A CombinedDirectional andFaulted PhaseSelector ElementBasedonIncremental Quantities

Thispaper analyzes theproblem oftransformer differen- tial protection. First, wereview theconcept oftransformer differential protection. Wethen analyze magnetizing inrush, overexcitation, andcur- rent transformer (CT)saturation phenomena aspossible causes ofrelay misoperation. Finally, wesummarize theexisting methods fordiscrimi- nating internal faults frominrush andoverexcitation conditions. InPart IIofthepaper wepropose anewapproach fortransformer differential AuthorAffiliation: FengChiaUniversity Abstract: Thewestern Taiwan railway transportation system con- sists mainly onamountain route andoceanroute. Taiwan Railway Ad- ministration (TRA)hasconducted aseries ofexperiments ontheocean route inrecent years toidentify thepossible causes ofunknown events that cause thetrolley contact wires tomeltdownfrequently. Thecon- ducted tests include theshort-circuit fault test within thepowersupply zoneoftheHoLongSubstation (ZhuNantoTongXiao) that hadthe highest probability forthemeltdownevents. Those test results, based ontheactual measured maximumshort-circuit current, provide avalu- ablereference forTRAwhencomparing against thesaid events. TheLeBlanctransformer isthemaintransformer oftheTaiwan railway electrification system. TheLeBlanc transformer mainly trans- forms theTaiwan PowerCompany (TPC) generated three-phase alter- nating powersupply system(69kV, 60Hz)intotwosingle-phase alternating powerdistribution systems (Mphase andTphase) (26kV, 60Hz) needed forthetrolley traction. Asaunique winding connection transformer, theconventional software forfault analysis will notbe able tosimulate its internal current andphase difference between each phase current. Therefore, besides extracts oftheshort-circuit test re- sults, this workpresents anEMTP modelbasedontheTaiwanRailway Substation equivalent circuit modelwithaLeBlanc transformer. The proposed circuit modelcansimulate thesameshort-circuit test toverify theactual fault current andaccuracy oftheequivalent circuit model. Abstract: Anewmethod forestimating fault sections inpowersub- stations isproposed. Inthis paper, theknowledge representation andin- ference procedures based onthecause-effect networks (CE-Nets) and rule matrix transformation techniques arepresented. Thematrix-based inference procedures areproposed toestimate thepossible fault sec- tions through simple matrix operations bytransforming theestablished CE-Nets into matrix forms. Themethod issuperior toexisting produc- tion systems intheinference speed andtheprocess ofimplementation. Bytesting onatypical Taiwan PowerCompany's (Taipower) second- arysubstation, theexperimental results showtheeffectiveness ofthe proposed method evenforthefault domains involving multiple faults andfailure operations ofprotective devices. Moreover, itiseasytoim- plement andtransplant into different substations.