ABB RELION REX640, Техническое руководство, Страница: 1256 / 1960

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.
In
Figure 714 , in case of internal faults, the
CS_BLOCKING
signal is not sent as the
fault is not seen by the reverse-looking overreaching function.
~ ~
DEFL_START
(Forward)
TRIP_CB_A
TRIP_CB_B
DEFL_START
(Forward)
Bus A Bus B
3 3
Figure 714: Simplified functional diagram of the blocking scheme, internal fault
In
Figure 715
, in case of external faults, the protection relay at bus B sees the fault
in the reverse direction and sends a blocking signal
CS_BLOCKING
to the protection
relay at bus A. There is no CB operation at either end.
Protection related functions 1MRS759142 F
1256 REX640
Technical Manual