against electric shock.</i>       |
+| [IEC 61558-1]      | IEC 61558-1:2017, <i>Safety of transformers, reactors, power supply units and combinations thereof – Part 1: General requirements and tests.</i> |
+| [IEC 62305-2]      | IEC 62305-2 (2010), <i>Protection against lightning – Part 2: Risk management.</i>                                                               |
+| [IEC 62368-1]      | IEC 62368-1:2018, <i>Audio/video, information and communication technology equipment – Part 1: Safety requirements.</i>                          |
+| [ETSI EN 301 605]  | ETSI EN 301 605 V1.1.1 (2013), <i>Environmental Engineering (EE); Earthing and bonding of 400 VDC data and telecom (ICT) equipment.</i>          |
+| [ETSI EN 302 099]  | ETSI EN 302 099 V2.1.1 (2014), <i>Environmental Engineering (EE); Powering of equipment in access network.</i>                                   |
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 breakdown** [b-IEC 61340-1]: Failure, at least temporarily, of the insulating properties of an insulating medium under electric stress.
+
+**3.1.2 distant power receiver** [ETSI EN 302 099]: Power equipment electrically connected to a Remote Power Unit.
+
+NOTE – Its function is to supply telecommunications equipment situated at the same location. It may be combined with the item of telecommunications equipment itself.
+
+**3.1.3 equipment class I** [ITU-T K.66]: Equipment where protection against electric shock is achieved by:
+
+- 1) using basic insulation; and also
+- 2) providing a means of connecting to the protective earthing conductor in the building wiring those conductive parts that are otherwise capable of assuming hazardous voltages if the basic insulation fails.
+
+**3.1.4 equipment class II** [ITU-T K.66]: Equipment in which protection against electric shock does not rely on basic insulation only, but in which additional safety precautions, such as double insulation or reinforced insulation are provided, there being no reliance on either protective earthing or installation conditions.
+
+**3.1.5 equipotential bonding** [b-ITU-T Handbook]: An electrical connection putting various exposed conductive parts and extraneous conductive parts at a substantially equal potential.
+
+Distinction is made between:
+
+- the main equipotential bonding;
+- supplementary equipotential bonding;
+- earth-free equipotential bonding.
+
+Equipotential bonding does not necessarily have to connect to earth.
+
+**3.1.6 impulse withstand voltage** [b-IEC 60664-2-1]: Highest peak value of impulse voltage of prescribed form and polarity which does not cause breakdown of insulation under specified conditions.
+
+**3.1.7 inherent protection** [b-ITU-T K.44]: Inherent protection is protection that is provided within the equipment either by virtue of its intrinsic characteristics, by specific design, or by suitable protection components.
+
+**3.1.8 insulation** (electrical) [b-IEC 62477-1]: Electrical separation between circuits or conductive parts provided by clearance or creepage distance or solid insulation or combinations of them.
+
+**3.1.9 isolation transformer** [b-IEC 60065]: Transformer with protective separation between the input and output windings
+
+**3.1.10 miniature base station** [ITU-T K.120]: A type of radio base station (RBS) whose size and RF power are much smaller than typical macro-base station or DBS base stations.
+
+**3.1.11 multiservice surge protective device (MSPD)** [ITU-T K.85]: A surge protective device (SPD) containing both telecommunications and mains protection. It may also include port protection for video or Ethernet.
+
+**3.1.12 remote powering (RP)** [ETSI EN 302 099]: Power feeding of a telecommunications equipment by a remote power circuit.
+
+NOTE – Such a circuit consists of a remote power unit, distribution wiring, and fed receivers.
+
+**3.1.13 remote power unit (RPU)** [ETSI EN 302 099]: Power unit, connected to the mains or from a centralized power plant, which supplies distant telecommunications equipment.
+
+**3.1.14 surge isolating transformer (SIT)** [b-IEC 61643-351]: Isolation transformer which has high impulse withstand voltage with/without electrostatic screen between input and output windings.
+
+**3.1.15 system** [b-ITU-T Handbook]: An electrical system consisting of a single source of electrical energy and an installation. Types of system are identified as follows, depending upon the relationship of the source, and of exposed-conductive-parts of the installation, to Earth. Further details of these systems can be found in the document IEC 60364-4:
+
+- **TN system**: a system having one or more points of the source of energy directly earthed, the exposed-conductive-parts of the installation being connected to that point by protective conductors.
+- **TN-C system**: in which neutral and protective functions are combined in a single conductor throughout the system,
+- **TN-S system**: having separate neutral and protective conductors throughout the system,
+- **TN-C-S system**: in which neutral and protective functions are combined in a single conductor in part of the system.
+- **TT system**: a system having one point of the source of energy directly earthed, and exposed-conductive-parts of the installation being connected to earth electrodes electrically independent of the earth electrodes of the source.
+- **IT system**: a system having no direct connection between live parts and Earth, the exposed-conductive-parts of the electrical installation being earthed.
+
+## **3.2 Terms defined in this Recommendation**
+
+This Recommendation defines the following terms:
+
+**3.2.1 enclosure live voltage detection**: Function intended to detect whether or not a conductive enclosure is live.
+
+**3.2.2 poor earthing conditions**: The actual situations which hinder the construction of valid earthing and bonding configurations compliant with the requirements of the relevant ITU-T K-series Recommendations, e.g., [ITU-T K.66] and [ITU-T K.120], due to the restriction of circumstance or expense.
+
+**3.2.3 small-size telecommunication installation (SSI):** A telecommunication installation which meets the following conditions:
+
+- the volume is small. The installation may contain a single equipment or a case, or a site with several interconnected equipment in close proximity;
+- power consumption is low and usually less than 1 kW.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|     |                                           |
+|-----|-------------------------------------------|
+| LPS | Lightning Protection System               |
+| PE  | Protective Earth                          |
+| PEN | Protective Earth Neutral                  |
+| RP  | Remote Powering                           |
+| RPU | Remote Power Unit                         |
+| SIT | Surge Isolating Transformer               |
+| SPC | Surge Protective Component                |
+| SPD | Surge Protective Device                   |
+| SSI | Small-Size telecommunication Installation |
+| VDR | Voltage Dependent Resistor                |
+
+# **5 Conventions**
+
+None.
+
+# **6 General consideration**
+
+The concept and purpose of earthing is introduced in [b-ITU-T Handbook]. [ITU-T K.66] and [ITU-T K.120] also provide requirements on valid bonding and earthing for customer premises and miniature base stations, respectively. In some scenarios, it may be very difficult or expensive to satisfy these requirements. There may be a conflict between installation requirements of a small-size telecommunication installation (SSI) and their practical circumstances. If ignored, there is a risk of equipment damage or human safety due to lightning surges or electric shock.
+
+Poor earthing conditions, often met in practice, are as follows:
+
+- no earthing connection;
+- long earthing conductor;
+- high earth resistance.
+
+In general, for the condition of no earthing connection, there may be electrical safety hazards and lightning protection issues. For the other two conditions, the possible issues are protection from lightning surges.
+
+NOTE 1 – There are also electrical safety hazards when the resistance of the earthing conductor or earth resistance is extremely high, which is not considered in this Recommendation. For more information, refer to [IEC 60364 series].
+
+These possible hazards are also related to other factors such as the type of equipment concerned with protection against electrical shock, the type of power feeding system, lightning risk level, etc. Considering the complexity of these scenarios, it is convenient and feasible to adopt additional engineering solutions for these SSIs according to local circumstances. The selection of appropriate
+
+and feasible solutions depends on local conditions and is helpful when implementing the best technology to cost ratio.
+
+Appropriate earthing conditions must be satisfied in the following scenarios:
+
+- valid earthing conditions are required for functional (e.g., signalling or testing) purposes or electromagnetic compatibility (EMC) requirements;
+- the SSI is located in a highly-exposed environment where there is a significant risk of a direct lightning strike to it or to the line immediately adjacent to it.
+
+NOTE 2 – If there is an inconsistency between a requirement in this Recommendation and a requirement of the domestic laws and regulations relating to electrical safety, the requirement of the domestic laws and regulations shall apply.
+
+# **7 Protection under no earthing connection**
+
+The risk derived from the absence of earthing connection is electric shock and lightning; these may lead to human injury and/or equipment damage. The selection of additional protection measures should consider the possible influence on lightning protection and safety according to practical conditions.
+
+## **7.1 Protection for electric safety**
+
+### **7.1.1 Analysis of risk scenarios**
+
+The possible hazard concerning electric safety under no earthing connection is related to the type of equipment and power feeding system, as follows.
+
+- Type of equipment concerning the precaution against electric shock.
+
+The common types of SSIs are class I and class II. For class II equipment with non-metallic enclosures, the hazard of electric shock has nothing to do with poor earthing conditions. But for class I equipment and class II equipment with metallic enclosures, the influence of no earthing connection on safety should be considered.
+
+- Type of power feeding system.
+
+For a.c. TN systems, the protective earth (PE) or protective earth neutral (PEN) conductor is always laid along with live conductors, the earthing connection is easy to achieve in TN systems as long as it has been confirmed valid on site. However, if equipment is outside the main equipotential bonding network, e.g., some outdoor equipment powered by an adjacent building, the possible hazards of electric shock also exist in special conditions. Related information and requirements are introduced in Appendix I.
+
+For a.c. TT and IT system, the earthing connection should be implemented through hard-wired conductors to local earth. If there are no earthing connections, the risk of electric shock shall be considered. Related information and requirement are introduced in Appendix II.
+
+For up to 400 VDC systems, d.c. IT systems are generally used. Earthing connections should be implemented through hard-wired conductors to local earth. If there are no earthing connections, the risk of electric shock shall be considered. Related information and requirements are introduced in Appendix III.
+
+### **7.1.2 Protection measures**
+
+When a reliable earthing connection is difficult to achieve, the following measures can be selected according to local conditions.
+
+#### 7.1.2.1 Adopting class II equipment
+
+If requirements for mechanical strength or other relative abilities can be degraded, then class II equipment can be adopted.
+
+The following design guidelines are suggested to avoid the hazard of electric shock:
+
+- reinforced or double insulation shall be used between live parts and the enclosure, the detailed design requirements shall comply with class II equipment of [IEC 62368-1]; and
+- equipment with metallic enclosures may be 'live' under some fault conditions. It is recommended to use enclosure live voltage detection to warn service personnel that there may be dangerous voltage on the enclosure; this is described in Annex A; and
+- to protect an installation against a lightning surge, a surge protective device (SPD) or surge protective component (SPC) between live parts and the metallic enclosure is permitted. The SPD or SPC shall comply with the electric strength and the external clearance and creepage distance requirements with reinforced insulation, and the relevant IEC standard (e.g., IEC 61643 series). A voltage dependent resistor (VDR) alone, cannot be used to bridge reinforced or double insulation;
+- it is also recommended to add an insulating surface on the metallic enclosure or other accessible conductive parts to avoid contact with the public.
+
+#### 7.1.2.2 Adding insulation
+
+An SSI can be placed into an insulation case whose degree of protection level is not less than IPxxB or IP2X. This case should be locked or managed to ensure that the inner conducted parts cannot be handled by the public. The insulation case acts as double insulation and the entire case could be regarded as "class II equipment". All conducted parts in the case should be interconnected through local equipotential bonding. For detailed requirements refer to clause 412.2.2 in [IEC 60364-4-41].
+
+To remind service personnel of the potential for electric shock in this case, the following warning sign and language shall be required to be placed on the equipment case.
+
+![Warning sign: a lightning bolt inside a triangle, representing electric shock hazard.](53298644c66fa3fca81d6eec654afec5_img.jpg)
+
+Warning sign: a lightning bolt inside a triangle, representing electric shock hazard.
+
+IEC 60417-6042
+
+"WARNING" or equivalent word or text, and
+
+"HIGH TOUCH CURRENT" or equivalent text
+
+"DISCONNECT SUPPLY ESSENTIAL BEFORE MAINTENANCE EQUIPMENT" or equivalent text.
+
+The large area metallic parts of the service access area in the insulation case may be live under some fault conditions, and enclosure live voltage detection may be used to warn service personnel that there may be dangerous voltage on the enclosure.
+
+#### 7.1.2.3 Using an isolation transformer for electrical separation
+
+##### 7.1.2.3.1 Rational
+
+Using an isolation transformer for electrical separation is a valid protection measure against indirect contact electric shock. Figure 1 shows a typical layout. When a contact fault of single phase to conducted parts occurs, because the secondary side of the transformer is floating and the fault current ( $I_d$ ) would flow back to the transformer (T) through the contact resistance ( $R_A$ ) and the very small capacitance to earth (C), the fault current and the fault voltage ( $U_t$ ) on the conducted part is very low and electric shock can be avoided to the most extent.
+
+The length of the wiring system served by an isolation transformer shall not exceed 50 m. Flexible cables and cords shall be visible throughout any part of their length susceptible to mechanical damage.
+
+Any equipment with a metallic enclosure may be "live" under some fault conditions; it is recommended to use enclosure live voltage detection to warn service personnel that there is a possibility of dangerous voltage on the enclosure, and/or to install a residual current device, which opens the circuit at 10 mA, on the secondary side of the isolation transformer.
+
+To remind service personnel of the potential risk of electric shock in some cases, a warning sign and language as described in clause 7.1.2.2 shall be required.
+
+When there is a fault between two phases, the circuit would be disconnected by the disconnection device due to high fault current.
+
+![Figure 1 – A typical layout using an isolation transformer for electrical separation](ff0952ef692c9d960ce5f6708bcc9711_img.jpg)
+
+The diagram illustrates an electrical circuit for isolation. On the left, input lines L and N enter an isolation transformer (T). The secondary side of the transformer has a fuse on the top line. A current  $I_d$  flows through the top conductor. A load is shown on the right, enclosed in a metallic box. A fault is indicated by a jagged arrow pointing from the top conductor to the enclosure. A voltage  $U_t \ll 50\text{ V}$  is measured between the enclosure and the ground. A capacitor  $C$  is shown connected between the bottom conductor and ground. A resistance  $R_E$  is shown in series with a ground connection from the enclosure, with current  $I_d$  flowing through it. The diagram is labeled K.134(18)\_F01 at the bottom right.
+
+Figure 1 – A typical layout using an isolation transformer for electrical separation
+
+**Figure 1 – A typical layout using an isolation transformer for electrical separation**
+
+- NOTE – 1) The installation location of equipment shall be selected to avoid the risk of possible contact with other live conductors;
+- 2) The isolation transformer should conform with the requirements for Class II transformer which are regulated in [IEC 61558-1].
+
+###### 7.1.2.3.2 Protection methods for small systems
+
+An isolation transformer can also serve a small system including several equipment and not be connected to local earth. When the  $L_1$  (or  $L_2$ ) conductor of one piece of equipment makes contact with the enclosure while the  $L_2$  (or  $L_1$ ) conductor of another piece of equipment contacts the enclosure, the power supply of both pieces of equipment is not interrupted. An electric shock may happen if service personnel accidentally come in contact with both equipment enclosures simultaneously. Therefore, the risk of electric shock shall be considered.
+
+The available solutions for this hazard is as follows:
+
+If equipment is interconnected through local equipotential bonding without earthing, protection against electric shock can be achieved. Equipotential bonding without earthing can be implemented through hard-wired conductors or via the PE conductor of the triplex hole outlet at the secondary side of the transformer. Typical layouts are shown in Figures 2 and 3.
+
+Additionally, it is recommended to use enclosure live voltage detection to warn service personnel that there is dangerous voltage on the enclosure.
+
+![Figure 2: A typical layout for serving equipment through hard-wired conductors as equipotential bonding. The diagram shows a power source with terminals L and N connected to an isolation transformer. The secondary of the transformer is connected to lines L1 and L2. A current I_d is shown flowing from the transformer. Two pieces of equipment are connected to L1 and L2. Each piece of equipment has a ground connection labeled R_E1 and R_E2. A dashed line labeled 'Equipotential bonding' connects the ground connections of the two pieces of equipment. The diagram is labeled K.134(18)_F02.](4801720824e4b5e2361a5564f91cfb70_img.jpg)
+
+Figure 2: A typical layout for serving equipment through hard-wired conductors as equipotential bonding. The diagram shows a power source with terminals L and N connected to an isolation transformer. The secondary of the transformer is connected to lines L1 and L2. A current I\_d is shown flowing from the transformer. Two pieces of equipment are connected to L1 and L2. Each piece of equipment has a ground connection labeled R\_E1 and R\_E2. A dashed line labeled 'Equipotential bonding' connects the ground connections of the two pieces of equipment. The diagram is labeled K.134(18)\_F02.
+
+**Figure 2 – A typical layout for serving equipment through hard-wired conductors as equipotential bonding**
+
+![Figure 3: A typical layout for serving equipment through the PE conductor of the triplex hole outlet as equipotential bonding. The diagram shows an isolation transformer connected to a plug and outlet. The plug and outlet are connected to two pieces of equipment. A dashed line labeled 'Equipotential bonding using PE conductor in triplex hole outlet' connects the ground connections of the two pieces of equipment. The diagram is labeled K.134(18)_F03.](4ee27dbf5ef12e7b58b0ef0937bc5a5e_img.jpg)
+
+Figure 3: A typical layout for serving equipment through the PE conductor of the triplex hole outlet as equipotential bonding. The diagram shows an isolation transformer connected to a plug and outlet. The plug and outlet are connected to two pieces of equipment. A dashed line labeled 'Equipotential bonding using PE conductor in triplex hole outlet' connects the ground connections of the two pieces of equipment. The diagram is labeled K.134(18)\_F03.
+
+**Figure 3 – A typical layout for serving equipment through the PE conductor of the triplex hole outlet as equipotential bonding**
+
+## 7.2 Lightning protection
+
+### 7.2.1 Protection against lightning
+
+The need for lightning protection is determined by performing a risk assessment according to [IEC 62305-2], which compares the risk value  $R_s$  as the sum of all risk components, with the tolerable risk value  $R_T$ . In this Recommendation, the risk of loss of human life ( $R_1$ ) and the risk of loss of service ( $R_2$ ) are considered.
+
+The related information about the installation environment should first be investigated to perform a risk assessment. The main factors to be considered are as follows:
+
+- the geographical environment where the SSI is installed, e.g., urban environment, suburban environment or rural environment, as defined in [IEC 62305-2];
+- the lightning ground flash density, or roughly the keraunic level;
+- the lightning protection zone (LPZ) where the SSI is installed;
+- the type of telecommunication network, e.g., buried or aerial cable, screened or unscreened cable, cable shield installed or not installed;
+- the type of power network, e.g., buried or aerial cable, screened or unscreened cable, cable shield installed or not installed, neutral bonded or not bonded to PE;
+
+- the type of structure construction e.g., timber, brick or reinforced concrete;
+- whether or not protection measures have been used at the structure or by the services;
+- equipment resistibility level.
+
+The risk of loss of human life ( $R_1$ ) for telecommunication equipment users or maintenance personnel is normally only required to be considered when there is a significant risk of a direct lightning strike to the SSI or a direct strike to one of the services near the SSI. When the risk  $R_1$  is less than the tolerable risk  $R_{T1}$ , the SSI is considered inherently protected against direct lightning. When  $R_1 > R_{T1}$ , valid earthing via a connection to a lightning protection system (LPS) and the corresponding SPDs are normally the best measures to be adopted.
+
+To minimize the risk of damage to equipment, the risk of loss of service ( $R_2$ ) should be evaluated and compared to the tolerable risk of loss of service value  $R_{T2} = 10^{-3}$  or a lower value according to the decision of the network operator. Even when  $R_1 < R_{T1}$ ,  $R_2$  should be evaluated in accordance with [IEC 62305-2]. [ITU-T K.85] also provides assessment methods and examples of  $R_2$  for equipment installed in customer premises.
+
+When the risk  $R_2$  is less than the tolerable risk  $R_{T2}$ , the protection for electric safety is only considered, the corresponding measures are introduced in clause 7.1.
+
+When  $R_2 > R_{T2}$ , protection is recommended and the knowledge of the risk component values guides the protection designer in selecting the most adequate protective measures to protect the equipment. The selection of protection measures depends on the convenience of valid earthing and a comparison of expenses. For protection measures under valid earthing refer to [ITU-T K.66], [ITU-T K.120] and other relative recommendations. The protection measures under no earthing connection are introduced in clause 7.2.2.
+
+At times, to avoid an excessive workload resulting from risk assessment where there are large numbers of sites in a project, a simplified approach for the evaluation of the lightning risk level according to installation scenarios is also adopted. For relative information refer to [ITU-T K.120].
+
+### 7.2.2 Protection measures under no earthing connection
+
+A lightning surge along the connected metal lines needs to be withstood via an insulation barrier, or by bypassing via SPDs or SPCs, to attain reliable protection for SSIs. The absence of an earthing connection means there is no safe path to bleed the lightning surge; this may cause damage to equipment or injury to personnel when the insulation barrier breaks down due to the lightning overvoltage.
+
+Using isolation protection to block the surge and prevent the breakdown between ports of the SSI or its surroundings is an appropriate solution under no earthing connection. However, when considering the restrictions of volume and expense, the isolation level of the isolation protection is not enough to bear the overvoltage derived from a direct lightning hit. The lightning risk introduced in clause 7.2.1 and the configuration of ports of an SSI should be considered.
+
+The SSI can be viewed as a "black box" with a variety of ports. For information on the classification of external and internal ports, refer to [ITU-T K.75]. A mains port is always an external port. The most important item for lightning protection of SSIs is the protection between these ports. The implementation of isolation protection for an SSI depends on the configuration of ports.
+
+For an SSI with a single port (a.c. mains), if the type of equipment is class II or a high level of isolation to surroundings is ensured, only the transverse overvoltage for the external port needs to be considered; if not, isolation measures may be required to prevent possible flashover to its surroundings. A common measure is adding a power surge isolating transformer (SIT) or insulation. Figure 4 provides an illustration for the protection of an SSI with a single port.
+
+![Figure 4: Illustration for protection of an SSI with a single port (a.c. mains).](fa859e4e468bfb2710a94527f2c504af_img.jpg)
+
+Figure 4 consists of two sub-diagrams, (a) and (b), illustrating the protection of an SSI with a single port connected to AC mains.
+
+- a) for Class II SSI:** A Class II SSI is connected to AC mains (L and N lines). A differential surge protector (1) is connected between the L and N lines before the SSI. The SSI itself is labeled with 1).
+- b) for Class I SSI:** A Class I SSI is connected to AC mains (L and N lines) through a Power SIT (2). A differential surge protector (1) is connected between the L and N lines before the Power SIT. The Power SIT is labeled with 2). The diagram is identified by the code K.134(18)\_F04.
+
+Figure 4: Illustration for protection of an SSI with a single port (a.c. mains).
+
+**Figure 4 – Illustration for protection of an SSI with a single port (a.c. mains)**
+
+NOTE – 1) When the differential surge is expected to exceed the inherent resistibility of equipment or the SIT, the differential protection is needed;
+
+2) The power SIT needs to conform the corresponding requirements in clause 7.1.2.3 simultaneously.
+
+For a multi-port SSI, the isolation level between ports and the surroundings should be ensured and the transverse overvoltage for the external ports needs to be attenuated. If the inherent level is not sufficient or the external cables have a hazard of power contact or induction, isolation measures should be adopted. A common measure is adding power SIT, signal SIT or using optical-electric transfer isolation. Figure 5 provides an illustration for the protection of a multi-port SSI.
+
+![Figure 5: Illustration for protection of a multi-port SSI.](a83ba9e3e2c1e21dd69953a7b09e45b4_img.jpg)
+
+Figure 5 consists of three sub-diagrams, (a), (b), and (c), illustrating the protection of a multi-port SSI.
+
+- a) for Class II SSI with two port:** A Class II SSI has two ports. The input port is connected to AC mains (L and N lines) through a differential surge protector (1). The output port is connected to an external or internal cable through a Signal SIT (3). The Signal SIT is labeled with 3).
+- b) for Class I SSI with two port:** A Class I SSI has two ports. The input port is connected to AC mains (L and N lines) through a Power SIT (2) and a differential surge protector (1). The output port is connected to an external cable through a Signal SIT (3). The Power SIT is labeled with 2).
+- c) for SSI with multi-port:** A multi-port SSI has multiple ports. The input port is connected to AC mains (L and N lines) through a Power SIT (2) and a differential surge protector (1). Two output ports are shown, each connected to an external cable through a Signal SIT. The Signal SITs are labeled with 1) and 2). The diagram is identified by the code K.134(18)\_F05.
+
+Figure 5: Illustration for protection of a multi-port SSI.
+
+**Figure 5 – Illustration for protection of a multi-port SSI**
+
+NOTE – 1) When the differential surge is expected to exceed the inherent resistibility of equipment or the SIT, the differential protection is needed;
+
+2) The power SIT needs to conform the corresponding requirements in clause 7.1.2.3 simultaneously;
+
+3) If the external cable has the risk of power contact or induction, the signal SIT is needed.
+
+The relative requirements about the surge parameters of signal SIT could refer to [ITU-T K.95].
+
+In any case, equipotential bonding within the SSI should be ensured. A metal-free optical-fibre cable is recommended, if possible. If an optical-fibre cable with a metallic component or metallic sheath is used, the metallic component or sheath should be isolated with other metal parts.
+
+The rated impulse withstand voltage for these isolation measures is required to be not less than 10 kV (1.2/50 us). In field applications, some protection measures, e.g., the power SIT and insulation case, are easy to implement in order to provide a higher isolation level (e.g., 30 kV or even higher), which can meet the requirement of higher reliability or applying in some severe circumstances.
+
+NOTE – A power isolation transformer should also have enough insulation level or valid measures to ensure electric safety under fault conditions when a breakdown happens.
+
+# 8 Protection under long earthing conductor
+
+## 8.1 Consideration of hazards
+
+[ITU-T K.66] provides requirements for the maximum length of an earthing conductor, which are shown in Table 2.
+
+**Table 2 – Requirements for the maximum length of an earthing conductor**
+
+NOTE – Table 2 taken from [ITU-T K.66].
+
+| Mechanism                     | Maximum length/resistance             |
+|-------------------------------|---------------------------------------|
+| Direct strikes                | 1.5 m                                 |
+| Induced surges                | 10 m                                  |
+| Power induction/power contact | 1 Ω (< 50 V a.c. @ 2 times 24 A a.c.) |
+
+When the earthing conductor of an SSI is long, the possible hazards, which are illustrated through an example in Figure 6, would be:
+
+- the overvoltage drop on the long earthing conductor is so high that there is a big potential difference between the SSI and its surroundings, which maybe lead to a flashover;
+- the bleeding of lightning current would be influenced and the conducted surge along external wires may shift to other vulnerable ports and associated interconnected equipment. Some simulation results under defined conditions for this scenario are provided in [ITU-T K.98] and also demonstrate this influence.
+
+![Figure 6: Illustration of the hazards under a long earthing conductor. The diagram shows a central 'SSI' (Surge Suppressor Interface) block. On the left, power lines 'L' and 'N' enter the SSI, with a lightning strike symbol 'I' above the 'L' line. On the right, an 'External cable' with conductors 'a' and 'b' connects the SSI to 'Associated equipment'. An 'Internal cable' also connects the SSI to the 'Associated equipment'. A long earthing conductor connects the SSI to a 'MET' (Main Earthing Terminal) which is grounded. A 'surroundings' point is indicated near the earthing conductor. A curved arrow shows a potential difference between the SSI and the surroundings. The diagram is labeled 'K.134(18)_F06'.](b0d4609bc46c2d88a8318706bb5321f7_img.jpg)
+
+Figure 6: Illustration of the hazards under a long earthing conductor. The diagram shows a central 'SSI' (Surge Suppressor Interface) block. On the left, power lines 'L' and 'N' enter the SSI, with a lightning strike symbol 'I' above the 'L' line. On the right, an 'External cable' with conductors 'a' and 'b' connects the SSI to 'Associated equipment'. An 'Internal cable' also connects the SSI to the 'Associated equipment'. A long earthing conductor connects the SSI to a 'MET' (Main Earthing Terminal) which is grounded. A 'surroundings' point is indicated near the earthing conductor. A curved arrow shows a potential difference between the SSI and the surroundings. The diagram is labeled 'K.134(18)\_F06'.
+
+**Figure 6 – Illustration of the hazards under a long earthing conductor**
+
+## 8.2 Protection measures
+
+For scenarios with long earthing conductors, implementing protection measures need to consider the the lightning risk level, configuration of ports and local circumstances. Common protection measures are shown as follows.
+
+### 1) Optimization through local equipotential bonding
+
+Figure 7 shows an example of optimization through local equipotential bonding. The sub-bar is installed close to the SSI and is interconnected with the associated equipment and metal surroundings, which reduces the potential difference and eliminates the risk. However, local equipotential bonding cannot reduce pressure on the external port.
+
+![Diagram illustrating local equipotential bonding for an SSI (Surge Sensitive Equipment). The SSI is connected to a lightning protection system (L, N) and has external cables (a, b) and internal cables connecting to associated equipment. A sub-bar is connected to the SSI and the associated equipment, and is bonded to the metal surroundings (MET) via a sub-bar. The potential difference between the SSI and the sub-bar is labeled ΔU'.](9b9d2abd741ed4bafe7f78f89961c663_img.jpg)
+
+The diagram shows a central box labeled 'SSI'. On the left, two lines labeled 'L' and 'N' enter the box, with a lightning symbol and current 'I' indicated above the 'L' line. On the right, two lines labeled 'a' and 'b' exit the box, collectively labeled 'External cable'. Below the SSI, a box labeled 'Associated equipment' is connected via an 'Internal cable'. Below the SSI, a horizontal bar labeled 'sub-bar' is connected. A line labeled 'surroundings' connects the sub-bar to the SSI, with a potential difference  $\Delta U'$  indicated. The sub-bar is connected to a ground symbol labeled 'MET'.
+
+Diagram illustrating local equipotential bonding for an SSI (Surge Sensitive Equipment). The SSI is connected to a lightning protection system (L, N) and has external cables (a, b) and internal cables connecting to associated equipment. A sub-bar is connected to the SSI and the associated equipment, and is bonded to the metal surroundings (MET) via a sub-bar. The potential difference between the SSI and the sub-bar is labeled ΔU'.
+
+Figure 7 – Illustration of local equipotential bonding
+
+### 2) Adding SPDs on vulnerable ports
+
+Adding SPDs on vulnerable ports of the SSI and the interconnected equipment can improve endurance capacity of the ports. The coordination between SPDs and inherent protection should be ensured. For more information, refer to [ITU-T K.66] and [ITU-T K.85].
+
+This method cannot reduce the potential difference between the SSI and its surroundings.
+
+### 3) Adding SITs to block the conducted surge
+
+The use of external SITs can reduce the magnitude of a conducted surge current to a very small level (capacity current), which prevents the hazards caused by long earthing conductors. For more information about this application, refer to clause 7.2.2 of this Recommendation and [b-ITU-T K.126]. Figure 8 shows an illustration of using SITs.
+
+SITs cannot bear the overvoltage derived from a direct lightning strike. Thus, this method shall not be used in highly exposed environments where there is a significant risk of a direct lightning strike to it or to the line immediately adjacent to it.
+
+![Diagram illustrating the use of Signal Isolation Transformers (SITs) for an SSI. A central box labeled 'SSI' is connected to a 'Power SIT' on the left and a 'Signal SIT' on the right. The 'Power SIT' is connected to lines 'L' and 'N' with an arrow labeled 'I'. The 'Signal SIT' is connected to two external cables labeled 'a' and 'b'. An 'Associated equipment' box is connected to the 'SSI' via an 'Internal cable' and to the 'External cable' via an 'Internal cable'. The 'SSI' is also connected to 'surroundings' and a 'MET' (Main Earth Terminal) which is grounded.](9c6461e1e94afae4dec455e69a2ce152_img.jpg)
+
+K.134(18)\_F08
+
+Diagram illustrating the use of Signal Isolation Transformers (SITs) for an SSI. A central box labeled 'SSI' is connected to a 'Power SIT' on the left and a 'Signal SIT' on the right. The 'Power SIT' is connected to lines 'L' and 'N' with an arrow labeled 'I'. The 'Signal SIT' is connected to two external cables labeled 'a' and 'b'. An 'Associated equipment' box is connected to the 'SSI' via an 'Internal cable' and to the 'External cable' via an 'Internal cable'. The 'SSI' is also connected to 'surroundings' and a 'MET' (Main Earth Terminal) which is grounded.
+
+**Figure 8 – Illustration of using SITs**
+
+### 4) Using enclosure live voltage detection to alarm for possible danger
+
+Any equipment with metallic enclosure may be ‘live’ under some fault conditions. Enclosure live voltage detection should be used to warn service personnel that there is dangerous voltage on the enclosure.
+
+# 9 Protection under high earth resistance
+
+For lightning protection, the function of the earth network is to provide a valid bleeding path for lightning current and decrease the risk to personnel due to touch and step voltages. The architecture of the earth network seems more important than the specific values of earth resistance. It is also difficult to establish definite requirements about earth resistance, but lower earth resistance is preferred. High earth resistance leads to more pressure for primary protection for external cables from a direct lightning strike. However, it is unreasonable to attempt to achieve lower earth resistance without regard for the expense to implement protection.
+
+For an SSI located in a low exposure environment, the influence of earth resistance is very small and equipotential bonding is more important.
+
+For an SSI located in highly exposed environment, the implementation of earth network shall first meet the requirements regulated in [ITU-T K.66] and [ITU-T K.120]. If earth resistance is high, the capacity of primary protection for external cables should be confirmed to be sufficient. Detailed information can be found in Annex E of [b-IEC 62305-1]. In most cases, it is not recommended to intentionally decrease earth resistance for low-cost SSIs.
+
+## Annex A
+
+### Enclosure live voltage detection
+
+(This annex forms an integral part of this Recommendation.)
