high voltage engineering and testing 2nd edition（上）

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1、ChapterIElectricpowertransmissionanddistributionsystemsI.A.Erinmez1.1Natureanddevelopmentoftransmissionanddistributionsystems1.1.INatureoftransmissionanddistributionsystemsToday,inallcountriesintheworldthatutiliseelectricityasanefficientsourceoflightandenergy,someformofatransmissionan

2、ddistributionsystemexists.Bothsystemscarryelectriccurrent,albeitatdifferentvolt-agesandtheyareconnectedtoeachother.Theyarepartofthebulktransportanddistributionsystemthatessentiallydeliversanddistributestheelectricalenergy,convertedfromprimaryenergysources,totheendusers.Theonlycleardif

3、ferencesbetweenthetwosystemsisbasedontheperceptionoftheirenduseandfunctionality.Transmissionsystemsprovidethebulktransportpathsforelectricalenergyfromgenerationcentreslocatedclosetotheprimaryenergysourcestothemajorloadcentreswithinalargegeographicalarea,thusfacilitatingeconomicandeffi

4、cientbulkpowertransfer.Ontheotherhanddistributionsystemsareconcernedwiththedeliveryofelectricalenergytoindividualcustomerswithinasmallergeo-graphicalarea.Inthisrespectadistributionsystemmayhaveanumberofdeliverypointstoitsmajorloadcentres,fromoneormoretransmissionsystemsand/orelementso

5、fatransmissionsystem,thefinalshapeofthesystemstructurebeingdependentonthemagnitudeandthepatternofdemandwithinitsgeographicalarea.Itisalsousualfortransmissionsystemstobeinterconnectedtoenablesharedeconomicbenefitsandoperationalaccesstogeneratingcapacity.10Highvoltageengineeringandtesti

6、ngGenerallymoderntransmissionsystemstransportelectricalenergybyalternatingcurrent(AC)atafrequencyof50or60cyclespersecondoperatingatvoltagesof220kVandabove,withotherstandardvoltagesof275kV,330kV,400kV,500kV,765kVand1000kV.Assystemsdevelop,eachtimeanewtransmissionvoltageisaddedthelowest

7、trans-missionvoltagelevelrevertstoplaymoreofadistributionnetworkrole.Forexample,the132kVtransmissionnetworkdevelopedintheearlydaysintheUKassumedadistributionroleaftertheadditionof275and400kVtransmissionnetworks.Itisusualforoneormoreofthesestand-ardvoltagenetworkstobeemployedwithtransf

8、ormer