1、 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 K.98 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (08/2014) SERIES K: PROTECTION AGAINST INTERFERENCE Overvoltage protection guide for telecommunication equipment installed in customer premises Recommendation ITU-T K.98
2、Rec. ITU-T K.98 (08/2014) i Recommendation ITU-T K.98 Overvoltage protection guide for telecommunication equipment installed in customer premises Summary Recommendation ITU-T K.98 provides information which can help protect telecommunication equipment installed in the customer premises against damag
3、e due to the lightning strikes to the power and telecommunication lines/cables. It shows that, it is possible to protect equipment against a direct strike to power or telecommunication lines provided that the strike point is at a distance of more than a couple hundred metres from the customer premis
4、es in an urban area. The information provided takes into consideration the impact of different types of power distribution systems. It determines the impact of both the length of the telecommunication surge protection device (SPD) bonding conductor and the resistance to earth at the customer premise
5、s. The necessary isolation level for the protection of equipment without the use of primary protection is also calculated. It recommends the installation of a multiservice surge protective device (MSPD) or equivalent protection as the first level of protection. When necessary, primary protection is
6、required to protect the MSPD or equivalent protection devices. For strikes to the services closer to the customer premises, an engineering solution is required. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T K.98 2014-08-29 5 11.1002/1000/12288 1.1 ITU-T K.98 (2014) Cor. 1
7、2015-03-01 5 11.1002/1000/12410 Keywords Bonding, earthing, lightning flash, lightning strike, MOV, protection, simulation, surge. _ * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, ht
8、tp:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T K.98 (08/2014) 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 Se
9、ctor (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 eve
10、ry 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-Ts purvie
11、w, 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 volunt
12、ary. 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
13、 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 RIGHTSITU draws attention to the possibility that the practice or implementation of this Recommendation may involve t
14、he 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 Recommend
15、ation, 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 htt
16、p:/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. Rec. ITU-T K.98 (08/2014) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 2 3.1 Terms defined elsewhere
17、2 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 2 5 Conventions 3 6 Factors influencing surge levels . 3 6.1 Surge coupling and mechanisms of damage 4 6.2 Elements of protection 21 6.3 Equipment resistibility 21 6.4 Correct classification and use of ports 23 6.5 Cable rou
18、ting 24 6.6 Earthing and bonding . 24 6.7 SPDs . 24 6.8 Direct strike protection of a structure . 27 6.9 Installation of protection . 27 6.10 Conclusions 29 Annex A Simulations 31 A.1 Introduction 31 A.2 Stress applied to the equipment via the mains port 38 A.3 Stress applied to the equipment via th
19、e telecommunication port . 81 A.4 Waveform after primary protection and coordination 124 Appendix I Calculation of cable current in a telecommunication line versus distance from the strike point 135 I.1 Introduction 135 I.2 Resistance to earth at the strike point . 136 I.3 Equivalent circuit of a st
20、rike to earth . 137 I.4 Simulation results for a 30 pair 0.64 mm MB cable with a zero ohm resistance to earth at the customer end . 139 I.5 Simulation results for a 30 pair 0.4 mm non-shielded cable 145 I.6 Conclusions drawn from the simulations . 145 I.7 Calculation of cable current 145 I.8 Determi
21、nation of the cable surge generator. . 145 Appendix II Impact of local environment . 149 Bibliography. 151 iv Rec. ITU-T K.98 (08/2014) Introduction This Recommendation can be used as a guide on how to protect telecommunication equipment from overvoltage damage due to lightning strikes to the power
22、and telecommunication lines/cables. For both the telecommunication and mains ports, only longitudinal surge voltages/currents are considered. A number of different power distribution systems are used in the premises and ones where the neutral is not earthed at the structure, either directly or via a
23、 spark gap, may increase the probability of telecommunication equipment damage. This Recommendation investigates the issues of surge protection device (SPD) bond wire length and structure earth electrode resistance in relation to the different types of power distribution systems. The available curre
24、nt at customer premises has been investigated in more detail than in Recommendation ITU-T K.67. Rec. ITU-T K.98 (08/2014) 1 Recommendation ITU-T K.98 Overvoltage protection guide for telecommunication equipment installed in customer premises 1 Scope This Recommendation provides guidance on how to pr
25、otect telecommunication equipment installed in the customer premises from overvoltage damage due to lightning strikes to the power and telecommunication service lines/cables. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this tex
26、t, 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 o
27、f 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.1
28、2 (2010), Characteristics of gas discharge tubes for the protection of telecommunications installations. ITU-T K.21 Recommendation ITU-T K.21 (2011), Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents. ITU-T K.44 Recommendation ITU-T K.44 (20
29、12), Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents Basic Recommendation. ITU-T K.66 Recommendation ITU-T K.66 (2011), Protection of customer premises from overvoltages. ITU-T K.67 Recommendation ITU-T K.67 (2006), Expected surges on telecommunications a