+
+Enclosure live voltage detection is used to detect dangerous voltage caused by insulation impedance degradation or breakdown between any input live conductor or circuit and the metallic enclosure of the equipment.
+
+Enclosure live voltage detection consists of an isolation module, a voltage signal collection (or division) module, a signal regulation module (optional), a signal processing (or comparison) module, and an alarm (local or remote) module, as shown in Figure A.1.
+
+The isolation module shall comply with the electric strength and the clearance and creepage distance requirements of double or reinforced insulation detailed in [IEC 62368-1].
+
+Enclosure live voltage detection shall provide a local or remote alarm on the equipment to remind service personnel that there is dangerous voltage on the equipment.
+
+Enclosure live voltage detection shall not rely on the earthing of equipment within metallic enclosures.
+
+![Figure A.1 – Enclosure live detection function diagram. The diagram shows a block diagram of the enclosure live voltage detection system. It includes an Isolation module, a Signal collection module, an Optional Signal regulation module, a Signal processing module, and an Alarm module. The system is connected to live conductors (L or N connection X and N or L connection Y) and the Metal enclosure. The Signal collection module is connected to the Metal enclosure and has an Optional connection with or without earthed. The Signal processing module is connected to the Signal regulation module and the Alarm module. The Signal regulation module is Optional. The Signal collection module, Signal regulation module, and Signal processing module are connected to a common GND line. The diagram is labeled K.134(18)_FA.1.](1a85642ed2356d183ce598f2c8b3ee8b_img.jpg)
+
+The diagram illustrates the functional architecture of an enclosure live voltage detection system. On the left, two input lines, 'L or N connection X' and 'N or L connection Y', enter a 'Metal enclosure'. These lines connect to an 'Isolation module'. Below the metal enclosure, there is an 'Optional connection with or without earthed' point connected to ground. The 'Isolation module' has an 'Optional connection' to the 'Metal enclosure' and its output connects to a 'Signal collection module'. The 'Signal collection module' is also connected to the 'Metal enclosure' and has an 'Optional connection' to ground. Its output connects to an 'Optional Signal regulation module', which in turn connects to a 'Signal processing module'. The 'Signal processing module' is connected to an 'Alarm module' and to a common 'GND' line. The 'GND' line is also connected to the 'Metal enclosure' via an 'Optional connection'.
+
+Figure A.1 – Enclosure live detection function diagram. The diagram shows a block diagram of the enclosure live voltage detection system. It includes an Isolation module, a Signal collection module, an Optional Signal regulation module, a Signal processing module, and an Alarm module. The system is connected to live conductors (L or N connection X and N or L connection Y) and the Metal enclosure. The Signal collection module is connected to the Metal enclosure and has an Optional connection with or without earthed. The Signal processing module is connected to the Signal regulation module and the Alarm module. The Signal regulation module is Optional. The Signal collection module, Signal regulation module, and Signal processing module are connected to a common GND line. The diagram is labeled K.134(18)\_FA.1.
+
+Figure A.1 – Enclosure live detection function diagram
+
+Example:
+
+The enclosure live voltage detection circuit contains a detection circuit and a detection method.
+
+The enclosure live voltage detection circuit consists of an isolation module, a voltage signal collection module, a signal regulation module, a signal processing module, and a remote alarm module.
+
+The isolation module is used to isolate hazardous live parts, it uses two high-impedance isolation modules with symmetrical impedance.
+
+The signal collection module is used to sample the voltage  $U_x$  that is the ratio voltage between a live conductor and the metallic enclosure, it uses  $R_1$  and  $R_2$  of equal resistance value to divide voltage,  $U_x$  is a differential voltage between the voltage at both ends of the  $R_1$  and the voltage at both ends of the  $R_2$  multiplied by a certain proportion.
+
+The signal regulation module is used to regulate the voltage to match the signal processing, it adjusts the signal to a level within an acceptable range of the signal processing module to protect the signal processing module from overvoltage or negative voltage damage.
+
+The signal processing module is used to calculate the value of  $\frac{U_x}{U_{in}}$ , and judge if the device is faulty according to the detection method.  $U_{in}$  is the ratio input voltage that the input voltage of the equipment is multiplied by a certain proportion, and is necessary in the detection method. The signal of  $U_{in}$  should be connected to the signal processing module.
+
+The principle detection method is to compare  $\frac{U_x}{U_{in}}$  with a setting value or range, when the result meets the setting conditions it indicates that the device is faulty.
+
+The faults include at least one of the cases as below:
+
+- 1) the metallic enclosure of equipment is lived;
+- 2) the phase conductor and neutral conductor are reversed.
+
+A detailed circuit diagram is shown in Figure A.2.
+
+Note:
+
+X is connected to a target live conductor,
+
+E is a metallic enclosure of equipment with or without earthing.
+
+![Circuit diagram for enclosure live voltage detection. The diagram shows five main modules: 1. The first isolation module (containing two isolation transformers, 1A and 1B); 2. The first signal collection module (containing op-amps OPA1, OPA2, OPA3 and resistors R1, R2, R3, R4, R5, R6); 3. The signal regulation module (containing a regulation source, resistors R7, R8, and diodes D1, D2); 4. The signal processing module (containing an AD converter and an MCU with pins aa, ab, ac, ma, mb); 5. An Alarm module. Input X is connected to the live conductor, and E is the metallic enclosure. The isolation module outputs are connected to the signal collection module. The signal collection module output (2c) is connected to the signal regulation module (4a). The signal regulation module output (4b) is connected to the signal processing module (3a). The signal processing module is connected to the alarm module. A common ground (GND) is shown at the bottom.](608f1b5ef8f3dc0723f2b4ea1fb72be2_img.jpg)
+
+Circuit diagram for enclosure live voltage detection. The diagram shows five main modules: 1. The first isolation module (containing two isolation transformers, 1A and 1B); 2. The first signal collection module (containing op-amps OPA1, OPA2, OPA3 and resistors R1, R2, R3, R4, R5, R6); 3. The signal regulation module (containing a regulation source, resistors R7, R8, and diodes D1, D2); 4. The signal processing module (containing an AD converter and an MCU with pins aa, ab, ac, ma, mb); 5. An Alarm module. Input X is connected to the live conductor, and E is the metallic enclosure. The isolation module outputs are connected to the signal collection module. The signal collection module output (2c) is connected to the signal regulation module (4a). The signal regulation module output (4b) is connected to the signal processing module (3a). The signal processing module is connected to the alarm module. A common ground (GND) is shown at the bottom.
+
+K.134(18)\_FA.2
+
+Figure A.2 – Circuit diagram for enclosure live voltage detection
+
+## Appendix I
+
+### Possible hazards of electric shock for SSIs in a.c. TN system
+
+(This appendix does not form an integral part of this Recommendation.)
+
+When an SSI is outside the main equipotential bonding network, e.g., some outdoor equipment powered by an adjacent building, the conducted fault voltage along PE or PEN conductors may lead to accidental electric shock. The fault voltage can be produced due to various reasons. In the example demonstrated in Figure I.1, the L conductor is in contact with the earth and the power supply is uninterrupted. For example, if the L conductor falls into a pond. Due to the restriction of the earth resistance of fault point ( $R_E$ ) and the power transformer ( $R_B$ ), the fault current ( $I_d$ ) is small. If the value of  $R_B$  and  $I_d$  are assumed to be 4 Ω and 20 A, the persistent fault voltage ( $U_f$ ) along PE or PEN conductors is 80 V. For the equipment within the main equipotential bonding network in the building, there is no hazard of electric shock. But for equipment outside the main equipotential bonding network, the persistent fault voltage can lead to an accident. Although there is an RCD on the circuit for the building, it cannot cut off this fault because there is no trigger current. When the earth resistance of the power transformer ( $R_B$ ) is very small or there are many customers which have repetitive earthing in parallel with  $R_B$ , these hazards would be decreased.
+
+![Diagram of a TN-C-S system showing a fault scenario. A power transformer on the left has its secondary connected to L, PEN, and PE conductors. The PEN conductor is earthed at the transformer via resistance R_B. A fault occurs where the L conductor touches the earth at a point with resistance R_E. Fault current I_d flows from the L conductor through the earth back to the transformer. This results in a fault voltage U_f = I_d * R_B across the transformer's earthing resistance. Inside a building, the PEN conductor is split into N and PE. An RCD is installed on the L and N conductors. The building's main equipotential bonding network is connected to the PE conductor and earthed via resistance R_A. Two pieces of equipment are shown: one inside the building connected to the local PE conductor (at 0V), and another outside the building connected to the PE conductor at the fault point. A person touching the outdoor equipment is shown with red dashed lines indicating current flow through their body to the earth, representing a shock hazard. The diagram is labeled 'TN-C-S' and 'K.134(18)_FI.1'.](09955ff8214ffb6947951fc0f60eb6ab_img.jpg)
+
+Diagram of a TN-C-S system showing a fault scenario. A power transformer on the left has its secondary connected to L, PEN, and PE conductors. The PEN conductor is earthed at the transformer via resistance R\_B. A fault occurs where the L conductor touches the earth at a point with resistance R\_E. Fault current I\_d flows from the L conductor through the earth back to the transformer. This results in a fault voltage U\_f = I\_d \* R\_B across the transformer's earthing resistance. Inside a building, the PEN conductor is split into N and PE. An RCD is installed on the L and N conductors. The building's main equipotential bonding network is connected to the PE conductor and earthed via resistance R\_A. Two pieces of equipment are shown: one inside the building connected to the local PE conductor (at 0V), and another outside the building connected to the PE conductor at the fault point. A person touching the outdoor equipment is shown with red dashed lines indicating current flow through their body to the earth, representing a shock hazard. The diagram is labeled 'TN-C-S' and 'K.134(18)\_FI.1'.
+
+Figure I.1 – Example of possible hazards of electric shock in a.c. TN system
+
+The available solutions for these hazards include:
+
+- a local earthing TT system for the outdoor equipment, which is shown in Figure I.2; or
+- class II equipment as described in clause 7.1.2.1, which is shown in Figure I.3; or
+- an insulation case as described in clause 7.1.2.2; or
+- an isolation transformer as described in clause 7.1.2.3 as electrical separation, which is shown in Figure I.4.
+
+NOTE – For the first solution, a local earthing connection is needed. The relative requirements can refer to the TT system in [IEC 60364 series]. But in some scenarios, it may be very difficult or expensive to satisfy these requirements.
+
+![Diagram of a TN-C-S system transitioning to a Local TT system for outdoor equipment. The TN-C-S part includes a transformer with L, PEN, and N conductors, an RCD, and a main equipotential bonding network. The Local TT part includes a separate earth electrode (RA) and a PE' conductor connected to it. A fault current Id flows through the earth. The formula Uf = Id * RB is shown on the left.](c914f51f4427bc672dd0526cfc90ebe9_img.jpg)
+
+Diagram illustrating the solution of building a local a.c. TT system for outdoor equipment. The system is divided into two parts: TN-C-S and Local TT. The TN-C-S part includes a transformer with L, PEN, and N conductors, an RCD, and a main equipotential bonding network. The Local TT part includes a separate earth electrode ( $R_A$ ) and a PE' conductor connected to it. A fault current  $I_d$  flows through the earth. The formula  $U_f = I_d \cdot R_B$  is shown on the left. The diagram is labeled K.134(18)\_FI.2.
+
+Diagram of a TN-C-S system transitioning to a Local TT system for outdoor equipment. The TN-C-S part includes a transformer with L, PEN, and N conductors, an RCD, and a main equipotential bonding network. The Local TT part includes a separate earth electrode (RA) and a PE' conductor connected to it. A fault current Id flows through the earth. The formula Uf = Id \* RB is shown on the left.
+
+**Figure I.2 – Solution of building a local a.c. TT system for outdoor equipment**
+
+![Diagram showing the use of Class II equipment (double insulation) for electrical separation. It shows a transformer with L, PEN, and N conductors. Equipment A is connected to the PE conductor and has a fault voltage Uf. Equipment B is a Class II appliance with double insulation and is connected to the N conductor, resulting in 0V at its exposed conductive parts. The diagram is labeled K.134(18)_FI.3.](d734a6ea1b381280f043fcf70391b6db_img.jpg)
+
+Diagram illustrating the solution of adopting a class II equipment as electrical separation. The system includes a transformer with L, PEN, and N conductors. Equipment A is connected to the PE conductor and has a fault voltage  $U_f$ . Equipment B is a Class II appliance with double insulation and is connected to the N conductor, resulting in 0V at its exposed conductive parts. The diagram is labeled K.134(18)\_FI.3.
+
+Diagram showing the use of Class II equipment (double insulation) for electrical separation. It shows a transformer with L, PEN, and N conductors. Equipment A is connected to the PE conductor and has a fault voltage Uf. Equipment B is a Class II appliance with double insulation and is connected to the N conductor, resulting in 0V at its exposed conductive parts. The diagram is labeled K.134(18)\_FI.3.
+
+**Figure I.3 – Solution of adopting a class II equipment as electrical separation**
+
+![Diagram showing the use of an isolation transformer for electrical separation. It shows a transformer with L, PEN, and N conductors. Equipment A is connected to the PE conductor and has a fault voltage Uf. Equipment B is connected to the secondary of an isolation transformer, resulting in 0V at its exposed conductive parts. The diagram is labeled K.134(18)_FI.4.](844077b3034f0030b404207db0ad76b4_img.jpg)
+
+Diagram illustrating the solution of adopting an isolation transformer as electrical separation. The system includes a transformer with L, PEN, and N conductors. Equipment A is connected to the PE conductor and has a fault voltage  $U_f$ . Equipment B is connected to the secondary of an isolation transformer, resulting in 0V at its exposed conductive parts. The diagram is labeled K.134(18)\_FI.4.
+
+Diagram showing the use of an isolation transformer for electrical separation. It shows a transformer with L, PEN, and N conductors. Equipment A is connected to the PE conductor and has a fault voltage Uf. Equipment B is connected to the secondary of an isolation transformer, resulting in 0V at its exposed conductive parts. The diagram is labeled K.134(18)\_FI.4.
+
+**Figure I.4 – Solution of adopting an isolation transformer as electrical separation**
+
+## Appendix II
+
+### Possible hazards of electric shock for SSIs in a.c. TT or IT system
+
+(This appendix does not form an integral part of this Recommendation.)
+
+If class I equipment is powered by an a.c. TT system and is not connected to local earth, the equipment within the metallic enclosure may be lived under a single fault condition, and the risk of electric shock shall be considered. This is shown in Figure II.1.
+
+![Figure II.1: Diagram of a TT system showing a fault condition. A transformer with L and N windings is connected to a fault voltage source U_f and a grounding resistor R_B. The N conductor is connected to earth. A metallic enclosure A contains a resistor and is connected to the L and N conductors. A person touches the enclosure, and a fault current flows through the body to earth, indicated by a red dashed line. The voltage across the body is labeled U_f. The diagram is labeled K.134(18)_FII.1.](4b87467ad9642943235f48f7d4b59449_img.jpg)
+
+Figure II.1: Diagram of a TT system showing a fault condition. A transformer with L and N windings is connected to a fault voltage source U\_f and a grounding resistor R\_B. The N conductor is connected to earth. A metallic enclosure A contains a resistor and is connected to the L and N conductors. A person touches the enclosure, and a fault current flows through the body to earth, indicated by a red dashed line. The voltage across the body is labeled U\_f. The diagram is labeled K.134(18)\_FII.1.
+
+Figure II.1 – Example of possible hazards of electric shock in a.c. TT system
+
+If class I equipment are powered by an a.c. IT system not connected to local earth, the L (or N) conductor contact with the earth and the power supply does not interrupt, for example, if the L (or N) conductor falls into a pond or its insulation is damaged. The equipment within the metallic enclosure may be lived under a single fault condition, and the risk of electric shock shall be considered. This is shown in Figure II.2.
+
+![Figure II.2: Diagram of an IT system showing a fault condition. A transformer with L and N windings is connected to a fault voltage source U_f and a grounding resistor R_B. The N conductor is connected to earth through a high impedance resistor R_A. The L conductor is connected to earth through a grounding resistor R_E. A metallic enclosure A contains a resistor and is connected to the L and N conductors. A person touches the enclosure, and a fault current flows through the body to earth, indicated by a red dashed line. The voltage across the body is labeled U_f. The diagram is labeled K.134(18)_FII.2.](5132b3a97ac70fe4765c1e07e66b72b3_img.jpg)
+
+Figure II.2: Diagram of an IT system showing a fault condition. A transformer with L and N windings is connected to a fault voltage source U\_f and a grounding resistor R\_B. The N conductor is connected to earth through a high impedance resistor R\_A. The L conductor is connected to earth through a grounding resistor R\_E. A metallic enclosure A contains a resistor and is connected to the L and N conductors. A person touches the enclosure, and a fault current flows through the body to earth, indicated by a red dashed line. The voltage across the body is labeled U\_f. The diagram is labeled K.134(18)\_FII.2.
+
+Figure II.2 – Example of possible hazards of electric shock in a.c. IT system
+
+The available solutions for these hazards include:
+
+- class II equipment as described in clause 7.1.2.1; or
+- an insulation case as described in clause 7.1.2.2; or
+- for the equipment powered by a TT system, an isolation transformer as described in clause 7.1.2.3 as electrical separation; or
+- for equipment within a metallic enclosure powered by a TT and IT system, an enclosure live voltage detection as described in Annex A.
+
+## Appendix III
+
+### Possible hazards of electric shock for SSIs powered by up to 400 VDC IT system
+
+(This appendix does not form an integral part of this Recommendation.)
+
+If class I equipment (distant power receiver/SSI) is powered by a d.c. IT system (remote power unit (RPU)) and is not connected to local earth, the power supply does not interrupt when the + (or -) conductor contacts the earth in the case of an earth fault or insulation breakdown. The metallic enclosure may be lived under a single fault condition, and the risk of electric shock shall be considered, as shown in Figure III.1.
+
+![Figure III.1: Example of possible hazards of electric shock in d.c. IT system. The diagram shows a Remote Power Unit (RPU) connected to a Cable system. The RPU has two output conductors, V+ (red) and V- (blue). The V+ conductor is connected to the metallic enclosure of a Remote Power Receiver/SSI (RPR/SSI). The V- conductor is connected to a high impedance resistor (RA) and a metal enclosure (MET) which is connected to local earth. The RPR/SSI is also connected to local earth. A person is shown touching the metallic enclosure of the RPR/SSI. The voltage across the person is labeled UF. The diagram is labeled K.134(18)_FIII.1.](e354b57563dae469c00b412b2abdf765_img.jpg)
+
+Figure III.1: Example of possible hazards of electric shock in d.c. IT system. The diagram shows a Remote Power Unit (RPU) connected to a Cable system. The RPU has two output conductors, V+ (red) and V- (blue). The V+ conductor is connected to the metallic enclosure of a Remote Power Receiver/SSI (RPR/SSI). The V- conductor is connected to a high impedance resistor (RA) and a metal enclosure (MET) which is connected to local earth. The RPR/SSI is also connected to local earth. A person is shown touching the metallic enclosure of the RPR/SSI. The voltage across the person is labeled UF. The diagram is labeled K.134(18)\_FIII.1.
+
+Figure III.1 – Example of possible hazards of electric shock in d.c. IT system
+
+If several pieces of class I equipment (RPR/SSI) are powered by a d.c. IT small system (RPU) and are not connected to local earth, when one equipment has a + (or -) conductor in contact with the enclosure and the other equipment also has a - (or +) conductor in contact with the enclosure, both pieces of equipment do not interrupt the power supply. If, for example, two body parts of a service person accidentally contact both enclosures forming an electric shock circuit, then the risk of electric shock shall be considered, as shown in Figure III.2.
+
+![Figure III.2: Example of possible hazards of electric shock in several class I equipment powered by a d.c. IT system. The diagram shows a Remote Power Unit (RPU) connected to a Cable system. The RPU has two output conductors, V+ (red) and V- (blue). The V+ conductor is connected to the metallic enclosure of a Remote Power Receiver/SSI (RPR/SSI). The V- conductor is connected to a high impedance resistor (RA) and a metal enclosure (MET) which is connected to local earth. The RPR/SSI is also connected to local earth. A person is shown touching the metallic enclosure of the RPR/SSI. The current flowing through the person is labeled Id. The diagram is labeled K.134(18)_FIII.2.](8d325fc12b494e42c9ea7ed2a7f327a6_img.jpg)
+
+Figure III.2: Example of possible hazards of electric shock in several class I equipment powered by a d.c. IT system. The diagram shows a Remote Power Unit (RPU) connected to a Cable system. The RPU has two output conductors, V+ (red) and V- (blue). The V+ conductor is connected to the metallic enclosure of a Remote Power Receiver/SSI (RPR/SSI). The V- conductor is connected to a high impedance resistor (RA) and a metal enclosure (MET) which is connected to local earth. The RPR/SSI is also connected to local earth. A person is shown touching the metallic enclosure of the RPR/SSI. The current flowing through the person is labeled Id. The diagram is labeled K.134(18)\_FIII.2.
+
+Figure III.2 – Example of possible hazards of electric shock in several class I equipment powered by a d.c. IT system
+
+The available solutions for these hazards include:
+
+- for equipment within a metallic enclosure, enclosure live voltage detection, as described in Annex A; or
+- class II equipment as described in clause 7.1.2.1; or
+- an insulation case as described in clause 7.1.2.2.
+
+## Bibliography
+
+- [b-ITU-T K.44] Recommendation ITU-T K.44 (2017), *Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents – Basic Recommendation*.
+- [b-ITU-T Handbook] ITU-T handbook on Earthing and Bonding (2003).
+- [b-IUT-T K.126] Recommendation ITU-T K.126 (2017), *Surge protective component application guide - High frequency signal isolation transformers*.
+- [b-IEC 60065] IEC 60065 (2014), *Audio, video and similar electronic apparatus – Safety requirements*.
+- [b-IEC 60664-1] IEC 60664-1 (2007), *Insulation coordination for equipment within low-voltage systems – Part 1: Principles, requirements and tests*.
+- [b-IEC 60664-2-1] IEC TR 60664-2-1 (2011), *Insulation coordination for equipment within low-voltage systems – Part 2-1: Application guide – Explanation of the application of the IEC 60664 series, dimensioning examples and dielectric testing*.
+- [b-IEC 61340-1] IEC 61340-1 (2012), *Electrostatics – Part 1: Electrostatic phenomena – Principles and measurements*.
+- [b-IEC 61643-351] IEC 61643-351 (2016), *Components for low-voltage devices – Part 351: Performance requirements and test methods for telecommunications and signalling network surge isolation transformers (SIT)*.
+- [b-IEC 62305-1] IEC 62305-1 (2010), *Protection against lightning – Part 1: General principles*.
+- [b-IEC 62477-1] IEC 62477-1 (2012), *Safety requirements for power electronic converter systems and equipment – Part 1: General*.
+- [b-IEC 62631-1] IEC 62631-1 (2011), *Dielectric and resistive properties of solid insulating materials – Part 1: General*.
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| Series E        | Overall network operation, telephone service, service operation and human factors                                                                         |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| <b>Series K</b> | <b>Protection against interference</b>                                                                                                                    |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/K/T-REC-K.135-201811-I_PDF-E/raw.md

@@ -0,0 +1,514 @@
+
+
+International Telecommunication Union
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**K.135**
+
+(11/2018)
+
+SERIES K: PROTECTION AGAINST INTERFERENCE
+
+---
+
+**Technical parameters for residual current  
+operated protective devices with automatic  
+reclosing feature for telecom applications**
+
+Recommendation ITU-T K.135
+
+ITU-T
+
+![ITU logo](84a1d09fb489061482111515543b60dc_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a globe with a red lightning bolt striking it, symbolizing telecommunications. To the right of the globe, the text "International Telecommunication Union" is written in blue.
+
+ITU logo
+
+International  
+Telecommunication  
+Union
+
+
+
+# Recommendation ITU-T K.135
+
+# Technical parameters for residual current operated protective devices with automatic reclosing feature for telecom applications
+
+## Summary
+
+Recommendation ITU-T K.135 provides an overview of the parameters of residual current operated protective devices with an automatic-reclosing feature for telecom applications.
+
+Such devices with an automatic-reclosing feature (herein referred to as residual current devices with automatic reclosing (RCDAs)), also known as trip-free devices, are used in telecom applications based in central offices or in bureaux and/or stations. They are usually mounted as supplementary protection devices to other forms of protection against direct contact. The parameters reference built-in residual current operated protective devices with automatic-reclosing functionality.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T K.135    | 2018-11-13 | 5           | <a href="http://handle.itu.int/11.1002/1000/13714">11.1002/1000/13714</a> |
+
+## Keywords
+
+Automatic-reclosing, overcurrent protection, residual current devices (RCDs), self-restoring, trip-free.
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2019
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+###### Page
+
+|      |                                                                             |    |
+|------|-----------------------------------------------------------------------------|----|
+| 1    | Scope.....                                                                  | 1  |
+| 2    | References.....                                                             | 1  |
+| 3    | Definitions .....                                                           | 2  |
+| 3.1  | Terms defined elsewhere .....                                               | 2  |
+| 3.2  | Terms defined in this Recommendation .....                                  | 3  |
+| 4    | Abbreviations and acronyms .....                                            | 3  |
+| 5    | Conventions .....                                                           | 3  |
+| 6    | Technical requirements.....                                                 | 3  |
+| 6.1  | Appearance and structure .....                                              | 3  |
+| 6.2  | Enclosure requirement.....                                                  | 3  |
+| 6.3  | Dielectric properties .....                                                 | 4  |
+| 6.4  | Temperature rise .....                                                      | 4  |
+| 6.5  | Operating characteristics .....                                             | 4  |
+| 6.6  | Mechanical and electrical life.....                                         | 6  |
+| 6.7  | Short-circuit current performance .....                                     | 6  |
+| 6.8  | Test function of the device .....                                           | 6  |
+| 6.9  | Technical requirements for RCD functionally dependent on line voltage ..... | 6  |
+| 6.10 | RCD working conditions upon over current of main circuits .....             | 6  |
+| 6.11 | RCD performance with surge current.....                                     | 7  |
+| 6.12 | Technical requirements for automatic-reclosing devices .....                | 7  |
+| 6.13 | Environmental adaption.....                                                 | 7  |
+| 6.14 | Safety warning.....                                                         | 7  |
+|      | Annex A – RCDA with electric residual current detection function.....       | 8  |
+| A.1  | Technical rationale .....                                                   | 8  |
+|      | Bibliography.....                                                           | 11 |
+
+
+
+# Recommendation ITU-T K.135
+
+# Technical parameters for residual current operated protective devices with automatic reclosing feature for telecom applications
+
+# 1 Scope
+
+This Recommendation applies to residual current devices (RCDs) with automatic reclosing (RCDAs) and provides an overview of parameters and testing methods. RCDAs are equipped with an automatic-reclosing feature, called trip-free functionality. This Recommendation also covers built-in RCDAs.
+
+The following device parameters are covered:
+
+- appearance and structure;
+- enclosure;
+- dielectric properties;
+- temperature rise;
+- operating characteristics;
+- mechanical and electrical life;
+- performance at short-circuit current;
+- test function of the device;
+- technical requirements for RCDs functionally dependent on line voltage;
+- working conditions upon over current of main circuits;
+- surge current performance;
+- technical requirements for automatic-reclosing devices;
+- environmental adaption.
+
+This Recommendation does not cover:
+
+- quality assurance requirements.
+
+This Recommendation covers RCDs with automatic reclosing which are owned by network operators and under the supervision of skilled persons, and used within restricted access areas.
+
+NOTE – If there is an inconsistency between a requirement in this Recommendation and a requirement of the domestic laws and regulations which relates to electrical safety, the requirement of the domestic laws and regulations shall take priority.
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+[IEC 60529] IEC 60529 (2013), *Degrees of protection provided by enclosures (IP Code) Edition 2.2.*
+
+- [IEC 60898-2] IEC 60898-2 (2016), *Electrical accessories – Circuit-breakers for overcurrent protection for household and similar installations – Part 2: Circuit-breakers for AC and DC operation*.
+- [IEC 60947-2] IEC 60947-2 (2016), *Low-voltage switchgear and control gear – Part 2: Circuit-breakers*.
+- [IEC 61008-1] IEC 61008-1 (2013), *Residual current operated circuit-breakers without integral overcurrent protection for household and similar uses (RCCBs) – Part 1: General rules*.
+
+# 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 automatic reclosing** [b-IEC 61936-1]: Automatic reclosing of a circuit-breaker associated with a faulted section of a network after an interval of time which permits that section to recover from a transient fault.
+
+**3.1.2 auxiliary circuit (of a circuit-breaker)** [b-IEC 60898-1]: All the conductive parts of a circuit-breaker intended to be included in a circuit other than the main circuit and the control circuit of the circuit-breaker.
+
+**3.1.3 conditional residual short-circuit current** [b-IEC 62873-2],  $I_{\Delta C}$ : Value of the AC component of a residual prospective current which a residual current device (RCD) without integral short-circuit protection, but protected by a short-circuit protective device in series, can withstand under specified conditions of use and behaviour.
+
+**3.1.4 conditional short-circuit current (for a residual current device)** [b-IEC 60050-442]: Value of the alternating component of a prospective current, which a residual current device (RCD) without integral short-circuit protection, but protected by a short-circuit protective device in series, can withstand under specified conditions of use and behaviour.
+
+NOTE – The conditional short-circuit current value is represented by the symbol  $I_{NC}$ .
+
+**3.1.5 mechanical switching device** [b-IEC 62873-2]: Switching device designed to close and open one or more electric circuits by means of separable contacts.
+
+**3.1.6 rated residual operating current** [b-IEC 61557-6],  $I_{\Delta N}$ : Fault current for which the residual current protective device is designed.
+
+**3.1.7 residual current** [b-IEC 62752],  $I_{\Delta}$ : Vector sum of the instantaneous values of the current flowing in the main circuit of the residual current function (expressed as r.m.s. value).
+
+**3.1.8 residual current device (RCD)** [b-IEC 60755]: Mechanical switching device or association of devices designed to make, carry and break currents under normal service conditions and to cause the opening of the contacts when the residual current attains a given value under specified conditions.
+
+NOTE – An RCD may also be referred to as a residual current operated protective device.
+
+**3.1.9 residual making and breaking capacity** [b-IEC 62640],  $I_{\Delta M}$ : Value of the alternating component of a residual prospective current which a socket-outlet residual current device (RCD) can make, carry for its opening time and break under specified conditions of use and behaviour.
+
+**3.1.10 residual non-operating current** [b-IEC 62640],  $I_{\Delta NO}$ : Value of residual current at which and below which the residual current device (RCD) does not operate under specified conditions.
+
+**3.1.11 restricted access area** [b-IEC 62368-1]: Area accessible only to skilled persons and instructed persons with the proper authorization.
+
+**3.1.12 skilled person** [b-IEC 62368-1]: Person with relevant education or experience to enable him or her to identify hazards and to take appropriate actions to reduce the risks of injury to themselves and others.
+
+**3.1.13 trip-free mechanism of a residual current device** [b-IEC 60755]: Mechanism, the moving contacts of which return to and remain in the open position when the opening operation is initiated after the initiation of the closing operation, even if the closing command is maintained.
+
+NOTE – To ensure proper breaking of the current which may have been established, it may be necessary that the contacts momentarily reach the closed position.
+
+## **3.2 Terms defined in this Recommendation**
+
+None.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+RCD Residual Current Device
+
+RCDA Residual Current Device with Automatic reclosing
+
+NOTE – In the USA, an RCD is referred to as a ground fault interrupter (GFI).
+
+# **5 Conventions**
+
+None.
+
+# **6 Technical requirements**
+
+### **6.1 Appearance and structure**
+
+An RCD is mechanical switching device, which breaks the main circuit current by opening the switch contacts when the residual current reaches or exceeds a predetermined value.
+
+The device is equipped with a power disconnect mechanical indication. The RCD surface shall be even, clean, uniform in colour, and free from scratches, cracks and deformation. All fastening parts shall be firmly attached. All product labels shall be intact, clear and readable.
+
+The test button should be functional, see clause 6.8.
+
+RCDs' operational characteristics shall not be verified by any external loads except for the special equipment designed for verifying residual operation current levels.
+
+In multi-pole RCDs the moving contacts on all poles shall be mechanically connected to enable simultaneous breaking and closing manually or automatically except for switched neutral poles (if any).
+
+RCDs shall be trip-free and give a reliable indication of switch open and closed conditions.
+
+If indicator lights are used, they should be clearly visible when RCDs are in the closed position. Indicator lights shall not be the only method indicating the closed position.
+
+### **6.2 Enclosure requirement**
+
+#### **6.2.1 Protection against electric shock**
+
+RCDs' structure shall ensure its electrified parts are inaccessible after they are installed and wired correctly.
+
+RCDs' enclosure protection degree shall meet IP2X as specified in [IEC 60529].
+
+#### 6.2.2 Enclosure fire risks
+
+Enclosure insulation components shall be non-flammable or self-extinguishing.
+
+### 6.3 Dielectric properties
+
+RCD insulation shall have adequate dielectric properties.
+
+The DC high voltage generated from normal circuit insulation tests shall not damage the control circuit connected to the main circuit after RCDs are installed.
+
+### 6.4 Temperature rise
+
+The temperature rise of the accessible RCD parts shall not exceed the limits specified in Table 1. RCDs shall not suffer damage influencing their functions and safety use.
+
+**Table 1 – Limits of temperature rise (based on [IEC 61008-1])**
+
+| Parts                                                                                                                                               | Temperature rise / K |
+|-----------------------------------------------------------------------------------------------------------------------------------------------------|----------------------|
+| Terminals connecting outer conductors                                                                                                               | 60                   |
+| Outer accessible parts during manual operation of RCDs including operating parts of insulation materials and insulated metal parts connecting poles | 40                   |
+| Outer metal parts of operating components                                                                                                           | 25                   |
+| Other outer parts including the surface of RCDs directly in contact with mounting surfaces                                                          | 60                   |
+
+Ambient air temperature: the temperature rise limits listed in Table 1 are applicable only if the ambient air temperature is kept at the range of normal working conditions.
