1、 International Telecommunication Union ITU-T K.67TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2006) SERIES K: PROTECTION AGAINST INTERFERENCE Expected surges on telecommunications and signalling networks due to lightning ITU-T Recommendation K.67 ITU-T Rec. K.67 (02/2006) i ITU-T Recommendati
2、on K.67 Expected surges on telecommunications and signalling networks due to lightning Summary This Recommendation gives the characteristics (waveshapes and peak values) of the expected surges (overvoltages and overcurrents) due to lightning on telecommunication lines of the access network and on si
3、gnalling lines at customers premises using metallic conductors. These values of the expected surges are presented as a function of a set of lightning current parameters which define lightning as the source of damage by any type of electromagnetic coupling on a telecommunication or signalling line. T
4、his Recommendation allows evaluation of the effectiveness of the protective measures (e.g., surge protective devices) that are intended to withstand the expected surge current at the installation point. Source ITU-T Recommendation K.67 was approved on 13 February 2006 by ITU-T Study Group 5 (2005-20
5、08) under the ITU-T Recommendation A.8 procedure. Keywords Lightning, overcurrent, overvoltage, surge, transition point. ii ITU-T Rec. K.67 (02/2006) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecomm
6、unication 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 Asse
7、mbly (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 whi
8、ch fall within ITU-Ts 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 t
9、his 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 langu
10、age 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 R
11、ecommendation 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
12、 approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the
13、 TSB patent database. ITU 2006 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. K.67 (02/2006) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations 3 5 Reference configuration 3
14、 6 Protective measures 4 6.1 Inherent protection 4 6.2 Primary protection 5 6.3 Bonding, earthing and shielding. 5 7 Expected surges due to lightning 6 7.1 Direct lightning flashes to a structure (source of damage S1): Lightning current flowing through telecommunication or signalling lines entering
15、the structure (exchange or customers building or remote site) 6 7.2 Lightning flashes near, or to, a structure (source of damage S1 or S2): Induced surges in telecommunication or signalling lines inside the structure (exchange or customers building or remote site) 7 7.3 Direct lightning to the telec
16、ommunication or signalling lines . 9 7.4 Lightning flashes near telecommunication lines 10 Annex A Induced surges inside the structure due to lightning near, or to, the structure 13 A.1 General . 13 A.2 Lightning near the structure 13 A.3 Lightning to the structure . 17 Annex B Induced surges on tel
17、ecommunication lines due to lightning near the line: Perfectly conducting soil 20 Appendix I Induced surges inside the structure due to lightning near, or to, the structure: Experimental setup and results. 23 I.1 Introduction 23 I.2 Theoretical model. 23 I.3 Experimental test site and test set-up .
18、25 BIBLIOGRAPHY 30 iv ITU-T Rec. K.67 (02/2006) Introduction The origin of dangerous overvoltages and overcurrents on telecommunication and signalling networks is lightning (direct and indirect lightning strikes), induction from fault currents in power lines (including traction systems), contact wit
19、h power lines, and the rise of earth potential. Methods of protection, called “protective measures“, are relevant to “lines“ (e.g., use of shielded instead of unshielded cable) or to specific parts of the system. The latter fall broadly into 3 classes: the use of installation practices such as bondi
20、ng, earthing, and shielding in the facility and on external lines to reduce the coupling of the lightning energy to the line; 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
21、 example, fuses); these protective devices are defined as “primary protection“; the use of equipment with suitable dielectric strength, current carrying capacity and impedance so that it can withstand the conditions applied to it; this characteristic is defined as “inherent protection“. Protective d
22、evices (primary protection) are used against overvoltages (surge protective devices, (SPDs), e.g., air-gap protectors with carbon or metallic electrodes; gas discharge tubes (GDTs), semi-conductor protective devices) and against overcurrents (e.g., fuses, heat coils, self-restoring overcurrent prote
23、ctors, fusible links). For the specification of protective components and apparatus, the threat due to surges at their particular installation points need to be determined. The threat due to these surges must be lower than the withstand level of the affected protective components and equipment. This
24、 withstand level is determined by suitable tests. This Recommendation deals with the expected surges due to lightning at different installation points of these protective components and equipment on telecommunication and signalling networks. Certain formulas or assumptions for expected surges evalua
25、tion are severe approximations, and further refinement could improve them. ITU-T Rec. K.67 (02/2006) 1 ITU-T Recommendation K.67 Expected surges on telecommunications and signalling networks due to lightning 1 Scope The scope of this Recommendation is to define the expected surges (overvoltages and
26、overcurrents) due to lightning at different transition points of the telecommunication access network and signalling lines, both outside and inside structures, i.e., exchanges customers buildings and remote sites. The objects of this Recommendation are the effects of overvoltages and overcurrents on
27、 telecommunication and signalling networks that use metallic conductors due to lightning current as a source of damage, which depend on the position of the point of strike with respect to the line under consideration (see 3.6). The expected surges are defined by their peak values and waveshapes as a
