15.1.2.2 Delta blocking scheme GUID-D699D2D8-6479-4B40-8B09-7B24CA86C24B v1In the delta blocking scheme a fault inception detection element using delta basedquantities of voltage and current will send a block signal to the remote end to blockan overreaching zone.The delta based start is very fast and if the transmission channel is fast then there isno need for delaying the operation of remote distance element. If the fault is inforward direction, the sending is inhibited by a forward directed distance (ordirectional current or directional earth fault) element.Since the scheme is sending the blocking signal during conditions where theprotected line is healthy, it is common to use the line itself as communicationmedia (PLC). The scheme can be used on all line lengths.The blocking scheme is very dependable because it will operate for faultsanywhere on the protected line if the communication channel is out of service.Conversely, it is less secure than permissive schemes because it will trip forexternal faults within the reach of the tripping function if the communicationchannel is out of service.Inadequate speed or dependability can cause spurious tripping for external faults.Inadequate security can cause delayed tripping for internal faults.Since the blocking signal is initiated by the delta based detection which is very fastthe time delay tCoord can be set to zero seconds, except in cases where thetransmission channel is slow.The timer tSendMin for prolonging the send signal is proposed to set to zero.A BORBDeltaBasedDetection (deltaA)deltaA CS TRIPB = ORB+ tCoord+ CRIEC11000252-1-en.vsdIEC11000252 V1 EN-USFigure 190: Principle of delta blocking schemeOR: OverreachingCR: Communication signal receivedCS: Communication signal senddeltaA: Delta based fault inception detection on A side that gets inhibited for forward faults1MRK 511 401-UEN A Section 15Scheme communicationBay control REC670 2.2 IEC 435Application manual
