1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationEarthing of power installations exceeding 1 kV a.c.BS EN 50522:2010Incorporating corrigendum September 2012BS EN 50522:2010National forewordThis British Standard is the UK implem
2、entation of EN 50522:2010.Together with BS EN 61936-1:2010, it partially supersedes BS 7354:1990. Where conflict exists between BS EN 50522:2010 and BS 7354:1990 the provisions of BS EN 50522:2010 take precedence.The UK participation in its preparation was entrusted to Technical Committee PEL/99, Er
3、ection and operation of power installations. Preparation of this National Foreword and the National Annexes was entrusted to both PEL/99 and Technical Committee GEL/600, Earthing. A list of organizations represented on these committees can be obtained on request to their secretaries.NOTE To ensure w
4、ide participation in the process, GEL/600, in particular, has strengthened its membership to include more representation from the UK Electricity Supply industry (TSOs and DNOs) and an earthing test equipment manu-facturer. Furthermore, detailed consultation has been carried out with The Energy Netwo
5、rks Association (ENA) through its Earthing Co-ordination Group.National Annexes NA, NB and NC have been appended to this standard.Background and developments to IEC/CENELEC documentsIn recent years, two documents have existed side-by-side covering, among other things, the earthing of high voltage in
6、stallations. The first was HD 637 S1, Power installations exceeding 1kV, published in 1999 while the other was IEC 61936-1, of the same title, published in 2002. These docu-ments were produced by working groups of the committees CENELEC TC/99X and IEC TC/99, respectively. As these documents were not
7、 published at the same time and the composition of the working groups was to some extent different, a situation arose such that significant discrepancies existed between these two documents, notably, concerning the fundamental safety criterion of allowable human body current and body impedance value
8、s under step and touch voltage conditions. This situation was not ideal, and an initiative was taken to develop a revision to IEC 61936-1 under maintenance team IEC TC/99 MT4 and to release it as a European standard. At the same time, a working group CENELEC TC/99X WG1 was formed to extract the eart
9、hing content of HD 637 S1 and bring to publication a new European standard on earthing (EN 50522). Parallel voting of EN 61936-1 and EN 50522 was arranged, in order to achieve harmonization of the adopted electrocution safety criteria and both documents were published in 2010.Background and developm
10、ent of UK earthing design standardsOver a similar period, within the UK, there were three important concurrent documents concerning the earthing of HV power installations. The first, BS 7354:1990, Code of practice for design of high-voltage open-terminal stations, prepared by Technical Committee PEL
11、/92, covered similar topics to IEC 61936-1, with Section 7 devoted to earthing. The other two documents, exclusively concerning earthing, were published by the Energy Networks Association, and can be considered as a set. These are Technical Specification 41/24 Issue 1 1992, Guidelines for the instal
12、lation, testing and maintenance of main earthing systems in sub-stations and Engineering Recommendation S34, Amendment 2 1988, A guide for assessing the rise of earth potential at substation sites.BRITISH STANDARDIn the period of the preparation of EN 61936-1 and EN 50522, the BSI committees GEL/600
13、 and PEL/99 coordinated activities with the aim to:a) achieve pro-active representation of UK interests on CENELEC TC/99X and IEC TC/99 working groups; and b) bring about a harmonization of the criteria for station earthing design in the UK. From this work, the following important aspects of the Nat
14、ional Annexes in this document that differ from the EN 50522 are worth highlighting.1) Recognition of the probabilistic nature of electrical system safety There has been a reaffirmation in BS EN 61936-1:2010 of the explicit recognition that the parameters involved in assessing safety are probabilist
15、ic in nature, with regard to the fault current magnitude and duration, as well as the probability of the fault occurrence, and the pres-ence probability of a human being. This has led to the introduction of a new additional approach to earthing system design in the UK based on probabilistic methods,
