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Testing of Line Differential Protection

VOLUME 11 / ISSU

A PUBLICATION OF OMICRON 20

WORLD LEADER IN INNOVATIVE POWER SYSTEM TESTING SOLUTIONS

neDifferentialProtection

NewFeaturesofTU2.11

estBaseTM

eproducibilityofRAMeasurements

ComicRon

vents

MajorityTakeover-mtronix

NSIDE

MICRONelectronicsGmbH

eresRied16833Klaus,Austria

one:+435523507-0

:+435523507-999

ww.omicron.at

o@omicron.at

port@omicron.at

MICRONelectronicsAsiaLtd.

te2006,20/F,Tower2

eGateway,HarbourCity,

wloon,HongKongS.A.R.

one:+85226340377

:+85226340390

ww.omicron.at

o@asia.omicron.at

port@asia.omicron.at

MICRONelectronicsCorp.USA

GreenwayPlaza,Suite1510

uston,Texas77046

one:+1713-830-4660

0-OMICRON

+1713-830-4661

ww.omicronusa.com

o@omicronusa.com

hsupport@omicronusa.com

Differentiallineprotectiondevicescomparethephasecurrents (or relatedproperties) of the line ends andcheck fordeviations indicatingan internal fault.Highcurrentsresultingfromathrough-fault(faultoutsidetheprotectedzone)willincreasetheabsolutemeasurementerrorthuscreatinganapparentdifferentialcurrentthatcouldleadtofalsetripping.Thisiswhythedifferentialcurrentisbiased,forexample,bythesumofabsolutecurrentvaluesof thelineends.Therelaysat thelineends communicate for current comparison and biascalculation,formingadistributedprotectionsystem.

It is widely accepted that a proper relay test shouldpreferablybedonewithsettingsforon-siteoperation,verifyingallparametersshapingthecharacteristic.

Aneasywaytomakedifferentialrelaystripfortestingpurposesistoinjectcurrentsfromjustonesidesincethey will be seen as 100 % difference. This seemsespeciallyattractiveforlinedifferentialrelayssincetestsignalsarenotneededattheremotelocation,allowingaverysimpletestsetup.Thedisadvantageisthatusuallythe test result is restricted to a single point on therelaycharacteristicwherethesingle-injectiontrajectory

crosses the characteristic. Settings defining the e.g.multi-slope characteristics, important for high faultcurrents,canthereforenotbeverifiedbythistest.

Some relays select the highest biasing value of allphasesascommonbiasingquantity,allowingcontrolofthediff/biasrelationbyinjectingonecurrentinonephaseandadifferentoneinanotherphase.Amuchmoreversatileapproachistoinjectthecurrentsfor all line ends. This is the standard procedure fortestingtransformerdifferentialrelayswithmoderntestequipment delivering e.g. six test currents, allowingfull controlof thediff/bias relation for characteristics

verification. For a full on-site commissioning test adistributedsetupisrequired(seeFig.1).Thecurrentsatallendsmustbetightlyinsynchronisminordertoallowproperassessmentbytherelayswithinthedesiredtolerances.

The test devices are synchronized to a master clockrepresented by the time stamps transmitted by theGlobalPositioningSystem(GPS)satellites.EachtestunitiscontrolledbyadedicatedGPSreceiver.

Foreachtestshotalltestdeviceswaitforatimepulsefrom the GPS receiver. This ensures highly accuratesignal synchronism of all generated currents in the

rangeofmicroseconds.

Fig. 1: End-to-end test injection

For the benefit of a dedicated user interface andreportingforline-differentialtestsOMICRONhasnowintroduced GPS synchronization into its AdvancedDifferential test modules. This allows direct diff/biasplaneoperationjustlikethatfortransformerdifferential

relay testing, thus also supporting line differentialrelayswithatransformer intheprotectedzone.NewcheckboxesactivatetheGPSmodeandselectthepropercurrent triple for each end. The "GPS Configuration"buttonofthetestmoduleallowsforthesettingofthestarttimeandtheshotrate.

SampleTestResultFig.2showsasampletestresultwithSiemens7SD610linedifferentialrelay.ThechosencharacteristicfortheDifferential Operating Characteristic diagram is theclassic current difference versus the sum of currentamplitudesrepresentation.

