AS NZS 3000 5Word文档下载推荐.docx

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Earthingarrangementsforprotectivepurposesshallbecomprisedofprotectiveearthingconductorsusedwithovercurrentprotectivedevicesprovided,intheactive,forprotectionagainstindirectcontactandovercurrent.

NOTE:

Theprotectiveearthingconductorsshouldbeincorporatedinthesamewiringenclosureastheassociatedactiveconductorsorinthenearvicinity.

5.2.3Forfunctionalpurposes出于功能目的

Earthingarrangementsforfunctionalpurposesshallbecomprisedoffunctionalearthingconductorsprovidedtoensurecorrectoperationofelectricalequipmentortopermitreliableandproperfunctioningofelectricalinstallations.

Wherea‘cleanearth’isspecifiedforaparticularitemofelectricalequipment,themanufactureroftheelectricalequipmentshouldbeconsultedinordertoconfirmthenecessaryarrangements.

5.2.4Forcombinedprotectiveandfunctionalpurposes

Whereearthingforcombinedprotectiveandfunctionalpurposesisrequired,therequirementsforprotectivepurposes（seeClause5.2.2）shallprevail.

5.2.5Selectionandinstallation选择和安装

Theselectionandinstallationoftheequipmentoftheearthingarrangementsshallbesuchthat—

（a）thevalueofearthingresistanceisinaccordancewiththeprotectiveandfunctionalrequirementsoftheelectricalinstallationandexpectedtobecontinuouslyeffective;

and

（b）earth-faultcurrentsandearth-leakagecurrentscanbecarriedwithoutdanger,particularlyfromthermal,thermomechanicalandelectromechanicalstresses;

（c）itisadequatelyrobustorhasadditionalmechanicalprotectionappropriatetotheassessedconditionsofexternalinfluenceinaccordancewithClause3.3.

5.2.6Precautions防范措施

Precautionsshallbetakenagainsttheriskofdamagetotheearthingarrangementandothermetallicpartsoftheelectricalinstallationthroughelectrolysisorgalvanicaction.

5.3MULTIPLEEARTHEDNEUTRAL（MEN）SYSTEM多重接地中线系统

ThesystemofearthingthatshallbedeemedtosatisfytherequirementsofClause5.1isthemultipleearthedneutral（MEN）systeminwhichthepartsofanelectricalinstallationrequired,underthisStandard,tobeearthedareconnectedtothegeneralmassofearthand,inaddition,areconnectedwithintheelectricalinstallationtotheneutralconductorofthesupplysystem.

NOTES:

1ExamplesoftheMENsystemofearthingareshowninFigures5.1and5.2.

2Alternativeearthingsystemsthatsatisfythegeneralsafetyandfunctionalrequirementsmaybeused.

5.4EARTHINGREQUIREMENTS接地要求

5.4.1General概述

Theexposedconductivepartsofelectricalequipmentshallbeearthedwheretheelectricalequipmentis—

（a）installedormightoperateinanearthedsituation;

or

（b）notinstalledinanearthedsituationbutanyexposedconductivepartoftheelectricalequipmentiselectricallycontinuouswithconductivematerialwhichislocatedinanearthedsituation.

Thetermexposedconductivepartdoesnotapplytothefollowing:

（a）Conductivepartswithinanenclosurewherethepartscannotbetouchedunlessakeyoratoolisrequiredtoremovethecoversoftheenclosure.

（b）Conductivepartswithinelectricalequipmentwherethepartscannotbetouchedinnormaluseandmovementoftheelectricalequipmentduetoitsconfigurationandsize,e.g.sometypesofwashingmachines.

（c）Conductivepartswhichareseparatedfromlivepartsby—

（i）doubleinsulation;

（ii）otherconductivepartswhichareearthed.

（d）Conductivepartswhichareintheformofnameplates,screwheads,coversandsimilarattachmentsthatcannotbecomeliveintheeventoffailureofinsulationofliveparts,duetothemannerinwhichtheyaresupportedandfixed.

Onlysinglephaseconnectionsshownforclarity.

FIGURE5.1MULTIPLEEARTHEDNEUTRAL（MEN）SYSTEMOFEARTHING—MENLINKATCUSTOMER’SMAINSWITCHBOARD

DistributionasFigure5.1

FIGURE5.2MULTIPLEEARTHEDNEUTRAL（MEN）SYSTEMOFEARTHING—MENLINKREMOTEFROMCUSTOMER’SMAINSWITCHBOARD

5.4.2Connectionofelectricalequipmenttoearth电气设备接地连接

Electricalequipmentrequiredtobeearthedshallbearrangedforconnectionto—

（a）protectiveearthingconductorsintheformofcables,cords,busbarsorsimilarformsofcurrent-carryingmaterial;

（b）anotherearthingmediumsuchasmetallicpartsofcables,wiringenclosures,switchboardframeworkorthelike.

