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.107 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2015) SERIES K: PROTECTION AGAINST INTERFERENCE Method for determining the impedance to earth of earthing systems Recommendation ITU-T K.107 Rec. ITU-T K.107 (11/201
2、5) i Recommendation ITU-T K.107 Method for determining the impedance to earth of earthing systems Summary Telecommunication systems are vulnerable to the earth potential rise (EPR) that can occur in power systems, and they are also vulnerable to the transfer of EPR outside the zone of influence (ZOI
3、), which should also be considered. A quick estimate of the earth potential rise is obtained from the product (Ie Re) of the current Ie flowing through an earth electrode and the resistance Re to earth of that earth electrode. Recommendation ITU-T K.107 provides methods of varying complexity for mea
4、suring the resistance to earth of earth electrodes or even complex earthing systems. The methods provide describe both simple and more sophisticated measurements through the use of computer-based earthing multimeters. Guidance is given on the relevance of each of the different methods for various pu
5、rposes. Techniques are also given for the elimination of interference and disturbance voltages for earthing measurements. In practice it may be necessary to determine or at least estimate the impedance to earth of a power system installation already in the design phase. For these purposes, technique
6、s of calculating the resistance/impedance to earth of isolated, as well as interconnected earthing systems are also included. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T K.107 2015-11-29 5 11.1002/1000/12672 Keywords Earth electrode effect, earth fault, earth potential r
7、ise, EPR, fall-of-potential, impedance to earth, multi-earthed, screening factor. * 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, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. I
8、TU-T K.107 (11/2015) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is
9、 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
10、 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 purview, the necessary standards are prepared on a colla
11、borative 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 certa
12、in 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 requirem
13、ents. 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 the use of a claimed Intellectual Property Right. I
14、TU 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
15、 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 2016 All rights res
16、erved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T K.107 (11/2015) iii 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
17、Abbreviations and acronyms 4 5 Conventions 5 6 Characteristics of the impedance to earth . 5 6.1 General . 5 6.2 Impedance to earth . 5 7 Methods of measuring the resistance/impedance to earth 6 7.1 General . 6 7.2 Measuring methods 6 8 Methods of determining the resistance/impedance to earth by cal
18、culation 15 8.1 Equations for calculating impedance to earth of a stand-alone earth electrode . 15 Bibliography. 22 Rec. ITU-T K.107 (11/2015) 1 Recommendation ITU-T K.107 Method for determining the impedance to earth of earthing systems 1 Scope The earth potential rise (EPR) that can occur in power
19、 systems and that can be transferred to telecommunication systems is potentially dangerous to the people working in the telecommunication plant; damage to the plant itself can also occur. The impedance to earth of earthing systems of a power installation is one of the key parameters affecting the ma
20、gnitude of the EPR. This Recommendation aims to provide methods of different complexities for measuring the resistance to earth of earth electrodes or complex earthing systems. Techniques for calculating the resistance/impedance to earth of isolated, as well as interconnected earthing systems are al
21、so included. 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 subje
22、ct 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 w
23、ithin this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. 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.104 Recommendation ITU-T K.104
24、(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 networks. IEEE Std 81 IEEE Std 81 (2012), IEEE Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials
25、 of a Grounding System. EN 50522 Cenelec EN 50522 (2010), Earthing of power installations exceeding 1 kV a.c. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 cable with earth electrode effect EN 50522: (definition 3.4.33) Cable whose sh
26、eaths, screens or armourings have the same effect as a strip earth electrode. 3.1.2 circulating transformer neutral current EN 50522: (definition 3.4.31) Portion of fault current which flows back to the transformer neutral point via the metallic parts and/or the earthing system without ever discharg
27、ing into soil. 3.1.3 (local) earth b-IEC IEV: (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
28、conventionally taken as equal to zero. 2 Rec. ITU-T K.107 (11/2015) 3.1.4 earth electrode EN 50522: (definition 3.4.3) Earth electrode conductive part, which may be embedded in a specific conductive medium, e.g., in concrete or coke, in electric contact with the earth. 3.1.5 earth fault b-IEC IEV: (