Fig. 2: Sample Idiff/Ibias result with 7SD610

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Everydayprotectionengineersareconfrontedwiththechallengesofshorterandshorterinnovationcycles.Protectiverelaysbecomemorepowerfulandmorecomplex;relaysofdifferentgenerationsandfromdifferentsuppliers,areusedsidebysideandtheseareonlysomeofthereasonswhythetestandmaintenanceofprotectionrelaysremainachallengingtaskforengineersandtechnicians.

TestBase isapowerfuldatabaseformaintenancemanagement andtestautomation.Itsusereleasesstafffrommanyoftheadministrativetasks and paperwork associatedwith this work. It is designed forprotectiontestingwiththeTUsoftwareandCMCtestequipment,butcanbeusedformanyotherapplicationsandwithtestequipmentfrom

manymajormanufacturers.

UsefulApplications

1) Management of Protection Relay Settings The user caneasily compare nominal and actual settings and directly importsettings from the relay operating software. These settings can beautomaticallytransferredintotheTUtesttemplatefortestingwiththeCMCtestequipment.

2) AdministrationofTestTemplatesandTestResultsTestBaseensurestheselectionoftherighttesttemplatesforaspecifiedrelay.ExcelchecklistscanbefilledautomaticallywithindividualrelaymasterdatawhentheyarelaunchedfromTestBaseandalltestresultsareautomaticallystoredinthedatabase.

3) TestAutomationForanumberoftestapplications(e.g.routinetestingofdistancerelays)andrelaytypes,fullyautomatedtesttemplatesareavailable.

4) MaintenancePlanningSupportAlarmsignalsinthesoftwareshowobjectsdueoroverdueformaintenance.

5) Document management With the integrated documentmanagement facility the user gets easy access to the informationrequiredduringtesting(e.g.relaymanuals,testspecifications,safetyinstructions,certificates,individualnotes,etc.).

6) Management of other assets within power utilities Inadditiontoprotectiverelays,TestBasesupportsinstrumenttransformersandbatteries.Furtherequipmentcanbemodeledintothesystembytheuser.

7) Offline mode with data replications TestBase allowsautomatedsynchronizationwhenconnected tothe server. Theuserhasaccesstoallfeatureswhenworkingonsiteevenwithoutserverconnection.

TestBaseisavailableinawiderangeofformats;forsingleormulti-user;asastandardadd-onproducttotheOMICRONTestUniverse;orasanindividuallytailoredsolutionformaintenacemanagement.

FormoreinformationaboutTestBasepleasegetintouchwithyourlocaldistributorortheOMICRONofficenearestyou.

(Continuedfrompage1)

SomeHints:

Insearchmode thetestmoduleneeds consistentbehavior ofthetripsignal.Allendsmusttripatthesametimetoavoiddivergingiterations. So all relays must use the transfer trip function ifsynchronoustrippingisnotinherenttotherelayfunction.

Relays that allow different characteristics per end can be testedsequentiallybyenablingoneendtripatatimetogetherwithtransfertripping,thustestingeachcharacteristicaccordingtoitssettings.

ForanextendedversionofthisarticlepleasevisittheSupportsectionofwww.omicron.at.

TestBaseThe Administration Tool for ProtectionTesting with Test Universe

New features of TestUniverse 2.11Wearepleasedtoannouncetheavailabilityofthe2.11releaseofTestUniverseSoftwarewhichoffersmanyusefulenhancements:

GPS-synchronizedLine-Differentialtesting:Seealsothetitlestoryfortheapplicationofthispowerfulfeature.

XMLdataexport:ThismoderndataformatisaddedasanalternativetotheexistingCSVexportallowingeasyintegrationofexternalapplicationsand databases. XML can beexported fromOCC filesaswellas from

individualtestmodules.ApplicationexamplenotesareincludedtoshowhowtomakeuseofXMLdatatransferandtestresultanalysisinMicrosoftOfficeapplicationsand.NETprogramming.

The new software also provides changes and enhancements in thefollowingmodules:

GOOSEConfiguration:SupportofthefrequentlyusedEnumerationtypeandotherenhancementsincludingimprovedSCLimport.

AdvancedTransPlay:AsinesimulationwithdefinablelengthcannowbeinsertedbeforetheactualCOMTRADEplaybacktoallowextendedpre-faultdurationinadditiontotheloopingcapabilityofthetool.

CMGPS:Enhanced status information (e.g.AlmanacandUTCupdateprogress)andRestoreDefaults toquickly equalize thesettings onall

ends.

Ramping: Added(X+Y)/2function,e.g.forMTAassessment.

