IEC60287221995电缆电流定额的计算第2部分热阻第2节在室外敷防受阳光照射的电缆群的缩减因

BRITISHSTANDARDBS7769-2-2.1:1997IEC60287-2-1:1994IncorporatingAmendmentNo.1Electriccables—Calculationofthecurrentrating—Part2:Thermalresistance—Section2.1CalculationofthermalresistanceICS29.060.20

 
 LicensedCopy:LondonSouthBankUniversity,LondonSouthBankUniversity,TueMar1314:37:38GMT+00:002007,UncontrolledCopy,(c)BSIBS7769-2-2.1:1997ThisBritishStandard,havingbeenpreparedunderthedirectionoftheElectrotechnicalSectorBoard,waspublishedundertheauthorityoftheStandardsBoardandcomesintoeffecton15February1997©BSI24July2002ThefollowingBSIreferencesrelatetotheworkonthisstandard:CommitteereferenceGEL/20DraftannouncedinBSIUpdateMay1995ISBN0580269221CommitteesresponsibleforthisBritishStandardThepreparationofthisBritishStandardwasentrustedtoTechnicalCommitteeGEL/20,Electriccables,uponwhichthefollowingbodieswererepresented:AssociationofConsultingEngineersAssociationofManufacturersofDomesticElectricalAppliancesBEAMA(ElectricalCableandConductorAccessoryManufacturers’Association)BritishApprovalsServiceforCablesBritishCableMakersConfederationBritishIronandSteelProducers’AssociationBritishPlasticsFederationDepartmentofTradeandIndustry(ConsumerSafetyUnit,CAdivision)ElectricityAssociationLondonRegionalTransportThefollowingbodieswerealsorepresentedinthedraftingofthestandard,throughsubcommitteesandpanels:ERATechnologyLtd.InstitutionofIncorporatedExecutiveEngineersLondonUndergroundLtd.AmendmentsissuedsincepublicationAmd.No.DateComments1366524July2002SeenationalforewordLicensedCopy:LondonSouthBankUniversity,LondonSouthBankUniversity,TueMar1314:37:38GMT+00:002007,UncontrolledCopy,(c)BSI电缆情缘BS7769-2-2.1:1997©BSI24July2002iContentsPageCommitteesresponsibleInsidefrontcoverNationalforewordiiIntroduction11General11.1Scope11.2Symbols22Calculationofthermalresistances32.1Thermalresistanceoftheconstituentpartsofacable,T1,T2andT342.2ExternalthermalresistanceT493Digitalcalculationofquantitiesgivengraphically143.1General163.2Calculationof
sbymeansofadiagram(Figure8)19Figure1—Diagramshowingagroupofqcablesandtheirreflectionintheground-airsurface22Figure2—GeometricfactorGfortwo-corebeltedcableswithcircularconductors23Figure3—GeometricfactorGforthree-corebeltedcableswithcircularconductors24Figure4—Thermalresistanceofthree-corescreenedcableswithcircularconductorscomparedtothatofacorrespondingunscreenedcable25Figure5—Thermalresistanceofthree-corescreenedcableswithsector-shapedconductorscomparedwiththatofacorrespondingunscreenedcable26Figure6—GeometricfactorforobtainingthethermalresistancesofthefillingmaterialbetweenthesheathsandarmourofSLandSAtypecables27Figure7—Heatdissipationcoefficientforblacksurfacesofcablesinfreeair28Figure8—Graphforthecalculationofexternalthermalresistanceofcablesinair31Table1—Thermalresistivitiesofmaterials20Table2—ValuesforconstantsZ,Eandgforblacksurfacesofcablesinfreeair21Table3—Absorptioncoefficientofsolarradiationforcablesurfaces22Table4—ValuesofconstantsU,VandY22GLicensedCopy:LondonSouthBankUniversity,LondonSouthBankUniversity,TueMar1314:37:38GMT+00:002007,UncontrolledCopy,(c)BSI电缆情缘BS7769-2-2.1:1997ii©BSI24July2002NationalforewordThisSectionofBS7769hasbeenpreparedbyTechnicalCommitteeGEL/20.ItisidenticalwithIEC60287-2-1:1994,Electriccables—Calculationofthecurrentrating—Part2:Thermalresistance—Section1:Calculationofthermalresistance,includingamendment1:2001,publishedbytheInternationalElectrotechnicalCommission(IEC).Thestartandfinishoftextintroducedoralteredbyamendmentisindicatedinthetextbytags
.TagsindicatingchangestoIECtextcarrythenumberoftheIECamendment.Forexample,textalteredbyIECamendment1isindicatedby
.From1January1997,allIECpublicationshavethenumber60000addedtotheoldnumber.Forinstance,IEC27-1hasbeenrenumberedasIEC60027-1.Foraperiodoftimeduringthechangeoverfromonenumberingsystemtotheother,publicationsmaycontainidentifiersfrombothsystems.Cross-referencesTheBritishStandardswhichimplementinternationalorEuropeanpublicationsreferredtointhisdocumentmaybefoundintheBSICatalogueunderthesectionentitled“InternationalStandardsCorrespondenceIndex”,orbyusingthe“Search”facilityoftheBSIElectronicCatalogueorofBritishStandardsOnline.Thispublicationdoesnotpurporttoincludeallthenecessaryprovisionsofacontract.Usersareresponsibleforitscorrectapplication.CompliancewithaBritishStandarddoesnotofitselfconferimmunityfromlegalobligations.SummaryofpagesThisdocumentcomprisesafrontcover,aninsidefrontcover,pagesiandii,pages1to31andabackcover.TheBSIcopyrightnoticedisplayedinthisdocumentindicateswhenthedocumentwaslastissued.LicensedCopy:LondonSouthBankUniversity,LondonSouthBankUniversity,TueMar1314:37:38GMT+00:002007,UncontrolledCopy,(c)BSI电缆情缘BS7769-2-2.1:1997©BSI24July20021IntroductionIEC60287hasbeendividedintothreepartsandsectionssothatrevisionsof,andadditionsto,thedocumentcanbecarriedoutmoreconveniently.Eachpartisdividedintosectionswhicharepublishedasseparatestandards.—Part1:Formulaeofratingsandpowerlosses;—Part2:Formulaeforthermalresistance;—Part3:Sectionsonoperatingconditions.Thissectiono