6.9 Pole discrepancy protection CCRPLD (52PD)6.9.1 IdentificationFunction description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberPole discrepancy protection CCRPLDPDSYMBOL-S V1 EN52PD6.9.2 FunctionalityCircuit breakers and disconnectors can end up with their phases in different positions(close-open), due to electrical or mechanical failures. An open phase can cause negativeand zero sequence currents which cause thermal stress on rotating machines and can causeunwanted operation of zero sequence or negative sequence current functions.Normally the affected breaker is tripped to correct such a situation. If the situationwarrants the surrounding breakers should be tripped to clear the unsymmetrical loadsituation.The pole discrepancy function operates based on information from the circuit breakerlogic with additional criteria from phase selective current unsymmetry.6.9.3 Function blockANSI08000041-1-en.vsdCCRPLD (52PD)I3P*BLOCKCLOSECMDOPENCMDEXTPDINDTRIPPICKUPANSI08000041 V1 ENFigure 59: CCRPLD (52PD) function block1MRK 511 287-UUS A Section 6Current protection145Technical manual
