電力專業(yè)英語電力系統(tǒng)中的高電壓技術(shù)

電力專業(yè)英語電力系統(tǒng)中的高電壓技術(shù)第1頁，課件共40頁，創(chuàng)作于2023年2月TopicsInsulationGroundingOvervoltageLightningShielding第2頁，課件共40頁，創(chuàng)作于2023年2月Insulation1Insulationisrequiredtokeepelectricalconductorsseparatedfromeachotherandfromothernearbyobjects.Thechoiceofmaterialisdictatedbytherequirementsoftheparticularapplicationandbycost.第3頁，課件共40頁，創(chuàng)作于2023年2月Insulation2Thecoilsofgeneratorsandmotorsmaybeinsulatedwithvarioustapes.Theinsulationonpowertransformerwindingsiscommonlypapertapeandpressboardoperatedunderoil.第4頁，課件共40頁，創(chuàng)作于2023年2月Insulation3Overheadlinesaresupportedonporcelaininsulators.Betweenthesupportsairservesasinsulation.Porcelainischosenbecauseofitsresistancetodeteriorationwhenexposedtotheweather,itshighdielectricstrength,anditsabilitytowashcleanbyrain.第5頁，課件共40頁，創(chuàng)作于2023年2月Insulation4Thecostofequipmentandthesystemasawholeiscloselyrelatedtotheinsulationlevelwhichhasbeenadoptedforthenetwork.Thechoiceofinsulationlevelshouldtakeintoaccountboththeprobabilityofoccurrenceandtheseverityofstressthatthesystemmaybesubjectedto.第6頁，課件共40頁，創(chuàng)作于2023年2月500KV開關(guān)場switchyard第7頁，課件共40頁，創(chuàng)作于2023年2月500KV變壓器transformer第8頁，課件共40頁，創(chuàng)作于2023年2月220KV開關(guān)場switchyard第9頁，課件共40頁，創(chuàng)作于2023年2月220KV開關(guān)場switchyard第10頁，課件共40頁，創(chuàng)作于2023年2月電力電纜powercables第11頁，課件共40頁，創(chuàng)作于2023年2月電力電纜powercable第12頁，課件共40頁，創(chuàng)作于2023年2月鋼芯鋁絞線

aluminumconductorsteelreinforced

第13頁，課件共40頁，創(chuàng)作于2023年2月架空輸電線

overheadtransmissionline第14頁，課件共40頁，創(chuàng)作于2023年2月架空輸電線

overheadtransmissionline第15頁，課件共40頁，創(chuàng)作于2023年2月InsulationCoordinationElectricsystems’insulationdesignershavetwooptionsavailabletothem:chooseinsulationlevelsforcomponentsthatwouldwithstandovervoltages,deviseprotectivedevicesthatcouldlimitovervoltagesthere.第16頁，課件共40頁，創(chuàng)作于2023年2月GroundingGroundingisdefinedasaconductingconnection,whetherintentionaloraccidental,bywhichanelectriccircuitorequipmentisconnectedtotheearth,ortosomeconductingbodyofrelativelylargeextentthatservesinplaceoftheearth.第17頁，課件共40頁，創(chuàng)作于2023年2月GroundingThemostimportantreasonforgroundingissafety.Twoimportantaspectstogroundingrequirementswithrespecttosafetyandonewithrespecttopowerqualityarefollows:—Personnelsafety—Toassureprotectivedeviceoperation—Noisecontrol第18頁，課件共40頁，創(chuàng)作于2023年2月接地網(wǎng)施工

constructionofgroundgrid第19頁，課件共40頁，創(chuàng)作于2023年2月接地網(wǎng)施工

constructionofgroundgrid第20頁，課件共40頁，創(chuàng)作于2023年2月OvervoltagesTheovervoltagescanbedividedintoexternalovervoltagesandinternalovervoltagesaccordingtothelocationsofsources.Externalovervoltagesaregeneratedbysourcesthatexternaltothepowersystemnetwork.Theirmagnitudeisessentiallyindependentofthesystem.第21頁，課件共40頁，創(chuàng)作于2023年2月ExternalOvervoltagesLightningovervoltagesarecharacterizedbyveryhighpeakcurrentsandrelativelylowenergycontent.Theyareresponsiblefornearlyhalfofallshortcircuitsonlinesinsystemsof300kvandabove.Upto300kvthesysteminsulationhastobedesignedprimarilytowithstandlightningsurges.第22頁，課件共40頁，創(chuàng)作于2023年2月InternalOvervoltagesInternalovervoltagesareprincipallydeterminedbythesystemconfigurationanditsparameters.Theyaremainlyduetoswitchingoperationsandfollowingfaultconditions.Accordingtotheirduration,whichrangesfromhundredsofmicrosecondstoseveralseconds,threemaincategoriesofinternalovervoltagescanbedefined:第23頁，課件共40頁，創(chuàng)作于2023年2月InternalOvervoltages1TransientSwitchingSurges.2TemporaryOvervoltages.3.Steady-stateOvervoltages.第24頁，課件共40頁，創(chuàng)作于2023年2月LightningStrokesDuringstormyweather,byaprocessnotyetfullyunderstood,achargeseparationtakesplaceinsideclouds,sothatpositivechargesmovetotheupperpartofthecloudwhilenegativechargesstaybelow.Thistransferofelectricchargesetsupanelectricfieldwithinthecloud.第25頁，課件共40頁，創(chuàng)作于2023年2月LightningStrokesThenegativechargeatthebaseofthecloudrepelsthefreeelectronsonthegroundbelow.Consequently,thesurfaceofthegroundbecomespositivelycharged,byinduction.第26頁，課件共40頁，創(chuàng)作于2023年2月LightningStrokesAsmoreandmorepositivechargesaremoveupwardwithinthecloud,theelectricfieldbelowthecloudbecomesmoreandmoreintense.Ultimately,itreachesthecriticalionizationlevelwhereairbeginstobreakdown.Ionizationtakesplacesfirstatthetipsofhighbuildings,suchaschurchspires,andthetopofhightrees.第27頁，課件共40頁，創(chuàng)作于2023年2月LightingStroke第28頁，課件共40頁，創(chuàng)作于2023年2月LightingStroke第29頁，課件共40頁，創(chuàng)作于2023年2月LightingStroke第30頁，課件共40頁，創(chuàng)作于2023年2月LightingStrokes第31頁，課件共40頁，創(chuàng)作于2023年2月LightingConductors第32頁，課件共40頁，創(chuàng)作于2023年2月LightingConductors第33頁，課件共40頁，創(chuàng)作于2023年2月LightningShieldingofTransmissionLinesWhenlightningmakesadirecthitonatransmissionline,itdepositsalargeelectriccharge,producinganenormousovervoltagebetweenthelineandtheground.Thedielectricstrengthofairisimmediatelyexceededandaflashoveroccurs.第34頁，課件共40頁，創(chuàng)作于2023年2月LightningShieldingofTransmissionLinesThearcbetweenthelineandthegroundproducesahighlyionizedpathwhichbehaveslikeaaconductingshort-circuit.Consequently,thenormalAClinevoltageimmediatelydeliversalargeACcurrentthatfollowstheionizedpath.Thisfollow-throughcurrentmaysustainthearcuntilthecircuitbreakersopenattheendofline.第35頁，課件共40頁，創(chuàng)作于2023年2月LightningShieldingofTransmissionLinesDirecthitsonatransmissionlinearerare.Moreoften,lightningwillstriketheoverheadgroundwirethatshieldsth