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InternationalTelecommunicationUnionITU-TK.20TELECOMMUNICATIONSTANDARDIZATIONSECTOROFITU(04/2008)SERIESK:PROTECTIONAGAINSTINTERFERENCEResistibilityoftelecommunicationequipmentinstalledinatelecommunicationscentretoovervoltagesandovercurrentsRecommendationITU-TK.20Rec.ITU-TK.20(04/2008)iRecommendationITU-TK.20ResistibilityoftelecommunicationequipmentinstalledinatelecommunicationscentretoovervoltagesandovercurrentsSummaryRecommendationITU-TK.20specifiesresistibilityrequirementsandtestproceduresfortelecommunicationequipmentthatisinstalledinatelecommunicationcentre.OvervoltagesorovercurrentscoveredbythisRecommendationincludesurgesduetolightningonornearthelineplant,short-terminductionfromadjacenta.c.powerlinesorrailwaysystems,earthpotentialriseduetopowerfaults,directcontactsbetweentelecommunicationlinesandpowerlinesandelectrostaticdischarges.Thesourcesforovervoltagesininternallines,betweenequipment/racks,aremainlyinductivecouplingcausedbylightningcurrentsbeingconductedinnearbylightningstrokesorlightningcurrentsbeingconductedinnearbyconductors.Majorchangescomparedwiththe2003versionofthisRecommendationinclude:•removingthepowerinductiontestrequirementforantennaportswheretheinstallationiswithinthescopeofRecommendationITU-TK.71;•additionofinformationonequipmentincludedandexcludedinscope;•clearerdefinitionofwhentheinternalandexternalportclassificationappliestoantennaports.SourceRecommendationITU-TK.20wasapprovedon13April2008byITU-TStudyGroup5(2005-2008)underRecommendationITU-TA.8procedure.iiRec.ITU-TK.20(04/2008)FOREWORDTheInternationalTelecommunicationUnion(ITU)istheUnitedNationsspecializedagencyinthefieldoftelecommunications,informationandcommunicationtechnologies(ICTs).TheITUTelecommunicationStandardizationSector(ITU-T)isapermanentorganofITU.ITU-Tisresponsibleforstudyingtechnical,operatingandtariffquestionsandissuingRecommendationsonthemwithaviewtostandardizingtelecommunicationsonaworldwidebasis.TheWorldTelecommunicationStandardizationAssembly(WTSA),whichmeetseveryfouryears,establishesthetopicsforstudybytheITU-Tstudygroupswhich,inturn,produceRecommendationsonthesetopics.TheapprovalofITU-TRecommendationsiscoveredbytheprocedurelaiddowninWTSAResolution1.InsomeareasofinformationtechnologywhichfallwithinITU-T'spurview,thenecessarystandardsarepreparedonacollaborativebasiswithISOandIEC.NOTEInthisRecommendation,theexpressionAdministrationisusedforconcisenesstoindicatebothatelecommunicationadministrationandarecognizedoperatingagency.CompliancewiththisRecommendationisvoluntary.However,theRecommendationmaycontaincertainmandatoryprovisions(toensuree.g.interoperabilityorapplicability)andcompliancewiththeRecommendationisachievedwhenallofthesemandatoryprovisionsaremet.Thewordsshallorsomeotherobligatorylanguagesuchasmustandthenegativeequivalentsareusedtoexpressrequirements.TheuseofsuchwordsdoesnotsuggestthatcompliancewiththeRecommendationisrequiredofanyparty.INTELLECTUALPROPERTYRIGHTSITUdrawsattentiontothepossibilitythatthepracticeorimplementationofthisRecommendationmayinvolvetheuseofaclaimedIntellectualPropertyRight.ITUtakesnopositionconcerningtheevidence,validityorapplicabilityofclaimedIntellectualPropertyRights,whetherassertedbyITUmembersorothersoutsideoftheRecommendationdevelopmentprocess.AsofthedateofapprovalofthisRecommendation,ITUhadnotreceivednoticeofintellectualproperty,protectedbypatents,whichmayberequiredtoimplementthisRecommendation.However,implementersarecautionedthatthismaynotrepresentthelatestinformationandarethereforestronglyurgedtoconsulttheTSBpatentdatabaseat©ITU2009Allrightsreserved.Nopartofthispublicationmaybereproduced,byanymeanswhatsoever,withoutthepriorwrittenpermissionofITU.Rec.ITU-TK.20(04/2008)iiiCONTENTSPage1Scope............................................................................................................................12References.....................................................................................................................13Definitionsandabbreviations.......................................................................................14Tests..............................................................................................................................2AppendixI–Floatingtransversepowerinductionandearthpotentialrisetestforportsconnectedtoexternalsymmetricpaircables................................................................20I.1Introduction....................................................................................................20I.2Discussiononthereasonforthedamages......................................................20I.3Testset-upandtestvoltages...........................................................................21Bibliography.............................................................................................................................22Rec.ITU-TK.20(04/2008)1RecommendationITU-TK.20Resistibilityoftelecommunicationequipmentinstalledinatelecommunicationscentretoovervoltagesandovercurrents