IPickup: Current level for the Stub protection, set in % of IBase. This parameter should beset so that all faults on the stub can be detected. The setting should thus be based on faultcalculations.7.13 Pole discrepancy protection CCRPLD (52PD)7.13.1 IdentificationFunction description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberPole discrepancy protection CCRPLDPDSYMBOL-S V1 EN52PD7.13.2 ApplicationThere is a risk that a circuit breaker will get discrepancy between the poles at circuitbreaker operation: closing or opening. One pole can be open and the other two closed, ortwo poles can be open and one closed. Pole discrepancy of a circuit breaker will causeunsymmetrical currents in the power system. The consequence of this can be:• Negative sequence currents that will give stress on rotating machines• Zero sequence currents that might give unwanted operation of sensitive ground-faultprotections in the power system.It is therefore important to detect situations with pole discrepancy of circuit breakers.When this is detected the breaker should be tripped directly.Pole discordance protection CCRPLD (52PD) will detect situation with deviatingpositions of the poles of the protected circuit breaker. The protection has two differentoptions to make this detection:• By connecting the auxiliary contacts in the circuit breaker so that logic is created anda signal can be sent to the pole discrepancy protection, indicating pole discrepancy.• Each phase current through the circuit breaker is measured. If the difference betweenthe phase currents is larger than a CurrUnsymPU this is an indication of polediscrepancy, and the protection will operate.1MRK 506 334-UUS A Section 7Current protection239Application manual
