On Overcurrent Protection: Short-circuit Current, Protection Coordination and Fuse Sizing in IBRs Dominated-distribution Feeders
Name: MURILLO COBE VARGAS
Publication date: 17/11/2023
Examining board:
Name |
Role |
|---|---|
| OURESTE ELIAS BATISTA | Advisor |
Summary: Therapidintegrationof inverter-baseddistributedpowergeneratorsareposingchallenges fortheprotectionoftheelectricalpowersystem,especiallyduetotheuncertaintyand change inthe level of short-circuit current (SCC)of distribution feeders.This thesis proposesthreeapproaches.ThefirstisamethodologytoestimatethevalueoftheSCC levelattheinstallationpointsofovercurrentprotectiondevicesindistributionnetworks withhighpenetrationof inverter-basedresources(IBRs), forthree-phasefaults(3LG)and single-phasegroundfaults(LG).Thesecondproposesamethodologyforadjustingthe characteristiccurveof inverse-timeovercurrentrelays.Andthethird, twomethodologies forsizingfusestoavoidsolidaritytrippingortoprotecttheconductor.Themethodologies areappliedinscenarioswithhighpenetrationof IBRsanddonotrequirecommunication links,normeasurementofparameters inreal time:minimalneedtoreplaceequipment alreadyinstalled.ConsideringtheestimationofSCC,themethodologypresentsagood assertivenesswhencomparedwithacomputational simulationinMATLAB/Simulink. Errorsaresmallerfor3LGfaults(<2.1%).ForLGfaults,theerrorsaresmallerwhenthe IBRsareinstalledinthemainfaulttrunk(<10.3%)thaninthelateralones(<-13.0%). Despitethehigherrors, it ispossibletoestimateanextremevalueofSCCtobeused intheprotectionadjustment. Inascenarioof100%penetrationof IBRs, therewasa miscoordinationbetweentheprotectiondevices: relay-relayandrelay-fuse.Coordination wasre-establishedusingtheproposedmethodologyforextremeIBRinstallationsituations. In this coordinationof the inverse time-overcurrent protection, the timedial of the overcurrentrelayswasmodified.Thismodificationaccommodatesahighpenetrationrange of IBRsand, inthecaseof100%penetration, itdelayedtheprotectionactuationbyafew tensofms.Forfuses, itwasfoundthatdependingonthelevelofpenetrationof IBRson thelateralbranchthatthefuseprotects, theremaybeanincompatibilityofthelimits usedfor its sizing.This incompatibilityhappens forhighpenetrationlevelswhenthe maximumcurrentthroughthefuseishigherthanitsnominalvalue.Methodologiestoavoid sympathetictrippingandconductorprotectionwereappliedtocalculatetheappropriate fusetoprotectthelateralbranchandthemaximumlevelofpenetrationrequired.The maximumpenetrationleveldecreasesastheIBRcaninjectagreaterSCC(e.g.,1.2pu or2.0pu).Theappliedmethodologiesre-establishedthecoordinationofthedistribution feeder,bothforthemaintrunkandforthesidebranches.Theseproposalscanbeapplied tootherfeedersandthepenetrationrangetobemet isdefinedbythenetworkmanager.