16、 which is outlined in National Annex NA using a design flow chart and developed with case studies in National Annex NB.2) Deviations of UK safety limits compared to IEC/CENELEC limits The release of DD IEC/TS 60479-1:2005, Effects of current on human beings and livestock Part 1: General aspects, pro
17、vided new data on human electrocution safety parameters; specifically new and lower values of human body impedances. The CENELEC and IEC working groups were concerned that this would result in lower maximum tolerable values of touch voltages, and as a result, proposed a modified method for calculati
18、ng such voltagesbased on an average of different shock scenarios and based on bodyimpedances not exceeded for 50% of the population (note, the first editionof IEC 61936-1 was based on left-hand to feet body impedances notexceeded for 5% of the population). However, as a result of adviceobtained from
19、 the UK Health and Safety Executive (HSE), consensuswas reached between PEL/99 and GEL/600 that UK HV earthing systemshave to be designed according to tolerable voltages based on bodyimpedances not exceeded for 5% of the population, as given inDD IEC/TS 60479-1:2005, Table 1 (Column 2) rather than t
20、he 50% values(Column 3). Also worth noting has been the consensus among PEL/99and GEL/600 to move away from using the tolerable body current curvec1 to curve c2 from DD IEC/TS 60479-1:2005, again, based onadvice from the UK HSE. This marks a departure from the very strict deterministic limits observ
21、ed previously under ENATS 41-24. However,the reduction in values of IEC published body impedances means thatthe resultant values of tolerable voltages are not greatly affected and certainly not reduced.Accordingly, the UK obtained a variation to the new CENELEC and IEC standards which has been recog
22、nized in the foreword of BS EN 61936-1:2010 and BS EN 50522:2010, Annex Q (A-Deviations). Hence, these documents specify the required difference in approach to earthing design in the UK, based on the 5% body impedance values. This variation affects the fundamental design parameters and in National A
23、nnex NA, a revised set of tolerable voltage curves has been produced to replace EN 50522:2010, Figure 4 (Section 5.4.3) and Figure B.2 (Annex B). The new UK tolerable touch voltage figures are given in National Annex NA.3) Additional guidance on assessing fault current distribution, earth potential
24、rise, design and testing of earthing systems Differences in the UK approach to earthing designBS EN 50522:2010BS EN 61936-1:2010 partially supersedes BS 7354:1990, and in particular it supersedes the earthing section of BS 7354. However, EN 50522:2010 does not provide sufficient detailed guidance on
25、 specific aspects of design and testing of earthing systems. In view of this, the committees PEL/99 and GEL/600 have decided to recommend that reference is made to ENAS 34 for recommendations and guidance on assessing rise of earth potential and to ENATS 41-24 for recommendations and guidance for th
26、e design, installation, testing and maintenance of earthing systems in substations. It should be emphasised that the tolerable safety limits contained in ENAS 34 and ENATS 41-24 are not applicable and it is noted that both ENAS 34 and ENATS 41-24 are expected to be revised in the near future to take
27、 into account the new safety limits, as given in Annex A of this document.4) Recognition of the use of computer-aided earthing design toolsOver the past 20 years, UK power companies and consultants have increasingly relied on the use of computer-aided earthing design tools. It is recognized that com
28、putation of earth impedances and prospective safety voltages for complex earthing systems and soils using simplified equations may lead to inaccurate safety assessments. Accordingly, modern computa-tion software tools may be employed. It is advisable to verify calculated values through direct testin
29、g of the installation on commissioning and periodically throughout its lifetime. Additional guidance on earth system testing is given in National Annex NC.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The B
30、ritish Standards Institution 2012Published by BSI Standards Limited 2012ISBN 978 0 580 80537 0ICS 29.120.50Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 3 2012
31、.Amendments/corrigenda issued since publicationDate Text affected30 September 2012 National foreword / national annex correction0 SeptemberBS EN 50522:2010EUROPEAN STANDARD EN 50522 NORME EUROPENNE EUROPISCHE NORM November 2010 CENELEC European Committee for Electrotechnical Standardization Comit Eu
