8.7.6 Monitored dataTable 108:CCRPLD Monitored dataName Type Values (Range) Unit DescriptionIMin REAL - A Lowest phase currentIMax REAL - A Highest phase current8.7.7 Operation principleThe detection of pole discordance can be made in two different ways. If the contactbased function is used an external logic can be made by connecting the auxiliarycontacts of the circuit breaker so that a pole discordance is indicated, see figure 84.Pole discordance signal from circuit breaker+circuit breakeren05000287.vsdIEC05000287 V2 ENFigure 84: Pole discordance external detection logicThis binary signal is connected to a binary input of the IED. The appearance of thissignal will start a timer that will give a trip signal after the set time delay.Pole discordance can also be detected by means of phase selective currentmeasurement. The sampled analog phase currents are pre-processed in a discreteFourier filter (DFT) block. From the fundamental frequency components of eachphase current the RMS value of each phase current is derived. The smallest and thelargest phase current are derived. If the smallest phase current is lower than the settingCurrUnsymLevel times the largest phase current the settable trip timer (tTrip) isstarted. The tTrip timer gives a trip signal after the set delay. The TRIP signal is a pulse150 ms long. The current based pole discordance function can be set to be active eithercontinuously or only directly in connection to breaker open or close command.1MRK 504 135-UEN A Section 8Current protection187Technical manual
