tCoord: Delay time for trip from ECPSCH function. For Permissive under/overreaching schemes, this timer shall be set to at least 20 ms plus maximum resettime of the communication channel as a security margin. For Blocking scheme, thesetting should be > maximum signal transmission time +10 ms.Unblock: Select Off if unblocking scheme with no alarm for loss of guard is used.Set to Restart if unblocking scheme with alarm for loss of guard is used.tSendMin: Time duration, the carrier send signal is prolonged.tSecurity: The absence of CRG signal for a time duration of tSecurity is consideredas CR signal.13.5 Current reversal and weak-end infeed logic forresidual overcurrent protection ECRWPSCH IP14365-1 v413.5.1 IdentificationM14883-1 v2Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberCurrent reversal and weak-end infeedlogic for residual overcurrent protectionECRWPSCH - 8513.5.2 Application IP15041-1 v113.5.2.1 Fault current reversal logic M15285-3 v7Figure 124 and figure 125 show a typical system condition, which can result in afault current reversal.Assume that fault is near the B1 breaker. B1 Relay sees the fault in Zone1 and A1relay identifies the fault in Zone2.Note that the fault current is reversed in line L2 after the breaker B1 opening.It can cause an unselective trip on line L2 if the current reversal logic does notblock the permissive overreaching scheme in the IED at B2.1MRK 505 393-UEN B Section 13Scheme communicationLine differential protection RED650 2.2 IEC 291Application manual