NetSim:Twonewtestcasesfordoubleearthfaultsimulation(single-anddual-segmentlinewithfreelyassignablefaultlocations).

ThisreleaseisavailablenowonCDandonourwebsitefordownloadfrom the Customer Area.Thedownload isanUpdate version, i.e. itcomeswithoutalicensefileandcanbeinstalledontopofanexistingTU2.x installation.Users are invited tocontact theirOMICRON salespartner for a free update from TU2.x licensed components, orusetheonlineorderformprovidedintheCustomerAreaoftheOMICRONwebsite.Thelicensekeysstaythesamefortheseversions.

Formoreinformationincludingthedetailed"WhatsNew"documentforthis releaseuserscan getmore information fromthe CustomerAreaatwww.omicron.at.

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Transformers have to withstand a high level of mechanical stressduring through-faults with high currents. Themagnetic flux in the

straychannelcauseshighforcesbetweentheturnsofthewindings.Inparticular,whentheclampingpressureisnotcapableofrestrainingtheforces involved, substantialpermanentwinding deformationor evencollapsecanoccur.Oftenthedeformationoftransformerwindingsisnotrecognizedandthetransformersremaininservice.Inmanycasesdeformedwindings have a reduced ability towithstandhigh forcessubsequentlyandsohighthrough-faultscanleadtoanunpredictablebreakdownofthewholetransformer.

Frequencyresponseanalysis (FRA)providesapowerful toolto detectdeformationanddisplacementofwindingsbymeasuringthetransferfunctionofwindings over a wide frequency range. Changes in themeasured transfer function can be very small. Comparisons to theothertwophasesortosisterunitsareoftennothelpfulduetophysicaldifferences. Therefore a reference (fingerprint) measurement of thewindingsinagoodconditionisveryimportant.Toguaranteethatthemeasurements have good reproducibility, it is necessary to followsomeimportantguidelinesformaking thereferenceandsubsequentmeasurements.Thetestcircuitshouldbemadeexactlyinthesamewayforbothmeasurements,usingthesameequipmentoratleastequipmentwith the same measuring behavior. Important parameters are themeasuringprinciple,theinputimpedance,thecablesandparticularlythegroundingconcept.The groundingof themeasuringsystemandthecoaxialmeasuringcablescan greatlyaffectthemeasurement.Tominimizetheinfluenceoftheconnectionleadsitisveryimportanttoconnectthescreensofthe coaxial cableswith theminimumlevelofinductanceaspossibleandalwaysinthesamemanner.

Thefigureontherightsidepresentsacomparativetesttoinvestigatethe influence of different grounding concepts on the repeatabilityof the measurement. The first example used old-style connectiontechniques.Thepositionoftheinstrumentwaschangedwhich,inturn,changedthepositionofthemeasuringleadsrelativetothetransformerterminals.Changesinthesignaldampingwereobservedforfrequenciesof700kHzandaboveshowinglargechangesinthesignaltracesforhigherfrequencies.Usingtheadvancedbraidconnectionsinplaceofwiresthemeasurementsarestableoverthecompletefrequencyrange.Itcanbeseenintheexamplethatwherethenewbraidisusedfortheconnection,theredandbluetracesarenearlycoincident. Thiseffectis of importance for the practical use of FRA,because it is unlikelythat exactly the same arrangement ofmeasurement leads and FRAinstrumentwillbeachievedforsubsequentmeasurementsonthesametransformerorforsimilartransformersinothersubstations.

Theexample shows the importanceof the connection technique forreproducible FRA measurements. With the innovative connectiontechnique, OMICRON offers an important tool for professionalmeasurements.

FRA curves with wire and braid grounding. The results showing clearadvantage of grounding braids regarding wires.

Innovative OMICRON lead and grounding connection concept

Reproducibility of FRA Measurements

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PCOMING EVENTSQ: Weneedtodosometests,forexamplethetapchangertest,onourtransformersona

commonbasis.PreparingtheCPCtestcardsrequiredforthesetestsdoestakesometime.Furthermoreyouneedtohavecertainknowledgeaboutthewholetechnique.Isthereasolutiontosimplifythepreparationofthetests?

A: Especiallyfortestsusedregularly,wehavegeneratedstandard"templates"tosimplifytheprocess.

Insteadofgeneratingalltherequiredtestcardsmanuallytheuserjustneedstoinputsomesettingsinthetemplates.Thisimprovesefficiencyoverallbyreducingtheamountofworkandtime.

