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1、电气相关问题1electricalknowledge!1,PToperation,whynotallowshort-circuittwotimes?Answer:PTDuringnormaloperation,becausethetwoloadvoltagemeterandrelaycoilimpedanceofsomelarge,basicallyequivalenttothetransformerno-loadstate,currenttransformerbyitselfisverysmall,itdependsonthesizeoftwotimesthesizeoftheload
2、impedanee,becausePTImpedancesmall,capacityisnotlarge,whenthetwoshortcircuitedtransformer,twocurrent,twotimefusetoaffectthenormalworkcorrectlyindicatinginstrumentandprotection,whentheinsurancecapacityofimproperselectionoftwoshortcircuitedwhenthefuseisnotinsurance・PTburnsveryeasily.2,CTrunningtwoti
3、mes,whynotallowopencircuit?Answer:CTisoftenusedinhighcurrentconditions,andbecauseoftheCTloopcircuittwoseriesinstrumentandrelaydeviceandothercurrentcoilimpedanceisverysmall,basicallyshort-circuitstate,soCTNormaloperation,thetwovoltageisverylow,iftheCTtwocircuitdisconnection,theCTironcoreisseriousl
4、ysaturated,magneticfluxdensityisashighas1500Gauss,thenumberofturnsofthesecondarycoiltwosecondarycoilturnsandmorethanalotoftimes,andatbothendsofthesecondarycoilinductiontwohighvoltagethantheoriginalgreatmanytimes,thesafetyofhighvoltageelectricalequipmentonalltwocircuitandstaffwillcausegreatdanger,
5、becauseatthesametimeCTafterthetwocoilopencircuit,willmaketheironcorefluxsaturation,causeoverheatingandmayburn,andinthecoreofresidualmagnetismwillincreasetransformererror,soCTtwotimesnoopencircuit・3.Whatiscurrentprotection?Whatistheprincipleofoperation?Answer:whentheshortcircuitoccurs,oneoftheimpo
6、rtantfeaturesofthecurrentinthecircuitisincreasedsharplywhenthecurrentflowsthroughapredeterminedvalue,thereactiontothecurrentincreaseofprotectiondevicecalledovercurrentprotection,currentovercurrentprotectionisbasedonthemaximumloadcurrenttobeconsidered,thechoiceistorelyontheladdertomeetthedeadline・
7、5.Whatisfastbreakingprotection?Whatareitscharacteristics?Answer:overcurrentprotectionstartingcurrentisgreaterthanthemaximumloadcurrentinaccordancewiththeprincipleofsetting,inordertoensuretheselectivity,takethecharacter
