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1、9576_C06.fmPage271Friday,October14,20059:21AMCapacitorApplication271ControlpowertransformerVacuumswitchCapacitorunitFIGURE6.2Overheadlinecapacitorinstallation.(FromCooperPowerSystems,Inc.Withpermission.)Whilemostcapacitorsarepolemounted,somemanufacturersprovidepa
2、dmountedcapacitors.Asmorecircuitsareputunderground,theneedforpadmountedcapacitorswillgrow.Padmountedcapacitorscontaincapacitorcans,switches,andfusinginadeadfrontpackagefollowingstandardpad-mounted-enclosureintegrityrequirements(ANSIC57.12.28-1998).Theseunitsaremu
3、chlargerthanpadmountedtransformers,sotheymustbesitedmorecarefullytoavoidcomplaintsduetoaesthetics.Thebiggestobstaclesarecostandaesthetics.Themaincomplaintisthatpadmountedcapacitorsarelarge.Customerscomplainabouttheintrusionandtheaestheticsofsuchalargestructure(se
4、eFigure6.3).FIGURE6.3Examplepadmountedcapacitor.(FromNortheastPowerSystems,Inc.Withpermission.)Copyright©2006Taylor&FrancisGroup,LLC9576_C06.fmPage272Friday,October14,20059:21AM272ElectricPowerDistributionEquipmentandSystemsTABLE6.1Substationvs.FeederCapacitorsAd
5、vantagesDisadvantagesFeederCapacitorsReduceslinelossesMoredifficulttocontrolreliablyReducesvoltagedropalongthefeederSizeandplacementimportantFreesupfeedercapacityLowercostSubstationCapacitorsBettercontrolNoreductioninlinelossesBestplacementifleadingvarsareneededfo
6、rNoreductioninfeedervoltagedropsystemvoltagesupportHighercostSubstationcapacitorsarenormallyofferedasopen-airracks.Normallyelevatedtoreducethehazard,individualcapacitorunitsarestackedinrowstoprovidelargequantitiesofreactivepower.Allequipmentisexposed.Stackracksre
7、quirealargesubstationfootprintandarenormallyengineeredforthegivensubstation.Manufacturersalsooffermetal-enclosedcapacitors,wherecapacitors,switches,andfuses(normallycurrent-limiting)areallenclosedinametalhousing.Substationcapacitorsandfeedercapacitorsbothhavethei
8、ruses.Feedercapacitorsareclosertotheloads—capacitorsclosertoloadsmoreeffectivelyreleasecapacity,improvevoltageprofiles,andreducelinelosses.Thisisespeciallytrueo