Templatescompriseofoneormoretestcardsandaresuitableforthemostcommonrequirements.CPCExplorerallowsforthetestmeasurementstobeeasilydownloadedtoaPC.Also,sinceeachtemplateisactuallyatemplatepair,whichconsistsofanExceltemplateandaCPCtemplate,thetestreportwillbegeneratedautomaticallybyloadingthecorrespondingExceltemplate.Thistestreportiscompletelyadaptabletoyourneeds.Thenexttimeyouneedyour,moredetailedreportagain,youonlyhavetoloadthemeasurementdataintoyourpersonallyadaptedtemplate.Thereforeyouhave

tocreateyour"reporttemplate"onlyoncebutareabletouseitfrequently.

OMICRONprovidestemplatesforthemostcommonapplications.ThesetemplatesareautomaticallyinstalledwiththeCPCExplorer.YoucanfindtheminStart\Programms\CPCExplorer\Templates.TotakeadvantageoftheCPCtemplatesconcept,they(*.xmt)mustbeuploadedtotheCPC100priortothetest.TheyarealsoavailableintheCustomerAreaontheOMICRONhomepageandcanbedownloadedfromthesection"PrimaryTestingCPLine/CPC100andAccessories"forfree.

Q: Mynotebookisfairlynewanditdoesn'thaveaparallelport(DB25connector).WhatcanIdotostillusetheCMCwithaparallelportconnection?

A: ToaddaparallelporttoanycomputerwithaPCMCIAinterface,anextensioncardcanbeused.

ThereisabigrangeonthemarketofparallelportPCMCIACards.Mostoftheseextensioncardscanbeeasilyinstalledontothenotebook.Someofthemdonotevenneeddriversbutthecompatibility

mostlydependsontheoperatingsystemanditsversion.

WehavetestedanumberofcardsfortheparallelportconnectiontotheCMCusingPCMCIA.WefoundavarietyofusablecardsbutourspecificrecommendationisthetypeSPP-100fromQuatech.Thiscard canbeorderedatOMICRON.Further informationabout thisParallel PortPCMCIA cardisavailable in the "OMICRONCMLine catalogue" and aswell on our homepage, in the section"SecondaryTestingCMLine/Hardware/Accessories

FORTHERECORDWITHAseriesofquestionsmostcommonlyasked,andresponsesfromOMICRONsrenownedtestGuru...

COMICRON

CCigreExhibitionforelectricalipementchRotanaHotel&Toweroth#A8uDhabi,UnitedArabEmiratesvember29-30,2006w.ifpqatar.com

oTechConwnePlazaHotelester,UnitedKingdomvember28-30,2006

hcon.tjh2b.com/EuroTechCon06/index.htm

Automation&Control(ELEC)cdesExpositionsl6/5aL148sNordVillepinte,Francecember5-8,2006ww.scs-automation.com

rgyGenerationConferencemarck,ND,USAuary30-February1,2007

tribuTechDiegoConventionCenteroth#1625Diego,CA,USAruary4-6,2007

ddleEastElectricitybaiInternationalExhibitionntrebai,UnitedArabEmiratesruary11-14,2007

ww.middleeastelectricity.com

hConneysCoronadoSpringsResorteBuenaVista,FL,USAruary28-March2,2007

noverFairnover,Germanyril16-20,2007ww.hannovermesse.de

Majority Takeover of Berlin-based HighTech Company mtronix

Thechemistryisperfect!,saysMartinPfanner,ManagingDirectorofOMICRONelectronicsGmbH,andcontinues:BytakingoverthemajorityoftheGermanbusinessmtronix,wenotonlyextendourrangeofservicesinthefieldoftestandmeasurementengineeringforelectricalpowersystems,butwealsogainaccesstonewmarketsegments.mtronix,foundedin1997byateamofhighlymotivatedexperts,specializesinthefieldofpartialdischargemeasurementwhereitquicklybecameinternationaltechnologicalleaderwithinafewyears.Thisremindsusstronglyofourownbusinessdevelopment,inwhichOMICRONmanagedto takea leaptobecome theworldsmarket leader throughhighlyinnovativesolutions.

Thispartnershipwillallowusto:

Expandtechnologicallyinthedirectionofpartialdischargeanalysis

Deliverbetterandmorecomprehensivesolutionstoour

customers

Findoutmoredetailsonwww.omicron.at.