28、 function of the surge protection level (SPL, see 3.7) for each type (S1, S2, S3and S4) of source of damage (see 3.6). The waveshape of the expected surges is assumed to be a double exponential described by its front time, (T1), and time to half value, (T2). This Recommendation allows evaluation of
29、the effectiveness of the protective measures (e.g., surge protective devices) that are intended to withstand the expected surge current in the installation point. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitut
30、e 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 Recomm
31、endations 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. 1 ITU-T Lightning Handbooks, Chapter 10 (1995),
32、 Overvoltages and overcurrents measured on telecommunication subscriber lines. 2 ITU-T Recommendation K.46 (2003), Protection of telecommunication lines using metallic symmetric conductors against lightning-induced surges. 3 ITU-T Recommendation K.47 (2000), Protection of telecommunication lines usi
33、ng metallic conductors against direct lightning discharges. 4 ITU-T Recommendation K.56 (2003), Protection of radio base stations against lightning discharges. 5 IEC 62305-1:2006, Protection against lightning Part 1: General principles. 6 IEC 62305-2:2006, Protection against lightning Part 2: Risk m
34、anagement. 7 IEC 62305-4:2006, Protection against lightning Part 4: Electric and electronic systems within structures. 2 ITU-T Rec. K.67 (02/2006) 3 Definitions This Recommendation defines the following terms: 3.1 dangerous surge voltage due to lightning: A surge voltage whose peak value Upis greate
35、r than or equal to the surge voltage withstand level of the equipment or of the conductor insulation of the telecommunication line. 3.2 equivalent decay time to half value (T2) 1: The time to half value (T2) of an impulse voltage or current is the time interval between the virtual origin and the fir
36、st instant at which the voltage or current has decreased to half the peak value. (The virtual origin of an impulse voltage or current is the instant preceding that at which the voltage or current is 30% or 10% of the peak value by a time 0.3 or 0.1T1respectively.) 3.3 front time or rise time (T1) 1:
37、 The front time or rise time T1vof an impulse voltage is defined as 1.67 times the time interval between the instants when the impulse is 30% and 90% of the peak value. The front time T1iof an impulse current is defined as 1.25 times the interval between the instants when the impulse is 10% and 90%
38、of the peak value. 3.4 lightning protection level (LPL): A set of parameters that define protection levels against sources of damage represented by lightning current 4. NOTE Lightning protection level is used to design lightning protection components (e.g., cross section of conductors, thickness of
39、metal sheets, current capability of SPD, separation distance against dangerous sparking) and to define test parameters simulating the effects of lightning on such components, according to the relevant set of lightning current parameters. Four lightning protection levels (I to IV) are introduced in t
40、he IEC 62305 standards. For each LPL, a set of maximum lightning current parameters is fixed (Table 1). 3.5 peak value (xp) 1: The peak value (xp) of a surge voltage/current is defined as the maximum value observed during the surge. 3.6 source of damage: The source of damage depends on the position
41、of the point of strike relative to the line being considered: Source of damage S1: flashes to the structure (the exchange or the customers building or remote site) where the telecommunication or the signalling line enters; Source of damage S2: flashes near the structure (the exchange or the customer
42、s building or remote site) where the telecommunication or the signalling line enters; Source of damage S3: flashes to the telecommunications line entering the structure (the exchange or the customers building or remote site); Source of damage S4: flashes near the telecommunication line entering the
43、structure (the exchange or the customers building or remote site). 3.7 surge protection level (SPL): Peak values and waveshape of the expected dangerous surge voltages or currents which could appear in different points of the telecommunication networks due to the lightning current as source of damag
44、e. NOTE Three Surge Protection Levels (I to III) are introduced in this Recommendation. For each SPL, the peak values and the waveshape of the expected dangerous surge voltages and currents are estimated. 3.8 steepness of the front, or rate of rise (S) 1: The steepness of the front, or the rate of r
45、ise, (S) is the average rate of change of the voltage or current. It can be determined by the ratio between the peak value xpand the front time T1: 1TxSp= (1) ITU-T Rec. K.67 (02/2006) 3 3.9 surge: Temporary excessive voltage or current, or both, coupled on a telecommunication line, from an external
46、 electrical source. NOTE 1 Typical electrical sources are lightning and AC/DC power systems. NOTE 2 Electrical source coupling can be one or more of the following: electric field (capacitive), magnetic field (inductive), conductive (resistive), electromagnetic field. 3.10 surge due to lightning: A s
47、urge which is caused by lightning through any type of electromagnetic (conductive, inductive and capacitive) coupling. NOTE It is characterized by the following five parameters: peak value, front time (T1), time to half value, T2, (or time parameters T1/T2), steepness, and specific energy. 3.11 surg
48、e 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 restr
49、ict a terminal current. NOTE 3 Typically, the protection circuit has at least one non-linear voltage-limiting surge protective component. 4 Abbreviations This Recommendation uses the following abbreviations: BN Bonding Network CBN Common Bonding Network E Exchange LPL Lightning Protection Level MDF Main Distribution Frame MET Main Earthing Terminal NT Network Termination S Subscriber SPD Surge Protective Device SPL Surge Protection Level 5 Reference configuration Figure 1 shows the reference configurations for the te