5.4.3Resistanceoftheearthingsystem接地系统电阻

Theresistancefromanypointontheelectricalinstallationrequiredtobeearthedtothepointwherethemainearthingconductorisconnectedtotheneutralconductorofthesupplysystemshallbelowenoughtopermitthepassageofcurrentnecessarytooperatethecircuitprotectivedevices.

Theresistanceofthemainearthingconductorshallbenotmorethan0.5?

.

AsdescribedinAppendixB,themaximumresistanceoftheprotectiveearthingconductorassociatedwithanyparticularcircuitdependsonthetypeandratingoftheprotectivedeviceandtheimpedanceoftheliveconductorsthatcomprisethecircuit.

5.5EARTHINGCONDUCTORS接地导线

5.5.1Size尺寸

5.5.1.1General概述

ThesizeofanearthingconductorshallbesuchthatitmeetstherequirementsofClause5.2.

Guidanceonthedeterminationofthemaximumlengthofacircuit,inrelationtothecharacteristicsofprotectivedevicesandthesizeoftheprotectiveearthingconductor,isprovidedinAppendixB.

5.5.1.2Minimumsize最小尺寸

Theminimumsizeofanearthingconductorshallbedeterminedasfollows:

（a）GeneralExceptwherevariedbyItems（b）to（f）,theminimumsizeofanycopperearthingconductorrequiredfortheprotectionofanyportionofanelectricalinstallationshallbedeterminedfromTable5.1

inrelationtothecross-sectionalareaofthelargestactiveconductorsupplyingtheportionoftheelectricalinstallationtobeprotected.

ThedeterminationmethodusingTable5.1mayalsobeappliedinthefollowingsituations:

（i）Wheretheactiveconductorsinamultiphasecircuitcomprisedifferentsizeconductors,theearthingconductorshallbedeterminedinrelationtothecross-sectionalareaofthelargestactiveconductortobeprotected.

（ii）Wheretheactiveconductorcomprisesanumberofconductors,connectedinparallel,theearthingconductorshallbedeterminedinrelationtothesummationofthecross-sectionalareasoftheindividualconductorsformingthelargestactiveconductortobeprotected.

Wherethesummationofcross-sectionalareasdoesnotcorrespondexactlywiththenominalsizeoftheactiveconductorgiveninTable5.1,theconductorshallbedeterminedinrelationtothenearestlargersizeofactiveconductor.

TABLE5.1MINIMUMCOPPEREARTHINGCONDUCTORSIZE

Nominalsizeofactiveconductor

Nominalsizeofcopperearthingconductor

Withcopperactiveconductors

Withaluminiumactiveconductors

1

1.5

2.5

1*

1.5*

-

4

6

10

16

25

35

50

70

95

120

150

185

240

300

400

500

630

*Theseearthingconductorsmaybeusedonlywhereincorpratedinamulticorecableorflexiblecord,otherthanalifttravelingcable,inaccordancewithClause5.5.1.2（e）（ii）and（iii）.

（b）CalculationAsanalternativetothedeterminationmethoddescribedinItem（a）,theminimumsizeofanearthingconductorrequiredmaybedeterminedbycalculationprovidedthataccurateinformationisobtainedonthevalueoftheprospectivefaultcurrent,thedisconnectingtimeoftheprotectivedevice,andconductorandinsulationcharacteristics.

AsuitableequationforthecalculationofconductorsizesunderfaultcurrentconditionsisgiveninClause5.6.7.4.3.

（c）MainearthingconductorIngeneral,theminimumsizeofthemainearthingconductorshallbedeterminedinaccordancewithItem（a）andTable5.1inrelationtothecross-sectionalareaofthelargest

activeconductoroftheconsumersmains.

Thesizeofthemainearthingconductorneednotbedeterminedinrelationtothesizeofthelargestactiveconductoroftheconsumersmainsunderthefollowingconditions:

（i）Wheredoubleinsulationismaintainedbetweenthepointofsupplyandtheloadterminalsoftheprotectivedevicesonthesubmainsandfinalsubcircuitsoutgoingfromthemainswitchboard,theminimumsizeofthemainearthingconductormaybedeterminedinrelationtothecross-sectionalareaofthelargestactiveconductorofthelargestoutgoingsubmainorfinalsubcircuit.

（ii）Wherethecross-sectionalareaoftheconsumersmainsislargerthanthatrequiredtocarrythemaximumdemandoftheinstallationbecauseofvoltage-droplimitations,theminimumsizeofthemainearthingconductormaybedeterminedinrelationtothecross-sectionalareaoftheminimumcablesizerequiredtocarrythemaximumdemand.

Inanycase,thecross-sectionalareaofacoppermainearthingconductorshallbenotlessthan4mm2.

（d）AerialearthingconductorTheminimumsizeofanearthingconductorinstalledasanaerialconductorshallbedeterminedinaccordancewithItem（a）andTable5.1providedthatthecross-sectionalareaoftheearthingconductorsodeterminedshallbenotlessthanthesizespecifiedinCla