+
+## 6.5 Operating characteristics
+
+The values required in this clause may vary depending on national requirements and laws and regulations.
+
+#### 6.5.1 Rated residual operating current ( $I_{\Delta N}$ )
+
+The residual operating current value specified by manufacturers has preferred values of 0.006 A, 0.01 A, 0.03 A, 0.1 A, 0.3 A and 0.5 A. The levels of 0.03 A and below are intended to protect users from hazardous electric shock.
+
+#### 6.5.2 Rated residual non-operating current ( $I_{\Delta NO}$ )
+
+The residual non-operating current value specified by manufacturers, has a preferred value of 50% of the rated residual operating current ( $0.5 I_{\Delta N}$ ).
+
+#### 6.5.3 Rated make and break capacity ( $I_M$ )
+
+This parameter refers to the rated connecting/breaking capacity of RCDs with short-circuit protection. RCDs shall conform to the requirements of [IEC 60898-2] when the parts perform main circuit making/breaking functions with circuit breakers used for household and similar installations; RCDs shall conform to the requirements of [IEC 60947-2] when the parts perform main circuit making/breaking functions using low-voltage circuit breakers.
+
+Table 2 gives the minimum values of the rated making/ breaking current capability of RCDs without over-current protection. Table 3 gives corresponding power factors.
+
+**Table 2 – Minimum values of short-circuit test current (based on [IEC 61008-1])**
+
+| $I_N$ A              | Prospective current for $I_M$ , $I_{\Delta M}$ , $I_{NC}$ , $I_{\Delta C}$ tests A |
+|----------------------|------------------------------------------------------------------------------------|
+| $I_N \leq 10$        | 300                                                                                |
+| $10 < I_N \leq 50$   | 500                                                                                |
+| $50 < I_N \leq 100$  | 1000                                                                               |
+| $100 < I_N \leq 150$ | 1500                                                                               |
+| $150 < I_N \leq 200$ | 2000                                                                               |
+
+**Table 3 – Power factors of short-circuit tests**
+
+| Short-circuit current $I_C$ , A | Power factor |
+|---------------------------------|--------------|
+| $I_C \leq 500$                  | 1            |
+| $500 < I_C \leq 1500$           | 0.95         |
+| $1500 < I_C \leq 3000$          | 0.9          |
+
+#### **6.5.4 Rated residual making/breaking capacity ( $I_{\Delta M}$ )**
+
+Refer to Table 2 for the minimum values of rated residual making/breaking capacity and Table 3 for corresponding power factors.
+
+#### **6.5.5 Rated conditional short-circuit current ( $I_{NC}$ )**
+
+Refer to Table 2 for the minimum values of rated conditional short-circuit current and Table 3 for corresponding power factors.
+
+#### **6.5.6 Rated conditional residual short-circuit current ( $I_{\Delta C}$ )**
+
+Refer to Table 2 for the minimum values of rated conditional residual short-circuit current and Table 3 for corresponding power factors.
+
+#### **6.5.7 Break time**
+
+Table 4 gives the maximum break time of RCDs for protection against indirect contact.
+
+**Table 4 – Maximum break time of RCDs for protection against indirect contact**
+
+| $I_{\Delta M}$<br>A | $I_N$<br>A                                                                | Maximum break time, s |                 |                 |
+|---------------------|---------------------------------------------------------------------------|-----------------------|-----------------|-----------------|
+|                     |                                                                           | $I_{\Delta M}$        | $2I_{\Delta M}$ | $5I_{\Delta M}$ |
+| $I > 0.03$          | Any value                                                                 | 0.2                   | 0.1             | 0.04            |
+|                     | $\geq 40$ (only applicable to RCDs assembled with independent components) | 0.2                   | -               | 0.15            |
+
+Table 5 gives the maximum break time of RCDs for direct contact protection.
+
+**Table 5 – Maximum break time of RCDs for protection against direct contact**
+
+| $I_{\Delta M}$<br>A | $I_N$<br>A | Maximum break time, s |                 |
+|---------------------|------------|-----------------------|-----------------|
+|                     |            | $I_{\Delta M}$        | $5I_{\Delta M}$ |
+| $\leq 0.03$         | Any value  | 0.1                   | 0.04            |
+
+#### 6.5.8 Delay operating time
+
+For time delay operating characteristics, the preferred values of delay time are 0.2 s, 0.4 s, 0.8 s, 1 s, 1.5 s and 2 s. Time delay characteristics are only applicable to RCDs for indirect contact protection. This term does not apply to the products without any time delay operating characteristics.
+
+### 6.6 Mechanical and electrical life
+
+RCDs shall be able to withstand the number operations specified in Table 6 in which every operating cycle includes one time of connecting and one time of breaking.
+
+**Table 6 – Operating cycle times**
+
+| Rated current $I_n$ | Operating cycle times | Including          |                    |
+|---------------------|-----------------------|--------------------|--------------------|
+|                     |                       | On-load operations | No-load operations |
+| $I_n \leq 25$ A     | 4000                  | 2000               | 2000               |
+| $I_n > 25$ A        | 3000                  | 2000               | 1000               |
+
+### 6.7 Short-circuit current performance
+
+RCDs shall be able to carry out the specified number of short-circuit operations. Short-circuit operations shall not bring danger to any operator or form flashover among electrified conductive parts or between electrified conductive parts and earthing bonding parts.
+
+### 6.8 Test function of the device
+
+The RCD shall incorporate a test function and be equipped with a test load to simulate an operate residual current level to do scheduled tests on the operating capacity of the RCD.
+
+NOTE – A test device is used to check the trip function, but not to verify the validity of the function on the basis of rated residual operating current and break time.
+
+At rated voltage, the residual current flowing in the test load shall not exceed 2.5 times that of the residual current equal to  $I_{\Delta N}$  flowing through any main circuit of the protective device. If an RCD has more than one residual operating current setting, the lowest designed value shall be adopted.
+
+Upon operating a test device, the protected conductor shall not be electrified. When an RCD is in the open position in normal use, the load side shall not supply power to a test load.
+
+Test loads are not designed for breaking operation. Therefore, they are not to be used for routine disconnection.
+
+### 6.9 Technical requirements for RCD functionally dependent on line voltage
+
+RCDs are functionally dependent on the AC line voltage and shall work properly at any line voltage between 0.85 to 1.1 times the rated voltage. Under such conditions, multi-pole RCDs' all currents shall be supplied by phase lines and neutral lines (if any) of power sources.
+
+At abnormal line voltage, RCDs have two operating functions of opening and closing main circuits.
+
+### 6.10 RCD working conditions upon over current of main circuits
+
+RCDs without overcurrent protection shall not operate under specified overcurrent conditions. For overcurrent protected RCDs, use [IEC 60898-2] or [IEC 60947-2] according to relevant product standards.
+
+### **6.11 RCD performance with surge current**
+
+RCDs shall have sufficient resistance to surge current to earth when operating with a capacitive load, or in the event of a device flashover. Time delay RCDs shall have sufficient capacity to prevent a fault trip in the event of a surge current to earth due to flashover.
+
+No fault operation shall occur when 1.2/50–8/20 combination wave, 2 kV is applied to power lines (L-N). A sample shall work normally without any damage when 1.2/50, 4 kV surge voltage is applied to power lines (L-N).
+
+A sample shall work normally without any damage when an 8/20, 20 kA lightning current passes through the RCD L to N, when a surge protective device is installed. The device shall be able to operate and to open the circuit, in the event of short-circuit condition.
+
+### **6.12 Technical requirements for automatic-reclosing devices**
+
+#### **6.12.1 Automatic-reclosing devices without residual current detection function**
+
+If the RCDs do not have electric residual current detection function after the opening, the RCDs automatically reclose typically once after 20 s to 60 s of the opening; if this is not successful, the devices reclose for a second time typically after a 15-minute delay; if this is still not successful, the devices reclose for a third time typically after another 15-minute delay. If not successful, no further reclosing is allowed.
+
+Successful reclosing means that the device shall stay closed for typically 5 s after it recloses.
+
+When an RCD trips, the automatic recloser will check the circuit where the RCD is installed to avoid safety problems where residual current still exists after the RCD is reclosed.
+
+#### **6.12.2 Automatic-reclosing devices with electric residual current detection function**
+
+After automatic-reclosing devices open, the requirements on the residual current detection functions are as follows: 1) no further reclosing is allowed after 3 unsuccessful reclosing attempts, typically within 1 minute. 2) testing voltage is  $DC \leq 24\text{ V}$  or AC typical value  $\leq 17\text{ V}$ .
+
+### **6.13 Environmental adaption**
+
+Operating environmental conditions:
+
+Normal range:  $-5^{\circ}\text{C} \sim +40^{\circ}\text{C}$
+
+Extended range:  $-40^{\circ}\text{C} \sim +70^{\circ}\text{C}$
+
+Humidity: 5% to 95%
+
+Atmospheric pressure: 70 kPa ~ 106 kPa.
+
+### **6.14 Safety warning**
+
+To remind skilled persons of the potential electric shock risk in the insulation case, the following warning sign and language shall be required to be placed on the equipment case:
+
+IEC 60417-6042
+
+"WARNING " or equivalent word or text, and
+
+"HIGH TOUCH CURRENT" or equivalent text
+
+"Automatic-reclosing power devices" or equivalent text
+
+# Annex A
+
+## RCDAs with electric residual current detection function
+
+(This annex forms an integral part of this Recommendation.)
+
+## A.1 Technical rationale
+
+When an RCD trips, the automatic recloser will check the circuit where the RCD is installed to avoid safety problems where residual current still exists after the RCD is reclosed.
+
+Figure A.1-1 and Figure A.1-2 show the leakage fault detection circuit separately, representing single-phase and three-phase main power.
+
+The detecting signal passes through grounding, transformer and neutral line. The detecting circuit is installed on the output of an RCD phase and neutral line (a, b, c, n) respectively. Residual current detecting becomes a loop after checking the phase line, PE line, grounding resistance Re1 and Re2, the neutral line in the transformer and the detection circuit. The PE wire of the detection circuit does not need to connect to the equipment enclosure. The voltage of the detection circuit is 24 V d.c.
+
+![Figure A.1-1: Schematic diagram of a single-phase residual current detection circuit. The diagram shows three phase lines (L1, L2, L3) and a neutral line (N) entering from the top. A grounding resistor Re1 is connected between the neutral line and ground. A dotted line encloses the detection circuit, which includes a 'Detecting power supply' and a 'Detecting control' block. The power supply has terminals 'a' and 'b' connected to the phase and neutral lines respectively. The control block is connected to the power supply. A phase line (L1) is shown with a switch and a ground fault symbol (circle with a dot). The PE line is connected to the control block and to a grounding resistor Re2 via a PE terminal. The diagram is labeled K.135(18)_FA.1-1.](16c1175b5f05a4b55e6d396fc51b15b3_img.jpg)
+
+K.135(18)\_FA.1-1
+
+Figure A.1-1: Schematic diagram of a single-phase residual current detection circuit. The diagram shows three phase lines (L1, L2, L3) and a neutral line (N) entering from the top. A grounding resistor Re1 is connected between the neutral line and ground. A dotted line encloses the detection circuit, which includes a 'Detecting power supply' and a 'Detecting control' block. The power supply has terminals 'a' and 'b' connected to the phase and neutral lines respectively. The control block is connected to the power supply. A phase line (L1) is shown with a switch and a ground fault symbol (circle with a dot). The PE line is connected to the control block and to a grounding resistor Re2 via a PE terminal. The diagram is labeled K.135(18)\_FA.1-1.
+
+Figure A.1-1 – Dotted line represents single-phase residual current detection circuit
+
+![Schematic diagram of a 3-phase residual current detection circuit. The diagram shows three phase lines (L1, L2, L3) and a neutral line (N) entering a device enclosure. Inside, a 'Detecting power supply' is connected to phases a, b, c, and N. A 'Detecting control' unit is connected to the power supply. A dotted line represents the residual current detection circuit, which loops from the power supply, through the device enclosure, and to the PE (Protective Earth) line. The PE line is connected to an earth electrode (Re2). Another earth electrode (Re1) is shown connected to the neutral line (N) outside the enclosure. The diagram is labeled K.135(18)_FA.1-2.](33ed1f9b27c7c21c797aa928b0f06851_img.jpg)
+
+Schematic diagram of a 3-phase residual current detection circuit. The diagram shows three phase lines (L1, L2, L3) and a neutral line (N) entering a device enclosure. Inside, a 'Detecting power supply' is connected to phases a, b, c, and N. A 'Detecting control' unit is connected to the power supply. A dotted line represents the residual current detection circuit, which loops from the power supply, through the device enclosure, and to the PE (Protective Earth) line. The PE line is connected to an earth electrode (Re2). Another earth electrode (Re1) is shown connected to the neutral line (N) outside the enclosure. The diagram is labeled K.135(18)\_FA.1-2.
+
+**Figure A.1-2 – Dotted line represents 3-phase residual current detection circuit**
+
+Figure A.1-3 and Figure A.1-4 show reclosing devices for residual current detection.
+
+The detecting signal passes through the device enclosure. The residual current detection becomes a loop after checking the phase line, the device enclosure and the PE line. The PE wire of the detection circuit needs to connect to the equipment enclosure. The voltage of the detection circuit is 24 V d.c.
+
+![Circuit diagram for single-phase residual current detection. It shows four input lines: L1, L2, L3, and N. L1, L2, and L3 have inductor symbols. A ground connection with resistance Re1 is on the left. A switch symbol is on the N line. A 'Detecting power supply' block has terminals 'a' and 'b'. A 'Detecting control' block is connected to it. A dotted line encloses the 'Detecting power supply', 'Detecting control', and a switch symbol with terminals 'a' and 'b'. This dotted area is connected to a PE (protective earth) line. The PE line connects to a ground connection with resistance Re2. The diagram is labeled K.135(18)_FA.1-3.](fa859e4e468bfb2710a94527f2c504af_img.jpg)
+
+Circuit diagram for single-phase residual current detection. It shows four input lines: L1, L2, L3, and N. L1, L2, and L3 have inductor symbols. A ground connection with resistance Re1 is on the left. A switch symbol is on the N line. A 'Detecting power supply' block has terminals 'a' and 'b'. A 'Detecting control' block is connected to it. A dotted line encloses the 'Detecting power supply', 'Detecting control', and a switch symbol with terminals 'a' and 'b'. This dotted area is connected to a PE (protective earth) line. The PE line connects to a ground connection with resistance Re2. The diagram is labeled K.135(18)\_FA.1-3.
+
+Figure A.1-3 – Dotted line represents single-phase residual current detection circuit
+
+![Circuit diagram for 3-phase residual current detection. It shows four input lines: L1, L2, L3, and N. L1, L2, and L3 have inductor symbols. A ground connection with resistance Re1 is on the left. A switch symbol is on the N line. A 'Detecting power supply' block has terminals 'a', 'b', 'c', and 'N'. A 'Detecting control' block is connected to it. A dotted line encloses the 'Detecting power supply', 'Detecting control', and a switch symbol with terminals 'a', 'b', 'c', and 'n'. This dotted area is connected to a PE (protective earth) line. The PE line connects to a ground connection with resistance Re2. The diagram is labeled K.135(18)_FA.1-4.](0f985b39edc1d52ba3600c438bc8f0a5_img.jpg)
+
+Circuit diagram for 3-phase residual current detection. It shows four input lines: L1, L2, L3, and N. L1, L2, and L3 have inductor symbols. A ground connection with resistance Re1 is on the left. A switch symbol is on the N line. A 'Detecting power supply' block has terminals 'a', 'b', 'c', and 'N'. A 'Detecting control' block is connected to it. A dotted line encloses the 'Detecting power supply', 'Detecting control', and a switch symbol with terminals 'a', 'b', 'c', and 'n'. This dotted area is connected to a PE (protective earth) line. The PE line connects to a ground connection with resistance Re2. The diagram is labeled K.135(18)\_FA.1-4.
+
+Figure A.1-4 – Dotted line represents 3-phase residual current detection circuit
+
+## Bibliography
+
+- [b-IEC 60050-442] IEC 60050-442 (1998), *International Electrotechnical Vocabulary – Part 442: Electrical accessories*.
+- [b-IEC 60755] IEC 60755 (2017), *General safety requirements for residual current operated protective devices*.
+- [b-IEC 60898-1] IEC 60898-1 (2015), *Electrical accessories – Circuit-breakers for overcurrent protection for household and similar installations – Part 1: Circuit-breakers for a.c. operation*.
+- [b-IEC 61557-6] IEC 61557-6 (2007), *Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures – Part 6: Effectiveness of residual current devices (RCD) in TT, TN and IT systems*.
+- [b-IEC 61936-1] IEC 61936-1 (2014), *Power installations exceeding 1 kV a.c. – Part 1: Common rules*.
+- [b-IEC 62368-1] IEC 62368-1 (2018), *Audio/video, information and communication technology equipment – Part 1: Safety requirements*.
+- [b-IEC 62752] IEC 62752 (2016), *In-cable control and protection device for mode 2 charging of electric road vehicles (IC-CPD)*.
+- [b-IEC 62873-2] IEC 62873-2 (2016), *Residual current operated circuit-breakers for household and similar use – Part 2: Residual current devices (RCDs) – Vocabulary*.
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| Series E        | Overall network operation, telephone service, service operation and human factors                                                                         |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| <b>Series K</b> | <b>Protection against interference</b>                                                                                                                    |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/K/T-REC-K.148-202012-I_PDF-E/raw.md

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+
+
+I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n
+
+# **ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+# **K.148**
+
+(12/2020)
+
+SERIES K: PROTECTION AGAINST INTERFERENCE
+
+# --- **Multiservice surge protective device application guide**
+
+Recommendation ITU-T K.148
+
+**ITU-T**
+
+![ITU logo](84a1d09fb489061482111515543b60dc_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with a white grid pattern, and the letters 'ITU' in white, bold, sans-serif font, superimposed on the globe.
+
+ITU logo
+
+
+
+## Recommendation ITU-T K.148
+
+# Multiservice surge protective device application guide
+
+## Summary
+
+A multiservice surge protective device (MSPD) protects two or more services e.g., mains and telecommunications, and has a common bonding point for the service surge protective devices (SPDs) contained in the MSPD. Recommendation ITU-T K.148 provides application guidance on MSPDs and explains their uses, required performance parameters and usage consequences.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T K.148    | 2020-12-14 | 5           | <a href="http://handle.itu.int/11.1002/1000/14561">11.1002/1000/14561</a> |
+
+## Keywords
+
+ICT service, multiservice surge protective device, MSPD, power service, surge reference equaliser.
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2021
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+**Page**
+
+- 1 Scope 1
+- 2 References 1
+- 3 Definitions 1
+  - 3.1 Terms defined elsewhere 1
+  - 3.2 Terms defined in this Recommendation 2
+- 4 Abbreviations and acronyms 2
+- 5 Conventions 3
+- 6 Individual service SPDs 3
+  - 6.1 Surge mitigation functions 3
+  - 6.2 Power service protection 4
+  - 6.3 Signal service protection 5
+  - 6.4 Individual SPD earthing problems 5
+- 7 Surge reference equaliser (MSPD concept) 6
+- 8 MSPD implications 8
+  - 8.1 Protected-side earth loop currents 8
+  - 8.2 SPD cross-coupling 8
+  - 8.3 High impedance or missing local earth connection 8
+- 9 Summary 8
+- Bibliography 9
+
+
+
+# Multiservice surge protective device application guide
+
+## 1 Scope
+
+This Recommendation provides application guidance on multiservice surge protective devices (MSPDs) and explains how MSPDs provide local overvoltage protection for the services used by an equipment or equipment cluster. The requirements of the individual service surge protective devices (SPDs) are outlined, together with possible interactions on the MSPD protected side. This Recommendation also explains how the MSPD interacts with the surges on the services and the consequences of these surges when the local protective earthing (PE) connection is high impedance or is missing.
+
+## 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+None.
+
+## 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 common mode conversion** [b-ITU-T K.96]: Process by which a differential mode electrical signal is produced in response to a common mode electrical signal.
+
+**3.1.2 common-mode surge** [b-ITU-T K.96]: Surge appearing equally on all conductors of a group at a given location.
+
+NOTE 1 – The reference point for common-mode surge voltage measurement can be a chassis terminal, or a local earth/ground point.
+
+NOTE 2 – Also known as longitudinal surge or asymmetrical surge.
+
+**3.1.3 band-pass filter** [b-ITU-T K.96]: Filter that allows passage of a desired range of frequencies and attenuates frequencies outside the desired range.
+
+NOTE – This definition is based on the definition provided in [b-IEEE Std 802.7].
+
+**3.1.4 common-mode choke filter** [b-ITU-T K.96]: Series in-line transformer used to mitigate common-mode current flow without affecting differential current flow.
+
+**3.1.5 common-mode rejection filter** [b-ITU-T K.96]: Filter type, usually a balanced filter that attenuates the signal common to both input lines; that signal is called the common-mode signal.
+
+NOTE – This definition is based on the definition provided in [b-IEEE Std 1549].
+
+**3.1.6 differential-mode surge** [b-ITU-T K.96]: Surge occurring between any two conductors or two groups of conductors at a given location.
+
+NOTE 1 – The surge source maybe be floating, without a reference point or connected to reference point, such as a chassis terminal, or a local earth/ground point.
+
+NOTE 2 – Also known as metallic surge or transverse surge or symmetrical surge or normal surge.
+
+**3.1.7 filter** [b-IEEE Std 802.7]: Circuit that selects or rejects one or more components of a signal related to frequency.
+
+**3.1.8 high-pass filter** [b-ITU-T K.96]: Electrical network that passes higher frequencies, attenuates lower frequencies and blocks DC levels.
+
+NOTE – This definition is based on the definition provided in [b-IEEE Std 1149.6].
+
+**3.1.9 low-pass filter** [b-IEEE Std 1149.6]: Electrical network that passes lower frequencies, including DC levels, and attenuates higher frequencies.
+
+**3.1.10 modes of protection (of a voltage limiting surge protective device (SPD) or equipment port)** [b-ITU-T K.99]: List of terminal-pairs where the diverted surge current is directly between that terminal-pair without flowing via other terminals.
+
+**3.1.11 multiservice surge protective device** [b-ITU-T K.85]: A surge protective device (SPD) containing both telecommunications and mains protection. It may also include port protection for video or Ethernet.
+
+**3.1.12 surge protective component (SPC)** [b-ITU-T K.96]: Component specifically included in a device or equipment for the mitigation of the onward propagation of overvoltages or overcurrents or both.
+
+**3.1.13 surge protective device (SPD)** [b-ITU-T K.96]: Device that mitigates the onward propagation of overvoltages or overcurrents or both.
+
+**3.1.14 surge reference equalizer** [b-IEC TR 62066]: Device used for connecting equipment to external systems whereby all conductors connected to the protected load are routed, physically and electrically, through a single enclosure with a shared reference point between the input and output ports of each system.
+
+NOTE – Sharing the reference point may be accomplished within the device either by a direct bond or through a suitable device, such as an SPD which maintains isolation during normal conditions but provides an effective bond during the occurrence of a surge in one or both systems.
+
+### **3.2 Terms defined in this Recommendation**
+
+This Recommendation defines the following terms:
+
+**3.2.1 earth loop:** Potentially detrimental loop formed when two or more points in an electrical system that are connected to their local earth potential are also interconnected by earth referenced conductors, which creates a loop that will carry current if the local earths are not at the same potential.
+
+## **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|      |                                          |
+|------|------------------------------------------|
+| GDT  | Gas Discharge Tube                       |
+| IP   | Ingress Protection                       |
+| ICT  | Information and Communication Technology |
+| MOV  | Metal-oxide Varistor                     |
+| MSPD | Multiservice Surge Protective Device     |
+| PE   | Protective Earthing                      |
+| SPC  | Surge Protective Component               |
+| SPD  | Surge Protective Device                  |
+
+## 5 Conventions
+
+None.
+
+## 6 Individual service SPDs
+
+### 6.1 Surge mitigation functions
+
+SPDs are normally fitted to cabling when failures have occurred due to overvoltages or there are concerns about the service overvoltage levels. Common-mode surge overvoltages occur on all conductors within the cable. Figure 1 shows several mitigation options for a common-mode surge:
+
+- voltage limit the surge voltage from an earth reference potential by using non-linear voltage limiting components,
+- block the voltage surge with an isolating transformer,
+- filter out the surge frequencies if the service and lightning spectrums do not overlap,
+- use a common-mode choke, which has a high impedance to common-mode surge and a low impedance to the differential signal,
+- use a series electronic current limiter as these are fast enough to operate under surge conditions.
+
+![Figure 1 – Common-mode surge mitigation options](dbe553cf16dd14073b89a8263a428664_img.jpg)
+
+The diagram illustrates common-mode surge mitigation options across two parallel lines connecting an 'Equipotential conductor group' on the left to a 'Protected load' on the right. A 'Surge' is indicated entering from the left. The mitigation stages are labeled a) through e):  
+ a) Shunt voltage limiter: Two non-linear components (labeled V) connected from each line to the 'Reference potential and functional bonding' line at the bottom.  
+ b) In-line isolating transformer: A transformer symbol in series with the lines. A dashed line indicates a 'Screened version' connected to the reference potential.  
+ c) Series and shunt filter: A box containing a Z-shaped symbol representing a filter network.  
+ d) Common-mode choke: A dual-winding inductor symbol.  
+ e) Series current limiter: Two circular symbols with vertical lines, one in series with each conductor.  
+ The entire circuit is referenced to a bottom line labeled 'Reference potential and functional bonding'. The figure is identified as K.148(20)\_F01.
+
+Figure 1 – Common-mode surge mitigation options
+
+**Figure 1 – Common-mode surge mitigation options**
+
+The Figure 1 a) shunt voltage limiter could be realised by many technologies such as metal-oxide varistor (MOV), gas discharge tube (GDT), PN junction diode, foldback diode and punch-through diode. The description and operation of these protection technologies is covered in [b-ITU-T K.96].
+
+Differential mode surge overvoltages occur between conductors or sets of cable conductors. Figure 2 shows several mitigation options for a differential-mode surge:
+
+- voltage limit the surge voltage between the conductors by using non-linear voltage limiting components,
+- if the signal transformer core saturates, stopping transformer action, surge truncation will occur, see [b-ITU-T K.126],
+- filter out the surge frequencies if the service and lightning spectrums do not overlap,
+- use a series electronic current limiter as these are fast enough to operate under surge conditions.
+
+![Figure 2: Differential-mode surge mitigation options. The diagram shows four options (a, b, c, d) for protecting a load from surges. Option a) is a shunt voltage limiter (MOV) connected in parallel with the load. Option b) is an in-line isolating transformer. Option c) is a series and filter (inductor and capacitor) connected in series with the load. Option d) is a series current limiter (diode) connected in series with the load. A surge waveform is shown on the left. A reference potential and functional bonding line is shown at the bottom. The diagram is labeled K.148(20)_F02.](a5ee5c23b6dc52ec1d724b76d5a5f58f_img.jpg)
+
+Figure 2: Differential-mode surge mitigation options. The diagram shows four options (a, b, c, d) for protecting a load from surges. Option a) is a shunt voltage limiter (MOV) connected in parallel with the load. Option b) is an in-line isolating transformer. Option c) is a series and filter (inductor and capacitor) connected in series with the load. Option d) is a series current limiter (diode) connected in series with the load. A surge waveform is shown on the left. A reference potential and functional bonding line is shown at the bottom. The diagram is labeled K.148(20)\_F02.
+
+**Figure 2 – Differential-mode surge mitigation options**
+
+The description and operation of these protection technologies is covered in [b-ITU-T K.96].
+
+### 6.2 Power service protection
+
+The main requirement for power service protection is to limit the common mode surge overvoltage and generally the approach of Figure 1a) is used. Figure 3 shows different ways MOVs can be connected to protect a two-wire power source. Circuit a) has one MOV (MOV1) to directly protect the power source and a second MOV (MOV2) to protect the power source insulation to earth. Circuit b) has one MOV (MOV1) protecting the power feed conductor to earth and a second MOV (MOV2) to protect the power return conductor to earth. Circuit c) has one MOV (MOV1) protecting the power feed conductor to earth, a second MOV (MOV2) protecting the power return conductor to earth and a third MOV (MOV3) directly protecting the power source. Circuit d) has two series connected MOVs (MOV1 and MOV3) directly protecting the power source and one MOV (MOV2), connected to the junction of MOV1 and MOV3, protecting the power source insulation to earth.
+
+![Figure 3: Circuit examples of powering feed protection. The diagram shows four circuit examples (a, b, c, d) for protecting a two-wire power source. Circuit a) shows MOV1 connected between the power feed and power return, and MOV2 connected between the power return and earth. Circuit b) shows MOV1 connected between the power feed and earth, and MOV2 connected between the power return and earth. Circuit c) shows MOV1 connected between the power feed and earth, MOV2 connected between the power return and earth, and MOV3 connected between the power feed and power return. Circuit d) shows MOV1 and MOV3 connected in series between the power feed and power return, and MOV2 connected between their junction and earth. The diagram is labeled K.148(20)_F03.](b8661c6c54f72ecc7ff6cb05e47b2891_img.jpg)
+
+Figure 3: Circuit examples of powering feed protection. The diagram shows four circuit examples (a, b, c, d) for protecting a two-wire power source. Circuit a) shows MOV1 connected between the power feed and power return, and MOV2 connected between the power return and earth. Circuit b) shows MOV1 connected between the power feed and earth, and MOV2 connected between the power return and earth. Circuit c) shows MOV1 connected between the power feed and earth, MOV2 connected between the power return and earth, and MOV3 connected between the power feed and power return. Circuit d) shows MOV1 and MOV3 connected in series between the power feed and power return, and MOV2 connected between their junction and earth. The diagram is labeled K.148(20)\_F03.
+
+**Figure 3 – Circuit examples of powering feed protection**
+
+Circuits a) and b) are the least cost using only two MOVs. Circuits c) and d) are more expensive using 3 MOVs. For DC supplies, if the voltage polarity of the powering conductors is known, diode steering, D1 and D2, can be added to the Figure 3 c) circuit to ensure that common-mode impulses of any polarity only charge and do not discharge the power source, see Figure 4. For any impulse polarity, the powering source voltage increase during an impulse is limited by MOV3.
+
+![Circuit diagram of a diode steering variant of circuit c). The diagram shows a 'Power feed +' line and a 'Power return -' line. MOV3 is connected between these two lines. Below the 'Power return -' line, MOV2 is connected between the return line and ground, and MOV1 is connected between the 'Power feed +' line and ground. Diodes D1 and D2 are connected in series between the 'Power return -' line and ground, with D1 pointing towards the 'Power feed +' line and D2 pointing towards ground. The entire assembly is connected to a common ground. The label 'K.148(20)_F04' is at the bottom.](cfef993dcc8fb513de79eb1f93cf26ae_img.jpg)
+
+Circuit diagram of a diode steering variant of circuit c). The diagram shows a 'Power feed +' line and a 'Power return -' line. MOV3 is connected between these two lines. Below the 'Power return -' line, MOV2 is connected between the return line and ground, and MOV1 is connected between the 'Power feed +' line and ground. Diodes D1 and D2 are connected in series between the 'Power return -' line and ground, with D1 pointing towards the 'Power feed +' line and D2 pointing towards ground. The entire assembly is connected to a common ground. The label 'K.148(20)\_F04' is at the bottom.
+
+**Figure 4 – Diode steering variant of circuit c)**
+
+Important power service SPD performance parameters are the maximum continuous operation voltage, limiting voltage and surge resistibility. For all the SPD parameters consult the appropriate international, regional or national standards and manufacturers data sheets. Examples of power SPD standards are [b-IEC 61643-11] and [b-UL 1449]. Generally, power SPD standards do not cover the inclusion of filters simultaneous surge on all the powering lines. Outside use SPDs are likely to have an ingress protection (IP) rating indicating the enclosure sealing effectiveness against intrusion of foreign bodies and moisture.
+
+[b-IEC 60664-1] lists the following preferred overvoltage categories of 60 V, 330 V, 500 V, 800 V, 1.5 kV, 2.5 kV, 4 kV, 6 kV, 8 kV, 10 kV and 15 kV.
+
+### 6.3 Signal service protection
+
+Generally, ports for signal services have less surge resistance than power services, particularly for differential mode surge. Differential mode surges are often created by non-synchronous operation of common mode protection elements.
+
+Services supplied using co-axial cable only need voltage mitigation between the centre conductor and cable screen. In high frequency signal cases a passive quarter-wave shorting stub protector can be used to filter out the lightning frequency components.
+
+Services supplied with twisted pair cabling need voltage mitigation between the conductors. Multi-twisted pair cables supplying power may also need inter-pair voltage mitigation between the pairs of differing potentials.
+
+Important signal service SPD performance parameters are the maximum continuous operation voltage, limiting voltage and surge resistibility both for common mode and differential mode surges. For all the SPD parameters consult the appropriate international, regional or national standards and manufacturers data sheets. Outside use SPDs are likely to have an ingress protection IP rating indicating the enclosure sealing effectiveness against intrusion of foreign bodies and moisture.
+
+### 6.4 Individual SPD earthing problems
+
+When SPDs are individually applied to services, as shown in Figure 5, the common mode surge current from the SPD "C" terminal to the local earth reference via the earthing cable can create a potential difference from the true earth potential. Further the local earth references themselves may be at different potentials. For example, a 1 m connecting cable has an inductance of about
+
+1.5  $\mu\text{H/m}$ . A diverted surge current of 50 A/ $\mu\text{s}$  would create an inductive voltage of 75 V/m. This inductive voltage adds to the SPD limiting voltage.
