ensures the send signal from IED B2 is held back till the forward direction element is resetin IED A2.12.6.2.2 Weak-end infeed logicFigure 201 shows a typical system condition that can result in a missing operation. Notethat there is no fault current from node B. This causes that the IED at B cannot detect thefault and trip the breaker in B. To cope with this situation, a selectable weak-end infeedlogic is provided for the permissive overreaching scheme.en99000054_ansi.vsdLINE 1A BStrongsourceWeaksourceCLOSEDCLOSEDFAULTANSI99000054 V1 ENFigure 201: Initial condition12.6.3 Setting guidelinesThe parameters for the current reversal and weak-end infeed logic for residual overcurrentprotection function are set via the local HMI or PCM600.GlobalBaseSel: Selects the global base value group used by the function to define (IBase),(VBase) and (SBase).12.6.3.1 Current reversalThe current reversal function is set on or off by setting the parameter CurrRev to Enabledor Disabled. Time delays shall be set for the timers tPickUpRev and tDelayRev.tPickUpRev is chosen shorter (<80%) than the breaker opening time, but minimum 20 ms.tDelayRev is chosen at a minimum to the sum of protection reset time and thecommunication reset time. A minimum tDelayRev setting of 40 ms is recommended.The reset time of the directional residual overcurrent protection (EF4PTOC) is typically25 ms. If other type of residual overcurrent protection is used in the remote line end, itsreset time should be used.The signal propagation time is in the range 3 – 10 ms/km for most types of communicationmedia. In communication networks small additional time delays are added in multiplexersand repeaters. Theses delays are less than 1 ms per process. It is often stated that the totalpropagation time is less than 5 ms.Section 12 1MRK 506 334-UUS AScheme communication410Application manual
