VTXSupervision Relay

AREVA T&D

Customer Benefits

• High stability on external faults• Tuned to rated frequency• 25ms operating time at 5 times current setting

VTX relay is used for the continuous supervision of CT secondary wiring and connections of busbar protection schemes. A built in delay of 3 seconds is provided to avoid unwanted alarm during external/internal faults.The relay after operation will short the CT bus wires.

Features • Consistentaccuracy. • Reliability. • Lowburden. • Reducedmaintenance. • Immunitytotransientsandsurges, withstands5KVimpulsevoltagetest.

Application

Thisrelayisusedforthecontinuoussupervisionof CT secondary wiring and connections ofbusbar protection schemes. Each protectedzoneofthebusbarinstallationisequippedwithanalarmrelay,shouldtheCTsecondarywiringdevelopafaultwhileloadcurrentisflowing,analarmisgivenafteratimedelayof3seconds.The delay is given to prevent an alarm in thecaseofgenuinebusbar faultwhen thebusbarprotectionisrequiredtooperateandisolatethefaultysection.Further,duetoitssensitivesettingrequirement, the relay may be unstable underheavy external fault conditions, the time delayallowsthefaulttobeclearedbytheappropriateprotectionthuspreventingunwantedalarms.

Therearetwotypes:SinglephaseVTX11andthreephaseVTX31.ThefollowingTablegivesthefunctionaldetailsofboththetypes.

PROTECTION

DescriptionThe relay consists of three stages, pick-upvoltagecontrol stage, timingstageandoutputstage.TheblockdiagramofVTX11isshowninFigure1.ThethreephaseversionVTX31issameas VTX 11 except that a three phase rectifierbridgeisusedtoconvertacinputquantitiestodcsignal.

UnderhealthyconditionsoftheprotectedcircuitthereisnoacinputtotherelayandtheauxiliarydcsupplycausestransistorT1toconduct,shortingout thecapacitor in the timingcircuit.Whenavoltageappearsacross theac input terminals,the rectified dc output of the bridge tends tobiasoffthetransistorT1,incasetheacinputishigherthanthevoltagesetting.WithT1off,thetimingcircuitcapacitorbeginstochargeupfromthestabiliseddcsupply.Afteratimedelayof3seconds, the capacitor voltage reaches a pre-determinedvalueandtriggersthetransistorT2which inturnswitchesontheoutputtransistorT3.Theinternalelectromechanicalauxiliaryunit,being in the load circuit of transistor T3 picksup and initiates alarm and other functions.Continuous adjustment of the relay voltagesetting is provided by a potentiometer in thebridge output circuit. Protective devices havebeenincludedinthecircuitrytopreventdamagedue to spikes in the input voltages or reverseconnectionofthedcauxiliarysupply.

Singlephaseusedwithearthfaultschemes

Threephaseusedwithphaseandearthfaultschemes

Will detect open circuit ofcurrenttransformers.

Will detect open circuit ofcurrenttransformers

WilldetectbrokenorcrossedCTpilots

VTXrelaywithdrawnfromcase

Technical dataVoltage setting

2to14Vcontinuouslyadjustableat50Hz.

Thermal rating • Singlephaserelay: 600Vacrmsat50Hzbetweenthe inputterminalscontinuouslyonanysetting. • Threephaserelay: 300Vacrmsat50Hzbetweenany phaseandneutraloftheinputterminals continuouslyonanysetting.Therelay willalsowithstand2kVacrms50Hz forthreesecondsonanysetting.

Auxiliary supply

Therelaycanbesuppliedsuitableforoperationat30V,110Vand220Vdc.Forvoltagesabove30V, an external dropping resistor is used.Satisfactory operation is maintained over arangeof75%-120%.

Accuracy

• Atratedauxiliarysupplyandrated frequency,therelayhasanaccuracyof ±5%ofthesettingvalueonanysetting.

• Operatingtemperaturerange-5ºCto +50ºC.

Operating time

Nominal3seconds.

