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1、AprincipletoselectDCisolatorswitchforaPVsystemWithrisinginstalledPVcapacity,theamountofpowergenerateddrawsalotofattention.However,powerinvestorsareincreasinglyworriedaboutsafetyandsecurityissues,whichinrecentyearsfrequentlyoccurredtophotovoltaicpowerplants.ThePVDCswitchisoneofthemos
2、timportantpartsforthePVsystemsafety,whosereliabilityandstabilityrelatetothestablegenerationandprofitofphotovoltaicsystems,aswellasthesafeandreliableoperation.Germany,theNetherlandsandsomeotherEuropeancountriesrequireinvertermanufacturerstoconfigurewithbuilt-inDCisolatorswitch,whilec
3、ountriesliketheUK,India,andAustraliastipulatethatthePVsystemsmustbeinstalledwithexternalDCisolatorswitch.WiththeclarityoftheChinesePVpolicies,thenumberofPVinstallsriseseveryyear,especiallythatofdistributivePVsystems,andalsotherooftopsystemsaregettingmorepopular.However,theso-calledD
4、CisolatorswitchforPVinthemarketareACswitchesorrewiredversions,notrealDCisolatorswitchwithfunctionsofarcextinctionandhighpowercut.TheseACswitchesarefartoodeficientinarcingextinctionandpowerisolationwithloads,easilyleadingtooverheating,leakageandsparks,orevenburningdownofentirephotovo
5、ltaicpowerplants.Therefore,theselectionofqualifiedphotovoltaicDCisolatorswitchwillbecrucial.BS7671statesthatamethodofisolationmustbeprovidedontheDCsideofaPVinstallationandthiscanbeprovidedbyaswitch-disconnectorasclassifiedunderEN60947-3.Thisisalsocoveredby"GuidetotheinstallationofPV
6、systems".HowtosizearightDCswitchforthephotovoltaicsystem?HerearesomestepsonselectingtheDCisolator:1•SizingoftheVoltageofSystemTheratedoperationalvoltageoftheswitchshouldbeequaltoorgreaterthantherequirementsofthesystem.CommonaretomeettheUL508i600V,IEC60947-31000Vand1500V.Typicallythe
7、systemvoltagecormectedtosingle-phaseinverterisupto600V,three-phasestringinvertersorcentralizedinverterupto1000Vor1500V.2•Numberofstringstobeisolated2Pole・Singlestring,4Pole-Twostring,etc.Forbuilt-inDCisolatorswitch,thenumberofMPPT'softheinverterdeterminesthepolesofaDCswitch・Commonst
8、ringinvertersarewit