30、nd signalling networks due to lightning. ITU-T K.71 Recommendation ITU-T K.71 (2011), Protection of customer antenna installations. ITU-T K.73 Recommendation ITU-T K.73 (2008), Shielding and bonding for cables between buildings. ITU-T K.75 Recommendation ITU-T K.75 (2008), Classification of interfac
31、e 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. IEC 60364-4-44 IEC 60364-4-44 ed2.0 (2007), Low-voltage electr
32、ical installations Part 4-44: Protection for safety Protection against voltage disturbances and electromagnetic disturbances. IEC 60950-1 IEC 60950-1 ed2.0 (2005), Information technology equipment Safety Part 1: General requirements. IEC 61643-21 IEC 61643-21 ed1.2 (2012), Low voltage surge protecti
33、ve devices Part 21: Surge protective devices connected to telecommunications and signalling networks Performance requirements and testing methods. 2 Rec. ITU-T K.98 (08/2014) IEC 61643-22 IEC 61643-22 ed1.0 (2004), Low-voltage surge protective devices Part 22: Surge protective devices connected to t
34、elecommunications and signalling networks Selection and application principles. IEC 62305-2 IEC 62305-2 ed2.0 (2010), Protection against lightning Part 2: Risk management. IEC 62305-3 IEC 62305-3 ed2.0 (2010), Protection against lightning Part 2: Physical damage to structures and life hazard. 3 Defi
35、nitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 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 prot
36、ection components. 3.1.2 lightning flash b-IEC 60479-4: Atmospheric discharge consisting of one or more strokes. 3.1.3 lightning stroke (strike) b-IEC 60479-4: Single electrical discharge in a lightning flash. 3.1.4 multiservice surge protective device (MSPD) ITU-T K.85: A surge protective device (S
37、PD) containing both telecommunications and mains protection. It may also include port protection for video or Ethernet. 3.1.5 primary protector ITU-T K.44: An SPD used for the primary protection of an installation at the location (preferably the building entrance point) where it diverts most of the
38、surge current and prevents the majority of the surge stress from propagating further into the installation. This SPD must be accessible, removable and have equipotential bonding. 3.1.6 surge protective device (SPD) ITU-T K.44: Device that restricts the voltage of a designated port or ports, caused b
39、y a surge, when it exceeds a predetermined level: Secondary functions may be incorporated, such as a current-limiting device to restrict a terminal current. Typically, the protective circuit has at least one non-linear voltage-limiting surge protective component. Typically, the protective circuit ha
40、s at least one non-linear voltage-limiting surge protective component. An SPD is a combination of a protection circuit and holder. 3.2 Terms defined in this Recommendation There are no new terms defined in this Recommendation. 4 Abbreviations and acronyms This Recommendation uses the following abbre
41、viations and acronyms: CICR Conseil Internationale des Grands Rseaux lectriques CPE Customer Premises Equipment EPR Earth Potential Rise FXO Foreign exchange Office FXS Foreign exchange Subscriber GDT Gas Discharge Tube Rec. ITU-T K.98 (08/2014) 3 HV High Voltage IEEE Institute of Electrical and Ele
42、ctronics Engineers L Line (phase) conductor LPS Lightning Protection System LT Line Termination LV Low Voltage (power line of a.c. voltage 1 kV and 6 0 0 V ?Y esPri mary p ro t ect i o n i n s t al l ed t o IT U -T K . 6 6w h en req u i red ?Y es NoRec. ITU-T K.98 (08/2014) 23 This inherent protecti
43、on can be provided by using protection components or by insulation barriers or a combination of both within the equipment. The special requirements can be achieved by using a higher insulation withstand level within the equipment. This principle can also be applied external to the equipment. For exa
44、mple, an external to the equipment mains isolation transformer can be used to increase the effective isolation between mains and the telecommunication ports. When an MSPD is used to protect the equipment, it is the combination of mains and telecommunication SPDs within the MSPD and the safety isolat
45、ion barrier within the equipment which protects the equipment by preventing a breakdown of this insulation and the surge bypasses the equipment. It should be noted that, the use of SPDs may actually increase the magnitude of the surge current being conducted in the installation wiring while the use
46、of external isolation barriers may reduce the magnitude of the surge current being conducted in the wiring. However, if the insulation withstand level is exceeded, significant damage may take place and a may also result in safety hazard (fire and electric shock). If higher insulation levels are bein
47、g considered within the equipment (special requirements) or external to the equipment as a form of added protection, it is necessary to be aware of the voltages which may exist. An indication of the voltages which may arise can be found in Annex A. 6.4 Correct classification and use of ports As indi
48、cated above, equipment may have both external and internal ports. There are both damage and safety implications of not using the correct type of port. The equipment manufacturer should specify the correct use of the equipment ports. If this information is not available, ITU-T K.75 provides informati
49、on on classifying plain old telephone service (POTS), Ethernet and video ports. A mains port is always an external port. Manufacturers of customer equipment in particular assume that non-network equipment ports will only be connected to intra-building cabling. A problem then occurs if the network operator, or the customer, decides to extend the service to an outbuilding facility. Equipment designed for connection to intra-building cabling may have insufficient isolation fr
