fault voltage .pdf

Zone4info.com Fault Voltage Operated Earth Leakage Circuit Breakers (ELCB) Fault Voltage Operated Earth Leakage Circuit Breakers (ELCB) Posted by musa bahnasy May 1 A voltage operated earth leakage circuit breaker comprises a contact switching system together with a voltage sensitive trip coil. On installations, this coil is connected between the metalwork to be protected and as good a connection with earth as can be obtained. Any voltage rise above earth on that metalwork exceeding the setting of the coil will cause the breaker to trip so giving indirect shock risk protection. Tripping coils are designed so that a fault voltage operated device will operate on a 40 V rise when the earth electrode resistance is 500Ω or 24 V on a 200Ω electrode. Single and multiphase units, with or without overcurrent facilities, are available for load currents up to 100 A A test device is provided on a voltage operated unit to enable the operation of the circuit breaker to be checked, operation of the device applies a voltage to the trip coil so simulating a fault.

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5/10/2015 Zone4info.comFaultVoltageOperatedEarthLeakageCircuitBreakers(ELCB)

http://zone4info.com/articles/print/1136/format/smoothbox 1/2

Zone4info.comFaultVoltageOperatedEarthLeakageCircuitBreakers(ELCB)

FaultVoltageOperatedEarthLeakageCircuitBreakers(ELCB)

PostedbymusabahnasyMay1

Avoltageoperatedearthleakagecircuitbreakercomprisesacontactswitchingsystemtogetherwithavoltagesensitivetripcoil.Oninstallations,thiscoilisconnectedbetweenthemetalworktobeprotectedandasgoodaconnectionwithearthascanbeobtained.Anyvoltageriseaboveearthonthatmetalworkexceedingthesettingofthecoilwillcausethebreakertotripsogivingindirectshockriskprotection.

Trippingcoilsaredesignedsothatafaultvoltageoperateddevicewilloperateona40Vrisewhentheearthelectroderesistanceis500or24Vona200electrode.Singleandmultiphaseunits,withorwithoutovercurrentfacilities,areavailableforloadcurrentsupto100A

Atestdeviceisprovidedonavoltageoperatedunittoenabletheoperationofthecircuitbreakertobechecked,operationofthedeviceappliesavoltagetothetripcoilsosimulatingafault.
5/10/2015 Zone4info.comFaultVoltageOperatedEarthLeakageCircuitBreakers(ELCB)

http://zone4info.com/articles/print/1136/format/smoothbox 2/2

Trippingofthecircuitbreakerbymeansofthetestdeviceshowstheintegrityoftheelectricalmechanicalelementsthattheunitisoperatingwiththecorrectorderofoperatingvoltageand,inaddition,provestheconductorfromthecircuitbreakertotheearthelectrode.Itcannotproveotherfeaturesoftheinstallation.

Whilstthevoltageoperated()willoperatewhensubjectedtoafaultvoltageof20Vormore,itshouldbenotedthatitcannotrestrictthevoltageinmagnitudeonlyinduration.

CurrentOperatedEarthLeakageCircuitBreakers

Forindustrialapplications,earthleakagecircuitbreakersoperatingonmilliampereresidualcurrentsorworkingonfaultvoltageprincipleareoflittleuse,sincemilliamperesofearthleakagecurrentforanextensiveindustrialsystemisanormaloperatingsituation.Trippingbasedonthesecurrentswillresultinnuisanceforthenormaloperation.Milliamperesofcurrentinasystem,whereexposedconductivepartsofequipmentsareeffectivelyearthedandfaultloopimpedanceiswithinreasonablevalues,willgiveriseonlytoagroundpotential/contactpotentialriseofafewmillivolts.Thiswillinnowaycontributetoshockorfirehazard.Hereobjectionablefaultcurrentswillbeafeworafewtenthsofamperes.Insuchcases,residualcurrentoperateddevicessensitivetothesecurrentsmustbemadeuseofforearthfaultcurrentandstableoperationoftheplantwithoutnuisancetripping.Thisisachievedeitherbyseparaterelaysorinbuiltreleasesinitiatingtripsignalstothecircuitbreakers