ITU-T K 104-2015 Method for identifying the transfer potential of the earth potential rise from high or medium voltage networks to the earthing system or neutral of low voltage net.pdf

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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.104 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2015) SERIES K: PROTECTION AGAINST INTERFERENCE Method for identifying the transfer potential of the earth potential rise from high or medium voltage networks to the

2、 earthing system or neutral of low voltage networks Recommendation ITU-T K.104 Rec. ITU-T K.104 (03/2015) i Recommendation ITU-T K.104 Method for identifying the transfer potential of the earth potential rise from high or medium voltage networks to the earthing system or neutral of low voltage netwo

3、rks Summary In the case of earth faults in high or medium voltage AC networks, significant earth potential rise (EPR) can occur in the earthing structure where the current is discharged to the earth; typically this is in the earthing grid of the substation involved in the fault. When the earthing gr

4、id is connected metallically to long conductors such as earth wires, neutral conductors, counterpoises, cable sheaths, pipes and rails, the EPR can be transferred over far distances well beyond the zone of influence. Recommendation ITU-T K.104 describes the mechanism of potential transfer to a custo

5、mers premise with a special view of the transfer through the neutral conductor of a low-voltage network and the sheath of a telecommunication cable. Calculation techniques are given for the determination of the magnitude of EPR and transferred potential. Mitigation techniques for preventing the tran

6、sfer of EPR are proposed. Different isolation techniques are proposed as possible mitigation techniques applicable in a telecommunication plant. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T K.104 2015-03-01 5 11.1002/1000/12424 Keywords Double earth fault, earth electrode

7、 effect, earth fault, earthing, earth potential rise, EPR, impedance to earth, metallic transfer, multi earthed, screening factor, transferred potential. _ * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations uni

8、que ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T K.104 (03/2015) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunic

9、ation 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

10、 (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 f

11、all 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 this

12、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 languag

13、e 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 RIGHTSITU draws attention to the possibility that the practice or implementation of this Reco

14、mmendation 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 ap

15、proval 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 TS

16、B 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. Rec. ITU-T K.104 (03/2015) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 2 3.1

17、 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 5 4 Abbreviations and acronyms 5 5 Conventions 6 6 Earth potential rise in electric power systems 6 7 Metallic transfer of EPR . 7 7.1 Description of metallic transfer and influences on telecommunications 7 7.2 Calculation of meta

18、llic transfer 7 7.3 Transfer of the EPR by power lines . 10 7.4 Transfer of the EPR due to an HV fault . 10 7.5 Transfer of the EPR due to an MV fault and influence on customer premises 13 8 Mitigation techniques . 15 8.1 Protecting telecommunication lines serving LV installations (MV faults) 15 Ann

19、ex A Techniques for calculating the EPR in electric power systems . 22 A.1 Network parameters affecting the EPR 22 A.2 Techniques for calculating the EPR . 25 Appendix I Calculation of fault current distribution . 33 Appendix II Through tower earthing during power line faults . 38 II.1 Equivalent ci

20、rcuit of the earth wire with earth return . 38 II.2 Solution of the circuit . 39 II.3 Example of application . 40 Appendix III Impedance to earth of MV/LV transformer stations . 43 III.1 Types of measured transformer stations . 43 III.2 Measurement method . 43 III.3 Results of the measurements 46 II

21、I.4 Conclusions 46 Appendix IV Transferred voltage and current by means of LV neutral conductors . 50 IV.1 System modelling, options and parameters 50 IV.2 Feeding of the neutral-to-earth loop . 52 IV.3 Voltage and current profiles vs. length of the neutral 52 Appendix V Input impedance of the LV ne

22、utral-to-earth loop . 60 VI.1 Problem identification 63 iv Rec. ITU-T K.104 (03/2015) Page VI.2 Study of the relative importance of the network parameters and conditions . 64 VI.3 Main conclusions 65 Appendix VII Screening factor of a power cable with an imperfectly earthed sheath . 68 VII.1 Criteri

23、on for long cables . 68 VII.2 Short (finite length) cable sheaths with continuous earthing . 68 VII.3 Screening factor of a power cable with an insulating cover . 68 VII.4 Screening factors for non-uniform lines . 70 Appendix VIII Screening factors of telecommunication cables with imperfectly earthe

24、d sheaths . 71 VIII.1 Telecommunication cables affected by longitudinal induction 71 VIII.2 Telecommunication cables affected by EPR 73 Bibliography. 75 Rec. ITU-T K.104 (03/2015) 1 Recommendation ITU-T K.104 Method for identifying the transfer potential of the earth potential rise from high or medi

25、um voltage networks to the earthing system or neutral of low voltage networks 1 Scope This Recommendation specifically addresses the magnitude of transferred earth potential rise (EPR) to telecommunication systems due to faults in AC power systems, and how to mitigate these effects. The intent of th

26、is Recommendation is to provide a good source of information for engineers who need guidance on how to assess the magnitude of transferred EPR to telecommunication systems due to faults in AC power systems, and how they can mitigate such effects. The main objective of this Recommendation is to ident

27、ify situations where the transfer of EPR to telecommunication systems may cause problems. 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 edit

28、ions 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 vali

29、d 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 (2003), Resistibility of telecommunication equipment installed in customer premises

30、 to overvoltages and overcurrents. ITU-T K.26 Recommendation ITU-T K.26 (2008), Protection of telecommunication lines against harmful effects from electric power and electrified railway lines. ITU-T K.35 Recommendation ITU-T K.35 (1996), Bonding configurations and earthing at remote electronic sites

