IEC_TR_60099-3-1990_scan.pdf

RAPPORTCEiTECHNIQUEIECTECHNICAL99-3REPORTPremiere editionFirst edition1990-08。ParafoudresPartie 3:Essais de pollution artificielle des parafoudresSurge arrestersPart 3:Artificial pollution testing of surge arrestersCEI 1990 Droits de reproduction reserves-Copyright-ali rights reservedAucune partie de cette publication ne peut itre reproduite ni utiliseeNo parof this publicationmay be reprodudd in any formsous quelque forme que ce soit et par aucn procide.ilectroniquece by amy means.electronie or mechanical,including photocopynyand microfilm.without permission in writing from the publisher.Bureau Central de la Commission Electrotechniquenterationale3.rue de Varembe Geneve,SuisseCommission Electrotechnique InternationaleCODE PRIXInternational Electrotechnical CommissionPRICE CODEPoor prir,voir catalogve en viguewFor price.see en27n.54199-3IEC-3-CONTENTSPageForeword,.Clause1 Scope.72 Normative references3 Basic principles.14 Test objective.95General requirements116Voltage application157 Test procedure158 Methods of applying pollution.,179 Solid pollutants for the methods of 8.3 and 8.42110Pollutants for trial use with the methods of8.3or8.4.,.23g9-3IEC-5-INTERNATIONAL ELECTROTECHNICAL COMMISSIONSURGE ARRESTERSPart 3:Artificial pollution testing of surge arrestersFOREWORD1)The formal decisions or agreements of the IEC on technical matters,prepared by Technical Committees on which all theNational Committees having a special interest therein are represented.express.as nearly as possible.an internationalconsensus of opinion on the subjects dealt with.2)They have the form of recommendations for international use and they are accepted by the National Committees in thatsense.In order to promote international unification.theIECexpresses the wish that all National Committees should adopi the iextof the IEC recommendation for their national rules in so far as national conditions will permit.Any divergence between theIEC recommendation and the corresponding national rules should.as far as possible.be clearly indicated in the latter.This Technical Report has been prepared by IEC Technical Committee No.37:Surge arresters.It replaces and cancels Appendix D of Publication 99-1(1970).A new edition of Publication 99-1 isbeing prepared.The text of this report is based on the following documents:Six MonthsRuleReport on Voting37(C0)2437(C0)27Full information on the voting for the approval of this.report can be found in the Voting Reportindicated in the above table.9-3.IEC-7-SURGE ARRESTERSPart 3:Artificial pollution testing of surge arresters1 ScopeThis Technical Report gives the basic principles of artificial pollution testing of non-linear resistor type(valve type)surge arresters,together with details of pollutant compositions and methods of applicationand the test procedures associated with each mode of pollution.2 Normative referencesThe following standards contain provisions which,through reference in this text,constitute provisionsofthis Technical Report.At the time of publication,the editions indicated were valid.All standards aresubject to revision,and parties to agreements based on this Technical Report are encouraged toinvestigate the possibility of applying the most recent editions of the standards indicated below.Members of IEC and ISO maintain registers of currently valid International Standards.IEC 99-1:1970,Lightning arresters-Part 1:Non-linear resistor type arresters for a.c.systems.IEC 507:1975,Artificial pollution tests on high-voltage insulators to be used on a.c.systems.3Basic principlesIt is well known that a surge arrester can fail at normal service voltage under certain pollutionconditions,owing to the setting up of a very uneven voltage distribution on its external surface and/orbecause of very rapid changes in this distribution.These two stages arise as a consequence of theformation under such conditions of an initially nearly continuous conducting surface layer consistingtypically of an aqueous solution of electrolyte formed under high humidity by the moisture pick-up ofhygroscopic solid particles or liquid droplets deposited on the surface.Dusts may also be present,affecting the washing and drying characteristics of the surface.It is well established also that the effectof Jeakage current heating the surface layer,when the conductivity is high enough,is to cause drybandsto form,across which most of the voltage drop occurs and that surges of leakage-current occurwhen these bands are temporarily bridged by an arc.These phenomena can result in the voltage applied across some of the gaps exceeding their sparkovervalue,with consequential failure,in some cases,through disturbance of the gap potentials caused bycapacitive coupling between electrodes and wet bands.It is consequently the primary purpose of artificial pollution testing of surge arresters to simulaterelevant pollution conditions,representative of those occurring in service and establishing that whensubjected to these,the surge arrester,energized at appropriate power-frequency voltage does not suffergap sparkover.99-3IEC-9-Pollution flashover of the surge arrester surface is a serious matter operationally,and the performancein this respect also must be determined.This is discussed in the following paragraphs.There is now evidence both from service and testing that the pollution conditions which may result insurge arrester sparkover can be generally different from those leading to surface flashover.The latter isassociated typically with severe conditions characterized by frequent high-amplitude leakage-currentsurges,whereas gap sparkover is typically associated with pollution onset or drying-out of the pollutant.Accordingly,separate tests for these two distinct modes of failure may be needed,at least with some testmethods.Some artificial pollution test methods for surface flashover of high-voltage insulators have beendeveloped to a stage where they are generally accepted as giving a valid indication of pollutionperformance.These are fully described in IEC 507.The essential common feature of the tests,eventhough there are differefices in the polluting techniques,are the repeatable production of variousdegrees or severitiesof pollution,measured,for example,in terms of specific conductance of thepollutant,application of a suitable test voltage and consequent determination of the performance interms of a given severity.The mode of operation of surge arresters,however,is such that the methods used for insulator testingare not directly applicable to surge arresters,especially in respect of arrester sparkover.The testsdescribed in this report,though broadly based on those ofIEC 507,are essentially aimed at meeting thespecial requirements for surge arrester operation and bear specifically on gap sparkover.The methods of IEC 507 are directly applicable to surface flashover of insulation,and it is accordinglyrecommended that they should be used to determine performance in this respect.It should be noted that the tests according to IEC 507 with respect to such surface flashover perfor-mance and those proposed here to check sparkover performance are recommended only for surgearresters exposed to natural pollution,possibly with live washing,and not for those subject to periodiccleaning or greasing.From the foregoing account of the failure mechanism it follows that for pollution tests of both kinds,itis essential that they be performed on a complete service surge arrester assembly.When sufficient experience has been gained from the tests described in the following clauses,thisexperience will form the basis of a type test.NOTE-In service.surge arresters sometimes suffer long-term deterioration associated with intemal corona discharges.The tests described in this report do not demonstrate the performance of the surge arrester in this respect.4 Test objective2灯The objective of the test is to establish that the surge arrester can withstand a specified severity ofpollution without sparkover when energized at a specified voltage or voltage-application mode,bothseverity and voltage mode being representative of service conditions.