ABB RELION REX640 Technical Manual page 1150

Section 5
Protection related functions
1144
Bus A
~
3
CB_A
Z2_START
GUID-F5FA1AA0-B5B3-44CF-B9B9-28470FB638D3 V1 EN
Figure 619: 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 reverse-
looking 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
response times in transmitting the 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.
Z2
Z1
Z1
Z2
TRIP_CB_A
Z2_START
Z1_START
1MRS759142 C
Bus B
~
3
CB_B
TRIP_CB_B
REX640
Technical Manual