12.3 Current reversal and WEI logic for distance protectionphase segregated ZCWSPSCH (85)12.3.1 IdentificationFunction description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberCurrent reversal and WEI logic fordistance protection phase segregatedZCWSPSCH - 8512.3.2 FunctionalityThe current reversal function is used to prevent unwanted operations due to currentreversal when using permissive overreach protection schemes in application with parallellines when the overreach from the two ends overlap on the parallel line.The weak-end infeed logic is used in cases where the apparent power behind the protectioncan be too low to activate the distance protection function. When activated, receivedcarrier signal together with local undervoltage criteria and no reverse zone operation givesan instantaneous one- or three-phase trip. The received signal is also echoed back during200 ms to accelerate the sending end.12.3.3 Function blockANSI10000219-1-en.vsdZCWSPSCH (85)V3P*BLOCKIFWDIREVWEIBLK1WEIBLK2BLKZCBOPENCRLIRVLTRWEITRWEI_ATRWEI_BTRWEI_CECHOANSI10000219 V1 ENFigure 238: ZCWSPSCH (85) function blockSection 12 1MRK 506 335-UUS AScheme communication508Technical manual