+
+![Diagram illustrating individual SPD earthing for power and ICT services. It shows four SPD units (Power SPD, ICT SPD1, ICT SPDn, and Equipment ICT SPD) connected to a central ICT equipment cluster. Each SPD has its 'C' terminal connected to a local earth reference. The Power SPD receives 'Power in' and provides 'Cluster powering' to the cluster. ICT SPD1 receives 'ICT service 1 in' and provides 'ICT service 1 to cluster' to the cluster. ICT SPDn receives 'ICT service n in' via a 'Screened cable' and provides 'ICT service n to cluster' via a 'Screened cable' to the cluster. The Equipment ICT SPD receives 'ICT service from cluster' and provides 'ICT service out'.](007b053fe94a8348f75128a584503fd0_img.jpg)
+
+The diagram shows the earthing configuration for various Surge Protection Devices (SPDs) connected to an ICT equipment cluster. On the right is a large vertical rectangle labeled 'ICT equipment cluster'. To its left are four smaller boxes representing different SPDs, each with a 'C' terminal connected to a 'Local earth reference' (indicated by a ground symbol and the letter 'C').
+
+- Power SPD:** Located at the top. It receives 'Power in' from the left and provides three arrows labeled 'Cluster powering' to the ICT equipment cluster.
+- ICT SPD1:** Located below the Power SPD. It receives 'ICT service 1 in' from the left and provides an arrow labeled 'ICT service 1 to cluster' to the ICT equipment cluster.
+- ICT SPDn:** Located below ICT SPD1. It receives 'ICT service n in' from the left via a 'Screened cable' and provides an arrow labeled 'ICT service n to cluster' via a 'Screened cable' to the ICT equipment cluster.
+- Equipment ICT SPD:** Located at the bottom. It receives an arrow labeled 'ICT service from cluster' from the ICT equipment cluster and provides an arrow labeled 'ICT service out' to the left.
+
+The diagram is labeled 'K.148(20)\_F05' in the bottom right corner.
+
+Diagram illustrating individual SPD earthing for power and ICT services. It shows four SPD units (Power SPD, ICT SPD1, ICT SPDn, and Equipment ICT SPD) connected to a central ICT equipment cluster. Each SPD has its 'C' terminal connected to a local earth reference. The Power SPD receives 'Power in' and provides 'Cluster powering' to the cluster. ICT SPD1 receives 'ICT service 1 in' and provides 'ICT service 1 to cluster' to the cluster. ICT SPDn receives 'ICT service n in' via a 'Screened cable' and provides 'ICT service n to cluster' via a 'Screened cable' to the cluster. The Equipment ICT SPD receives 'ICT service from cluster' and provides 'ICT service out'.
+
+**Figure 5 – Individual SPD earthing**
+
+The power SPD will be connected to the mains plug/socket local earth reference. The incoming service SPD1 and outgoing service equipment SPD will be connected to whatever local earth reference is provided. For the screened cable SPDn the earth reference could be applied to the cable originating end.
+
+## 7 Surge reference equaliser (MSPD concept)
+
+A surge reference equaliser does two things; it brings together all the service SPDs by locating them in a single enclosure and provides a local earth reference for all the SPD "C" terminals to directly connect to. Figure 6 shows the configuration.
+
+![Diagram of SPDs in a surge reference equaliser configuration. A dashed box labeled 'SPD enclosure' contains a 'Power SPD', 'ICT SPD1', 'Common bonding point', 'ICT SPDn', and 'Equipment ICT SPD'. 'Power in' enters the Power SPD, which is connected to a 'Local earth reference' via a 'C' (capacitor/grounding) symbol. The Power SPD outputs three 'Cluster powering' lines to an 'ICT equipment cluster'. 'ICT service 1 in' enters the ICT SPD1, which outputs 'ICT service 1 to cluster' to the cluster. 'ICT service n in' enters the ICT SPDn, which is connected to a 'Local earth reference' via a 'C' symbol and a 'Screened cable'. The ICT SPDn outputs 'ICT service n to cluster' to the cluster. The 'Equipment ICT SPD' outputs 'ICT service out' and receives 'ICT service from cluster' from the cluster. All SPDs are connected to the 'Common bonding point' via green lines. The label 'K.148(20)_F06' is at the bottom right.](af7916c89a458fdab6c3f443217388ae_img.jpg)
+
+Diagram of SPDs in a surge reference equaliser configuration. A dashed box labeled 'SPD enclosure' contains a 'Power SPD', 'ICT SPD1', 'Common bonding point', 'ICT SPDn', and 'Equipment ICT SPD'. 'Power in' enters the Power SPD, which is connected to a 'Local earth reference' via a 'C' (capacitor/grounding) symbol. The Power SPD outputs three 'Cluster powering' lines to an 'ICT equipment cluster'. 'ICT service 1 in' enters the ICT SPD1, which outputs 'ICT service 1 to cluster' to the cluster. 'ICT service n in' enters the ICT SPDn, which is connected to a 'Local earth reference' via a 'C' symbol and a 'Screened cable'. The ICT SPDn outputs 'ICT service n to cluster' to the cluster. The 'Equipment ICT SPD' outputs 'ICT service out' and receives 'ICT service from cluster' from the cluster. All SPDs are connected to the 'Common bonding point' via green lines. The label 'K.148(20)\_F06' is at the bottom right.
+
+**Figure 6 – SPDs in a surge reference equaliser configuration**
+
+In Figure 6, the common bonding point, or "star" connection has two external earth reference points; one from the power SPD mains plug/socket local earth reference and the other from the screened cable remote earth reference. This means that the diverted surge current can split between the power and screened cable earth references.
+
+To avoid earth loops in normal operation, one SPDn option is to make the screened cable "C" connection to the common bonding point via an SPD with a switching function, which maintains isolation during normal conditions but provides a bond during the occurrence of a surge.
+
+The surge reference equaliser is now called an MSPD, although there may not be any SPDs in it, only SPCs giving the equivalent surge functionality of the replaced SPDs. Figure 7 shows a typical MSPD for protecting power, antenna, telephone and Ethernet services with warning lights for protection failure and missing earth connection.
+
+In terms of surge parameters for a particular service, [b-ITU-T K.44] and [b-ITU-T K.21] provide guidance on test circuits and values. Assuming the cluster equipment ports meet [b-ITU-T K.21] requirements, the MSPD should be regarded as [b-ITU-T K.21] primary protection that is coordinated with the equipment cluster port protection.
+
+![A black Multi-Service Protection Device (MSPD) unit. It has a power cord on the left and a red power switch. The front panel features several ports: four AC power outlets, two USB ports, two Ethernet (RJ45) ports, and two coaxial (F-type) ports. There are also two small indicator lights, one green and one red, and a label 'Power Surge Protection' above the Ethernet and coaxial ports.](0dd5ee731e9d7e34e498b5c926110773_img.jpg)
+
+A black Multi-Service Protection Device (MSPD) unit. It has a power cord on the left and a red power switch. The front panel features several ports: four AC power outlets, two USB ports, two Ethernet (RJ45) ports, and two coaxial (F-type) ports. There are also two small indicator lights, one green and one red, and a label 'Power Surge Protection' above the Ethernet and coaxial ports.
+
+**Figure 7 – MSPD for protecting power, antenna, phone and Ethernet services**
+
+## **8 MSPD implications**
+
+### **8.1 Protected-side earth loop currents**
+
+If there is a cluster of equipment, they are likely to be connected to the power service and possibly interconnected. This means there will be the possibility of earth loop currents if the MSPD earth referenced leads are ineffectively directly connected to the common bonding point. [b-IEEE C62.50] describes a surge test procedure that measures surge currents that flow in the protected side ground loops. Generally, such a test is not necessary provided all the earthed referenced conductors are correctly returned to the common bonding point.
+
+### **8.2 SPD cross-coupling**
+
+Localized electric, magnetic and electromagnetic fields within the MSPD can be caused by the operation of a power SPD. These fields can couple into the SPDs and wiring on other services causing signal disruption. [b-IEEE C62.50] has a test procedure that measures the coupled levels of surge open-circuit voltage and surge short-circuit current on to unsurged services. The loads that are normally connected to communications service ports are simulated by resistive terminations connected to both the service port protected and unprotected sides.
+
+### **8.3 High impedance or missing local earth connection**
+
+When SPD operation diverts surge current into the common bonding point, the voltage developed on the earthing system can appear as an earth potential rise on other service SPDs. If the potential rise is sufficiently large it can cause these other services SPDs into conduction, which will divert portions of the surge current on to these other services. If an earthing reference is not provided the surge will propagate to all services, see [b-ITU-T K.134]. Generally, the use of MSPD technology will not cause any additional hazards compared to individual SPDs applied to services.
+
+## **9 Summary**
+
+Use of an MSPD creates a zone of protection for the equipment cluster on the protected side of the MSPD. Individual SPDs located at various positions cannot do this. The MSPD protection types and their performance depends on the type of services required by the equipment cluster protection and the expected transient voltage environment.
+
+It should be remembered that equipment connected to the MSPD unprotected side may suffer surges diverted from other MSPD services and appropriate steps should be taken to protect such equipment from these diverted surges.
+
+## Bibliography
+
+- [b-ITU-T K.21] Recommendation ITU-T K.21 (2019), *Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents.*
+- [b-ITU-T K.44] Recommendation ITU-T K.44 (2019), *Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents – Basic Recommendation.*
+- [b-ITU-T K.85] Recommendation ITU-T K.85 (2011), *Requirements for the mitigation of lightning effects on home networks installed in customer premises.*
+- [b-ITU-T K.96] Recommendation ITU-T K.96 (2014), *Surge protective components: Overview of surge mitigation functions and technologies.*
+- [b-ITU-T K.98] Recommendation ITU-T K.98 (2014), *Overvoltage protection guide for telecommunication equipment installed in customer premises.*
+- [b-ITU-T K.99] Recommendation ITU-T K.99 (2017), *Surge protective component application guide – Gas discharge tubes.*
+- [b-ITU-T K.126] Recommendation ITU-T K.126 (2017), *Surge protective component application guide – High frequency signal isolation transformers.*
+- [b-ITU-T K.134] Recommendation ITU-T K.134 (2018), *Protection of small-size telecommunication installations with poor earthing conditions.*
+- [b-ITU-T K.143] Recommendation ITU-T K.143 (2019), *Guidance on safety relating to the use of surge protective devices and surge protective components in telecommunication terminal equipment.*
+- [b-IEC 60664-1] IEC 60664-1:2020, *Insulation coordination for equipment within low-voltage supply systems – Part 1: Principles, requirements and tests.*
+- [b-IEC 61643-11] IEC 61643-11:2011, *Low-voltage surge protective devices – Part 11: Surge protective devices connected to low-voltage power systems – Requirements and test methods.*
+- [b-IEC TR 62066] IEC TR 62066:2002, *Surge overvoltages and surge protection in low-voltage a.c. power systems – General basic information.*
+- [b-IEEE C62.50] IEEE C62.50 – 2012, *IEEE Standard for Performance Criteria and Test Methods for Plug-in (Portable) Multiservice (Multiport) Surge-Protective Devices for Equipment Connected to a 120 V/240 V Single Phase Power Service and Metallic Conductive Communication Line(s).*
+- [b-IEEE Std 802.7] IEEE 802.7-1989, *Local Area Networks: IEEE Recommended Practice: Broadband Local Area Networks (withdrawn).*
+- [b-IEEE Std 1149.6] 1149.6-2015, *IEEE Standard for Boundary-Scan Testing of Advanced Digital Networks.*
+- [b-IEEE Std 1549] 1549-2011, *IEEE Standard for Microwave Filter Definitions.*
+- [b-UL 1449] UL Standard (2021), *Surge Protective Devices.*
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| Series E        | Overall network operation, telephone service, service operation and human factors                                                                         |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| <b>Series K</b> | <b>Protection against interference</b>                                                                                                                    |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/K/T-REC-K.149-202012-I_PDF-E/raw.md

@@ -0,0 +1,485 @@
+
+
+International Telecommunication Union
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**K.149**
+
+(12/2020)
+
+SERIES K: PROTECTION AGAINST INTERFERENCE
+
+---
+
+**Passive intermodulation test methods of array  
+antenna systems in mobile communication  
+systems**
+
+Recommendation ITU-T K.149
+
+ITU-T
+
+![ITU logo](84a1d09fb489061482111515543b60dc_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with a white grid pattern, overlaid by the letters 'ITU' in a bold, sans-serif font. The globe is tilted on its axis.
+
+ITU logo
+
+
+
+# Recommendation ITU-T K.149
+
+# Passive intermodulation test methods of array antenna systems in mobile communication systems
+
+## Summary
+
+Recommendation ITU-T K.149 specifies methods for measuring the passive intermodulation level of array antenna systems in mobile communication systems, including test equipment and test procedures.
+
+This Recommendation covers the following frequency ranges, but is not limited to the following ranges: LTE 700, APT 700, LTE 800, Cellular 850, E-GSM 900, DCS 1800, PCS 1900, AWS 1700/2100, UMTS 2100 and LTE 2600 operating bands.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T K.149    | 2020-12-14 | 5           | <a href="http://handle.itu.int/11.1002/1000/14562">11.1002/1000/14562</a> |
+
+## Keywords
+
+Array antenna, measurement, mobile communication, passive intermodulation.
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2021
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+|                                                                    | Page |
+|--------------------------------------------------------------------|------|
+| 1 Scope .....                                                      | 1    |
+| 2 References.....                                                  | 1    |
+| 3 Definitions .....                                                | 1    |
+| 3.1 Terms defined elsewhere .....                                  | 1    |
+| 3.2 Terms defined in this Recommendation.....                      | 1    |
+| 4 Abbreviations and acronyms .....                                 | 1    |
+| 5 Conventions .....                                                | 2    |
+| 6 Measuring method of passive intermodulation.....                 | 2    |
+| 6.1 Requirements of test conditions .....                          | 2    |
+| 6.2 Measurement accuracy .....                                     | 2    |
+| 6.3 Safety.....                                                    | 2    |
+| 6.4 Test environment .....                                         | 3    |
+| 6.5 Test setup and procedure .....                                 | 4    |
+| 6.6 The measurement uncertainty.....                               | 6    |
+| Annex A – Antenna design and erection .....                        | 8    |
+| A.1 The impact of the environment on PIM .....                     | 8    |
+| A.2 Antenna port connection.....                                   | 8    |
+| A.3 Antenna erection method to avoid passive intermodulation ..... | 8    |
+| A.4 Adjacent passive intermodulation source.....                   | 8    |
+| Annex B – Design and evaluation of the PIM test chamber .....      | 9    |
+| B.1 Introduction .....                                             | 9    |
+| B.2 RF absorbing material .....                                    | 9    |
+| B.3 Support structure and walls .....                              | 10   |
+| B.4 RF shielding.....                                              | 10   |
+| B.5 RF chamber evaluation.....                                     | 10   |
+| Bibliography.....                                                  | 12   |
+
+# Introduction
+
+With the development of mobile communications, the data carried in the fixed bandwidth has increased rapidly. There are many signals of different frequencies in the same transmission medium. Since the transmission medium has certain nonlinear characteristics, when two or more signals with multiple different frequencies are mixed into the passive components, intermodulation products of different amplitudes are produced at other frequencies. This is called passive intermodulation (PIM).
+
+Passive components include antennas, radio frequency (RF) feeders, connectors, filters, duplexers, directional couplers, RF termination loads, and attenuators, etc. When the passive intermodulation falls within the receiving band of a base station, the sensitivity of the receiver is reduced, resulting in a decrease in the quality of the call or the carrier-to-interference ratio (C/I) of the system.
+
+With the gradual large-scale commercialization of 4G LTE and 5G networks, the number of communication systems and the number of users have greatly increased. Therefore, the design of communication systems requires the use of limited spectrum resources to be as efficient as possible, and passive intermodulation distortion becomes an important factor limiting the system capacity. Massive multi-input multi-output (MIMO) antennas are key technologies in the 5G era, and more post-stage passive components will be introduced, thus bringing more challenges to R&D and testing. In order to reduce this interference, it is very important to perform strict PIM testing on passive components during their production.
+
+This Recommendation provides a reference for the passive intermodulation (PIM) level measurement of array antennas in mobile communication systems.
+
+## Recommendation ITU-T K.149
+
+# Passive intermodulation test methods of array antenna systems in mobile communication systems
+
+# 1 Scope
+
+This Recommendation is applicable to the passive intermodulation (PIM) measurement of passive array antenna systems in mobile communication systems. This Recommendation defines the setup and test methods for antennas in low intermodulation applications that can be found in cellular mobile communications, satellite communications and other multifrequency communications.
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+[IEC 62037-6] IEC 62037-6:2013, *Passive RF and Microwave Devices, Intermodulation Level Measurement – Part 6: Measurement of Passive Intermodulation in Antennas*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 antenna** [b-ITU-R M.1797]: Any structure or device used to collect or radiate electromagnetic power.
+
+**3.1.2 mimo** [b-ITU-R M.1797]: A technique that utilizes multiple antennas on both ends of the transmit-receive channel, e.g., at both the base station and the terminal(s) in a wireless network, to provide significant improvements in the capacity or reliability of the system.
+
+## 3.2 Terms defined in this Recommendation
+
+This Recommendation defines the following term:
+
+**3.2.1 fully anechoic chamber**: Shielded enclosure in which all surfaces are covered with material that absorbs electromagnetic energy (i.e., RF absorber) in the frequency range of interest.
+
+# 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|      |                                        |
+|------|----------------------------------------|
+| AUT  | Antenna Under Test                     |
+| CDMA | Code Division Multiple Access          |
+| GSM  | Global System for Mobile communication |
+| MIMO | Multi-Input Multi-Output               |
+| PIM  | Passive Intermodulation                |
+
+|     |                  |
+|-----|------------------|
+| RF  | Radio Frequency  |
+| RSS | Root-Sum-Squares |
+
+# 5 Conventions
+
+None.
+
+# 6 Measuring method of passive intermodulation
+
+## 6.1 Requirements of test conditions
+
+In order to improve the test accuracy and to ensure test safety, the following conditions are required. These requirements help minimize errors within the test system.
+
+## 6.2 Measurement accuracy
+
+The accuracy of PIM tests may be affected by many factors external or internal in the test system. Factors affecting the results of PIM tests of antenna include, but are not limited to, the following:
+
+- a. Conductive material exposed to the electromagnetic fields radiated by the antenna under test (AUT);
+- b. Loose, damaged or corroded AUT mounting accessories;
+- c. Loose or corroded accessories exposed to the AUT radiation field;
+- d. Radio frequency signal from external sources;
+- e. Defective or poorly performing coaxial cables;
+- f. Dirty, contaminated and abrasion at the interface connections;
+- g. Improper interface connections;
+- h. Poorly shielded RF interface connections;
+- i. Unfiltered active intermodulation signal from the test equipment;
+- j. Transmission line loss should be considered;
+- k. Contaminated absorbing material;
+- l. Ineffective shielding enclosure;
+- m. Improper placed position of AUT in chamber;
+- n. Mismatch of test set;
+
+Since the power level of the PIM is generally very low, the components of the PIM test equipment should have high performance and low PIM characteristics. The residual intermodulation level generated by the synthesizer, directional coupler, filter, etc., shall be controlled below 10 dB of PIM level of the array antenna. For example, it is assumed that the intermodulation of the measured antenna is  $-150$  dBc, and the residual intermodulation of the measuring equipment is at least  $-160$  dBc. The matching load used in the test shall adopt cable load to ensure the normal operation of the test equipment.
+
+## 6.3 Safety
+
+High voltages and high radiant energy may be present within the AUT and test environment, so the AUT should be properly placed to ensure that testing personnel are not exposed to radiation that exceeds the limits defined in national regulations for workers.
+
+## 6.4 Test environment
+
+**In-situ test :** Passive intermodulation tests can be done in in-situ conditions if permitted by the electromagnetic noise and radio environment. The RF radiation level should meet the national regulations when performing such tests. In addition, the RF energy radiated by the AUT may generate passive intermodulation on surrounding objects and reflect it back into the antenna, resulting in test errors in the passive intermodulation results of the antenna. In addition, external RF signals may also affect the intermodulation test results. A survey of the frequencies locally in use is recommended before testing. PIM signals may be affected by external interference in open space. It is recommended that PIM signals measured in a microwave anechoic chamber can be used as a reference.
+
+**Test in anechoic chamber:** The absorbers and shielding enclosure of chambers may also produce PIM. These PIM products can be amplified by the antenna gain, and can interfere with the test results, causing measurement uncertainties. Standard anechoic test chambers may provide reasonable shielding and RF attenuation, but they may not be suitable for low PIM antenna measurements. Their residual PIM may be much too high. Besides the very high shielding, an ideal chamber provides lowest residual passive intermodulation. To achieve best results, special chamber shielding material with properly designed pyramidal electromagnetic absorbing material and special manufacturing techniques needs to be considered comprehensively. Related to this, the maximum measurable gain and power of PIM test chambers should be evaluated before the test. See Annex B for information on the construction and evaluation of the passive intermodulation test chamber.
+
+**Test signal configuration:** In the process of upgrading communication networks from 2G to 5G, the signal bandwidth of wireless communication increases from 200 kHz for GSM to 100 MHz and 400 MHz for 5G. Both continuous wave signals and modulated wave signals can be used in the test signal configuration. The use of modulation signals for intermodulation testing can truly reflect the situation and possible problems of the tested equipment when used in the actual network.
+
+Continuous wave signal is first considered (match test), and then, modulated wave signal is implemented if necessary (research, limitation test and compatibility test).
+
+### **a. Continuous wave signal**
+
+Continuous wave signals of frequencies  $f_1$  and  $f_2$ , with equal specified test port power levels, are combined and fed to the antenna array. The PIM is measured over a specified frequency range. The intermodulation products of order  $(2f_1 \pm f_2)$  or  $(2f_2 \pm f_1)$ , etc., are measured.
+
+In most cases, the third order intermodulation signals represent the worst condition of unwanted signals generated; Hence, the antenna array is sufficiently characterized by the measurement of these signals. However, the test settings given in clause 6.5 are also suitable for measuring other intermodulation products.
+
+### **b. Modulated wave signal**
+
+Modulated wave signals of frequencies  $f_1$  and  $f_2$ , with equal specified test port power levels, are combined and fed to the antenna array. According to the measured frequency band, the corresponding communication standard modulation signals are generated. The intermodulation product of two wideband modulation signals is a wideband signal, and the spectral bandwidth is calculated as follows:
+
+$$B_{IM}(m) = |m_1| \times B_1 + |m_2| \times B_2 + \dots + |m_n| \times B_n;$$
+
+Where
+
+$m = |m_1| + |m_2| + \dots + |m_n|$ ;  $m_1, m_2, \dots, m_n$  are integer in the formula
+
+$|m_n|$  is the absolute value of  $m_n$
+
+$B_1, B_2, \dots, B_n$  is the bandwidth corresponding to input signals  $f_1, f_2, \dots, f_n$ .
+
+The schematic diagram of intermodulation products of two broadband modulation signals with the same bandwidth is shown in Figure 1.
+
+![Figure 1: Schematic diagram of intermodulation products of two broadband modulation signals with the same bandwidth. The graph shows Power on the y-axis and Frequency on the x-axis. Two main signals, f1 and f2, are shown as tall bars. Between and around them are several smaller bars representing intermodulation products. From left to right, the bars are labeled with their frequency formulas and relative bandwidths: 4f1-3f2 (7B), 3f1-2f2 (5B), 2f1-f2 (3B), f1 (B), f2 (B), 2f2-f1 (3B), 3f2-2f1 (5B), and 4f2-3f1 (7B). The label 'K.149(20)_F01' is at the bottom right.](4e0ade2f41b66d5602160da5cc978274_img.jpg)
+
+Figure 1: Schematic diagram of intermodulation products of two broadband modulation signals with the same bandwidth. The graph shows Power on the y-axis and Frequency on the x-axis. Two main signals, f1 and f2, are shown as tall bars. Between and around them are several smaller bars representing intermodulation products. From left to right, the bars are labeled with their frequency formulas and relative bandwidths: 4f1-3f2 (7B), 3f1-2f2 (5B), 2f1-f2 (3B), f1 (B), f2 (B), 2f2-f1 (3B), 3f2-2f1 (5B), and 4f2-3f1 (7B). The label 'K.149(20)\_F01' is at the bottom right.
+
+**Figure 1– Intermodulation products of two broadband modulation signals with the same bandwidth**
+
+The modulation signal is adopted to take the corresponding standard channel bandwidth as the minimum step for scanning. For example, GSM signal takes 200 kHz as the step and code division multiple access (CDMA) signal takes 1.23 MHz as the step scan, which can cover the whole working frequency band.
+
+When testing intermodulation, the bandwidth of intermodulation products shall be calculated according to the above formula, and the energy value within the corresponding bandwidth shall be measured on the receiver as the intermodulation level.
+
+## 6.5 Test setup and procedure
+
+### 6.5.1 Testing the connection of coaxial cable
+
+Passive intermodulation testing using coaxial cable requires repeated connection and disconnection of the coaxial connector. The following points should be noted during the test:
+
+- a. The sealing O-rings of the connector interface should be removed. The O-rings will collect the debris generated during the tightening process of the joint and become another source of passive intermodulation.
+- b. Before connecting, check the connectors, dielectric, interface surfaces or flanges for contamination, especially metal fragments. In addition, check the connector's interface surface for burrs, scratches, dents, or damage to the electroplated layer. Properly install and rotate the accessories to minimize the passive intermodulation generated inside the AUT.
+- c. After each disconnection, it is recommended to use compressed air to clean the connector interface to remove metal debris.
+- d. Ensure that the cable is not stressed or damaged. Damage to the outer and inner conductors in the cable jacket is not recognized by the visual inspection, but intermittent intermodulation signals are generated. One way to detect this is to bend or tap the cable when measuring the intermodulation of the equipment itself. If the PIM signal is fluctuating, the cable may be damaged and should be replaced.
+- e. For threaded connectors, it is recommended to use a standard torque wrench to tighten the cable connectors to ensure reliable connection.
+
+### 6.5.2 Low intermodulation load
+
+A good low intermodulation load can be made up of a high quality coaxial cable with a long (single attenuation value greater than 10 dB) low intermodulation connector. This connector should be soldered to the inner and outer conductors of the coaxial cable. The entire cable should be secured by a fixture so that there are no metal fatigue cracks due to bending. The PIM level of a typical low intermodulation load can be better than  $-163\text{ dBc}$  ( $@2\times 43\text{ dBm}$ ).
+
+### 6.5.3 Standard connector components
+
+It is recommended to use the standard component with a fixed value of  $-153\text{ dBc}$  ( $@2\times 43\text{ dBm}$ ) and low intermodulation load for cascading tests to calibrate the PIM test instrument. The test result should be within the range of  $-153\text{ dBc} \pm 3\text{ dB}$ .
+
+### 6.5.4 PIM test configuration and test procedure
+
+The antenna reflected intermodulation test configuration is shown in Figure 2. The antenna transmitted intermodulation test configuration is shown in Figure 3. Different test configurations can be selected according to different scenarios. The antenna can be tested in an open field environment or in an anechoic chamber. The anechoic chamber design should meet the technical requirements of Annex A. For the antenna transmission intermodulation test, a low intermodulation antenna is required at the receiving end, which requires two low intermodulation antennas for evaluation of the test system and test site.
+
+![Block diagram of the antenna reflected PIM test configuration. Two signal generators, labeled f1 and f2, are connected to amplifiers. Each amplifier is followed by a transmit filter. The outputs of the transmit filters are combined in a combiner (labeled Σ). The output of the combiner is connected to a diplexer. The diplexer has two ports: one connected to the AUT (Antenna Under Test) inside a test chamber, and the other connected to a receive filter. The receive filter is connected to a low noise amplifier, which is then connected to a receiver. The receiver displays a spectrum with four distinct peaks. A label 'K.149(20)_F02' is present in the bottom right corner of the diagram area.](5e92d9e8e9ce204e405bff2367f88176_img.jpg)
+
+The diagram illustrates the antenna reflected PIM test configuration. It consists of two signal generators,  $f_1$  and  $f_2$ , each connected to an amplifier and a transmit filter. The outputs of these filters are combined in a combiner (labeled  $\Sigma$ ). The combined signal is then sent to a diplexer. One output of the diplexer is connected to the AUT (Antenna Under Test) inside a test chamber. The other output of the diplexer is connected to a receive filter, which is followed by a low noise amplifier and a receiver. The receiver displays a spectrum with four distinct peaks. A label 'K.149(20)\_F02' is present in the bottom right corner of the diagram area.
+
+Block diagram of the antenna reflected PIM test configuration. Two signal generators, labeled f1 and f2, are connected to amplifiers. Each amplifier is followed by a transmit filter. The outputs of the transmit filters are combined in a combiner (labeled Σ). The output of the combiner is connected to a diplexer. The diplexer has two ports: one connected to the AUT (Antenna Under Test) inside a test chamber, and the other connected to a receive filter. The receive filter is connected to a low noise amplifier, which is then connected to a receiver. The receiver displays a spectrum with four distinct peaks. A label 'K.149(20)\_F02' is present in the bottom right corner of the diagram area.
+
+**Figure 2 – Antenna reflected PIM test configuration**
+
+![Figure 3 – Antenna transmitted PIM test configuration. The diagram shows two signal paths, f1 and f2, each consisting of a Generator, an Amplifier, and a Transmit filter. These paths are combined in a Combiner (Σ). The output of the combiner is connected to a Transmit filter, which is then connected to a Test chamber. Inside the test chamber, the signal is transmitted by an AUT (Antenna Under Test) and received by a Receive antenna. The received signal is then connected to a Diplexer. One output of the diplexer is connected to a Load, and the other is connected to a Receive filter. The output of the receive filter is connected to a Low noise amplifier, which is then connected to a Receiver. The label K.149(20)_F03 is present at the bottom right.](d4af765160d04ecef538e5066006dc77_img.jpg)
+
+Figure 3 – Antenna transmitted PIM test configuration. The diagram shows two signal paths, f1 and f2, each consisting of a Generator, an Amplifier, and a Transmit filter. These paths are combined in a Combiner (Σ). The output of the combiner is connected to a Transmit filter, which is then connected to a Test chamber. Inside the test chamber, the signal is transmitted by an AUT (Antenna Under Test) and received by a Receive antenna. The received signal is then connected to a Diplexer. One output of the diplexer is connected to a Load, and the other is connected to a Receive filter. The output of the receive filter is connected to a Low noise amplifier, which is then connected to a Receiver. The label K.149(20)\_F03 is present at the bottom right.
+
+**Figure 3 – Antenna transmitted PIM test configuration**
+
+The diplexer in Figure 2 and the filter in Figure 3 are close to the input port of the AUT, and should have low intermodulation characteristics in order to minimize the intermodulation of the test system itself. The length of the transmission cable and the waveguide should be minimized to reduce the insertion loss and thus transmit more power. Also, coaxial-waveguide adapters should be avoided as much as possible.
+
+In order to avoid the generation of active intermodulation, each test system has two separate composite signal sources that are separately amplified. The two-carrier intermodulation test equipment generates discrete intermodulation products when passing through the AUT, and the levels of these intermodulation products are measured. To maximize the sensitivity of the test system, one or two low noise amplifiers are usually added before intermodulation signals entering the receiver or spectrum analyser.
+
+The AUT should keep a certain distance from the door of the chamber. It is recommended to be more than 1 meter.
+
+The test procedures are as follows:
+
+**6.5.4.1** The passive intermodulation analyser corresponding to the antenna working frequency band should be used. It is recommended to use the "sweep frequency" test.
+
+**6.5.4.2** Connecting the signal generator and the power meter with test cable, turn on the instrument transmit power, adjust the output power, to make the power of the test cable output meet the specified requirements.
+
+**6.5.4.3** During the test, the test cable shall remain stable in the required moving or bending state. It can be verified by connecting a low intermodulation load at one end of the cable.
+
+**6.5.4.4** Turn off the instrument's transmit power, place the geometric centre of the antenna under test at the centre of the field, and connect the measured antenna port to the measurement system and ensure reliable contact.
+
+**6.5.4.5** Turn on the instrument's transmit power and the intermodulation level is shown on the interface of the passive intermodulation analyser.
+
+## **6.6 The measurement uncertainty**
+
+The uncertainty of the result of a measurement generally consists of several components that can be grouped into two types according to the method used to estimate their numerical values.
+
+Type A: those evaluated by statistical methods,
+
+Type B: those evaluated by other means.
+
+The synthesis uncertainty of the passive intermodulation test system is defined as:
+
+$$\text{RSS}=U_c = \sqrt{U_1^2 + U_2^2 + \dots U_8^2} \quad (1)$$
+
+Where  $U_i, i = 1, \dots, 8$  refers to each component of the system.
+
+Type A:
+
+Here,  $U_1$  indicates the uncertainty caused by repeatability of the human test, which is implemented during a continuous time frame. Specifically, each test is independent, and intermodulation system is reset to initial state when each test finished. The mathematic average of all the human tests is calculated as follow:
+
+$$\bar{V} = \frac{1}{N} \sum_{i=1}^N V_i \quad (2)$$
+
+Where  $V_i$  refers to the volt value of each test, and  $N$  indicates the number of tests. Therefore, the variance is produced as:
+
+$$S^2(V_i) = \frac{1}{N} \sum_{i=1}^N (V_i - \bar{V})^2 \quad (3)$$
+
+Finally,  $U_1$  can be calculated as:
+
+$$S^2(V_i) = \sqrt{\frac{S^2(V_i)}{N-1}} \quad (4)$$
+
+Type B:
+
+For the uncertainty caused by the system links, it can be calculated as:
+
+$$U_i = \frac{e_i^{max}}{\varepsilon_i} \quad (5)$$
+
+Where  $e_i^{max}$  is the maximum error of component  $i$  ( $i = 2, \dots, 8$ ), and  $\varepsilon_i$  is its distribution factor based on the pattern of probability distribution, which is illustrated in Table 1.
