ABB RELION REX640 - Page 1241

In the permissive overreach scheme, the received signal CR_PRM, or CRL if the
unblocking function is enabled, is used to allow the overreaching zone Z2 to trip
(activation of the OPERATE output) after the settable pick-up delay Coordination
Time
. The start signal from the overreaching zone is connected to the CACC input.
Activating the BLOCK input totally blocks the permissive overreach scheme. The
CS_PRM and OPERATE outputs can be blocked by the BLK_CS_OPR input.
Z2
Z2
~ ~
Z1
Z1
Z1_START
CB_A
CB_B
Z2_START
Z2_START
TRIP_CB_A
TRIP_CB_B
Bus A
Bus B
3
3
Figure 706: 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 zone Z3 is
connected to the CSBLK input to create a CS_BLOCKING signal. The starting of the
reverselooking zone 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 overreaching zone Z2 to trip
(activation of the OPERATE output) after the settable Coordination Time has
elapsed, and if no blocking signal is received from the remote terminal. To prevent
a false trip in case of an external fault, the block signal CR_BLOCKING must be
received before the Coordination Time has elapsed. The start signal from the
overreaching zone Z2 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
1MRS759142 F Protection related functions
REX640
Technical Manual
1241