32、ropen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Management Centre: Avenue Marnix 17, B - 1000 Brussels 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 50522:2010 E ICS 29.120.50 Supers
33、edes HD 637 S1:1999 (partially) English version Earthing of power installations exceeding 1 kV a.c. Prises de terre des installations lectriques en courant alternatif de puissance suprieure 1 kV Erdung von Starkstromanlagen mit Nennwechselspannungen ber 1 kV This European Standard was approved by CE
34、NELEC on 2010-11-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national stand
35、ards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and noti
36、fied to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
37、 Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. 2 Foreword This European Standard was prepared by the Technical Committee CENELEC TC 99X, Power installations exceeding 1 kV a.c. (1,5 kV d.c.). I
38、t was submitted to formal vote and was accepted by CENELEC as EN 50522 on 2010-11-01. Together with EN 61936-1:2010 this document supersedes HD 637 S1:1999. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and CENELEC shall not
39、 be held responsible for identifying any or all such patent rights. The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2011-11-01 latest date by which the national standards conf
40、licting with the EN have to be withdrawn (dow) 2013-11-01 NOTE The text identical with IEC 61936-1 is written in italics. _ BS EN 50522:2010 EN 50522:2010 (E) 3 Contents 1 Scope .6 2 Normative references .7 3 Terms and definitions .8 3.1 General definitions .8 3.2 Definitions concerning installation
41、s 8 3.3 Definitions concerning safety measures against electric shock .9 3.4 Definitions concerning earthing 9 4 Fundamental requirements 18 4.1 General requirements 18 4.2 Electrical requirements .18 4.3 Safety criteria .19 4.4 Functional requirements .20 5 Design of earthing systems 20 5.1 General
42、 20 5.2 Dimensioning with respect to corrosion and mechanical strength .20 5.3 Dimensioning with respect to thermal strength 21 5.4 Dimensioning with regard to touch voltages 23 6 Measures to avoid transferred potential .27 6.1 Transferred potential from High voltage systems to Low voltage systems 2
43、7 6.2 Transferred potentials to telecommunication and other systems 28 7 Construction of earthing systems .29 7.1 Installation of earth electrodes and earthing conductors .29 7.2 Lightning and transients .29 7.3 Measures for earthing on equipment and installations 30 8 Measurements 30 9 Maintainabil
44、ity .30 9.1 Inspections .30 9.2 Measurements .30 Annex A (normative) Method of calculating permissible touch voltages .31 Annex B (normative) Touch voltage and body current .32 B.1 Calculation of permissible touch voltage .32 B.2 Calculation of prospective permissible touch voltage 33 Annex C (norma
45、tive) Type and minimum dimensions of earth electrode materials ensuring mechanical strength and corrosion resistance 36 Annex D (normative) Current rating calculation of earthing conductors and earth electrodes .37 Annex E (normative) Description of the recognized specified measures M .41 Annex F (n
46、ormative) Measures on earthing systems to reduce the effects of high frequency interference 44 Annex G (normative) Detailed measures for earthing of equipment and installations 45 G.1 Fences around substation installations .45 G.2 Pipes .45 G.3 Traction rails 45 G.4 Pole mounted transforming and/or
47、switching installations 45 G.5 Secondary circuits of instrument transformers 46 BS EN 50522:2010 EN 50522:2010 (E) 4 Annex H (normative) Measuring touch voltages .47 Annex I (informative) Reduction factors related to earth wires of overhead lines and metal sheaths of underground cables .48 I.1 Gener
48、al .48 I.2 Typical values of reduction factors of overhead lines and cables (50 Hz) 48 Annex J (informative) Basis for the design of earthing systems .50 J.1 Soil resistivity 50 J.2 Resistance to earth 50 Annex K (informative) Installing the earth electrodes and earthing conductors 54 K.1 Installati
49、on of earth electrodes .54 K.2 Installation of earthing conductors .54 Annex L (informative) Measurements for and on earthing systems 56 L.1 Measurement of soil resistivities 56 L.2 Measurement of resistances to earth and impedances to earth 56 L.3 Determination of the earth potential rise 57 L.4 Elimination of interference and disturbance voltages for earthing measurements 58 Annex M (normative) Details on site inspection and documentation of earthing systems 61 Annex N (informative) The use of reinforcing bars in concrete for earthing purpos