+
+**Table 1 – The type of system components**
+
+| Uncertainty component | Error source                             | Type | Probability distribution |
+|-----------------------|------------------------------------------|------|--------------------------|
+| $U_1$                 | Repeatability of human test              | A    | Defined by Eq. (4)       |
+| $U_2$                 | Effect of system intermodulation         | B    | uniform                  |
+| $U_3$                 | Receive link error                       | B    | uniform                  |
+| $U_4$                 | Power transition link error correcting   | B    | uniform                  |
+| $U_5$                 | Power synthesis link error correcting    | B    | uniform                  |
+| $U_6$                 | Port mismatch error                      | B    | uniform                  |
+| $U_7$                 | Receive link difference error correcting | B    | uniform                  |
+| $U_8$                 | Environment error                        | B    | uniform                  |
+
+# Annex A
+
+## Antenna design and erection
+
+(This annex forms an integral part of this Recommendation.)
+
+## A.1 The impact of the environment on PIM
+
+Any object near the antenna will affect the PIM test result. Ferromagnetic materials, other objects adjacent to the antenna (such as other antennas, supports, metal reflectors, DC and antistatic grounding hardware, loose mechanical connections), different metal junctions, etc., may have an adverse effect on the intermodulation performance of the communication system.
+
+## A.2 Antenna port connection
+
+Any antenna port that passes RF signals is a potential passive intermodulation source and should be considered for low intermodulation design. Care should be taken to ensure that the surfaces of all interfaces are clean. Whether it is a coaxial or waveguide joint, check for dirt, metal debris, burrs and other potential contamination. Any coaxial connection should be made in accordance with the manufacturer's specified torque requirements to ensure proper metal contact pressure. If a waveguide is used, the flanges should be connected in accordance with the manufacturer's recommended torque specifications. Be sure to keep the flange edges of the coaxial connector or waveguide aligned. The dielectric and conductors in the connector, including the electroplated layer, are important for the performance of passive intermodulation. Soft electroplated materials (such as gold, silver, etc.) are usually plated with a sufficient thickness (several skin depth) on a hard matrix material (brass, beryllium copper, etc.). The number of coaxial connectors and adapters at the antenna port should be minimized. This will reduce the number of metal contacts and therefore will also reduce the possibility of passive intermodulation generation.
+
+## A.3 Antenna erection method to avoid passive intermodulation
+
+The antenna should be safely and reliably installed on the test platform. Ensure that all bolts and clamps that secure the antenna to the supporting structure are fastened and tightened according to the manufacturer's requirements. The coaxial or waveguide transmission line of the antenna input port should also be connected securely and reliably, and friction or movement is prohibited.
+
+The test platform should facilitate the placement of antennas. The main radiation lobe of the antenna should point to the main test plane of the anechoic chamber. The specifications of the absorbing materials should meet the technical requirements in clause B.2. To reduce the PIM interference of the test platform, it is recommended that the test platform be made of non-metal and low-PIM materials, such as wood structure and glass fibre reinforced plastics.
+
+When taking the open field test, the impact of external interference should be minimized to meet the test requirements.
+
+The antenna should be placed away from potential passive intermodulation sources. Potential passive intermodulation sources are: other antennas, buildings, walls, metal reflectors, etc.
+
+## A.4 Adjacent passive intermodulation source
+
+It is important to know about the RF environment in which the antenna is mounted. Special attention should be paid to the location of the antenna and it should be kept away from all possible passive intermodulation sources. For example, the metal parts of the antenna should be prevented from being intimately contacted or corroded. In addition, it should be noted that other antenna transmit signals or their harmonics may fall in the AUT receiving band.
+
+# Annex B
+
+## Design and evaluation of the PIM test chamber
+
+(This annex forms an integral part of this Recommendation.)
+
+## B.1 Introduction
+
+This section provides guidance for constructing and evaluating an antenna intermodulation test anechoic chamber. Passive intermodulation tests of antennas are more difficult than other non-radiative components. During the intermodulation test, the antenna and the signal source transmit RF energy continuously, which may stimulate potential intermodulation sources in the test environment. In addition, when the outdoor open field test is conducted, it may contain other radio frequency signals, which may cause this test to be impossible. For an accurate and precise antenna PIM measurement system, an anechoic chamber which can shield RF signals and absorb internal reflections of radiated energy is necessary. However, the absorbers and shielding enclosure of chambers may also produce PIM. The noise of the PIM test chamber usually determines the accuracy of the PIM measurement.
+
+The main components of the RF anechoic chamber are:
+
+- a. RF absorbing material.
+- b. Support structure and wall.
+- c. RF shielding.
+
+## B.2 RF absorbing material
+
+Radio frequency absorbing materials are typically fabricated from carbon impregnated foam. These materials act as attenuating effects as the radio frequency signal passes. Signal attenuation (energy absorption) is essentially equivalent to a "load" of the antenna.
+
+There are many types and sizes of RF absorbing materials. The choice of type and size depends on the frequency of operation and the placement within the laboratory. The most critical factor in building a passive intermodulation test laboratory is the proper selection of RF absorbing materials.
+
+Absorbing material selection principle:
+
+- a. Select absorbing materials with RF absorption attenuation greater than 30 dB. The frequency range is consistent with the summary.
+- b. In order to obtain good results, a sharp-shaped absorbing material is placed in the radiation range of the antenna, and the absorbing material is preferably used in the direction perpendicular to the incident direction of the radiation field. However, the best results can be achieved if the interior of the laboratory is completely covered by RF absorbing material.
+- c. The area of the absorbing material to be laid should be large enough to avoid reflections. In addition, for safety reasons, the absorbing material should be flame retardant and have sufficient power tolerance.
+- d. When attaching the absorbing material to the shielding body in the anechoic chamber, it should be ensured that the installation position of the absorbing material is continuous to avoid gaps. Otherwise, signals may leak to the metal shielding layer through the gaps, causing PIM interference signals and affecting the PIM test precision.
+- e. It is recommended that special parts in the anechoic chamber, such as the ventilation waveguide port, shielding door, test platform, lighting burner, smoke sensor, and monitor, be paved with RF absorbing materials.
+
+- f. The lighting burner is recommended to be placed at the corner of the bottom surface of the chamber, and is not recommended to be placed on the main test surface of the chamber.
+- g. To prevent the metal door frame from being exposed when the chamber door is closed, it is recommended that the door frame be wrapped with RF absorbing materials instead of metal aluminium foil.
+
+## **B.3 Support structure and walls**
+
+The support structure and walls of the PIM test laboratory shall provide a suitably adhered inner surface for the RF absorbing material. Support structures and walls should also help to control the temperature, pressure, humidity, or other environmental conditions of the experiment.
+
+Materials and construction methods will vary depending on the application. For most applications, wood and plywood structures or cement structures can meet the requirements, cement bricks can provide better support, and the disadvantage is higher cost. Designing support structures and walls requires consideration of the following:
+
+- a. Avoid the use of metals as much as possible, especially the use of overlapping metal sheets.
+- b. The wooden support structure can be screwed and the screw connection is more reliable than nail fixing. Metal parts are not allowed to be directly connected to each other, even within the support structure.
+- c. The actual size of the absorbing material must be determined before the structural design is completed.
+- d. The laboratory should be large enough to keep the test antenna sufficiently far from any RF absorbing material to avoid coupling between the radiating antenna and the absorbing material.
+- e. Evaluate potential sources of passive intermodulation, such as hinges, fasteners, fixtures, fire sprinklers, mounting accessories, etc.
+
+## **B.4 RF shielding**
+
+The question of whether to use RF shielding depends on the application requirements. RF shielding ensures the tester's electromagnetic radiation safety and provides a low RF floor noise for the test site. You can determine whether RF shielding is required by calculating the power density. By calculation, it may be found that the RF level after the RF absorbing material is very low and therefore safe. Before the final test plan or procedure is passed, it is often necessary to investigate the RF environment around the laboratory.
+
+The method of RF shielding is also dependent on the application. A thin aluminium foil or aluminium plate is usually applied to the outer surface of the laboratory structure. Aluminium foil can be securely bonded with adhesive products. A plastic insulating material is placed on the edge of each aluminium plate to prevent direct contact between any aluminium plates. The small gap between the aluminium plates should not pass any RF energy except for the extremely small wavelengths compared to the aluminium plate gap. Although the RF power at the RF shield may be extremely low, it is still necessary to avoid selecting materials that may cause intermodulation, such as metal mesh.
+
+## **B.5 RF chamber evaluation**
+
+The radiation energy from AUT may generate PIM products on the surrounding objects, and the PIM products can be reflected into the AUT. At the same time extraneous RF signals may also distort the PIM test result. The role of the anechoic chamber is to isolate these unwanted RF signals and to minimize reflections by the absorbing material on the inside walls. Because of this the performance of a PIM test chamber is built up by the contributions of the PIM level magnitude from absorbers and from the shielding enclosure.
+
+The absorbers and shielding enclosure of chambers may also produce PIM. Figure B.1 shows the PIM generated from a test chamber. When the RF signal  $S_{an}$  radiated by the AUT transmits to the absorbing material, the PIM product  $PIM_{ab}$  is produced by the absorbing material. Meanwhile, part of the energy through the absorbers is reflected by the shielding enclosure that produces another kind of PIM,  $PIM_{sh}$ . These PIM products can be amplified by the antenna gain and the measuring power, and can interfere with the test results causing measurement uncertainties.
+
+![Diagram of a test chamber showing PIM products. The chamber is lined with 'Absorbers' (represented by sawtooth patterns) and enclosed by a 'Shielding enclosure' (represented by a solid outer boundary). An antenna on the left emits a signal S_an. Two arrows point to the absorbers: one labeled PIM_ab (representing PIM from the absorbers) and another labeled PIM_sh (representing PIM from the shielding enclosure). The diagram is labeled K.149(20)_FB.1 at the bottom right.](c85ded401105f62f2d6ff26b3b5eb4af_img.jpg)
+
+Diagram of a test chamber showing PIM products. The chamber is lined with 'Absorbers' (represented by sawtooth patterns) and enclosed by a 'Shielding enclosure' (represented by a solid outer boundary). An antenna on the left emits a signal S\_an. Two arrows point to the absorbers: one labeled PIM\_ab (representing PIM from the absorbers) and another labeled PIM\_sh (representing PIM from the shielding enclosure). The diagram is labeled K.149(20)\_FB.1 at the bottom right.
+
+**Figure B.1 – PIM products from a test chamber**
+
+The proposed methods of testing the maximum measurable antenna gain of chamber are as follows:
+
+- a) For small size PIM test chambers, the simple method to evaluate the performance is by using a low PIM omnidirectional antenna as a standard antenna. Omnidirectional antennas usually have a wide beam. When the omnidirectional antenna is placed in the centre of the small chamber, it achieves a full coverage for the chamber. If the measured PIM is close to the noise floor of the PIM instrument, the chamber can be considered qualified.
+- b) For large size PIM test chambers which can be used to measure the PIM of high gain antennas, one way is to use a series of high gain antennas, and this is a quite difficult task. On one hand, it is not easy to design a high gain antenna with low PIM. On the other hand, the high gain antennas usually have a narrow beamwidth. This characteristic makes it troublesome to scan each part of the chamber using the high gain antennas. In addition, the multiple movements may change the cable effect on the PIM level.
+- c) A chamber evaluation method with one medium gain low PIM antenna. The basic principle of the proposed method is providing gain compensation by changing the measurement distance (between AUT and absorbers). The measurement points in different measurement distances are defined by the 3 dB antenna beamwidth. Chambers can be measured by this method.
+- d) It is recommended that a standard antenna be used for acceptance in the test chamber. The PIM3 value of the standard antenna is  $-153 \text{ dBc}$  ( $-153 \text{ dBc} \pm 10 \text{ dB}$ ) (@ $2^{*}43 \text{ dBm}$ ). Move the grids on the left, right, and front sides of the antenna by nine positions. The distance between adjacent points is based on the half-wavelength of the centre frequency of the antenna. If the average values at nine positions are used as the reference values and the deviation between the test values at the nine positions and the reference values is less than  $\pm 3 \text{ dB}$ , the test result is qualified.
+
+# Bibliography
+
+- [b-ITU-R M.1797] Recommendation ITU-R M.1797 (2007), *Vocabulary of terms for the land mobile service*.
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| Series E        | Overall network operation, telephone service, service operation and human factors                                                                         |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| <b>Series K</b> | <b>Protection against interference</b>                                                                                                                    |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |

marked/K/T-REC-K.27-201503-I_PDF-E/raw.md

@@ -0,0 +1,811 @@
+
+
+International Telecommunication Union
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**K.27**
+
+(03/2015)
+
+SERIES K: PROTECTION AGAINST INTERFERENCE
+
+# --- **Bonding configurations and earthing inside a telecommunication building**
+
+Recommendation ITU-T K.27
+
+ITU-T
+
+![ITU logo](84a1d09fb489061482111515543b60dc_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) features a globe with a red lightning bolt striking it, symbolizing telecommunications. To the right of the globe, the text "International Telecommunication Union" is written in blue.
+
+ITU logo
+
+International  
+Telecommunication  
+Union
+
+
+
+## Recommendation ITU-T K.27
+
+# Bonding configurations and earthing inside a telecommunication building
+
+## Summary
+
+Recommendation ITU-T K.27 provides the procedures for implementing the bonding between metallic bodies and the earthing connections inside a telecommunication building. It provides the bonding configurations and earthing in order to achieve protection against electric shock and to minimize damage of the telecommunication equipment due to lightning flashes, as well as to limit interference between telecommunication equipment installed in the same building. Examples of the metallic bodies considered in this Recommendation are: equipment frame, shield of cables, metallic structure of the building, protective earth conductor, bonding conductors, earthing electrodes. This Recommendation provides several possibilities of bonding configurations and discusses their advantages and disadvantages. The theory of bonding and earthing is also presented and is used as rationale for the development of the procedures.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T K.27     | 1991-03-18 | V           | <a href="http://handle.itu.int/11.1002/1000/1397">11.1002/1000/1397</a>   |
+| 2.0     | ITU-T K.27     | 1996-05-08 | 5           | <a href="http://handle.itu.int/11.1002/1000/3349">11.1002/1000/3349</a>   |
+| 3.0     | ITU-T K.27     | 2015-03-01 | 5           | <a href="http://handle.itu.int/11.1002/1000/12405">11.1002/1000/12405</a> |
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2015
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+|                                                                     | Page |
+|---------------------------------------------------------------------|------|
+| 1 Scope.....                                                        | 1    |
+| 2 References.....                                                   | 1    |
+| 3 Definitions .....                                                 | 2    |
+| 3.1 Terms defined elsewhere .....                                   | 2    |
+| 3.2 Terms defined in this Recommendation.....                       | 3    |
+| 4 Abbreviations and acronyms .....                                  | 4    |
+| 5 Conventions .....                                                 | 4    |
+| 6 Principles of bonding and earthing.....                           | 5    |
+| 6.1 Summary of theory .....                                         | 5    |
+| 6.2 Implementation principles .....                                 | 6    |
+| 6.3 Protection against electric shock .....                         | 8    |
+| 6.4 Protection against lightning.....                               | 8    |
+| 6.5 Functional earthing.....                                        | 9    |
+| 7 Power distribution.....                                           | 9    |
+| 7.1 AC power distribution .....                                     | 9    |
+| 7.2 DC power distribution .....                                     | 10   |
+| 8 Comparison between IBN and mesh-BN installations .....            | 11   |
+| 9 Maintenance of bonding networks.....                              | 12   |
+| 10 Examples of connecting equipment configurations to the CBN ..... | 12   |
+| Annex A – Brief theory of bonding and earthing networks.....        | 13   |
+| A.1 Overview .....                                                  | 13   |
+| Annex B – Examples of bonding configurations .....                  | 16   |
+| B.1 Mesh-BN .....                                                   | 16   |
+| B.2 Mesh-IBN with a bonding mat configuration .....                 | 18   |
+| B.3 Star or sparse mesh-IBN with isolation of DC power return ..... | 20   |
+| Bibliography.....                                                   | 23   |
+
+# Introduction
+
+The transition from analogue to complex digital telecommunication systems has indicated inadequacies with earthing techniques of the past and has therefore caused renewed interest in bonding and earthing techniques and their impact on electromagnetic compatibility (EMC). Consequently, there is a need for an ITU-T Recommendation on bonding configurations and earthing inside a telecommunication building.
+
+Within the field of EMC, regulations restricting electromagnetic emissions must be satisfied, and for acceptable performance, equipment must possess a specific level of immunity. Electromagnetic compatibility may be achieved by the construction of a common, earthed, conductive shielding network or structure referred to as the common bonding network (CBN). The CBN is the principal bonding and earthing network inside the building. The CBN may be augmented with nested shielding structures having "single point" connections to the CBN. These single point connected structures will be referred to as isolated bonding networks (IBNs). In a telecommunication building, the bonding and earthing network takes the form of the CBN, to which equipment is attached by multiple connections (mesh-BN) or by a single point connection (IBN). The selection of the bonding configuration has an important influence on the responsibility for achieving EMC. A defined bonding configuration permits clear, structured cable routing and earthing. It facilitates control of electromagnetic emissions and immunity, which is especially important for buildings containing newly installed and existing equipment. A comparison of these approaches (IBN and mesh-BN), including their attributes as functions of frequency are discussed in clause 8 and Annex A. As part of its shielding function, the bonding and earthing network provides for personnel safety and lightning protection, and helps control electrostatic discharge (ESD).
+
+Since several different bonding and earthing configurations have been used, and it is desirable to promote standardization by defining generic versions of these configurations. Although there are differences among the configurations, there are many important common aspects. These are discussed in this Recommendation. In addition, three example configurations are described.
+
+## Recommendation ITU-T K.27
+
+# Bonding configurations and earthing inside a telecommunication building
+
+# 1 Scope
+
+Experience in the operation of telecommunication centres shows that the use of a bonding and earthing network that is coordinated with equipment capability and with electrical protection devices, has the following attributes:
+
+- promotes personnel safety and reduces fire hazards;
+- enables signalling with earth return;
+- minimizes service interruptions and equipment damage;
+- minimizes radiated and conducted electromagnetic emissions;
+- reduces radiated and conducted electromagnetic susceptibility;
+- improves system tolerance to discharge of electrostatic energy, and lightning interference.
+
+Within this framework, this Recommendation:
+
+- a) is a guide to bonding and earthing of telecommunication equipment in telephone exchanges and similar telecommunication switching centres;
+- b) is intended to comply with safety requirements imposed by [IEC 60364-4-41] and [IEC 60364-5-54] or national standardizing bodies on AC power installations;
+- c) can be used for installation of new telecommunication centres, and, if possible, for expansion and replacement of systems in existing centres;
+- d) treats coordination with external lightning protection, but does not provide details of protective measures specific to telecommunication buildings;
+- e) addresses the shielding contribution of the effective elements of the building;
+- f) addresses shielding provided by cabinets, cable trays and cable shields;
+- g) is intended to encourage EMC planning, which should include bonding and earthing arrangements that accommodate installation tests and routine diagnostics;
+- h) does not include:
+  - required values of surge current immunity and insulation withstand voltages;
+  - limits of radiated and conducted electromagnetic emission or immunity;
+  - techniques for verifying and maintaining bonding and earthing networks.
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [ITU-T K.20] Recommendation ITU-T K.20 (2011), *Resistibility of telecommunication equipment installed in a telecommunications centre to overvoltages and overcurrents*.
+
+- [IEC 60050-604] IEC 60050-604 (1987), *International Electrotechnical Vocabulary. Chapter 604: Generation, transmission and distribution of electricity – Operation.*
+- [IEC 60050-826] IEC 60050-826 (2004), *International Electrotechnical Vocabulary. Part 826: Electrical installations.*
+- [IEC 60364-4-41] IEC 60364-4-41 (2005), *Low-voltage electrical installations – Part 4-41: Protection for safety – Protection against electric shock.*
+- [IEC 60364-5-54] IEC 60364-5-54 (2011), *Amendment 1 – Low-voltage electrical installations – Part 5-54: Selection and erection of electrical equipment – Earthing arrangements and protective conductors.*
+- [IEC 62305-3] IEC 62305-3 (2010), *Protection against lightning - Part 3: Physical damage to structures and life hazard.*
+
+# 3 Definitions
+
+In this Recommendation, definitions with respect to earthing already introduced by the IEC in [IEC 60050-604] and [IEC 60050-826] are used to maintain conformity. For convenience, they are reproduced in clause 3.1. Definitions specific to telecommunication installations, and not covered by the IEC, are added in clause 3.2.
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 earth** [IEC 60050-826]: The conductive mass of the earth, whose electric potential at any point is conventionally taken as equal to zero (in some countries the term "ground" is used instead of "earth").
+
+**3.1.2 earth electrode** [IEC 60050-826]: A conductive part or a group of conductive parts in intimate contact with and providing an electrical connection with earth.
+
+**3.1.3 earthing conductor** [IEC 60050-826]: A protective conductor connecting the main earthing terminal or bar to the earth electrode.
+
+**3.1.4 earthing network** [IEC 60050-604]: The part of an earthing installation that is restricted to the earth electrodes and their interconnections.
+
+**3.1.5 equipotential bonding** [IEC 60050-826]: Electrical connection putting various exposed conductive parts and extraneous conductive parts at a substantially equal potential.
+
+**3.1.6 equipotential bonding conductor** [IEC 60050-826]: A protective conductor for ensuring equipotential bonding.
+
+**3.1.7 main earthing terminal** [IEC 60050-826]: A terminal or bar provided for the connection of protective conductors, including equipotential bonding conductors and conductors for functional earthing, if any, to the means of earthing.
+
+**3.1.8 neutral conductor (N)** [IEC 60050-826]: A conductor connected to the neutral point of a system and capable of contributing to the transmission of electrical energy.
+
+**3.1.9 protective conductor (PE)** [IEC 60050-826]: A conductor required by some measures for protection against electric shock by electrically connecting any of the following parts:
+
+- exposed conductive parts;
+- extraneous conductive parts;
+- main earthing terminal;
+
+- earth electrode;
+- earthed point of the source or artificial neutral.
+
+**3.1.10 PEN conductor** [IEC 60050-826]: An earthed conductor combining the functions of both protective conductor and neutral conductor.
+
+## 3.2 Terms defined in this Recommendation
+
+The definitions of BN configurations are illustrated in Figures 1 and 2.
+
+This Recommendation defines the following terms:
+
+**3.2.1 bonding network (BN)**: A set of interconnected conductive structures that provides an electromagnetic shield for electronic systems and personnel at frequencies from DC to low RF. The term "electromagnetic shield", denotes any structure used to divert, block or impede the passage of electromagnetic energy. In general, a BN need not be connected to earth but all BNs considered in this Recommendation will have an earth connection.
+
+**3.2.2 common bonding network (CBN)**: The CBN is the principal means for effecting bonding and earthing inside a telecommunication building. It is the set of metallic components that are intentionally or incidentally interconnected to form the principal bonding network (BN) in a building. These components include: structural steel or reinforcing rods, metallic plumbing, AC power conduit, protective conductors (PEs), cable racks and bonding conductors. The CBN always has a mesh topology and is connected to the earthing network.
+
+**3.2.3 common DC return (DC-C)**: A DC power system in which the return conductor is connected to the surrounding bonding network (BN) at many locations. This BN could be either a mesh-BN (resulting in a DC-C-MBN system) or an isolated bonding network (IBN) (resulting in a DC-C-IBN system). More complex configurations are possible (see clause 7.2).
+
+**3.2.4 isolated bonding network (IBN)**: A bonding network that has a single point connection (SPC) to either the common bonding network or another isolated bonding network. All IBNs considered here will have a connection to earth via the SPC.
+
+**3.2.5 isolated DC return (DC-I)**: A DC power system in which the return conductor has a single point connection to a bonding network (BN). More complex configurations are possible, see clause 7.2.
+
+**3.2.6 mesh-BN (MBN)**: A bonding network in which all associated equipment frames, racks and cabinets, and usually, the DC power return conductor, are bonded together as well as at multiple points to the CBN. Consequently, the mesh-BN augments the common bonding network (CBN).
+
+**3.2.7 mesh-IBN**: A type of isolated bonding network (IBN) in which the components of the IBN (e.g., equipment frames) are interconnected to form a mesh-like structure. This may, for example, be achieved by multiple interconnections between cabinet rows, or by connecting all equipment frames to a metallic grid (a "bonding mat") extending beneath the equipment. The bonding mat is, of course, insulated from the adjacent common bonding network (CBN). If necessary the bonding mat could include vertical extensions, resulting in an approximation to a Faraday-cage. The spacing of the grid is chosen according to the frequency range of the electromagnetic environment.
+
+**3.2.8 single point connection (SPC)**: The unique location in an IBN where a connection is made to the CBN. In reality, the SPC is not a "point" but, of necessity, has sufficient size to accommodate the connection of conductors. Usually, the SPC takes the form of a copper bus-bar. If cable shields or coaxial outer conductors are to be connected to the SPC, the SPC could be a frame with a grid or sheet metal structure.
+
+**3.2.9 SPC window (SPCW)**: The interface or transition region between an isolated bonding network (IBN) and the common bonding network (CBN). Its maximum dimension is typically 2 metres. The SPC bus-bar (SPCB), or frame, lies within this region and provides the interface between
+
+IBN and CBN. Conductors (e.g., cable shields or DC return conductors) that enter a system block and connect to its IBN must enter via the SPCW and connect to the SPCB or frame.
+
+**3.2.10 star-IBN:** A type of isolated bonding network (IBN) comprising clustered or nested IBNs sharing a common single point connection (SPC).
+
+**3.2.11 system block:** All the equipment whose frames and associated conductive parts form a defined bonding network (BN).
+
+![Figure 1 shows two bonding network configurations: Star topology and Mesh topology. The Star topology diagram shows six rectangular blocks (Rack, equipment, module) connected to a single central point by lines (Bonding conductor). The Mesh topology diagram shows six rectangular blocks arranged in a 2x3 grid, connected to each other by lines (Bonding conductor) in a mesh pattern. A legend below the diagrams shows a single rectangle labeled 'Rack, equipment, module' and a line labeled 'Bonding conductor'. The label 'K.27(15)_F01' is present near the bottom right of the mesh diagram.](e6df2733626a85205c1db682e6259c46_img.jpg)
+
+Star topology
+
+Mesh topology
+
+K.27(15)\_F01
+
+— Rack, equipment, module
+
+— Bonding conductor
+
+Figure 1 shows two bonding network configurations: Star topology and Mesh topology. The Star topology diagram shows six rectangular blocks (Rack, equipment, module) connected to a single central point by lines (Bonding conductor). The Mesh topology diagram shows six rectangular blocks arranged in a 2x3 grid, connected to each other by lines (Bonding conductor) in a mesh pattern. A legend below the diagrams shows a single rectangle labeled 'Rack, equipment, module' and a line labeled 'Bonding conductor'. The label 'K.27(15)\_F01' is present near the bottom right of the mesh diagram.
+
+**Figure 1 – Bonding network configurations forming a system block**
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|      |                                          |
+|------|------------------------------------------|
+| BN   | Bonding Network                          |
+| CBN  | Common Bonding Network                   |
+| EMC  | ElectroMagnetic Compatibility            |
+| ESD  | ElectroStatic Discharge                  |
+| IBN  | Isolated Bonding Network                 |
+| MBN  | Mesh-Bonding Network                     |
+| N    | Neutral                                  |
+| PCB  | Printed Circuit Board                    |
+| PEN  | Protective (earth) and Neutral conductor |
+| SPC  | Single Point Connection                  |
+| SPCB | Single Point Connection Bus bar          |
+| SPCW | Single Point Connection Window           |
+
+# **5 Conventions**
+
+None.
+
+# **6 Principles of bonding and earthing**
+
+## **6.1 Summary of theory**
+
+Bonding and earthing refer to the construction and maintenance of bonding networks (BNs) and their connection to earth. In this Recommendation, the acronym BN implies that a connection to earth exists. Also, BN is used to refer to common bonding networks (CBNs) and isolated bonding networks (IBNs) collectively.
+
+The primary purpose of a BN is to help shield people and equipment from the adverse effects of electromagnetic energy in the DC to low RF range. Typical energy sources of concern are lightning, and AC and DC power faults. Of generally lesser concern are quasi steady-state sources such as AC power harmonics, and "function sources" such as clock signals from digital equipment. All of these sources will be referred to generically as "emitters". People and equipment that suffer adversely from the energy from the emitters will be referred to as "susceptors". The coupling between a particular emitter and a particular susceptor may be characterized by a transfer function. The purpose of a BN is to reduce the magnitude of the transfer function to an acceptable level. This may be achieved by appropriate design of the CBN, and the mesh-BNs (MBNs) and IBNs attached to that CBN. Theoretical and quantitative aspects are discussed in Annex A. Practical aspects are discussed below.
+
+Other purposes of a BN are to function as a "return" conductor in some signalling applications, and as a path for power fault currents. The capability of the BN to handle large currents helps to rapidly de-energize faulted power circuits. Also the BN, and its connection to earth, is used in "ground return" signalling (see clause 6.5).
+
+![Star configuration diagram showing three racks connected to a single point on the CBN via Star-IBN. The connection point is labeled SPCW. A note indicates the connection 'May be of zero length'. Mesh configuration diagram showing three racks connected to the CBN via Mesh-IBN at a single point labeled SPCW. Mesh configuration diagram showing three racks connected to the CBN at multiple points via Mesh-IBN.](d4af765160d04ecef538e5066006dc77_img.jpg)
+
+|                                    |                | Star configuration                                       | Mesh configuration          |
+|------------------------------------|----------------|----------------------------------------------------------|-----------------------------|
+| Integration of the BN into the CBN | Single point   | <p>Star-IBN</p> <p>SPCW</p> <p>May be of zero length</p> | <p>Mesh-IBN</p> <p>SPCW</p> |
+|                                    | Multiple point | <p>Not applicable</p>                                    | <p>Mesh-BN</p>              |
+
+Rack, equipment, module, etc.
+
+Nearby elements of CBN
+
+Bonding conductor
+
+Connection to CBN
+
+BN Bonding network
+
+CBN Common bonding network
+
+IBN Isolated bonding network
+
+SPCW Single point connection window
+
+K.27(15)\_F02
+
+Star configuration diagram showing three racks connected to a single point on the CBN via Star-IBN. The connection point is labeled SPCW. A note indicates the connection 'May be of zero length'. Mesh configuration diagram showing three racks connected to the CBN via Mesh-IBN at a single point labeled SPCW. Mesh configuration diagram showing three racks connected to the CBN at multiple points via Mesh-IBN.
+
+**Figure 2 – Connection of system block to the CBN**
+
+## 6.2 Implementation principles
+
+### 6.2.1 Implementation principles for the CBN
+
+The theoretical concepts of Annex A are confirmed by practical experience and lead to the general principles listed below. A consequence of applying these principles is that the number of conductors and interconnections in the CBN is increased until adequate shielding is achieved. Concerning the important issue of electric shock, the following implementation principles apply to mitigation of electric shock as well as to equipment malfunction. Electric shock is discussed further in clause 6.3.
+
+- a) All elements of the CBN shall be interconnected. Multiple interconnections resulting in a three-dimensional mesh are especially desirable. Increasing the number of CBN conductors and their interconnections increases the CBN shielding capability and extends the upper frequency limit of this capability.
+- b) It is desirable that the egress points for all conductors leaving the building (including the earthing conductor), be located close together. In particular, the AC power entrance facilities, telecommunication cable entrance facilities, and the earthing conductor entry point, should be close together.
+
+- c) The facility should be provided with a main earthing terminal located as close as possible to the AC power and telecommunication cable entrance facilities. The main earthing terminal shall connect to:
+  - an earthing electrode(s) via a conductor of shortest length;
+  - the neutral conductor of the AC power feed (in TN systems);
+  - cable shields (at the cable entrance) either directly or via arresters or capacitors if required by corrosion considerations.
+- d) The CBN shall be connected to the main earthing terminal. Multiple conductors between CBN and the main earthing terminal are desirable.
+- e) As contributors to the shielding capability of the CBN, interconnection of the following items of the CBN is important:
+  - metallic structural parts of the building including I-beams and concrete reinforcement where accessible;
+  - cable supports, trays, racks, raceways and AC power conduit.
+- f) The coupling of surges into indoor cabling (signal or power) is reduced, in general, by running the cables in close proximity to CBN elements. However, in the case of external surge sources, the currents in the CBN will tend to be greater in peripheral CBN conductors. This is especially true of lightning down-conductors. Thus, it is best to avoid routing cables in the periphery of the building. When this is unavoidable, metallic ducts that fully enclose the cables may be needed. In general, the shielding effect of cable trays, etc., is especially useful, and metallic ducts or conduit that fully enclose the cables provide near perfect shielding.
+- g) In steel frame high-rise buildings, advantage may be taken of the shielding effect that the steel frame provides against lightning strokes. For cables extending between floors, maximum shielding is obtained by locating the cables near the centre of the building. However, as implied above, cables enclosed in metallic ducts may be located anywhere.
+- h) Where the facility to use over-voltage primary protection [ITU-T K.20] on telecommunication wires is provided, it should have a low impedance connection to the cable shield, if it exists, and also to the surrounding CBN.
+- i) Over-voltage protectors may be provided at the AC power entrance facility if the telecommunication building is located in an area where power lines are exposed to lightning. These protectors should be bonded with low impedance to the CBN.
+- j) Mechanical connections, in a protection path of the CBN, whose electrical continuity is questionable shall be bypassed by jumpers that are visible to inspectors. These jumpers shall comply with IEC requirements for safety. However, for EMC applications, the jumpers should have low impedance.