Figure1:BlockdiagramforVTX11relay

2>3

BurdenContinuousburdenimposedondcauxiliarysupplyisasshowninthetablebelow:

AuxiliAry voltAge 30V

relAy unoperAted (W)

110V 220V

1.0 3.5 7.0

relAy operAted (W) 1.7 4.0 7.7

Approximateacburdenperphaseforbothtypesofrelaysonanysettingisasfollows:

Applied voltAge 10V

Burden (vA)

300V 1414V

0.002 4.2 86

ContactsTwopairsofnormallyopen,selfresetcontactsareprovidedontheoutputattractedarmatureunit.

Contact ratings

MAke And cArry continuously

AC

MAke And cArry for 0.5 second

BreAk

1250VAwithmaximaof5Aand660V

7500VAwithmaximaof30Aand660V

1250VAwithmaximaof5Aand660V

DC 1250Wwithmaximaof5Aand660V

7500Wwithmaximaof30Aand660V

100W(resisitive)50W(inductive)withmaximaof5Aand660V

Operation indicator

A hand reset mechanical operation indicatoris fitted as standard on the output attractedarmatureunit.

Insulation

The relay will withstand 2.5 kV rms 50 Hz for1secondbetweenall livepartsandearth,andbetweenallcircuitsnotintendedtobeconnectedtogether.Itwillalsowithstand1.25kVrms50Hzfor1sacrossopencontacts.

Impulse withstand level

The relay will withstand 5 kV impulse voltagetestinaccordancewithIECrecommendations.

High frequency disturbance

The relay meets the IEC test recommendationfor the high frequency disturbance test. Therelay accuracy is unaffected by repetitive 1MHz bursts having an initial peak of 1.0 KVsuper-imposedacrossinputcircuitsand2.5KVbetweenindependentcircuitsandearth,withatimedelayof3to6microseconds,withtherelayenergised.

Case

Singlephaseandthreephaserelaysaresuppliedin size 1 drawout (1D) cases suitable for flushmounting and are finished eggshell black andtropicalised. The drawout feature considerablysimplifiesmaintenanceandpermitstestingtobecarriedouteasilyandquickly.Acradlemountedisolatingswitchisprovidedwhichautomaticallyisolatesthetripcircuitwhenthecradleassemblyis withdrawn from the case for maintenance.This prevents any inadvertent tripping of thecircuit breaker. A filter breather is fitted whichequalises the pressure inside and outside thecasewithoutadmittingdust.

Information required with order

1.Typeofrelay

2.Auxiliarydcvoltage

Figure2:Typical connection diagram ofVTX 31 relay in 3 phase buszone protection scheme forphaseandearthfaults.

4>5

Dimensions and weights

relAy cAse size

MAxiMuM overAll diMensions

VTX31

ApproxiMAte gross Weight

kgheightMM

WidthMM

depth* MM

1Dvert. 233 170 203 4.5

* Add76mmformaximumlengthofterminalstuds,alternatively,29mmforterminalscrews. Theapproximategrossweightsgivenaboveisinclusiveofcartons,mountingappendages andterminaldetails. TherelayscomplyfullywiththerequirementsofIS3231andaresuitableforuseinnormal tropicalenvironments.

AREVA T&D

Pallavaram Works19/1, G.S.T. Road,Pallavaram, Chennai - 600 043Tel: 91-44-2264 8000

Fax: 91-44-2264 0040

AREVA T&D Worldwide Contact Centre:http://www.areva-td.com/contactcentre/Tel.: +44 (0) 1785 250 070

www.areva-td.com

Our policy is one of continuous development. Accordingly thedesignofourproductsmaychangeatanytime.Whilsteveryeffortismadetoproduceuptodateliterature.Thisbrochureshouldonlybe regardedasaguideand is intended for informationpurposesonly. Itscontentsdonotconstituteanoffer forsaleoradviseontheapplicationofanyproductreferredtoinit.Wecannotbeheldresponsibleforanyrelianceonanydecisionstakenonitscontentswithoutspecificadvice.

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