IEC_60071-2ed3.0en-d.pdf

Insulation co-ordination Part 2:Application guideReference numberIEC 60071-2:1996(E)INTERNATIONALSTANDARDIEC60071-2Third edition1996-12This English-language version is derived from the originalbilingual publication by leaving out all French-languagepages.Missing page numbers correspond to the French-language pages.Publication numbering As from 1 January 1997 all IEC publications are issued with a designation in the 60000 series.For example,IEC 34-1 is now referred to as IEC 60034-1.Consolidated editions The IEC is now publishing consolidated versions of its publications.For example,edition numbers 1.0,1.1 and 1.2 refer,respectively,to the base publication,the base publication incorporating amendment 1 and the base publication incorporating amendments 1 and 2.Further information on IEC publications The technical content of IEC publications is kept under constant review by the IEC,thus ensuring that the content reflects current technology.Information relating to this publication,including its validity,is available in the IEC Catalogue of publications(see below)in addition to new editions,amendments and corrigenda.Information on the subjects under consideration and work in progress undertaken by the technical committee which has prepared this publication,as well as the list of publications issued,is also available from the following:IEC Web Site(www.iec.ch)Catalogue of IEC publications The on-line catalogue on the IEC web site(www.iec.ch/searchpub)enables you to search by a variety of criteria including text searches,technical committees and date of publication.On-line information is also available on recently issued publications,withdrawn and replaced publications,as well as corrigenda.IEC Just Published This summary of recently issued publications(www.iec.ch/online_news/justpub)is also available by email.Please contact the Customer Service Centre(see below)for further information.Customer Service Centre If you have any questions regarding this publication or need further assistance,please contact the Customer Service Centre:Email:custserviec.ch Tel:+41 22 919 02 11 Fax:+41 22 919 03 00 Insulation co-ordination Part 2:Application guideFor price,see current catalogue IEC 1996 Copyright-all rights reservedNo part of this publication may be reproduced or utilized in any form or by any means,electronic or mechanical,including photocopying and microfilm,without permission in writing from the publisher.International Electrotechnical Commission,3,rue de Varemb,PO Box 131,CH-1211 Geneva 20,SwitzerlandTelephone:+41 22 919 02 11 Telefax:+41 22 919 03 00 E-mail:inmailiec.ch Web:www.iec.chINTERNATIONALSTANDARDIEC60071-2Third edition1996-12XFCommission Electrotechnique InternationaleInternational Electrotechnical Commission PRICE CODE71-2 IEC:1996 3 CONTENTSPageFOREWORD.9Clause1General.111.1 Scope.111.2 Normative references.111.3 List of symbols and definitions.132Representative voltage stresses in service.212.1 Origin and classification of voltage stresses.212.2 Characteristics of overvoltage protective devices.232.3 Representative voltages and overvoltages.273Co-ordination withstand voltage.573.1 Insulation strength characteristics.573.2 Performance criterion.653.3 Insulation co-ordination procedures.674Required withstand voltage.834.1 General remarks.834.2 Atmospheric correction.834.3 Safety factors.875Standard withstand voltage and testing procedures.915.1 General remarks.915.2 Test conversion factors.935.3 Determination of insulation withstand by type tests.956Special considerations for overhead lines.1036.1 General remarks.1036.2 Insulation co-ordination for operating voltages and temporary overvoltages.1036.3 Insulation co-ordination for slow-front overvoltages.1056.4 Insulation co-ordination for lightning overvoltages.1057Special considerations for substations.1077.1 General remarks.1077.2 Insulation co-ordination for overvoltages.111Tables1Recommended creepage distances.712Test conversion factors for range I,to convert required switching impulses withstand voltages to short-duration power-frequency and lightning impulse withstand voltages.933Test conversion factors for range II to convert required short-duration power-frequencywithstand voltages to switching impulse withstand voltages.954Selectivity of test procedures B and C of IEC 60-1.99A.1 Correlation between standard lightning impulse withstand voltages and minimum airclearances.119A.2 Correlation between standard switching impulse withstand voltages andminimum phase-to-earth air clearances.121A.3 Correlation between standard switching impulse withstand voltages andminimum phase-to-phase air clearances.121C.1 Breakdown voltage versus cumulative flashover probability Single insulationand 100 parallel insulations.13571-2 IEC:1996 5 F.1 Corona damping constant Kco.175F.2 Factor A for various overhead lines.185G.1 Typical gap factors K for switching impulse breakdown phase-to-earth.195G.2 Gap factors for typical phase-to-phase geometries.197H.1 Summary of minimu