+- k) The CBN facilitates the bonding of cable shields or outer conductors of coaxial cables at both ends by providing a low impedance path in parallel and in proximity to the cable shields and outer conductors. Thus, most of the current driven by potential differences is carried by the highly conductive members of the CBN. Disconnection of one cable shield for inspection should minimally affect the current distribution in the CBN.
+
+### 6.2.2 Implementation principles for a mesh-BN
+
+The main feature of a mesh-BN is the interconnection, at many points, of cabinets and racks of telecommunication and other electrical equipment, and also multiple interconnections to the CBN.
+
+If the outer conductor of a coaxial cable interconnection between mesh-BN equipment has multiple connections to the CBN, it may need additional shielding. If the shielding provided by a cable tray is
+
+insufficient, additional shielding may be provided by use of shielded coaxial cable ("triax"), enclosing ducts, or conduit.
+
+Bonding methods, in increasing order of EMC quality are: screw fastenings, spot welds, and welded seams. The highest level of EMC shielding is provided by equipment cabinets and any sheet-metal enclosures within these cabinets.
+
+A proven countermeasure to undesirable emission or reception of electromagnetic energy, especially at high frequencies, is a shield that totally encloses the electronic circuit. Effective shielding of cables, especially when the shields are extensions of shielding cabinets, depends on shielding material, shield geometry, and especially the connection of the shield to the cabinet panels at which the shield terminates.
+
+It is easy to add shielding to a mesh-BN configuration. The need for additional shielding may arise for example, if a broadcast transmitter were installed nearby.
+
+In some situations, it may be advantageous to augment the mesh-BN by connecting all equipment frames of a system block to a conductive grid (a bonding mat) located either below or above a collection of equipment cabinets. This optional use of a bonding mat is shown in Figure B.1.
+
+### **6.2.3 Implementation principles for an IBN**
+
+The main feature of an IBN is that it is isolated from the surrounding CBN except for a single point connection where conductors entering the system block enter via the transition region between the IBN and CBN (see definition of single point connection window (SPCW)).
+
+Within the confines of an IBN, the importance of multiple interconnections between cabinets and racks, etc., depends on the details of DC power distribution and signal interconnection. For example, if the DC power return conductor has multiple connections to cabinet frames, then multiple interconnection of cabinet frames and racks is desirable for the following reason: it will tend to reduce surge coupling in the event of a DC fault in equipment within the IBN.
+
+Concerning cable shields of twisted pair cables, if a shield is left open-circuit at the end that terminates on IBN equipment, while the other end is connected to the CBN, surges in the CBN may result in induced common mode surges on the pairs in that cable. If those pairs terminate on devices that can operate satisfactorily in the presence of a steady state common mode (e.g., opto-isolators, transformers, or surge protectors), and if those devices can also withstand common mode surges, then there may be an advantage in having the electrostatic shielding afforded by an open circuited shield.
+
+In the case of coaxial cable, the outer conductor will, of necessity, terminate on the interface circuits at each end. Interface circuits containing transformers or opto-isolators may be used to isolate the outer conductor. If a shielded cable or waveguide enters the IBN from the CBN, the most generally effective strategy is to connect each end of the shield or waveguide to the equipment frame and to bond the shield or waveguide to the single point connection.
+
+## **6.3 Protection against electric shock**
+
+A densely interconnected BN, together with its connection to earth, substantially reduces the likelihood of significant voltages appearing between adjacent metallic components. However, additional measures need to be taken, especially in regard to AC power distribution (see clause 7.1). [IEC 60364-4-41] and [IEC 60364-5-54] discuss protection against electric shock, and installations should conform to its recommendations.
+
+## **6.4 Protection against lightning**
+
+A CBN conforming to clause 6.2.1 should adequately shield against lightning surges arriving at the building on conductors such as cable shields and power lines. However, in the event of a direct stroke to the building, the CBN may not provide sufficient shielding. Consequently, buildings without steel frames or reinforcements may require external lightning protection; especially so if the building has
+
+a radio tower on its roof. Concerning the protective measures against the effects of a direct lightning stroke to a building, refer to [IEC 62305-3]. Where necessary to further reduce risk, these protective measures may have to be enhanced, e.g., by conductive roof layers, closer spacing of down-conductors, interconnection of the reinforcement of concrete buildings, and interconnection of metallic façade elements. It is advantageous to introduce all conductive elements of services, e.g., cables and pipes, into the building at one location and in close proximity.
+
+## 6.5 Functional earthing
+
+Telecommunication techniques sometimes use circuits for signalling with earth return, e.g., lines with ground start, three wire inter-exchange connection, etc. Equipment interconnected by these circuits needs functional earthing. The signalling range is normally determined by the resistance of the current path. Most of this resistance is contributed by the earth electrodes. The performance provided by the earthing network via the main earthing terminal is generally sufficient for this signalling purpose.
+
+# 7 Power distribution
+
+AC and DC power distribution in telecommunication buildings should be designed to limit coupling to telecommunication circuits arising from:
+
+- mutual impedance of shared conductors;
+- mutual inductive coupling (especially during short circuit conditions);
+- common source impedances.
+
+## 7.1 AC power distribution
+
+It is recommended that the indoor mains installation within a telecommunication building be of type TN-S in order to improve the EMC performance of the telecommunication installation. This requires that there shall be no protective (earth) and neutral (PEN) conductor within the building. Consequently, a three-phase network within a telecommunication building is, physically, a five-wire installation (L1, L2, L3, N, PE).
+
+Depending on the type of outdoor mains distribution network serving a telecommunication building, one of the following requirements shall apply:
+
+- a) Service by a TN-S section of the outdoor mains distribution network:
+  - 1) solely the protective conductor (PE) shall be connected to the main earthing terminal (see Figure 3, mode 1).
+- b) Service by a TN-C section of the outdoor mains distribution network:
+  - 1) the PEN conductor shall be connected to the main earthing terminal only;
+  - 2) from the main earthing terminal to and within customer locations inside the building, the neutral conductor (N) shall be treated as a live conductor;
+  - 3) a dedicated PE shall be provided (see Figure 3, mode 2).
+- c) Service by a TT or IT section of the outdoor mains distribution network:
+  - 1) the PE shall be derived via the main earthing terminal from the earthing network;
+  - 2) the dimensioning of the PE shall follow the rules of the TN-S system.
+
+If the outdoor mains distribution is of type IT or TT, a separation transformer dedicated to that building allows for the recommended TN-S installation. In this case the indoor mains installation must conform to Figure 3, mode 1.
+
+## 7.2 DC power distribution
+
+In telecommunication buildings, DC power is generally distributed from a centralized DC power plant, with the positive terminal connected to the CBN. This polarity is chosen to minimize corrosion in the outside cable plant. There may be exceptions for specific transmission systems.
+
+The DC power return network may be connected to its surrounding BNs at a single point only. This case will be referred to as an "isolated DC return" system (DC-I).
+
+![Figure 3: Arrangements for the transition from the outdoor mains distribution system to the indoor AC distribution systems other than TN-S. The figure shows three modes: Mode 1 (TN-S/TN-S), Mode 2 (TN-C/TN-S), and Mode 3 (IT/IT or TT/TT). Each mode illustrates the connection between outdoor mains distribution, indoor AC distribution, and a DC power distribution system including PE, DC-return, and Ring conductor connected to a main earthing terminal.](1a827b10290f33d4fec04d0e8ef7a897_img.jpg)
+
+**Mode 1: TN-S/TN-S**
+
+The diagram shows the transition from an outdoor TN-S distribution system to an indoor TN-S installation. The outdoor system has separate PE and N conductors. The indoor installation also has separate PE and N conductors. The DC power distribution system includes a PE conductor connected to the main earthing terminal, a DC-return conductor, and a ring conductor. The PE conductor is connected to the indoor PE conductor.
+
+**Mode 2: TN-C/TN-S**
+
+The diagram shows the transition from an outdoor TN-C distribution system to an indoor TN-S installation. The outdoor system has a combined PEN conductor. The indoor installation has separate PE and N conductors. The DC power distribution system includes a PE conductor connected to the main earthing terminal, a DC-return conductor, and a ring conductor. The PE conductor is connected to the indoor PE conductor.
+
+**Mode 3: IT/IT or TT/TT**
+
+The diagram shows the transition from an outdoor IT or TT distribution system to an indoor IT or TT installation. The outdoor system has separate PE and N conductors. The indoor installation also has separate PE and N conductors. The DC power distribution system includes a PE conductor connected to the main earthing terminal, a DC-return conductor, and a ring conductor. The PE conductor is connected to the indoor PE conductor.
+
+NOTE – Mode 1 is obligatory if a separation transformer is dedicated to the building and the TN-S system consequently originates at the transformer load side.
+
+K.27(15)\_F03
+
+Figure 3: Arrangements for the transition from the outdoor mains distribution system to the indoor AC distribution systems other than TN-S. The figure shows three modes: Mode 1 (TN-S/TN-S), Mode 2 (TN-C/TN-S), and Mode 3 (IT/IT or TT/TT). Each mode illustrates the connection between outdoor mains distribution, indoor AC distribution, and a DC power distribution system including PE, DC-return, and Ring conductor connected to a main earthing terminal.
+
+**Figure 3 – Arrangements for the transition from the outdoor mains distribution system to the indoor AC distribution systems other than TN-S**
+
+Alternatively, the DC return may connect to the BN at multiple points (in which case some DC current will be conducted by the BN). This system will be referred to as a "DC return common to a BN" and denoted by "DC-C-BN". Typical configurations are DC-C-CBN (DC return common to the CBN), and DC-C-IBN (DC return common only to an IBN). Also, a DC return could, for example, traverse both the CBN and an IBN, and be common to the CBN but isolated from the IBN. This case is denoted by DC-C-CBN: DC-I-IBN. These are discussed in Annex B. Other more complicated interconnections of BNs and DC returns are also in use.
+
+The advantage of a DC-C-BN system is that it cannot support a DC feed common-mode and hence unwanted coupling via this mode cannot occur. On the other hand, there will be coupling between the BN and the DC feed. The advantage of the DC-I-IBN system is that it avoids BN to DC feed coupling. However, it supports a common-mode and may introduce unwanted coupling. The choice between the two systems depends on the overall design strategy. Some recommendations are given below.
+
+A DC-C-CBN feed may be used in systems in which the DC feed-to-CBN coupling has been minimized by the following measures:
+
+- DC feed conductors have large cross-sections enabling them to carry high currents with minimal temperature rise;
+- voltage drop at maximum load current is low;
+- there is low source impedance, and low mutual impedance between the branches of the DC feed system.
+
+The use of a DC-I feed results in a much lower DC feed-to-CBN coupling and is preferable in DC distribution networks designed with:
+
+- loads in more than one system of electronic equipment (i.e., shared battery plant); and
+- loads that are sensitive to transients occurring during short circuit conditions.
+
+# **8 Comparison between IBN and mesh-BN installations**
+
+The advantage of installing equipment in an IBN is that a high level of shielding is attainable from DC through tens of kHz or perhaps hundreds of kHz depending on the size of the IBN (see clause A.1.2). The reason is that, within this frequency range, the single point connection between the IBN and CBN results in negligible current flowing between CBN and IBN. Some digital switches are designed specifically for installation within an IBN.
+
+Mesh-IBNs and star-IBNs are both currently in use. Clause B.2 describes a mesh-IBN in the form of a "bonding-mat", and clause B.3 describes a star-IBN system. Sparsely interconnected mesh-IBNs have also been used successfully, and this is mentioned in clause B.3.
+
+To limit the risk of electric shock between an IBN and the surrounding CBN, it is necessary to limit the size of the IBN (both horizontal and vertical extent). Passageways that form the boundary between IBN and CBN, should have a minimum width imposed.
+
+Disadvantages of IBN installation are cable routing restrictions and the additional expense (compared to mesh-BN) of maintaining the isolation.
+
+The advantage of installing equipment in a mesh-BN configuration is that equipment frames may be connected to the surrounding CBN without restriction. Also, shielded cables and coaxial cables may be routed, and their shields or outer conductors connected to cabinet frames, without restriction. If the CBN design and equipment susceptibility has been coordinated, the CBN provides shielding from DC through several megahertz. A mesh-BN installation also has maintenance advantages as described in clause 9.
+
+A disadvantage of the mesh-BN installation is the need for quantitative design procedures and appropriate immunity data for equipment.
+
+# **9 Maintenance of bonding networks**
+
+One advantage of mesh-BN installation is that small changes that occur in the CBN generally have only a small effect on its shielding capability. Moreover, when necessary, additional shielding may be obtained by introduction of additional conductors (e.g., bonding conductors, cable trays, and conduit). Such modifications are usually straightforward.
+
+IBN systems are more difficult to maintain, because craft-person activity is liable to result in inadvertent interconnections between IBN and CBN, violating the desired single point connection, and introducing surge currents into the IBN. Closely related to this is maintenance of DC-I power systems. Verification of single point connection in a DC-I system is facilitated if this connection is made with a conductor, around which, a DC clamp-on ammeter can be clamped. Zero current confirms single point connection.
+
+It is recommended that systematic verification be performed on all bonding configurations and earthing connections inside a telecommunication building.
+
+# **10 Examples of connecting equipment configurations to the CBN**
+
+The bonding configuration that is used depends upon the type of equipment to be connected to the CBN.
+
+The following three examples are described in Annex B:
+
+- 1) mesh-BN (see clause B.1);
+- 2) mesh-IBN with a bonding mat configuration (see clause B.2);
+- 3) star, or sparse mesh-IBN with isolation of DC power return (see clause B.3).
+
+# Annex A
+
+## Brief theory of bonding and earthing networks
+
+(This annex forms an integral part of this Recommendation.)
+
+## A.1 Overview
+
+The basic theoretical notions of shielding apply to the entire electromagnetic spectrum extending from DC through microwave frequencies. The essence of these basic notions is represented by the circuit model of Figure A.1 a). The description of energy sources as "emitters", and susceptible equipment (and people) as "susceptors" is taken from [b-Keiser]. In Figure A.1 a),  $V_{em}$  is the frequency domain representation of the emitter (e.g., a Laplace or Fourier transform), and  $Z_{em}$  is the emitter source impedance. The susceptor is represented by its impedance  $Z_{su}$ . The electromagnetic interaction between emitter and susceptor is modelled by a two-port network (port A with terminals A0, and A1, and port B with terminals B0, and B1). In Figure A.1 a) this two-port is represented by a T-network, but a  $\pi$  representation is often useful, as is a Norton equivalent for the emitter.
+
+Although Figure A.1 a) is a simplification of reality, it is usually an adequate model for any specific emitter-susceptor pair. Moreover, it can be used as the starting point whenever a more complex model is necessary.
+
+Figure A.1 a) illuminates the two main strategies for increasing the shielding of the susceptor from the emitter: the "short-circuit" and "open-circuit" strategies. It is clear that if  $Z_C$  is zero, no energy from the emitter  $V_{em}$  can reach the susceptor and  $V_{su} = 0$ . The energy that leaves the emitter is "reflected by the short-circuit" and dissipates in the resistive components of  $Z_{em}$  and  $Z_A$ . (Energy can also be returned to the source but this is not significant here.) Similarly, it is clear that if either  $Z_A$  or  $Z_B$  are infinite in magnitude (i.e., open circuit), no emitter energy will reach the susceptor (and again  $V_{su} = 0$ ). In this case, the energy that leaves the emitter is reflected by the open circuit. Suppose  $Z_B$  is the open circuit. Then  $Z_B = \infty$ , and the energy will dissipate in the resistive parts of  $Z_{em}$ ,  $Z_A$  and  $Z_C$ . Note that in general,  $V_{su}$  and all impedances are functions of frequency.
+
+The two-port in Figure A.1 a) (A1, A0, B1, B0) will be referred to as the shielding network relative to some specific emitter and susceptor. If a different emitter or susceptor were considered, new impedance functions  $Z_A$ ,  $Z_B$  and  $Z_C$  would apply.
+
+A most useful characterization of the shielding network is a frequency domain transfer function. Here, the transfer function  $T(\omega)$  will be defined as either  $I_{su}(\omega)/V_{em}(\omega)$  or  $V_{su}(\omega)/V_{em}(\omega)$ . Thus  $T(\omega)$ , as defined here, is a function of  $Z_{em}$  and  $Z_{su}$  as well as  $Z_A$ ,  $Z_B$  and  $Z_C$ .
+
+To summarize, for each emitter-susceptor pair there is a transfer function,  $T(\omega)$ , that characterizes the shielding network.
+
+Returning to the topic of shielding strategies, note that in general, perfect short and open circuits are not possible to achieve, since the best implementations possess inductance and capacitance respectively. As a result, instead of perfect shielding, the most that can be achieved is a transfer function,  $T(\omega)$ , whose magnitude is less than some prescribed value over some prescribed frequency range.
+
+#### A.1.1 Application to BNs in general
+
+In typical bonding networks, resistive components are small, and for transient events with spectra in the 1 kHz to 1 MHz range, the shielding network is primarily inductive. Consequently, the general representation of Figure A.1 a) reduces to Figure A.1 b). As noted above, the specific component values depend on a particular emitter-susceptor pair. However, the  $L_A$ ,  $L_B$  and  $L_C$  in Figure A.1 b) are constants; they are not functions of frequency. An observation of fundamental importance is as follows: Increasing the number of conductors and interconnections in the BN (especially in the region
+
+lying between the emitter and susceptor) will, in general, reduce  $L_C$  and hence reduce the transfer function of the BN relative to that emitter-susceptor pair. In the limiting case, the susceptor could be given near-total shielding by enclosing it in an unbroken sheet of metal (i.e., a Faraday cage).
+
+A susceptor may be characterized by a "susceptibility threshold"  $I_{sut}(\omega)$ , or  $V_{sut}(\omega)$ . Sinusoidal excitation will be assumed, but the following theory may be adaptable to pulse excitation. As an example, consider as a susceptor, equipment whose frame is connected to the CBN at several points. Choose one of these points to be the test point. Suppose the CBN connection at the test point is made by a conductor, around which split-core transformers can be clamped for purposes of excitation and current measurement. Let the current at the test point be sinusoidal with angular frequency  $\omega$  and amplitude  $I_{sut}(\omega)$ . [ $I_{sut}(\omega)$  real and positive.]
+
+Suppose that for each  $\omega$ , an  $I_{sut}(\omega)$  is found such that the equipment functions normally for those  $I_{sut}(\omega)$  that satisfy:
+
+$$I_{sut}(\omega) < I_{sut}(\omega) \text{ for } \omega_1 < \omega < \omega_2$$
+
+and functions abnormally for  $I_{sut}(\omega)$  that fails to satisfy this inequality. Then  $I_{sut}(\omega)$  is the equipment susceptibility threshold for the frequency range  $[\omega_1, \omega_2]$ , and for that specific test point and connection configuration.
+
+Also, suppose a worst-case emitter has been characterized (e.g., let  $V_{em}$  be that worst case), then the design of a bonding and earthing network may now be expressed quantitatively as follows: for every emitter-susceptor pair of concern, the network's transfer function shall satisfy the following inequality:
+
+$$|T(\omega)V_{em}(\omega)| < I_{sut}(\omega) \text{ for } \omega_1 < \omega < \omega_2$$
+
+Where:
+
+$\omega_1$  and  $\omega_2$  specify the frequency range of concern. Typically,  $\omega_1 \sim 0$  and  $\omega_2 \sim 1$  MHz.
+
+Note that  $I_{sut}(\omega)$  is specific to a particular test point, and to the particular configuration of equipment-to-CBN interconnections. It may not apply if the equipment or its interconnections are modified.
+
+#### A.1.2 Some important features of IBNs
+
+Isolated bonding networks use an open-circuit shielding strategy. However, because IBNs are invariably installed within an enclosing CBN, short and open circuit strategies operate in cascade as shown in Figure A.1 c). Here, node B2 could, for example, represent the frame of an equipment ( $Z_{su}$ ) that is isolated except for a single point connection to the CBN at node B0. Node B1 represents all of the immediately surrounding CBN metalwork. Capacitor C represents the capacitance between the equipment frame and the surrounding CBN. Figure A.1 c) shows clearly that for low frequencies,  $|T(\omega)|$  will be small (it has a zero at  $\omega = 0$ ), but at a sufficiently high frequency there will be one or more resonances where  $|T(\omega)|$  will have maxima. In the neighbourhood of these resonant frequencies, shielding will be poor. However, if there are no significant emitters in these spectral regions, or if the equipment has additional shielding that is effective in these spectral regions, then no malfunctions will occur.
+
+![Circuit diagram of the fundamental shielding model. It features a voltage source V_em in series with an impedance Z_em connected between terminals A0 and A1. A series impedance Z_A is connected between A1 and a central node. From this central node, an impedance Z_C is connected to the common reference line (B0). A series impedance Z_B is connected from the central node to terminal B1. At terminal B1, a voltage V_su is indicated, and a current I_su flows through an impedance Z_su connected to terminal B0.](5b8a756d9a71c35f17db8bcb90b438a3_img.jpg)
+
+a) Fundamental shielding model
+
+Circuit diagram of the fundamental shielding model. It features a voltage source V\_em in series with an impedance Z\_em connected between terminals A0 and A1. A series impedance Z\_A is connected between A1 and a central node. From this central node, an impedance Z\_C is connected to the common reference line (B0). A series impedance Z\_B is connected from the central node to terminal B1. At terminal B1, a voltage V\_su is indicated, and a current I\_su flows through an impedance Z\_su connected to terminal B0.
+
+![Circuit diagram of the shielding model for intra-CBN coupling. It features a voltage source V_em in series with an impedance Z_em connected between terminals A0 and A1. A series inductor L_A is connected between A1 and a central node. From this central node, an inductor L_C is connected to the common reference line (B0). A series inductor L_B is connected from the central node to terminal B1. At terminal B1, an impedance Z_su is connected to terminal B0.](812e188283162af0b54fb3e30ffee51b_img.jpg)
+
+b) Shielding model for intra-CBN coupling
+
+Circuit diagram of the shielding model for intra-CBN coupling. It features a voltage source V\_em in series with an impedance Z\_em connected between terminals A0 and A1. A series inductor L\_A is connected between A1 and a central node. From this central node, an inductor L\_C is connected to the common reference line (B0). A series inductor L\_B is connected from the central node to terminal B1. At terminal B1, an impedance Z\_su is connected to terminal B0.
+
+![Circuit diagram of the shielding model for CBN-IBN coupling. It features a voltage source V_em in series with an impedance Z_em connected between terminals A0 and A1. A series inductor L_A is connected between A1 and a central node. From this central node, an inductor L_C is connected to the common reference line (B0). A series inductor L_B is connected from the central node to terminal B1. Between terminal B1 and terminal B2, there is a capacitor C. At terminal B2, an impedance Z_su is connected to terminal B0.](c5655e700cc3e9aac7e9f4f07f30264d_img.jpg)
+
+c) Shielding model for CBN-IBN coupling
+
+Circuit diagram of the shielding model for CBN-IBN coupling. It features a voltage source V\_em in series with an impedance Z\_em connected between terminals A0 and A1. A series inductor L\_A is connected between A1 and a central node. From this central node, an inductor L\_C is connected to the common reference line (B0). A series inductor L\_B is connected from the central node to terminal B1. Between terminal B1 and terminal B2, there is a capacitor C. At terminal B2, an impedance Z\_su is connected to terminal B0.
+
+K.27(15)\_FA.1
+
+**Figure A.1 – Shielding model representations**
+
+# Annex B
+
+## Examples of bonding configurations
+
+(This annex forms an integral part of this Recommendation.)
+
+### B.1 Mesh-BN
+
+A mesh-BN is a densely interconnected BN in which equipment frames are an extension of the CBN. In this example, which is shown in Figure B.1, the DC power system is of type DC C-MBN.
+
+The DC power system operating at relatively high voltages (e.g., 400 V DC) shall be balanced about earth (positive and negative) by a resistive divider, whose centre point is connected to earth as shown in Figure B.1.
+
+#### B.1.1 Components of a mesh-BN
+
+In mesh-BNs, extensive interconnection among the following conductive elements is recommended:
+
+- cabinets and cable racks of telecommunication and peripheral equipment;
+- frames of all systems housed within the telecommunication building;
+- the protective conductor PE of the TN-S type AC power installation;
+- all metal parts, which according to [IEC 60364-5-54] must be connected to the protective conductor;
+- the main earthing terminal, including earthing conductors and earth electrodes;
+- each DC power return conductor along its entire length.
+
+Multiple interconnections between CBN and each DC return along its entire length is usually a feature of the mesh-BN configuration. The DC return conductor of such a configuration may be entrusted with the functions of protective conductor for systems associated with AC loads or sockets, provided that continuity and reliability complies with [IEC 60364-5-54].
+
+#### B.1.2 General design objectives
+
+Safety requirements supersede all other requirements. To ensure continuity of bonding conductors, reliable connection methods shall be used, e.g., crimping, welding. However, if several options exist for fulfilling safety requirements, only that one shall be used which best coordinates with EMC requirements.
+
+##### B.1.2.1 Non-telecommunication installations
+
+Within the whole telecommunication building, there shall be no exception from the TN-S-type AC power installation [IEC 60364-5-54]. This requires, except at the main earthing terminal for a TN-C to TN-S transition at the entrance of the building, that the neutral conductor and protective conductor are nowhere interconnected in the building, neither in permanently connected equipment, nor in equipment connected by plug and socket.
+
+##### B.1.2.2 Telecommunication equipment and systems
+
+Telecommunication equipment with electronic circuitry is generally provided with a "potential reference" metallization that extends widely over the surface of the printed circuit boards (PCBs). If PCBs are connectorized, a number of pins are used to interconnect to adjoining cabling, backplanes, or motherboards. At this interface there starts the interconnection to the mesh-BN via equipment frames, shelf-racks, etc.
+
+![Figure B.1 – Mesh-BN installation inside a telecommunication building. This is a detailed cross-sectional diagram of a multi-story building showing the electrical and bonding infrastructure. The building levels are labeled: Floor n+1, Floor n, Lower floor, and Basement. Key components and connections shown include:
+  - Support column of the building and Reinforcement.
+  - 400 V DC equipment and 400 V DC power supply on Floor n+1.
+  - System block 1 Mesh-BN equipment on Floor n+1, connected to a Bonding ring conductor and a Bonding mat. A note indicates 'Connection of cable shield to the rack is recommended'.
+  - Interconnection and Interconnected reinforcement between floors.
+  - Mesh-BN equipment and System block 2 mesh-BN equipment on Floor n.
+  - AC distribution, PE (Protective Earth), Plumbing, and Aircon units on the Lower floor.
+  - 48V dc service panel and Frame of dc powerplant on the Basement level.
+  - Main earthing terminal (PE) on the Basement level, connected to Telecom cables, a Bonding ring conductor (recommended), To earth electrode, and To foundation reinforcement/ring conductor.
+  - A legend at the bottom right defines the line types:
+    - DC return conductor (+48 V) [long dash-dot line]
+    - Interconnected reinforcement and building steel [long dashed line]
+    - Intra-system cabling [short dashed line]
+    - Shielded inter-system cabling [line with a circle symbol]
+    - Bonding conductor [solid line]
+    - 400 V dc conductor (for +200 V and -200 V, indicated as potential) [dotted line]
+  - The diagram is labeled K.27(15)_FB.1.](c914f51f4427bc672dd0526cfc90ebe9_img.jpg)
+
+Figure B.1 – Mesh-BN installation inside a telecommunication building. This is a detailed cross-sectional diagram of a multi-story building showing the electrical and bonding infrastructure. The building levels are labeled: Floor n+1, Floor n, Lower floor, and Basement. Key components and connections shown include:
+ - Support column of the building and Reinforcement.
+ - 400 V DC equipment and 400 V DC power supply on Floor n+1.
+ - System block 1 Mesh-BN equipment on Floor n+1, connected to a Bonding ring conductor and a Bonding mat. A note indicates 'Connection of cable shield to the rack is recommended'.
+ - Interconnection and Interconnected reinforcement between floors.
+ - Mesh-BN equipment and System block 2 mesh-BN equipment on Floor n.
+ - AC distribution, PE (Protective Earth), Plumbing, and Aircon units on the Lower floor.
+ - 48V dc service panel and Frame of dc powerplant on the Basement level.
+ - Main earthing terminal (PE) on the Basement level, connected to Telecom cables, a Bonding ring conductor (recommended), To earth electrode, and To foundation reinforcement/ring conductor.
+ - A legend at the bottom right defines the line types:
+ - DC return conductor (+48 V) [long dash-dot line]
+ - Interconnected reinforcement and building steel [long dashed line]
+ - Intra-system cabling [short dashed line]
+ - Shielded inter-system cabling [line with a circle symbol]
+ - Bonding conductor [solid line]
+ - 400 V dc conductor (for +200 V and -200 V, indicated as potential) [dotted line]
+ - The diagram is labeled K.27(15)\_FB.1.
+
+**Figure B.1 – Mesh-BN installation inside a telecommunication building**
+
+The equipment racks shall be interconnected by low impedance leads or copper bars. Since the mesh-BN technique usually incorporates the DC return conductor into the CBN, the leads or bars can serve as the DC return. The leads or bars of each row have to be interconnected via the shortest route to minimize inductance. One or more DC return conductors may be used to interconnect the system to the centralized common power distribution cabinet or an intermediate power distribution panel. It is recommended that these leads be paired in close proximity with the corresponding negative DC power feed leads to reduce loop areas and enhance EMC. Small gauge DC power conductors should be twisted.
+
+DC/DC converters generally have one input conductor and one output conductor connected to the mesh-BN. There may be exceptions in specific equipment.
+
+An independent AC power supply network, derived from the DC supply by DC/AC converters, is best implemented as a TN-S type [IEC 60364-5-54].
+
+Unrestricted fastening of the system to the floor and walls provides, in general, sufficient bypassing of stray capacitance for acceptable EMC performance of the system.
+
+#### **B.1.3 Cabling**
+
+Regarding EMC, cables can act as antennas, and support common modes that can transport extraneous energy into otherwise well-designed equipment. This antenna and common-mode propagation phenomenon can be mitigated by proper routing and shielding.
+
+Routing of indoor cabling shall be in close proximity to conductive elements of the CBN and follow the shortest possible path. The shielding afforded by interconnected cable racks, trays, raceways, etc., shall be intentionally used. This shielding is effective only if it is continuous.
+
+#### **B.1.4 EMC performance**
+
+Equipment in an appropriately designed mesh-BN configuration, together with the use of DC power distribution with a return that is common to the mesh-BN (i.e., DC-C-MBN), is known to give acceptable EMC performance.
+
+The incorporation of DC power return conductors into the mesh-BN limits voltage drops caused by short circuit currents in the DC power distribution network.
+
+### **B.2 Mesh-IBN with a bonding mat configuration**
+
+A high level of shielding may be obtained by connecting all equipment frames within a system-block into a bonding-mat configuration. This configuration is isolated from the surrounding CBN. The result is a very effective type of mesh-IBN; an example is shown in Figure B.2.
+
+The technical goals of this installation method are:
+
+- a) prevention of CBN currents from flowing in the bonding-mat or any other part of the system-block;
+- b) achievement of satisfactory EMC performance by controlled interconnection of system-blocks;
+- c) provision of bonding and cabling facilities that allow for:
+  - systematic EMC planning;
+  - use of well-defined and reproducible EMC test methods.
+
+The DC power system operating at relatively high voltages (e.g., 400 V DC) shall be balanced about earth (positive and negative) by a resistive divider, whose centre point is connected to earth as shown in Figure B.2.
+
+![Figure B.2 – Mesh-IBN with bonding mat. This is a 3D perspective diagram showing the electrical bonding and grounding configuration for three new system blocks (1, 2, and 3) and existing equipment (system 4). System block 1 is on the floor, containing 400 V DC equipment and a power supply. It is interconnected by a bonding mat (Bonding mat 1) which is insulated from the floor's steel reinforcement. System block 2 and 3 are below the floor level. Single point connections (SPC1, SPC2, SPC3) are shown between the system blocks and the bonding mat or cable ducts. A low impedance cable duct (CBN element) is also shown. The diagram includes various line styles representing different types of connections: solid for equipotential bonding, dashed for steel reinforcement, dash-dot for unshielded cabling, and dashed with a central line for shielded cabling. Dots along the bonding mat indicate its SPC. A note indicates that connecting the cable screen to the frame is recommended. The diagram is labeled K.27(15)_FB.2.](7133ccf78043568ca62ecbcd43628a4a_img.jpg)
+
+Figure B.2 – Mesh-IBN with bonding mat. This is a 3D perspective diagram showing the electrical bonding and grounding configuration for three new system blocks (1, 2, and 3) and existing equipment (system 4). System block 1 is on the floor, containing 400 V DC equipment and a power supply. It is interconnected by a bonding mat (Bonding mat 1) which is insulated from the floor's steel reinforcement. System block 2 and 3 are below the floor level. Single point connections (SPC1, SPC2, SPC3) are shown between the system blocks and the bonding mat or cable ducts. A low impedance cable duct (CBN element) is also shown. The diagram includes various line styles representing different types of connections: solid for equipotential bonding, dashed for steel reinforcement, dash-dot for unshielded cabling, and dashed with a central line for shielded cabling. Dots along the bonding mat indicate its SPC. A note indicates that connecting the cable screen to the frame is recommended. The diagram is labeled K.27(15)\_FB.2.
+
+- SPC Single point connection
+- Equipotential bonding conductor
+- - - - Steel reinforcement
+- · - · Unshielded intra- or inter-system cabling
+- - 0 - - Shielded intra- or inter-system cabling
+- ..... 400 V dc conductor (for +200 V and -200 V, indicated as potential)
+- Dots along the edge at a bonding mat denote its SPC.  
+Inter-system cabling entering the system block must enter close to the SPC.
+
+NOTE 1 – System blocks 1, 2 and 3 are new installations conforming to the mesh-IBN method. They may be connected to existing installations (system 4) that use any method of bonding.
