Wavecom WMO2 GSM 900 Specifikace stáhnout pdf (Strana 11)

VärmeKabelTeknik Switchpointheating

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Functiontestsandfaultdetection

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Checkingthefunctionoftheswitchpointheating

elements

Theswitchpointheatingelementsaremadeoutof

double‐insulatedself‐limitingheatingcablewithan

outputpowerof100W/mat+10°C‐230Vac≈160–

170W/mat–15°C.

Thistypefheatingelementhasacoreofdipped

fluoretheneplastic

whichhastheeffectthatits

resistanceincreaseswhenthetemperaturerises.

Thispropertyallowstheelementstoautomaticallysave

energywhentheweatheriswarm.Italsomeansthat,in

coldweathertherewillbeanextraamountofheat

added.

Resistancemeasuringofself‐limitingelementsisnot

possibleastheresistancevaluereadingdoesnotshowa

valuecorrespondingtothepoweroutput.

Elementtestsaretobeconducted,withvoltage

switchedon,throughmeasuringthecurrentafterabout

15minutes’operation.Thecurrenthasthenstabilized

andcanbecomparedwiththevaluethatwasmeasured

when

theelementwasinstalled.Itshouldbenoted,

however,thatiftestingisdoneinthesummer,thenthe

currentvaluewillbelowerthaninthewinter.Ifthe

currentislessthan0,2A,theelementshouldbe

considereddefective.

99percentofanyvoltageleakagesor

directshort‐

circuitsderivefromfeedercablesorjunctionboxes.The

elementplugscanbeeasilydisconnectedfromthe

distributionboxwhenmeasuring.

Theconnectionblocksmountedonthetracksleeper

areofrubberandcastinonepieceandsocannotcause

ashort‐circuit.Aconnectionblock’sterminalsare

fedby

separateconductorsviaan8‐polecablecastintegral

withtheblock.Currenttestscanthusbeconveniently

carriedoutoneachelement,offtrack,inajointboxin

thecableduct.

Theelementsaredouble‐insulatedandlackprotective

earthing.However,theinsulationresistancebetween

element

andrailmaybetestedbyjoiningthetwopins

oftheplugtoeachotherandthenconnectingthem

jointlytooneoftheterminalsoftheinsulationtester,

theotherterminalbeingconnectedtotherail.

Whenconductingsuchtests,youmustmakesurethat

youdonotcause

anysignallingerrors.

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