29、definition 151-03-40) Fault caused by a conductor being connected to earth or by the insulation resistance to earth becoming less than a specified value. 3.1.6 earth fault current, IF EN 50522: (definition 3.4.28) Current which flows from the main circuit to earth or earthed parts at the fault locat
30、ion. NOTE 1 For single earth faults, this is: in systems with isolated neutral, the capacitive earth fault current, in systems with 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 impedanc
31、e neutral earthing, the line-to-earth short-circuit current. NOTE 2 Further earth fault current may result from double earth fault and line to line to earth. 3.1.7 earth potential rise, EPR UE EN 50522: (definition 3.4.12) Voltage between an earthing system and reference earth. 3.1.8 earthing conduc
32、tor b-IEC IEV: (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 part of the installation and the earth electrode is made
33、 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. 3.1.9 earthing system b-IEC IEV: (definition 604-04-02) Arrangement of connections and
34、 devices necessary to earth equipment or a system separately or jointly. 3.1.10 electric resistivity of soil, E EN 50522: (definition 3.4.9) Resistivity of a typical sample of soil. 3.1.11 foundation earth electrode b-IEC IEV: (definition 826-13-08, modified) Conductive structural embedded in concre
35、te which is in conductive contact with the earth via a large surface. 3.1.12 high voltage (HV) IEC 60050-151:2001, 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 systems. NOTE 2 In the case of three phas
36、e system the voltage refers to the line-to-line voltage. 3.1.13 impedance to earth, Ze EN 50522: (definition 3.4.11) 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 the direct
37、ly 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, P
38、EN conductors or in another way. 3.1.14 low voltage (LV) b-IEC IEV: (definition 151-15-03) Voltage having a value below a conventionally adopted limit. NOTE 1 For the distribution of AC electric power, the upper limit is generally accepted to be 1000 V. NOTE 2 In the case of three phase system the v
39、oltage refers to the line-to-line voltage. 3.1.15 medium voltage (MV) b-IEC IEV: (definition 601-01-28) (not used in the UK in this sense, nor in Australia). Any set of voltage levels lying between low and high voltage. NOTE 1 The boundaries between medium and high voltage levels overlap and depend
40、on local circumstances and history or common usage. Nevertheless, the band 30 kV to 100 kV frequently contains the accepted boundary. Rec. ITU-T K.107 (11/2015) 3 NOTE 2 The medium voltage is not a standardized term. It is specified as a system voltage class by IEEE b-Terms. NOTE 3 The preferred med
41、ium nominal (line-to-line) voltages in North America: 4.16 kV, 12.46 kV, 13.8 kV, 34.5 kV and 69 kV b-Terms. Typical MV system voltages for public distribution: in Europe 10 kV (mainly underground) 20 kV and 35 kV (mainly overhead) b-Lacroix, in Japan 6.6 kV. 3.1.16 multi-earthed HV neutral conducto
42、r EN 50522: (definition 3.4.20) Neutral conductor of a distribution line connected to the earthing system of the source transformer and regularly earthed. 3.1.17 PEN conductor b-IEC IEV: (definition 826-13-25) Conductor combining the functions of both protective earthing conductor and neutral conduc
43、tor. 3.1.18 potential EN 50522: (definition 3.4.13) Voltage between an observation point and reference earth. 3.1.19 protective bonding conductor EN 50522: (definition 3.4.5) Protective conductor for ensuring equipotential bonding. 3.1.20 reduction factor, r or screening factor ks EN 50522: (definit
44、ion 3.4.30) Factor r of a three phase line is the ratio of the current to earth IE over the sum of the zero sequence currents 3I0 in the phase conductors of the main circuit (r = IE / 3 I0) at a point remote from the short-circuit location and the earthing system of an installation, (also referred t
45、o as screening factor, ks). 3.1.21 reference earth b-IEC IEV: (definition 195-01-01, modified) (remote earth) Part of the earth considered as conductive, the electric potential of which is conventionally taken as zero, being outside the zone of influence of the relevant earthing arrangement. NOTE Th
46、e concept “earth“ means the planet and all its physical matter. 3.1.22 resistance to earth, Re EN 50522: (definition 3.4.10) Real part of the impedance to earth. 3.1.23 solidly earthed neutral system IEC 601-02-25:1985: System whose neutral point(s) is(are) earthed directly. 3.1.24 structural earth
47、electrode EN 50522: (definition 3.4.8) Metal part, which is in conductive contact with the earth or with water directly or via concrete, whose original purpose is not earthing, but which fulfils all requirements of an earth electrode without impairment of the original purpose. NOTE Examples of struc
48、tural earth electrodes are pipelines, sheet piling, concrete reinforcement bars in foundations and the steel structure of buildings, etc. 3.1.25 substation b-IEC IEV: (definition 605-01-01) Part of a power system, concentrated in a given place, including mainly the terminations of transmission or di
49、stribution lines, switchgear and housing and which may also include transformers. It generally includes facilities necessary for system security and control (e.g., the protective devices). NOTE According to the nature of the system within which the substation is included, a prefix may qualify it. EXAMPLE Transmission substation (of a transmission system), distribution substation, 400 kV substation, 20 kV substation. 3.1.26 system with isolated neutral b-IEC IEV: (definitio