+
+NOTE 2 – The SPC is the only metallic interface between the mesh-IBN and the CBN. It must be directly connected to the reinforcement of the floor. All cables leading to the system enter here. All conductors that are bonded to the mesh-IBN must be connected to the SPC (e.g., cable screens, battery return).
+
+**Figure B.2 – Mesh-IBN with bonding mat**
+
+#### B.2.1 Equipment configuration
+
+The system block comprises equipment agreed upon by the operating agencies and manufacturer(s) to be interconnected to the mesh-IBN (Figure 2). (Note that this agreement facilitates assignment of responsibility to either the supplier or the operating agency.)
+
+Peripheral equipment denotes equipment location beyond the boundaries of the system block, but which relies functionally on a connection to the IBN.
+
+Equipment serving air conditioning, lighting, etc., is considered to be external to the system block and may be installed or operated as part of the CBN of the building.
+
+However, provision for the following is recommended:
+
+- protective earthing;
+- AC power distribution;
+- DC power distribution up to the SPC, with the DC power return conductor(s) incorporated into the CBN (DC-C-CBN).
+
+##### **B.2.1.1 Single point connection**
+
+It is recommended that the SPC be established in the vicinity of its system, serving as the only connection between IBN and CBN.
+
+##### **B.2.1.2 Cabling**
+
+All conductors and cables connecting to the system block shall pass near to the SPC (i.e., through the SPC window). Metalwork near the system block shall be bonded to the SPC to avoid electric shock or flash-over in the event of a lightning strike to the building. Installation of a distribution frame at the SPC is recommended since this facilitates connection of cable shields to the SPC. It is recommended that the shields of all cables passing the SPC be connected to the SPC.
+
+Alien cables crossing the area of the IBN must be spaced sufficiently apart from cables connecting to the SPC and the system block.
+
+##### **B.2.1.3 Equipment powered by external AC sources**
+
+Equipment with IEC class II certification (no PE connected) may be used without restriction within the system block area or at its periphery.
+
+Equipment with IEC class I certification (relying on PE protection methods) shall be powered via isolating transformers, if not connected to DC/AC converters or AC power sockets belonging to the system block.
+
+#### **B.2.2 EMC performance**
+
+Equipment in an appropriately designed mesh-IBN configuration, together with the use of the DC power distribution with a return that is common to the mesh-IBN (i.e., DC-C-IBN), is known to give acceptable EMC performance.
+
+## **B.3 Star or sparse mesh-IBN with isolation of DC power return**
+
+In this configuration, the framework of the switch is connected to form either a star or a mesh-IBN (see Figure 1). The cabinet framework and metallic panels are the major components of this IBN (there is no bonding mat). This type of IBN (whether star or mesh) will be denoted by "frame-IBN". The mesh topology is typically achieved by the cross-aisle interconnections afforded by cable trays. The result is a "sparse-mesh" IBN. The single point interconnection between a "frame-IBN" and the CBN is made at the SPC bus-bar located within the SPCW. The SPCW has a fixed dimension that allows the SPCB to be of sufficient size for connecting conductors, while limiting the voltage drop across the SPCB in the event of lightning surges or power system faults.
+
+An example of this configuration (in its star form) is shown in Figure B.3. The DC feed section leaving the power plant is isolated (i.e., of type DC-I-CBN). This feed splits into a DC-I-IBN feed serving the frame-IBN equipment (the system block), and a DC-C-CBN feed serving mesh-IBN equipment. For the branch feeding the mesh-IBN equipment, a connection between DC return and CBN is made at the SPCB. Beyond the SPCW, this branch is of type DC-C-CBN (i.e., it has multiple connections to the CBN). The DC feed to the frame-IBN equipment need not pass through the SPCW since, within the frame-IBN, it is isolated. However, it is advantageous if most of the DC feed cable is in close proximity to bonding conductors, because this will reduce surge voltages that appear across the isolation barriers of the DC/DC converters on which the DC feed terminates.
+
+To summarize, the main features of the system are:
+
+- insulation of the frame-IBN from the surrounding CBN;
+- connection of the frame-IBN to the CBN only at the SPCB;
+- isolation of the DC return within the frame-IBN and between the power plant and the SPCW.
+
+Systems of this type (both star and mesh configurations) have shown satisfactory EMC performance.
+
+Note that this example demonstrates how a bonding and earthing network combines, in one building, systems using IBNs and mesh-BNs. The example also shows how all systems may share one DC power plant.
+
+The DC power system operating at relatively high voltages (e.g., 400 V DC) shall be balanced about earth (positive and negative) by a resistive divider, whose centre point is connected to earth as shown in Figure B.3.
+
+#### **B.3.1 The DC power return configuration**
+
+In the DC power system, the frame-IBN branch and the power plant branch are isolated, resulting in no conductive coupling from the CBN in these branches. However, surges (e.g., lightning and short circuit fault currents) arising in the DC-C-CBN branch (that feeds mesh-BN equipment) can couple *indirectly* into the frame-IBN equipment via the common source impedance presented by the power plant and the DC-I-CBN section. This impedance is kept to a low value by running the –48 V conductors and DC return conductors in close proximity.
+
+The bonding conductor from the SPCB to the frame of the power plant is run in close proximity to all DC feed conductors in the DC-I-CBN section. This reduces DC feed common-mode surge voltages at the power plant and enables fault clearing in the event of a fault between –48 V and frame in the power plant.
+
+#### **B.3.2 System installation**
+
+Cable shields from outside the IBN that terminate within the IBN (i.e., on the system block) have their shields:
+
+- a) bonded to the frame-IBN and to no other point (such cables shall not extend more than one floor from the SPC); or
+- b) bonded to the frame-IBN, bonded to the SPCB, and, outside of the system block, bonded to the CBN.
+
+Sub-systems that are part of the system block should be located within one floor of the SPC of the main system. This avoids excessive voltage differences between the extremities of the IBN and nearby CBN.
+
+Peripheral equipment that is to use an IBN and that is located more than one floor from the SPC of the main system shall use a dedicated SPC that is within one floor. The equipment shall be powered through an isolation barrier, e.g., by using DC/DC or AC/DC converters.
+
+The isolation barrier inside any DC power equipment must have sufficient voltage withstand capability to meet local authority requirements. Installation and wiring of converters should comply with these isolation requirements.
+
+Framework of equipment, and metal structural components, in a CBN that is located within two metres of an IBN should be bonded to the SPCB for reasons of personnel safety.
+
+Other equipment that is in the telecommunication building, and that uses the mesh-BN configuration, is installed using the techniques of clause B.1, with or without an isolated DC return.
+
+#### B.3.3 Maintainability of isolated bonding networks
+
+IBNs need careful installation and ongoing surveillance to assure isolation. Also, the use of an isolated DC power return may require ongoing monitoring to check its isolation, especially if maintenance work is performed on different or mixed configurations by the same personnel. Violation of isolation during, or as a consequence of, maintenance work, may lead to failures in system operation or even to physical damage during lightning or power fault events.
+
+![Diagram of Star-IBN with isolation of DC power return across multiple floors (Floor N, Floor N+1, and a lower floor).](b235edb1dbe659e2782c9a0e47775ca4_img.jpg)
+
+The diagram illustrates a Star-IBN configuration with isolation of DC power return across multiple floors. It shows the following components and connections:
+
+- Floor N+1:** Support column of building, FGB (Floor ground bar), Mesh-BN equipment (may be more than one floor from SPCB), IBN (DC return conductor not shown), Insulation, Building steel (CBN).
+- Floor N:** 400 V DC equipment, 400 V DC power supply, Resistor for mid point connection, Mesh-BN equipment (DC return conductor not shown), SPCB (Single point connection bus-bar), SPCW (Single point connection window), Unshielded twisted pair to switch, Main distributing frame (mesh-BN equipment), IBN.
+- Lower floor (may be more than one floor from SPCB):** FGB, Shielded twisted pair to cable entrance facility, Closely coupled, Insulated DC return bus-bar, Frame of principal power plant.
+- Vertical Connections:** To earth electrode, Interconnected re-inforcement and building steel.
+
+**Legend:**
+
+- Bonding conductor
+- - - - Interconnected re-inforcement and building steel
+- .-.-.- dc return conductor (+48 V) (-48 V conductor, not shown, closely parallels this)
+- ..... 400 V dc conductor (for +200 V and -200 V, indicated as potential)
+- .-.-.- Intra- or inter-system cabling
+
+**Other labels:**
+
+- FGB Floor ground bar (part of CBN)
+- SPCB Single point connection bus-bar
+- SPCW Single point connection window
+
+K.27(15)\_FB.3
+
+Diagram of Star-IBN with isolation of DC power return across multiple floors (Floor N, Floor N+1, and a lower floor).
+
+**Figure B.3 – Star-IBN with isolation of DC power return**
+
+# Bibliography
+
+- [b-Keiser] Keiser, B.E. (1987), *Principles of Electromagnetic Compatibility*, 3rd edition, Norwood, MA, Artech House.
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                             |
+|-----------------|---------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                           |
+| Series D        | General tariff principles                                                                   |
+| Series E        | Overall network operation, telephone service, service operation and human factors           |
+| Series F        | Non-telephone telecommunication services                                                    |
+| Series G        | Transmission systems and media, digital systems and networks                                |
+| Series H        | Audiovisual and multimedia systems                                                          |
+| Series I        | Integrated services digital network                                                         |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals |
+| <b>Series K</b> | <b>Protection against interference</b>                                                      |
+| Series L        | Construction, installation and protection of cables and other elements of outside plant     |
+| Series M        | Telecommunication management, including TMN and network maintenance                         |
+| Series N        | Maintenance: international sound programme and television transmission circuits             |
+| Series O        | Specifications of measuring equipment                                                       |
+| Series P        | Terminals and subjective and objective assessment methods                                   |
+| Series Q        | Switching and signalling                                                                    |
+| Series R        | Telegraph transmission                                                                      |
+| Series S        | Telegraph services terminal equipment                                                       |
+| Series T        | Terminals for telematic services                                                            |
+| Series U        | Telegraph switching                                                                         |
+| Series V        | Data communication over the telephone network                                               |
+| Series X        | Data networks, open system communications and security                                      |
+| Series Y        | Global information infrastructure, Internet protocol aspects and next-generation networks   |
+| Series Z        | Languages and general software aspects for telecommunication systems                        |

marked/K/T-REC-K.34-202012-I_PDF-E/raw.md

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+
+
+International Telecommunication Union
+
+**ITU-T**
+
+TELECOMMUNICATION  
+STANDARDIZATION SECTOR  
+OF ITU
+
+**K.34**
+
+(12/2020)
+
+SERIES K: PROTECTION AGAINST INTERFERENCE
+
+# --- **Classification of electromagnetic environmental conditions for telecommunication equipment – Basic EMC Recommendation**
+
+Recommendation ITU-T K.34
+
+![ITU logo](6ed175c791b5e156d9c98a8dbcc3318c_img.jpg)
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with a white grid pattern, overlaid by a stylized 'ITU' text in blue.
+
+ITU logo
+
+
+
+## Recommendation ITU-T K.34
+
+## Classification of electromagnetic environmental conditions for telecommunication equipment – Basic EMC Recommendation
+
+## Summary
+
+Recommendation ITU-T K.34 defines electromagnetic environmental classes for telecommunication equipment covering all relevant electromagnetic environmental parameters. This Recommendation applies to telecommunication equipment installed in telecommunication centres, outdoor locations and customer premises. This is a basic EMC Recommendation for telecommunications.
+
+## History
+
+| Edition | Recommendation | Approval   | Study Group | Unique ID*                                                                |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0     | ITU-T K.34     | 1996-05-08 | 5           | <a href="http://handle.itu.int/11.1002/1000/3345">11.1002/1000/3345</a>   |
+| 2.0     | ITU-T K.34     | 2000-02-25 | 5           | <a href="http://handle.itu.int/11.1002/1000/4906">11.1002/1000/4906</a>   |
+| 3.0     | ITU-T K.34     | 2003-07-29 | 5           | <a href="http://handle.itu.int/11.1002/1000/6494">11.1002/1000/6494</a>   |
+| 4.0     | ITU-T K.34     | 2020-12-14 | 5           | <a href="http://handle.itu.int/11.1002/1000/14566">11.1002/1000/14566</a> |
+
+## Keywords
+
+Customer premises, EMC, environmental conditions, outdoor locations, telecommunication, telecommunication centres.
+
+---
+
+\* To access the Recommendation, type the URL <http://handle.itu.int/> in the address field of your web browser, followed by the Recommendation's unique ID. For example, <http://handle.itu.int/11.1002/1000/11830-en>.
+
+## FOREWORD
+
+The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.
+
+The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.
+
+The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.
+
+In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.
+
+## NOTE
+
+In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
+
+Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.
+
+## INTELLECTUAL PROPERTY RIGHTS
+
+ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.
+
+As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at <http://www.itu.int/ITU-T/ipr/>.
+
+© ITU 2021
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## Table of Contents
+
+|                                                                               | Page |
+|-------------------------------------------------------------------------------|------|
+| 1 Scope.....                                                                  | 1    |
+| 2 References.....                                                             | 1    |
+| 3 Definitions .....                                                           | 1    |
+| 3.1 Terms defined elsewhere.....                                              | 1    |
+| 3.2 Terms defined in this Recommendation.....                                 | 2    |
+| 4 Abbreviations and acronyms .....                                            | 3    |
+| 5 Conventions .....                                                           | 4    |
+| 6 Electromagnetic environmental parameters .....                              | 4    |
+| 6.1 Electrostatic voltage .....                                               | 4    |
+| 6.2 Electrical fast transient/burst (EFT/B).....                              | 5    |
+| 6.3 Conducted radio-frequency voltages.....                                   | 5    |
+| 6.4 Radio-frequency fields .....                                              | 5    |
+| 6.5 d.c. voltages.....                                                        | 5    |
+| 6.6 16 2/3 Hz voltages.....                                                   | 5    |
+| 6.7 50 Hz/60 Hz voltages .....                                                | 6    |
+| 6.8 Audio frequency voltages.....                                             | 6    |
+| 6.9 Surges .....                                                              | 6    |
+| 6.10 Voltage variation .....                                                  | 6    |
+| 6.11 Voltage fluctuation .....                                                | 6    |
+| 6.12 Voltage interruption.....                                                | 6    |
+| 6.13 Audio frequency magnetic fields.....                                     | 6    |
+| 6.14 Lightning electromagnetic pulse .....                                    | 6    |
+| 6.15 Low frequency repetitive impulses .....                                  | 6    |
+| 7 Characteristics of environments .....                                       | 7    |
+| 7.1 Telecommunication centres (common features for class 1 and class 2) ..... | 7    |
+| 7.2 Class 3 – Outdoor locations.....                                          | 8    |
+| 7.3 Class 4 – Customer premises.....                                          | 8    |
+| 8 Characteristic severities of the environmental parameters .....             | 9    |
+| Bibliography.....                                                             | 17   |
+
+## Introduction
+
+This Recommendation is a compilation of data concerning electromagnetic environmental conditions.
+
+The phenomena covered by this Recommendation are:
+
+- electrostatic discharges (ESD);
+- electrical fast transients/bursts (EFT/B);
+- conducted radio-frequency disturbances;
+- radiated radio-frequency disturbances;
+- d.c. voltages;
+- 16 2/3 Hz voltages;
+- 50 Hz/60 Hz voltages;
+- audio frequency voltages;
+- surges;
+- voltage variations;
+- voltage fluctuations;
+- voltage interruptions;
+- audio frequency magnetic fields;
+- lightning electromagnetic pulses;
+- low frequency repetitive impulses.
+
+The data included in this Recommendation are based on calculation, analysis and experience, supported by comprehensive environmental surveys where such surveys exist.
+
+Certain assumptions on the installation practice are necessary when characterizing the electromagnetic environment. If these assumptions are not satisfied in a particular case, the environmental characteristic may not apply.
+
+Each environment is characterized in two ways:
+
+- by a short verbal description;
+- by a quantitative statement of the characteristic severities of the phenomena.
+
+The appropriate EMC requirements for telecommunication equipment should be based on the severity of the electromagnetic environment. The EMC requirements ensure that the equipment has a sufficient intrinsic immunity to enable it to operate as intended in its environment. It is emphasized that the characteristic severity of a phenomenon or parameter does not automatically indicate the test level used in immunity testing. Other considerations, e.g., priority of service of the equipment in question and technical and economic circumstances should also be taken into account when selecting the test level of those given in basic standards on test methods.
+
+This Recommendation is a basic EMC Recommendation for telecommunications.
+
+## Recommendation ITU-T K.34
+
+# Classification of electromagnetic environmental conditions for telecommunication equipment – Basic EMC Recommendation
+
+# 1 Scope
+
+This Recommendation defines classification of the electromagnetic environmental conditions encountered where telecommunication equipment is installed.
+
+This Recommendation applies to telecommunication equipment installed in telecommunication centres, outdoor locations and customer premises. It does not make references to equipment dependent details.
+
+Telecommunication equipment intended for installations in industrial environment, power station and sub-station environments and in railways environment are not covered by this Recommendation because they are already covered by specific EMC standards, e.g., [b-IEC 61000-6-5], [b-IEC 62236-4] and [b-IEC 61000-6-2].
+
+# 2 References
+
+The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation.
+
+- [ITU-T K.18] Recommendation ITU-T K.18 (1988), *Calculation of voltage induced into telecommunication lines from radio station broadcasts and methods of reducing interference*.
+- [ITU-T K.23] Recommendation ITU-T K.23 (1988), *Types of induced noise and description of noise voltage parameters for ISDN basic user networks*.
+- [ITU-T K.27] Recommendation ITU-T K.27 (2015), *Bonding configurations and earthing inside a telecommunication building*.
+- [ITU-T K.68] Recommendation ITU-T K.68 (2006), *Operator responsibilities in the management of electromagnetic interference by power systems on telecommunication systems*.
+
+# 3 Definitions
+
+The following definitions apply only in the context of this Recommendation, except where the reference to the International Electrotechnical Vocabulary [IEC 60050-161] is given adjacent to the subclause title.
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 burst** [b-IEC 60050-161], (161-02-07): A sequence of a limited number of distinct pulses or an oscillation of limited duration.
+
+**3.1.2 commercial, public and light-industrial location** [b-IEC 61000-2-5]: Location which exists as areas of the city centre, offices, public transport systems (road/train/underground), and
+
+modern business centres containing a concentration of office automation equipment (PCs, fax machines, photocopiers, telephones, etc.), and characterized by the fact that equipment is directly connected to a low-voltage public mains network or connected to a dedicated DC source which is intended to interface between the equipment and the low-voltage mains network.
+
+Examples of commercial, public or light-industrial locations are:
+
+- retail outlets, for example shops, supermarkets;
+- business premises, for example offices, banks, hotels, data centres;
+- areas of public entertainment, for example cinemas, public bars, dance halls;
+- places of worship, for example temples, churches, mosques, synagogues;
+- petrol stations, car parks, amusement and sports centres;
+- general public locations, for example park, amusement facilities, public offices;
+- hospitals, educational institutions, for example schools, universities, colleges;
+- public traffic area, railway stations, and public areas of an airport;
+- light-industrial locations, for example workshops, laboratories, service centres.
+
+**3.1.3 continuous disturbance** [b-IEC 60050-161], (161-02-11): Electromagnetic disturbance the effect of which on a particular device or equipment cannot be resolved into a succession of distinct effects.
+
+**3.1.4 immunity (to a disturbance)** [b-IEC 60050-161], (161-01-20): The ability of a device, equipment or system to perform without degradation in the presence of an electromagnetic disturbance.
+
+**3.1.5 pulse** [b-IEC 60050-161], (161-02-02): An abrupt variation of short duration of a physical quantity followed by a rapid return to the initial value.
+
+**3.1.6 residential location** [b-IEC 61000-2-5]: Location which exists as an area of land designated for the construction of domestic dwellings, and is characterized by the fact that equipment is directly connected to a low-voltage public mains network or connected to a dedicated DC source which is intended to interface between the equipment and the low-voltage mains network.
+
+Examples of residential locations are houses, apartments, and farm buildings used for living.
+
+**3.1.7 rise time (of a pulse)** [b-IEC 60050-161], (161-02-05): The interval of time between the instants at which the instantaneous value of a pulse first reaches a specified lower value and then a specified upper value.
+
+NOTE – Unless otherwise specified, the lower and upper values are fixed at 10% and 90% of the pulse magnitude.
+
+**3.1.8 transient (adjective or noun)** [b-IEC 60050-161], (161-02-01): Pertaining to or designating a phenomenon or a quantity which varies between two consecutive steady states during a time interval short compared with the time scale of interest.
+
+### **3.2 Terms defined in this Recommendation**
+
+This Recommendation defines the following terms:
+
+**3.2.1 audio frequencies (AF)**: The frequency range from 50 Hz to 20 kHz.
+
+**3.2.2 characteristic severity**: The characteristic severity for a certain detail parameter in an environmental class states a severity which has only a low probability, generally less than 1%, of being exceeded. The term relates to duration, rate of occurrence or location. It applies to requirements on the environment and to immunity requirements. In [b-IEC/TR 61000-2-5], the term "disturbance degree" is used as the quantitative characterization of the environmental parameters.
+
+**3.2.3 customer premises:** Physical location in the residential, commercial, public and light-industrial locations where telecommunication equipment is installed or used. In this environment the electromagnetic disturbance protection and earthing and bonding conditions might be uncontrolled. The electromagnetic environmental conditions for customer premises are described in this Recommendation.
+
+**3.2.4 environment; environmental conditions:** The electromagnetic conditions external to the equipment, to which it is subjected for a certain time. The environmental conditions comprise a combination of single environmental parameters and their severities.
+
+**3.2.5 environmental class:** A representation of the environment on locations with similar properties. They are specified and standardized to provide an operational frame of reference for:
+
+- requirements on the environment;
+- immunity requirements.
+
+The class is described using an envelope of environmental conditions expressed in terms of a number of environmental parameters and their characteristic severities or other characteristics. The environmental parameters specified for the class are limited to those which may affect equipment performance.
+
+**3.2.6 environmental parameters:** The environmental parameters present one or more properties of the electromagnetic environment.
+
+**3.2.7 radio frequencies (RF):** The frequency range above 9 kHz.
+
+**3.2.8 shielding effectiveness:** For a given external source, the ratio (usually expressed in dB) of electric or magnetic field strength at a point before and after the placement of the shield in question.
+
+**3.2.9 telecommunication centre:** Physical location hosting telecommunication equipment which is managed and operated exclusively by the telecom operator and other business entities. This definition includes the data centres. This environment is dedicated to telecommunication network equipment and is better controlled in terms of electromagnetic disturbance protection and earthing and bonding. The electromagnetic environmental conditions for telecommunication centres are described in this Recommendation.
+
+## 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+|       |                                                |
+|-------|------------------------------------------------|
+| a.c.  | alternating current                            |
+| AF    | Audio Frequency                                |
+| d.c.  | direct current                                 |
+| EFT/B | Electrical Fast Transient/Burst                |
+| EMC   | Electromagnetic Compatibility                  |
+| ESD   | Electrostatic Discharge                        |
+| HV    | High Voltage                                   |
+| IEC   | International Electrotechnical Commission      |
+| ISM   | Industrial, Scientific and Medical (equipment) |
+| ITE   | Information Technology Equipment               |
+| RF    | Radio Frequency                                |
+
+## 5 Conventions
+
+None.
+
+# 6 Electromagnetic environmental parameters
+
+### 6.1 Electrostatic voltage
+
+Persons walking on the floor or moving otherwise or handling electrostatically charged objects are charged to an electrostatic voltage resulting as an electrostatic discharge (ESD) which may cause malfunction or even damage of equipment.
+
+The discharge may normally occur when the equipment is operated manually, or during maintenance or repair. The discharge may take place from the fingertips or via metallic tools to all accessible parts of the equipment.
+
+The risk is particularly high in locations with synthetic flooring materials or when the relative humidity is low, e.g., due to low outdoor temperature. The severity of the discharge depends on the clothing materials and the insulating properties of the soles of the shoes worn by the operator. The risk is almost eliminated if the relative humidity is above 50%.
+
+Figures 1 and 2 give guidance on the levels that may be observed dependent on the materials used and the environment in which the system is operating. This information has been used in the classification.
+
+![Figure 1: A line graph showing the maximum values of electrostatic voltages (kV) on the y-axis (0 to 16) versus relative humidity (%) on the x-axis (0 to 100). Three lines represent different materials: Synthetic, Wool, and Antistatic. The Synthetic line starts at 15 kV at 5% RH and decreases to about 1.5 kV at 100% RH. The Wool line starts at 5 kV at 5% RH and decreases to about 0.5 kV at 80% RH. The Antistatic line starts at 4 kV at 5% RH and decreases to about 0.5 kV at 70% RH. Vertical dashed lines are drawn at 5% RH and 35% RH.](df476ed6ad0bb890c67aa63e7647d071_img.jpg)
+
+| Relative humidity (%) | Synthetic (kV) | Wool (kV) | Antistatic (kV) |
+|-----------------------|----------------|-----------|-----------------|
+| 5                     | 15             | 5         | 4               |
+| 10                    | 14             | 4.5       | 3.5             |
+| 20                    | 12.5           | 3.5       | 2.5             |
+| 30                    | 11             | 2.5       | 1.5             |
+| 35                    | 10             | 2         | 1               |
+| 40                    | 9              | 1.5       | 0.5             |
+| 50                    | 7.5            | 1         | 0.5             |
+| 60                    | 6              | 0.5       | 0.5             |
+| 70                    | 4.5            | 0.5       | 0.5             |
+| 80                    | 3              | 0.5       | 0.5             |
+| 90                    | 1.5            | 0.5       | 0.5             |
+| 100                   | 1.5            | 0.5       | 0.5             |
+
+Figure 1: A line graph showing the maximum values of electrostatic voltages (kV) on the y-axis (0 to 16) versus relative humidity (%) on the x-axis (0 to 100). Three lines represent different materials: Synthetic, Wool, and Antistatic. The Synthetic line starts at 15 kV at 5% RH and decreases to about 1.5 kV at 100% RH. The Wool line starts at 5 kV at 5% RH and decreases to about 0.5 kV at 80% RH. The Antistatic line starts at 4 kV at 5% RH and decreases to about 0.5 kV at 70% RH. Vertical dashed lines are drawn at 5% RH and 35% RH.
+
+**Figure 1 – Maximum values of electrostatic voltages to which operators may be charged while in contact with the materials in the absence of any electrostatic protection measures**
+
+![Figure 2: A line graph showing the maximum value of electrostatic voltage (kV) versus relative humidity (%) for operators in a telecommunication central office. The graph compares 'Run' and 'Walk' activities for two types of shoes: 'Ordinary shoes' (open circles and squares) and 'Antistatic shoes' (filled circles and squares) on a 'Linoleum floor'. The voltage decreases as relative humidity increases. Ordinary shoes show higher voltages than antistatic shoes. Running generates higher voltages than walking.](d48475a25698b1c0592e4cfe07138f2a_img.jpg)
+
+| Relative humidity (%) | Ordinary shoes (Run) [kV] | Ordinary shoes (Walk) [kV] | Antistatic shoes (Run) [kV] | Antistatic shoes (Walk) [kV] |
+|-----------------------|---------------------------|----------------------------|-----------------------------|------------------------------|
+| 30                    | 4.8                       | 2.8                        | 1.8                         | 0.8                          |
+| 50                    | 5.2                       | 1.8                        | 1.2                         | 0.5                          |
+| 70                    | 3.8                       | 1.8                        | 0.8                         | 0.2                          |
+
+Figure 2: A line graph showing the maximum value of electrostatic voltage (kV) versus relative humidity (%) for operators in a telecommunication central office. The graph compares 'Run' and 'Walk' activities for two types of shoes: 'Ordinary shoes' (open circles and squares) and 'Antistatic shoes' (filled circles and squares) on a 'Linoleum floor'. The voltage decreases as relative humidity increases. Ordinary shoes show higher voltages than antistatic shoes. Running generates higher voltages than walking.
+
+**Figure 2 – Maximum value of electrostatic voltage to which operators may be charged in telecommunication central office**
+
+### 6.2 Electrical fast transient/burst (EFT/B)
+
+Breaking of currents in a.c. and d.c. power supplies results in intermittent arcing across the contact. The phenomenon is repetitious and continues until the energy stored in the circuit has been dissipated. A sequence of voltage spikes is generated on the leads. These transients propagate on the line in question and couple to adjacent signal and power lines.
+
+### 6.3 Conducted radio-frequency voltages
+
+Different types of radio transmitters and switch mode power supplies induce common and differential mode voltages to power and signal lines. [ITU-T K.18] and [ITU-T K.23] contain more information on this parameter.
+
+### 6.4 Radio-frequency fields
+
+Telecommunication equipment is directly exposed to fields of broadcasting, amateur and mobile radio transmitters. Particularly the modern cellular mobile and personal communication service systems operating at high frequencies may couple effectively to printed circuit board level and not only to long lines.
+
+### 6.5 d.c. voltages
+
+d.c. voltages apply to signal lines entering the building. Telecommunication equipment may be exposed to high d.c. voltages because of the use of cable fault location equipment.
+
+d.c. power plants for traction systems causing d.c. potential differences on telecommunication lines are not taken into account. Also induced voltages from geomagnetic activity are not included.
+
+### 6.6 16 2/3 Hz voltages
+
+Telecommunication equipment connected to signal lines entering the building may be exposed to common mode 16 2/3 Hz voltages induced to signal lines entering the building in countries where electrical traction systems use this frequency.
+
+### **6.7 50 Hz/60 Hz voltages**
+
+Telecommunication equipment connected to signal lines entering the building may be exposed to common mode mains frequency voltages caused by earth faults of high voltage power lines via induction or earth potential rise. 50 Hz/60 Hz electrical traction systems may as well cause exposure to common mode induced voltages. Direct contact to the low voltage mains may cause both common mode and differential mode exposure.
+
+### **6.8 Audio frequency voltages**
+
+Telecommunication equipment connected to signal lines entering the building may be exposed to 50 Hz-20 kHz voltages induced to the lines by normal use of neighbouring high voltage power lines and electric traction lines. Non-linear loads on mains may cause audio frequency voltage exposure also via signal lines remaining within the building. Ripple voltages from rectifiers are superimposed on the voltage in d.c. power supplies and contribute to the parameter.
+
+### **6.9 Surges**
+
+Telecommunication equipment connected to signal lines entering the building may be exposed to surges coupled into the lines from lightning discharges. Voltage and current surges caused by lightning may enter the equipment also via the a.c. mains. Lightning discharges hitting telecommunication stations, or closely located antenna towers, may expose equipment connected to signal lines remaining within the building via induction or earth potential rise.
+
+### **6.10 Voltage variation**
+
+The a.c. or d.c. power supply voltage may vary within certain limits due to varying loads and adjustments of the voltage made to cope with the demand for energy in busy hours. Only the long term variations of the average voltage are included.
+
+### **6.11 Voltage fluctuation**
+
+Abrupt changes of loading may cause short term voltage drops and over-voltages of the a.c. or d.c. power supply voltage.
+
+### **6.12 Voltage interruption**
+
+Faults in power supply systems may cause intermittent conditions of zero instantaneous voltage of short durations.
+
+### **6.13 Audio frequency magnetic fields**
+
+Telecommunication equipment may be exposed to magnetic fields in the frequency band 50 Hz-20 kHz caused by currents at mains frequency and their harmonics in electrical power installations: the distribution network, transformers, motors, power drive and uninterruptible power systems. Fields from audio-frequency inductive wire loops also contribute to these magnetic fields.
+
+### **6.14 Lightning electromagnetic pulse**
+
+Telecommunication equipment in the vicinity of a lightning flash may be exposed to magnetic field pulses generated by lightning discharges.
+
+### **6.15 Low frequency repetitive impulses**
+
+Telecommunication equipment connected to signal lines entering a building may be exposed to common mode voltages coupled onto lines from long electric fences. The induced disturbance can be characterized in terms of a repetitive impulse (one per second) with a well-damped oscillatory nature. Shorter fences which are not installed properly may also cause this type of interference.
+
+# 7 Characteristics of environments
+
+### 7.1 Telecommunication centres (common features for class 1 and class 2)
+
+The internal electrical power distribution can be up to 400 V d.c. (this includes the 48 V d.c. nominal) and a 230 V/400 V, 127 V/220 V or 100 V a.c. nominal 50 Hz or 60 Hz. It is assumed that switching of loads on the d.c. supply seldom occurs and, therefore, has not been taken into account. Battery back-up is available on d.c. power distributions.
+
+It is assumed that there is no separation between d.c. power cables and signal cables, while internal a.c. power cables are kept separate at some distance to d.c. power cables and signal cables in order to reduce mutual coupling. Normal practice is to use grounded, metallic cable supports. [ITU-T K.68] provides guidance to reduce coupling between telecommunication systems/lines and power systems/lines.
+
+Cables from telecommunication centres to customer's premises are assumed to be unshielded.
+
+A dedicated earthing and bonding network is implemented according to [ITU-T K.27]. Also, the a.c. power distribution inside the building is in accordance with the requirements of this reference.
+
+Some ESD preventive measures are either incorporated in the building installation (e.g., charge dissipating floors or control of the relative humidity) or through guidelines for handling and operation of the equipment (e.g., use of wrist-straps, charge dissipating shoes).
+
+Some distance to high power broadcast transmitters is assumed. In cases where radiocommunication transmitters are present at the premises, it is assumed that special precautions are taken in order to prevent exposure of the emitted field. Use of mobile radio equipment is assumed in telecommunication centres. The telecommunication operator cannot control the external radio-frequency environment.
+
+#### 7.1.1 Class 1 – Major telecommunication centres
+
+This environmental class applies to major telecommunication centres in dedicated, separate buildings or parts of buildings which are controlled by the network operator. These would typically be located in urban areas.
