sequence differential protection TRNSSENS and common trip TRIP are issued. Thisfeature is called the sensitive negative sequence differential protection.5. If a pickup signal is issued in a phase (see signal PU_A), even if the fault has beenclassified as an external fault, then the instantaneous differential current of that phase(see signal ID_A) is analyzed for the 2nd and the 5th harmonic contents (see the blockswith the text inside: 2nd Harmonic; Wave block and 5th Harmonic). If there is lessharmonic pollution, than allowed by the settings I2/I1Ratio, and I5/I1Ratio, (then theoutputs from the blocks 2nd harmonic and 5th harmonic is 0) then it is assumed thata minor simultaneous internal fault must have occurred. Only under these conditionsa trip command is allowed (the signal TRIPRES_A is = 1). The cross-block logicscheme is automatically applied under such circumstances. (This means that the crossblock signals from the other two phases B and C is not activated to obtain a trip on theTRIPRES_A output signal in figure 38)6. All pickup and blocking conditions are available as phase segregated as well ascommon signals.ANSI06000546-2-en.vsd&IDiffAlarmaa>bbIDMAG_C DiffIDiffAlarmaa>bbIDMAG_B DiffIDiffAlarmaa>bbIDMAG_A DiffIDALARM00-tAlarmDelayANSI06000546 V2 ENFigure 42: Differential current alarm logic6.1.4 Technical dataTable 30:T2WPDIF, T3WPDIF (87T) technical dataFunction Range or value AccuracyOperating characteristic Adaptable ± 1.0% of In for I < In± 1.0% of I for I > InReset ratio >94% -Unrestrained differential current limit (1.00-50.00)xIBase onhigh voltage winding± 1.0% of set valueTable continues on next page1MRK 502 048-UUS A Section 6Differential protection117Technical manual
