Delta Blocking Scheme - ABB REC670 Applications Manual

1MRK 511 401-UEN A
15.1.2.2
Bay control REC670 2.2 IEC
Application manual

Delta blocking scheme

In the delta blocking scheme a fault inception detection element using delta based
quantities of voltage and current will send a block signal to the remote end to block
an overreaching zone.
The delta based start is very fast and if the transmission channel is fast then there is
no need for delaying the operation of remote distance element. If the fault is in
forward direction, the sending is inhibited by a forward directed distance (or
directional current or directional earth fault) element.
Since the scheme is sending the blocking signal during conditions where the
protected line is healthy, it is common to use the line itself as communication
media (PLC). The scheme can be used on all line lengths.
The blocking scheme is very dependable because it will operate for faults
anywhere on the protected line if the communication channel is out of service.
Conversely, it is less secure than permissive schemes because it will trip for
external faults within the reach of the tripping function if the communication
channel 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 fast
the time delay tCoord can be set to zero seconds, except in cases where the
transmission channel is slow.
The timer tSendMin for prolonging the send signal is proposed to set to zero.
DeltaBasedDetection (deltaA)
OR
B
deltaA
IEC11000252 V1 EN-US
Figure 190: Principle of delta blocking scheme
OR: Overreaching
CR: Communication signal received
CS: Communication signal send
deltaA: Delta based fault inception detection on A side that gets inhibited for forward faults
Scheme communication
A
CS
Section 15
GUID-D699D2D8-6479-4B40-8B09-7B24CA86C24B v1
B
TRIP = OR + tCoord+ CR
B B
IEC11000252-1-en.vsd
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