31、. ITU-T K.45 Recommendation ITU-T K.45 (2011), Resistibility of telecommunication equipment installed in the access and trunk networks to overvoltages and overcurrents. ITU-T K.57 Recommendation ITU-T K.57 (2003), Protection measures for radio base stations sited on power line towers. ITU-T K.66 Rec

32、ommendation ITU-T K.66 (2011), Protection of customer premises from overvoltages. ITU-T K.68 Recommendation ITU-T K.68 (2008), Operator responsibilities in the management of electromagnetic interference by power systems on telecommunication systems. EN 50122-1 CENELEC EN 50122-1 (2011), Railway appl

33、ications Fixed installations Electrical safety, earthing and the return circuit Part 1: Protective provisions against electric shock. EN 50310 CENELEC EN 50310 (2006), Application of equipotential bonding and earthing in buildings with information technology equipment. 2 Rec. ITU-T K.104 (03/2015) E

34、N 50522 CENELEC EN 50522 (2010), Earthing of power installations exceeding 1 kV a.c. IEC 61936-1 IEC 61936-1 (2010), Power installations exceeding 1 kV a.c. Part 1: Common rules. IEEE 80-2000 IEEE Std 80-2000 (2000), IEEE Guide for Safety in AC Substation Grounding. IEEE 81-2012 IEEE Std 81-2012 (20

35、12), IEEE Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials of a Grounding System. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined in EN 50522, IEC 61936-1 and b-Electropedia: 3.1.1 cable with earth electrode effect:

36、Cable whose sheaths, screens or armouring have the same effect as a strip earth electrode. 3.1.2 circulating transformer neutral current: Portion of fault current which flows back to the transformer neutral point via the metallic parts and/or the earthing system without ever discharging into soil. 3

37、.1.3 (local) earth b-Electropedia: (definition 195-01-03, modified) Part of the earth, which is in electric contact with an earth electrode and the electric potential of which is not necessarily equal to zero. NOTE The conductive mass of the earth, whose electric potential at any point is convention

38、ally taken as equal to zero. 3.1.4 earthing conductor b-Electropedia: (definition 195-02-03) Conductor which provides a conductive path, or part of the conductive path, between a given point in a system or in an installation or in equipment and an earth electrode. NOTE Where the connection between p

39、art of the installation and the earth electrode is made via a disconnecting link, disconnecting switch, surge arrester counter, surge arrester control gap etc., then only that part of the connection permanently attached to the earth electrode is an earthing conductor. 3.1.5 earth electrode b-Electro

40、pedia: (definition 195-02-01) Conductive part, which may be embedded in a specific conductive medium, e.g., in concrete or coke, in electric contact with the earth. 3.1.6 earth fault b-Electropedia: (definition 151-03-40) Fault caused by a conductor being connected to earth or by the insulation resi

41、stance to earth becoming less than a specified value. 3.1.7 earth fault current, IF: Current which flows from the main circuit to earth or earthed parts at the fault location. NOTE 1 For single earth faults, this is: in systems with isolated neutral, the capacitive earth fault current; in systems wi

42、th high resistive earthing, the RC composed earth fault current; in systems with resonant earthing, the earth fault residual current; in systems with solid or low impedance neutral earthing, the line-to-earth short-circuit current. NOTE 2 Further earth fault current may result from double earth faul

43、t and line to line to earth. 3.1.8 earth potential rise, EPR UE: Voltage between an earthing system and reference earth. 3.1.9 electric resistivity of soil, E: Resistivity of a typical sample of soil. Rec. ITU-T K.104 (03/2015) 3 3.1.10 earthing system b-Electropedia: (definition 604-04-02) Arrangem

44、ent of connections and devices necessary to earth equipment or a system separately or jointly. 3.1.11 foundation earth electrode b-Electropedia: (definition 826-13-08, modified) Conductive structural embedded in concrete which is in conductive contact with the earth via a large surface. 3.1.12 globa

45、l earthing system: Equivalent earthing system created by the interconnection of local earthing systems that ensures, by the proximity of the earthing systems, that there are no dangerous touch voltages. NOTE 1 Such systems permit the division of the earth fault current in a way that results in a red

46、uction of the earth potential rise at the local earthing system. Such a system could be said to form a quasi equipotential surface. NOTE 2 The existence of a global earthing system may be determined by sample measurements or calculation for typical systems. Typical examples of global earthing system

47、s are in city centres; urban or industrial areas with distributed low- and high-voltage earthing. 3.1.13 high voltage (HV) b-Electropedia: (definition 151-15-05) Voltage having a value above a conventionally adopted limit. NOTE 1 An example is the set of upper voltage values used in bulk power syste

48、ms. NOTE 2 In the case of a three-phase system the voltage refers to the line-to-line voltage. 3.1.14 impedance to earth, Ze: Impedance at a given frequency between a specified point in a system or in an installation or in equipment and reference earth. NOTE The impedance to earth is determined by t

49、he directly connected earth electrodes and also by connected overhead earth wires and wires buried in earth of overhead lines, by connected cables with earth electrode effect and by other earthing systems which are conductively connected to the relevant earthing system by conductive cable sheaths, shields, PEN conductors or in another way. 3.1.15 low voltage (LV) b-Electropedia: (definition 151-15-03) Voltage having a value below a conventionally ado