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Case Study - Importance of Relay Coordination in Process Industries

Case Study - Importance of Relay Coordination in Process Industries<br>

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Case Study - Importance of Relay Coordination in Process Industries

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  1. ISO 9001:2015 ISO 45001:2015 (OH & S) Certified Company Case Study Importance of Relay Coordination in Process Industries www.systemprotection.in +91-265-2225137

  2. Therearecertainlyquiteafewcasesofinadvertenttrippingincementplants, steelplants, fertilizerplants, FMCGandotherindustriesthatmanyElectricalEngineerswitnessatacertain pointoftime. Suchscenariosoccurinthemajorityofindustries, notforthereasonthatthe protectionplanoftheseindustriesisnotproperlycoordinatedbutbecausechangesinthe electricalsystemtakeplaceonaday-to-daybasis. PinnedbelowistheSLDofaCementPlant whichfailedduetopoorRelayCoordination, wewilldiscussthesameinthiscasestudy. Duringoneinstance, theClinkerHammer CrusherMotortrippedinoverloaddueto jamming. Itwasafter30secondsthatthe controlroomgavethecommandtostart thecrusheragainasitwasobservedinthe pastthatjammingcouldbeclearedby heavystartingtorquebutthistime unexpectedlywhenthecommandwas giventocrushermotor, theentireplant tripped. Itwasunexpectedbecausethe Clinkercrusherjamminghappensatleast3 to4timesinayearandtheplantwas runningforthelast4yearsandsuchco- ordinationproblemsneveroccurred. This issuehadarisenforthesecondtimeinthe last3monthsandourteamwascalledto addresstheissue. Theveryfirstthingthatwedidwastocheck whetherthecompleteelectricalsystemwas properlycoordinatedornotanditwas foundthatthesystemwaswellcoordinated sincethecommissioningstageandthey hadtherecordsforthesame. www.systemprotection.in +91-265-2225137

  3. Thereafter, weinquiredaboutany modificationdoneinthedistributionteam likereplacingtheexistingmotorwithless KWoraddinganyextraloadonthatMCC becauseofanyprocessrequirement. They toldusthata37kWoldcompressorwas removedasitwasnolongerbeingusedand one18- kWcompressorwasshiftedfrom anotherMCCtothepresentMCCasthe loadonthatMCCwasaround100 %. They alsotoldusthatonemorechangewas made. A75kWhigh-pressurepumpthat wasusedforbreakingjamminginKilnwas installedaspertherequirementof process/production. Therefore, atotalof around217kWwasaddedandthesettings weremanuallyadjustedaccordingtothe MCCincomerandPCCoutgoingpanel. Itwasa5000TPDplantandthis breakdowncosttheplantaround410tons ofclinkerwhichisapproximately500tons ofcement (10000Bagsofcement). It turnedaroundtobealossofINR2.5to2.8 millionsinjust2hours (TotalofINR5 – 5.5 millionfor2breakdowns). Besides, thetime, alltheeffortsputinforthemodificationto improvestabilityandefficiencywentwaste. Ideally, theMCC-6Incomershouldhave trippedandnotthemotorbecausethe motorstartednormallywithjusttheextra loadonit. Thus, itwasconcludedthattoavoidsuch anissuewhichincursheavylosses, each timeanykindofbigmodificationismade totheelectricaldistributionsystemviz. addingloadoraddinganysource, the completerelayingandprotectionshouldbe coordinatedagain. Knowingallthesedetails, weconcluded thatthereasonforsuchaproblemwasthat therewasaclinkerlumpandtheclinker crushermotorwastripped. Basedonthe experience, theytookactionandrestartedit againafter30secondsbutasthewhole plantwasrunningexceptclinkercrusher, MCCwasalreadyat80% loadandwhenthe 315kWmotorstarted, thestartingcurrent wasaround4to5timesofmotorFLC. The totalcurrentcrossedthethresholdofthat relaysandtheyforgottomakechangesin thesettingof6.6kVSideasmentionedin SLD. ThismadethecompletePCCbusdead andthetotalplantwascompletelytripped andittookaround2hourstostartback. www.systemprotection.in +91-265-2225137

  4. CONTACT INFORMATION 301/2/306, SilverlineComplex,OppositeBBC Tower,Sayajigunj,Vadodara - 390005, Gujarat, India. bdm@systemprotection.in www.systemprotection.in +91-265-2225137

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