+
+The telecommunication centre has its own electricity power transformed from the public distribution network. The a.c. power distribution inside the building is of the type TN-S, TT or IT.
+
+External signal lines may be of any type, size or length, normally entering via underground routes. Risk of coupling to high voltage electricity lines or electric traction lines exists.
+
+The shielding effectiveness from the building structure may give a frequency-dependent attenuation of about 10 dB provided that the structural reinforcement elements of the building are adequately bonded together to form an integral mesh.
+
+#### 7.1.2 Class 2 – Minor telecommunication centres
+
+This environmental class applies to minor telecommunication centres in dedicated, separate buildings or parts of buildings which are controlled by the network operator. These would typically be located in rural areas serving the local community and may often be unattended.
+
+The telecommunication centre may draw its electrical power from the public distribution network either via a dedicated transformer or a transformer shared with the local community. The a.c. power distribution inside the building may be of the type TN-S, TN-C, TT or IT.
+
+External signal lines may be overhead cables of considerable length. There is a high risk of coupling to high voltage electricity lines or electric traction lines.
+
+No shielding effectiveness from the building structure can be assumed.
+
+### 7.2 Class 3 – Outdoor locations
+
+This environmental class applies to an unattended telecommunications site such as street cabinets, telephone boxes, repeaters and amplifiers on trunk cables, concentrators and cable distribution boxes and to equipment installed on poles or towers or on roofs or external sides of buildings.
+
+This environmental class may apply also to equipment buried below ground level. Repeaters of submarine cables are not covered by this class.
+
+External signal lines may be of any type, size or length. There is a high risk of coupling to high voltage electricity lines or electric traction lines. Remote power supplies on signal lines are considered as being intrinsic to the systems and are not considered as being environmental parameters.
+
+Remote repeaters in rural areas are equipped with overvoltage protection devices. A local ground electrode may not be present in all cases. Other outdoor locations may not be protected, and an external lightning protection system is not assumed.
+
+The distance to electricity distribution transformers may be small and the mains-related magnetic field exposure may be high.
+
+The outdoor locations are considered as being low risk areas in terms of electrostatic charges.
+
+Some distance to high power broadcasting transmitters is assumed. However, amateur transmitters may be closer, and mobile and portable radio transmitters may come very close.
+
+The installation is enclosed in some housing or cabinet for weather protection purposes. The enclosure is not assumed to shield against electromagnetic fields.
+
+### 7.3 Class 4 – Customer premises
+
+This class encompasses the residential, commercial and light industrial environments. An attempt has been made to fit the "disturbance degrees" specified by the [IEC 61000-2-5] onto the tables of clause 8 where the electromagnetic environmental classes are quantitatively specified. The highest disturbance degree is given in the table instead the lower values, if any, are given in Notes below the tables.
+
+#### 7.3.1 Attributes of customer premises
+
+#### Media
+
+##### Radiated
+
+- No amateur radio closer than 100 m.
+- No CB radio closer than 20 m.
+- No broadcast transmitter closer than 1 km.
+- No cellular communication systems with remote base station closer than 200 m (e.g., GSM, LTE etc.).
+- No aviation radar closer than 5 km.
+- High concentration of ITE.
+- Possible proximity to low power ISM.
+- Possible presence of medical therapy equipment.
+- Possible presence of audio/hearing aid systems.
+
+###### a.c. power
+
+- Relatively high network impedance.
+- Cables or overhead lines.
+- High harmonic levels.
+
+- Roof-top mounted equipment.
+
+###### **d.c. power**
+
+- Not applicable (no presence of extended d.c. power cables).
+
+#### **Signal/control**
+
+- Overhead telecom cables or lines.
+- Cables or short overhead spans.
+- Close coupling between signal systems and switched power systems.
+- Significant lightning exposure.
+- Control lines are usually short, less than 10 m.
+
+#### **Reference**
+
+- Abundant metallic structures which may or may not be bonded, earthed or grounded.
+- Frequent interfaces of power and telecom (including local) systems.
+- Local ground can be absent, or present high impedance.
+- Multiple local grounds might not be coordinated.
+
+#### **Additional notes**
+
+- Interfaces with customer systems.
+- HV lines may be routed over buildings.
+
+# **8 Characteristic severities of the environmental parameters**
+
+In Tables 1 to 5, the characteristic severities and other characteristics of the relevant environmental parameters are stated for each environmental class for telecommunication equipment.
+
+It is often not feasible to model the disturbances/parameters in every detail. For instance, the temporal evolution of transients is much too complex to be described realistically. In such cases, simplified models are used which select the characteristic details as appropriate to the standardized test pulses. This approach presumes that the test pulses do emphasize the crucial features.
+
+In the case of continuous disturbances, the postulated frequency dependence and modulation mode are gross simplifications of reality. A frequency analysis will show that the disturbances are confined within narrow frequency bands separated by "silent" intervals. This complicated (and time-dependent) pattern is replaced by a smooth frequency variation using few levels of amplitude.
+
+The environmental parameters are arranged in tables according to the coupling path. Five coupling paths are included:
+
+- 1) **Signal lines entering the building**, which include all telecommunications lines of the extended networks where metallic conductors are used.
+- 2) **Signal lines remaining within the building**, which include all signal lines in the local installation using metallic conductors. They are of relatively short lengths, and are confined to the local premises.
+- 3) **a.c. power mains** is the low voltage distribution network.
+- 4) **d.c. power distribution** is the local power distribution system. This does not include d.c. supplies integrated in the equipment.
+- 5) **Enclosure**, which includes the coupling of electromagnetic fields to the internal wiring of the equipment, and the discharge of static electricity.
+
+**Table 1 – Signal lines entering the building**
+
+| Coupling path                      | Environmental parameter                                      |                                                                          | Class 1 major telecom centres          | Class 2 minor telecom centres                                                                                       | Class 3 outdoor locations              | Class 4 customer premises      |
+|------------------------------------|--------------------------------------------------------------|--------------------------------------------------------------------------|----------------------------------------|---------------------------------------------------------------------------------------------------------------------|----------------------------------------|--------------------------------|
+| Signal lines entering the building | DC common mode voltage (Note 1)                              | Ampl. V<br>Impedance M $\Omega$                                          | 500<br>> 1                             |                                                                                                                     |                                        |                                |
+|                                    | 16 2/3 Hz common mode voltage (Note 2)                       | Ampl. V (rms)<br>Impedance $\Omega$                                      | 20<br>100                              | 50<br>100                                                                                                           |                                        |                                |
+|                                    | 50/60 Hz differential mode voltage (Note 3)                  | Ampl. V (rms)<br>Impedance $\Omega$<br>Duration min                      | 230/100<br>10 to 600<br>about 10       |                                                                                                                     |                                        |                                |
+|                                    | 50/60 Hz common mode voltage                                 | Ampl. V (rms)<br>Impedance $\Omega$<br>Duration s                        | (Note 3)                               | 2000; 1500; 1000; 650; 430<br>100 to 600<br>$\leq 0.1$ ; 0.1 to 0.2; 0.2 to 0.35; 0.35 to 0.5; 0.5 to 1<br>(Note 5) |                                        |                                |
+|                                    | Audio freq. common mode voltage                              | Frequency kHz<br>Ampl. V (rms)<br>Impedance $\Omega$                     | 0.05-1-20<br>20-0.5-0.5<br>100         | 0.05-1-20<br>30-0.75-0.75<br>100                                                                                    | 0.05-1-20<br>30-0.75-0.75<br>300       |                                |
+|                                    | Low freq. repetitive impulses                                | Frequency kHz<br>Impulses/second<br>Ampl. V (peak)                       | 2 (Note 6)<br>1<br>75                  |                                                                                                                     |                                        |                                |
+|                                    | Amplitude modulated radio freq. common mode voltage (Note 4) | Freq. MHz<br>Ampl. V (rms)                                               | 0.009-10<br>1                          | 0.009-10<br>3                                                                                                       |                                        | 0.009-0.15<br>3                |
+|                                    |                                                              | Freq. MHz<br>Ampl. V (rms)                                               | 10-100<br>1-0.1<br>(Note 7)            | 10-100<br>3-0.3<br>(Note 7)                                                                                         |                                        |                                |
+|                                    |                                                              | Freq. MHz<br>Ampl. V (rms)                                               |                                        |                                                                                                                     |                                        | 0.15-10<br>10                  |
+|                                    |                                                              | Freq. MHz<br>Ampl. V (rms)                                               |                                        |                                                                                                                     |                                        | 10-30<br>10-3.3<br>(Note 7)    |
+|                                    |                                                              | Freq. MHz<br>Ampl. V (rms)                                               |                                        |                                                                                                                     |                                        | 30-150<br>3.3-0.66<br>(Note 7) |
+|                                    | Common mode EFT/Bursts                                       | Ampl. V (peak)<br>Events/week<br>Rise time $\mu$ s<br>Impedance $\Omega$ | 250<br>several<br>1 to 100<br>40 to 80 |                                                                                                                     | 500<br>several<br>1 to 100<br>40 to 80 | 1000<br>several<br>5<br>50     |
+
+**Table 1 – Signal lines entering the building**
+
+| Coupling path                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   | Environmental parameter |                                                                                                          | Class 1 major telecom centres                            | Class 2 minor telecom centres                                       | Class 3 outdoor locations                                        | Class 4 customer premises                                           |
+|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------|----------------------------------------------------------------------------------------------------------|----------------------------------------------------------|---------------------------------------------------------------------|------------------------------------------------------------------|---------------------------------------------------------------------|
+|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 | Common mode surge       | Ampl. V (peak)<br>Rise time $\mu\text{s}$<br>Duration $\mu\text{s}$<br>Events/year<br>Impedance $\Omega$ | 300; 1000<br>1 to 1000<br>$< 3000$<br>6; 0.5<br>20 to 40 | 300; 1000; 3000<br>1 to 1000<br>$< 3000$<br>6; 0.5; 0.2<br>20 to 40 | 300; 1000; 3000<br>1 to 1000<br>$< 3000$<br>30; 3; 1<br>20 to 40 | 500; 1000<br>10; 1<br>1000; 50<br>Multiple<br>20 to 300;<br>1 to 10 |
+| NOTE 1 – 1 M $\Omega$ source impedance included in order to take into account, e.g., cable fault location equipment.<br>NOTE 2 – Only applicable in countries where 16 2/3 Hz electrical traction systems are in use.<br>NOTE 3 – For Major Telecom Centres (Class 1), 50 Hz/60 Hz common mode voltage due to earth faults in nearby high voltage electricity systems is not taken into account. The probability of this phenomenon occurring is extremely low.<br>NOTE 4 – All values given for the amplitudes with respect to radio frequency are the maximum values for common mode voltage, measured with a frequency analysis instrument with narrow frequency bandwidth. As the primary coupling occurs in the last few metres of the line, advantage is taken of the shielding effects of the building (e.g., metallic framework) of the Major Telecom Centre (Class 1).<br>NOTE 5 – The limits are based on [ITU-T K.68]. Protective measures are assumed on lines where these limits would otherwise be exceeded. In Japan, 650 V for $t \leq 0.06$ s; 430 V for $0.06$ s $< t \leq 0.1$ s; 300 V for $0.1$ s $< t \leq 1.0$ s apply.<br>NOTE 6 – Damped oscillatory waveform.<br>NOTE 7 – The level is inversely proportional to the frequency above 10 MHz (Level V = (level @10 MHz $\times$ 10/Frequency in MHz)). |                         |                                                                                                          |                                                          |                                                                     |                                                                  |                                                                     |
+
+**Table 2 – Signal lines remaining within the building**
+
+| Coupling path                              | Environmental parameter                                 |                                                      | Class 1 major telecom centres  | Class 2 Minor telecom centres | Class 3 outdoor locations | Class 4 customer premises      |
+|--------------------------------------------|---------------------------------------------------------|------------------------------------------------------|--------------------------------|-------------------------------|---------------------------|--------------------------------|
+| Signal lines remaining within the building | Audio freq. common mode voltage                         | Frequency kHz<br>Ampl. V (rms)<br>Impedance $\Omega$ | 0.05-1-20<br>20-0.5-0.5<br>100 |                               | Not applicable            | 0.05-1-20<br>10-0.5-0.5<br>300 |
+|                                            | Amplitude modulated radio frequency common mode voltage | Freq. MHz<br>Ampl. V (rms)                           | 0.15-10<br>1                   | 0.15-10<br>3                  | Not applicable            | 0.01-0.15<br>3                 |
+|                                            |                                                         | Freq. MHz<br>Ampl. V (rms)                           | 10-100<br>1-0.1<br>(Note)      | 10-100<br>3-0.3<br>(Note)     |                           |                                |
+|                                            |                                                         | Freq. MHz<br>Ampl. V (rms)                           |                                |                               |                           | 0.15-10<br>10                  |
+|                                            |                                                         | Freq. MHz<br>Ampl. V (rms)                           |                                |                               |                           | 10-30<br>10-3.3<br>(Note)      |
+
+**Table 2 – Signal lines remaining within the building**
+
+| Coupling path | Environmental parameter |                                                                          | Class 1 major telecom centres          | Class 2 Minor telecom centres | Class 3 outdoor locations | Class 4 customer premises    |
+|---------------|-------------------------|--------------------------------------------------------------------------|----------------------------------------|-------------------------------|---------------------------|------------------------------|
+|               |                         | Freq. MHz<br>Ampl. V (rms)                                               |                                        |                               |                           | 30-150<br>3.3-0.66<br>(Note) |
+|               | Common mode EFT/Bursts  | Ampl. V (peak)<br>Events/week<br>Rise time $\mu$ s<br>Impedance $\Omega$ | 250<br>several<br>1 to 100<br>40 to 80 |                               | Not applicable            | 1000<br>several<br>5<br>50   |
+
+NOTE – The level is inversely proportional to the frequency above 10 MHz (Level V = (level @10 MHz  $\times$  10/Frequency in MHz).
+
+**Table 3 – a.c. power ports**
+
+| Coupling path    | Environmental parameter                                          |                                                   | Class 1 major telecom centres                       | Class 2 minor telecom centres | Class 3 outdoor locations | Class 4 customer premises           |
+|------------------|------------------------------------------------------------------|---------------------------------------------------|-----------------------------------------------------|-------------------------------|---------------------------|-------------------------------------|
+|                  | Voltage variation                                                | Voltage changer %                                 | $\pm 10$                                            | $+10/-15$                     |                           | $\pm 8$                             |
+|                  | Voltage fluctuation                                              | Voltage changer %<br>Duration ms<br>Events/day    | $-50$ to $-20$ ; $+20$<br>10 to 1500<br>100 to 0.01 |                               |                           | 10 to 99<br>$< 3000$<br>unspecified |
+|                  | Voltage interruption                                             | Duration ms<br>Events/day                         | 10; 20; 40; 100 to 700<br>10; 1; 0.1; 0.05          |                               |                           | $< 6000$<br>unspecified             |
+| a.c. power mains | Amplitude modulated radio frequency common mode voltage (Note 1) | Freq. MHz<br>Ampl. V (rms)                        | 0.009-10<br>1                                       | 0.009-10<br>3                 |                           | 0.009-0.15<br>3                     |
+|                  |                                                                  | Freq. MHz<br>Ampl. V (rms)                        | 10-100<br>1-0.1<br>(Note 4)                         | 10-100<br>3-0.3<br>(Note 4)   |                           |                                     |
+|                  |                                                                  | Freq. MHz<br>Ampl. V (rms)                        |                                                     |                               |                           | 0.15-10<br>10                       |
+|                  |                                                                  | Freq. MHz<br>Ampl. V (rms)                        |                                                     |                               |                           | 10-150<br>3-0.2<br>(Note 4)         |
+|                  | Common and differential mode EFT/Bursts                          | Ampl. V (peak)<br>Events/day<br>Rise time $\mu$ s | 1000<br>1<br>1 to 100                               |                               |                           | 2000 (Note 2)<br>several<br>5       |
+
+**Table 3 – a.c. power ports**
+
+| Coupling path     | Environmental parameter |                                                                                                           | Class 1 major telecom centres | Class 2 minor telecom centres                    | Class 3 outdoor locations | Class 4 customer premises                                      |
+|-------------------|-------------------------|-----------------------------------------------------------------------------------------------------------|-------------------------------|--------------------------------------------------|---------------------------|----------------------------------------------------------------|
+|                   | Surge line/neutral      | Ampl. kV (peak)<br>Rise time $\mu\text{s}$<br>Duration $\mu\text{s}$<br>Events/year                       | 2<br>0.5 to 10<br>< 100<br>20 | 2; 4<br>0.5 to 10<br>< 100<br>100; 3             |                           |                                                                |
+| Surge line/ground |                         | Ampl. kV (peak)<br>Rise time $\mu\text{s}$<br>Duration $\mu\text{s}$<br>Events/year<br>Impedance $\Omega$ | (Note 3)                      | 2; 4<br>0.5 to 10<br>< 100<br>100; 3<br>10 to 20 |                           | 1; 4<br>10; 1<br>1000; 50<br>Multiple<br>20 to 300;<br>1 to 10 |
+
+NOTE 1 – All values given for the amplitudes with respect to radio frequency are the maximum values for common mode voltage, measured with a frequency analysis instrument with narrow frequency bandwidth. As the primary coupling occurs in the last few metres of the line, advantage is taken of the shielding effects of the building (e.g., metallic framework) of the Major Telecom Centre (Class 1).
+
+NOTE 2 – Only specified for certain types of customer premises.
+
+NOTE 3 – Not applicable because Major Telecom Centres (Class 1) have their own electricity power transformers.
+
+NOTE 4 – The level is inversely proportional to the frequency above 10 MHz (Level V = (level @10 MHz  $\times$  10/Frequency in MHz)).
+
+**Table 4 – d.c. power ports**
+
+| Coupling path           | Environmental parameter                             |                                                          | Class 1 major telecom centres         | Class 2 minor telecom centres | Class 3 outdoor locations   | Class 4 customer premises |
+|-------------------------|-----------------------------------------------------|----------------------------------------------------------|---------------------------------------|-------------------------------|-----------------------------|---------------------------|
+|                         | Voltage variation                                   | Voltage V                                                | 40.5/57                               |                               |                             |                           |
+| d.c. power distribution | Voltage fluctuation and interruption                | Voltage V<br>Duration ms<br>Events/year                  | 0 to 40.5; 57 to 60<br>< 50<br>3      |                               |                             | Not applicable            |
+|                         | Audio freq. differential mode voltage               | Frequency kHz<br>Ampl. mV (rms)                          | 0.025-0.3-1-20-150<br>50-50-7-7/50-50 |                               |                             |                           |
+|                         | Amplitude modulated radio freq. common mode voltage | Freq. MHz<br>Ampl. V (rms)                               | 0.15-10<br>1                          | 0.15-10<br>3                  | 0.15-10<br>1                |                           |
+|                         |                                                     | Freq. MHz<br>Ampl. V (rms)                               | 10-100<br>1-0.1<br>(Note 3)           | 10-100<br>3-0.3<br>(Note 3)   | 10-100<br>1-0.1<br>(Note 3) |                           |
+|                         | Common and differential mode EFT/Bursts             | Ampl. V (peak)<br>Events/week<br>Rise time $\mu\text{s}$ | 250<br>several<br>1 to 100            |                               |                             |                           |
+
+**Table 4 – d.c. power ports**
+
+| Coupling path | Environmental parameter                     |                                                                                    | Class 1 major telecom centres | Class 2 minor telecom centres | Class 3 outdoor locations | Class 4 customer premises |
+|---------------|---------------------------------------------|------------------------------------------------------------------------------------|-------------------------------|-------------------------------|---------------------------|---------------------------|
+|               | Common and differential mode surge (Note 1) | Ampl. V (peak)<br>Rise time $\mu\text{s}$<br>Duration $\mu\text{s}$<br>Events/year | 200<br>5<br>50<br>3           |                               | Not applicable            |                           |
+
+NOTE 1 – From fuse blowing.
+
+NOTE 2 – Class 3 does not apply to remote d.c. supplies via the signal lines. In such cases, the appropriate classification for "Signal lines entering the building" is to be used.
+
+NOTE 3 – The logarithm of the level linearly decreases with the logarithm of the frequency in the range 10 to 100 MHz.
+
+**Table 5 – Enclosure**
+
+| Coupling path | Environmental parameter                                   |                                 | Class 1 major telecom centres | Class 2 minor telecom centres | Class 3 outdoor locations        | Class 4 customer premises          |
+|---------------|-----------------------------------------------------------|---------------------------------|-------------------------------|-------------------------------|----------------------------------|------------------------------------|
+| Enclosure     | Audio freq. magnetic field                                | Frequency Hz<br>Ampl. A/m (rms) | 50 to 20 000<br>10 to 0.025   | 50 to 20 000<br>3 to 0.008    | 50 to 20 000<br>10 to 0.025      | $16^{2/3}$ ; 50 to 20k<br>1; 0.015 |
+|               |                                                           | Frequency Hz<br>Ampl. A/m (rms) |                               |                               |                                  | 50; 100 to 3000<br>10; 1.8 to 0.6  |
+|               | Pulse modulated radio freq. electromagnetic field         | Freq. GHz<br>Ampl. V/m (peak)   | 1-20<br>1                     | 1-20<br>3                     | 1-20<br>10                       | 1-20<br>3                          |
+|               | Modulated radio freq. of Amateur radio bands below 30 MHz | Freq. MHz<br>Ampl. V/m (rms)    |                               |                               | 0.13-29,7<br>1<br>(Note 1)       | 0.13-29,7<br>1<br>(Note 1)         |
+|               | Modulated radio freq. of CB band 27 MHz                   | Freq. MHz<br>Ampl. V/m (rms)    |                               |                               | 26.560-27.991<br>0,3<br>(Note 2) | 26.560-27.991<br>0,3<br>(Note 2)   |
+|               | Analogue radio communication services below 30 MHz        | Freq. MHz<br>Ampl. V/m (rms)    | 0.150-30<br>3<br>(Note 3)     | 0.150-30<br>3<br>(Note 3)     | 0.150-30<br>3<br>(Note 3)        | 0.150-30<br>3<br>(Note 3)          |
+
+**Table 5 – Enclosure**
+
+| Coupling path | Environmental parameter                                             |                 | Class 1 major telecom centres | Class 2 minor telecom centres | Class 3 outdoor locations | Class 4 customer premises |
+|---------------|---------------------------------------------------------------------|-----------------|-------------------------------|-------------------------------|---------------------------|---------------------------|
+|               |                                                                     |                 |                               |                               |                           |                           |
+|               | Analogue radio communication services above 30 MHz                  | Freq. MHz       | 48-853                        | 48-853                        | 48-853                    | 48-853                    |
+|               |                                                                     | Ampl. V/m (rms) | 3<br>(Note 4)                 | 3<br>(Note 4)                 | 3<br>(Note 4)             | 3<br>(Note 4)             |
+|               | Modulated radio communication services (mobile and portable phones) | Freq. MHz       | 890-915                       | 890-915                       | 890-915                   | 890-915                   |
+|               |                                                                     | Ampl. V/m (rms) | 3<br>(Note 5)                 | 3<br>(Note 5)                 | 3<br>(Note 5)             | 3<br>(Note 5)             |
+|               |                                                                     | Freq. MHz       | 1710-1784                     | 1710-1784                     | 1710-1784                 | 1710-1784                 |
+|               |                                                                     | Ampl. V/m (rms) | 3<br>(Note 6)                 | 3<br>(Note 6)                 | 3<br>(Note 6)             | 3<br>(Note 6)             |
+|               |                                                                     | Freq. MHz       |                               |                               |                           | 1880-1960                 |
+|               |                                                                     | Ampl. V/m (rms) |                               |                               |                           | 3<br>(Note 7)             |
+|               | Modulated radio communication services (base stations)              | Freq. MHz       | 1900-1980                     | 1900-1980                     | 1900-1980                 | 1900-1980                 |
+|               |                                                                     | Ampl. V/m (rms) | 3<br>(Note 8)                 | 3<br>(Note 8)                 | 3<br>(Note 8)             | 3<br>(Note 8)             |
+|               |                                                                     | Freq. MHz       | 450-7125/24250-27900          | 450-7125/24250-27900          | 450-7125/24250-27900      | 450-7125/24250-27900      |
+|               |                                                                     | Ampl. V/m (rms) | 3<br>(Note 15)                | 3<br>(Note 15)                | 3<br>(Note 15)            | 3<br>(Note 15)            |
+|               |                                                                     | Freq. MHz       | 935-960                       | 935-960                       | 935-960                   | 935-960                   |
+|               |                                                                     | Ampl. V/m (rms) | 3<br>(Note 9)                 | 3<br>(Note 9)                 | 3<br>(Note 9)             | 3<br>(Note 9)             |
+|               |                                                                     | Freq. MHz       | 1805-1880                     | 1805-1880                     | 1805-1880                 | 1805-1880                 |
+|               |                                                                     | Ampl. V/m (rms) | 3<br>(Note 10)                | 3<br>(Note 10)                | 3<br>(Note 10)            | 3<br>(Note 10)            |
+|               |                                                                     | Freq. MHz       |                               |                               |                           | 1880-1960                 |
+|               |                                                                     | Ampl. V/m (rms) |                               |                               |                           | 3<br>(Note 11)            |
+|               |                                                                     | Freq. MHz       | 1900-2170                     | 1900-2170                     | 1900-2170                 | 1900-2170                 |
+|               |                                                                     | Ampl. V/m (rms) | 3<br>(Note 12)                | 3<br>(Note 12)                | 3<br>(Note 12)            | 3<br>(Note 12)            |
+|               |                                                                     | Freq. MHz       | 450-7125                      | 450-7125                      | 450-7125                  | 450-7125                  |
+|               |                                                                     | Ampl. V/m (rms) | 3<br>(Note 16)                | 3<br>(Note 16)                | 3<br>(Note 16)            | 3<br>(Note 16)            |
+|               |                                                                     | Freq. MHz       | 24250-27900                   | 24250-27900                   | 24250-27900               | 24250-27900               |
+|               |                                                                     | Ampl. V/m (rms) | 3<br>(Note 16)                | 3<br>(Note 16)                | 3<br>(Note 16)            | 3<br>(Note 16)            |
+|               |                                                                     | Freq. MHz       | 3                             | 3                             | 3                         |                           |
+|               |                                                                     | Ampl. V/m (rms) | (Note 16)                     | (Note 16)                     | (Note 16)                 |                           |
+
+**Table 5 – Enclosure**
+
+| Coupling path | Environmental parameter         |                                                                | Class 1 major telecom centres | Class 2 minor telecom centres | Class 3 outdoor locations   | Class 4 customer premises                |
+|---------------|---------------------------------|----------------------------------------------------------------|-------------------------------|-------------------------------|-----------------------------|------------------------------------------|
+|               | High speed wireless LANs        | Freq. GHz<br>Ampl. V/m (rms)                                   | 2400-2483<br>3<br>(Note 13)   | 2400-2483<br>3<br>(Note 13)   | 2400-2483<br>3<br>(Note 13) | 2400-2483<br>3<br>(Note 13)              |
+|               |                                 | Freq. GHz<br>Ampl. V/m (rms)                                   | 5150-5875<br>3<br>(Note 14)   | 5150-5875<br>3<br>(Note 14)   | 5150-5875<br>3<br>(Note 14) | 5150-5875<br>3<br>(Note 14)              |
+|               | Electrostatic Voltage           | Ampl. kV (peak)                                                | 4<br>(Note 15)                | 4<br>(Note 15)                | 2                           | 8<br>(Note 16)                           |
+|               | Lightning electromagnetic pulse | Ampl. A/m (peak)<br>Rise time µs<br>Duration µs<br>Events/year | Not applicable                | 500<br>0.2<br>100<br>0.1      | Not applicable              | Specified by the slew rate<br>100 V/m/ns |
+
+NOTE 1 – Max field at 271 m from the source of 1500 W (ERP), [b-IEC/TR 61000-2-5].
+
+NOTE 2 – Max field at 63,2 m from the source of 4 W ERP (AM, FM), [b-IEC/TR 61000-2-5].
+
+NOTE 3 – Max field at 1650 m from the source of 500 kW AM broadcasting, [b-IEC/TR 61000-2-5].
+
+NOTE 4 – Max field at 1650 m from the source of 500 kW TV UHF, [b-IEC/TR 61000-2-5].
+
+NOTE 5 – Max field at 10,5 m from the GSM source of 20 W Mobile, . [b-IEC/TR 61000-2-5].
+
+NOTE 6 – Max field at 4,7 m from the DCS1800 source of 4 W, [b-IEC/TR 61000-2-5].
+
+NOTE 7 – Max field at 1,2 m from the DECT source of 0,25W, [b-IEC/TR 61000-2-5].
+
+NOTE 8 – Max field at 1,2 m from the IMT2000 source of 0,25 W, [b-IEC/TR 61000-2-5].
+
+NOTE 9 – Max field at 206 m from the GSM source of 320 W (ERP), [b-IEC/TR 61000-2-5].
+
+NOTE 10 – Max field at 163 m from the DCS1800 source of 200 W (ERP), [b-IEC/TR 61000-2-5].
+
+NOTE 11 – Max field at 5,7 m from the DECT source of 0,25W (ERP), [b-IEC/TR 61000-2-5].
+
+NOTE 12 – Max field at 52 m from the IMT2000 source of 20 W (ERP), [b-IEC/TR 61000-2-5].
+
+NOTE 13 – Max field at 5,8 m from the source of 0,1 W (ERP), [b-IEC/TR 61000-2-5].
+
+NOTE 14 – Max field at 18 m from the source of 1 W (ERP), [b-IEC/TR 61000-2-5].
+
+NOTE 15 – Max field at 0,6 m from the IMT2020 source of 17,95 dBm at antenna port and antenna gain of 2.4 dBi.
+
+NOTE 16 – Max field at 23 m from the IMT2020 source of 35 dBm at antenna port and antenna gain of 17 dBi, [b-3GPP 38.104].
+
+NOTE 17 – If limited electrostatic protection is applied, a higher level of electrostatic may occur.
+
+NOTE 18 – In higher humidity environments, lower levels of electrostatic may occur. [b-IEC/TR 61000-2-5] specifies 4 kV.
+
+NOTE 19 – To determine the field strength at other distances from the source reported in this table, in far field condition can use the following dipole formula:
+
+$$E = k \sqrt{P}/d,$$
+
+where:
+
+- E is the field strength (RMS value) (V/m);
+- k is a constant, with a value of 7, for free-space propagation in the far field;
+- P is the power (ERP) (W);
+- d is the distance from the antenna (m).
+- If the ERP of the transmitter is not known, the power provided to the antenna may be used and, in this case, a value of  $k = 3$  is typically applicable for mobile radio transmitters.
+
+# Bibliography
+
+- [b-IEC 60050-161] IEC 60050-161:1990, *International Electrotechnical Vocabulary (IEV) – Part 161: Electromagnetic Compatibility.*
+- [b-IEC/TR 61000-2-5] IEC/TR 61000-2-5:2017, *Electromagnetic compatibility (EMC) – Part 2-5: Environment – Description and classification of electromagnetic environments.*
+- [b-IEC 61000-6-2] IEC 61000-6-2:2016, *Electromagnetic compatibility (EMC) – Part 6-2: Generic standards – Immunity standard for industrial environments.*
+- [b-IEC 61000-6-5] IEC 61000-6-5:2015, *Electromagnetic compatibility (EMC) – Part 6-5: Generic standards – Immunity for equipment used in power station and substation environment.*
+- [b-IEC 62236-4] IEC 62236-4:2018, *Railway applications – Electromagnetic compatibility – Part 4: Emission and immunity of the signalling and telecommunications apparatus.*
+- [b-3GPP 38.104] 3GPP 38.104: Release 16, NR; Base Station (BS) radio transmission and reception.
+- [b-ANSI C63.12] ANSI C63.12 (1999), *American National Standard for Electromagnetic Compatibility Limits – Recommended Practice.*
+- [b-ETSI TR 101 651] ETSI TR 101 651 V1.1.1 (1999), *Electromagnetic compatibility and radio spectrum matters (ERM); Classification of the electromagnetic environment conditions for equipment in telecommunication networks.*
+
+
+
+
+
+## SERIES OF ITU-T RECOMMENDATIONS
+
+|                 |                                                                                                                                                           |
+|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Series A        | Organization of the work of ITU-T                                                                                                                         |
+| Series D        | Tariff and accounting principles and international telecommunication/ICT economic and policy issues                                                       |
+| Series E        | Overall network operation, telephone service, service operation and human factors                                                                         |
+| Series F        | Non-telephone telecommunication services                                                                                                                  |
+| Series G        | Transmission systems and media, digital systems and networks                                                                                              |
+| Series H        | Audiovisual and multimedia systems                                                                                                                        |
+| Series I        | Integrated services digital network                                                                                                                       |
+| Series J        | Cable networks and transmission of television, sound programme and other multimedia signals                                                               |
+| <b>Series K</b> | <b>Protection against interference</b>                                                                                                                    |
+| Series L        | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant |
+| Series M        | Telecommunication management, including TMN and network maintenance                                                                                       |
+| Series N        | Maintenance: international sound programme and television transmission circuits                                                                           |
+| Series O        | Specifications of measuring equipment                                                                                                                     |
+| Series P        | Telephone transmission quality, telephone installations, local line networks                                                                              |
+| Series Q        | Switching and signalling, and associated measurements and tests                                                                                           |
+| Series R        | Telegraph transmission                                                                                                                                    |
+| Series S        | Telegraph services terminal equipment                                                                                                                     |
+| Series T        | Terminals for telematic services                                                                                                                          |
+| Series U        | Telegraph switching                                                                                                                                       |
+| Series V        | Data communication over the telephone network                                                                                                             |
+| Series X        | Data networks, open system communications and security                                                                                                    |
+| Series Y        | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities                               |
+| Series Z        | Languages and general software aspects for telecommunication systems                                                                                      |