IEC_60076-5ed2.0en-d.pdf

Power transformers Part 5:Ability to withstand short circuit Reference number IEC 60076-5:2000(E)INTERNATIONAL STANDARD IEC60076-5 Second edition2000-07 This English-language version is derived from the original bilingual publication by leaving out all French-language pages.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committees and date of publication.On-line information is also available on recently issued publications,withdrawn and replaced publications,as well as corrigenda.IEC Just Published This summary of recently issued publications(www.iec.ch/online_news/justpub)is also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 Power transformers Part 5:Ability to withstand short circuit For price,see current catalogue IEC 2000 Copyright-all rights reserved No 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.ch INTERNATIONAL STANDARD IEC60076-5 Second edition2000-07 S Commission Electrotechnique InternationaleInternational Electrotechnical Commission PRICE CODE 60076-5 IEC:2000 3 CONTENTSPageFOREWORD.5Clause1Scope.92Normative references.93Requirements with regard to ability to withstand short circuit.93.1General.93.2Overcurrent conditions.114Demonstration of ability to withstand short circuit.174.1Thermal ability to withstand short circuit.174.2Ability to withstand the dynamic effects of short circuit.23Annex A(informative)Guidance for the identification of a similar transformer.41Annex B(normative)Calculation method for the demonstration of the abilityto withstand the dynamic effects of short circuit.43Figure 1 Star/delta connected transformer.29Figure 2 Star/star auto-transformer.31Table 1 Recognized minimum values of short-circuit impedance for transformerswith two separate windings.13Table 2 Short-circuit apparent power of the system.13Table 3 Maximum permissible values of the average temperature of each windingafter short circuit.21Table 4 Values for factor k 2.2560076-5 IEC:2000 5 INTERNATIONAL ELECTROTECHNICAL COMMISSION_POWER TRANSFORMERS Part 5:Ability to withstand short circuitFOREWORD1)The IEC(International Electrotechnical Commission)is a worldwide organization for standardization comprisingall national electrotechnical committees(IEC National Committees).The object of the IEC is to promoteinternational co-operation on all questions concerning standardization in the electrical and electronic fields.Tothis end and in addition to other activities,the IEC publishes International Standards.Their preparation isentrusted to technical committees;any IEC National Committee interested in the subject dealt with mayparticipate in this preparatory work.International,governmental and non-governmental organizations liaisingwith the IEC also participate in this preparation.The IEC collaborates closely with the InternationalOrganization for Standardization(ISO)in accordance with conditions determined by agreement between thetwo organizations.2)The formal decisions or agreements of the IEC on technical matters express,as nearly as possible,aninternational consensus of opinion on the relevant subjects since each technical committee has representationfrom all interested National Committees.3)The documents produced h