ABB RELION REX640 Technical Manual page 1165

1MRS759142 C
REX640
Technical Manual
Bus A
~
3
Z2_START
GUID-66C6BD9F-8FF4-4B66-9C08-9F7426F312FF V1 EN
Figure 626: Simplified functional diagram of the permissive overreach scheme
Directional comparison blocking scheme DCB
The directional comparison blocking scheme is enabled with Scheme type =
"Blocking".
In the blocking scheme, the START signal from the reverse-looking residual
overcurrent function DEFLPDEF set to operate for the reverse direction earth fault, is
connected to the CSBLK input to create a CS_BLOCKING signal. The starting of the
reverse-looking function indicates that the fault is located outside the protected feeder.
The duration of the CSBLK input signal can be prolonged with the Carrier Min Dur
setting to ensure a sufficient duration of the CS_BLOCKING signal.
The blocking scheme is mainly used to allow the forward-looking overreaching
residual overcurrent function to trip (activation of the OPERATE output) after the
settable Coordination time, and if no block signal is received from the remote
terminal. To prevent a false trip in case of external faults, the CR_BLOCKING signal
must be received before the Coordination time has elapsed. The start signal from the
overreaching residual overcurrent function DEFLPDEF is connected to the CACC
input.
The Coordination time setting in the blocking scheme depends, for
example, on the communication system delay and on the terminal's
response times in transmitting a CS_BLOCKING signal to the other
feeder end. The Coordination time setting must not be zero.
Activating the BLOCK input totally blocks the directional comparison blocking
scheme. The CS_PRM and OPERATE outputs can be blocked by the BLK_CS_OPR
input.
Protection related functions
CB_A
TRIP_CB_A
DEFL_START
DEFH_START
Section 5
Bus B
~
3
CB_B
TRIP_CB_B
1159