ABB RELION REX640, Техническое руководство, Страница: 1255 / 1960

underreaching function is connected to the
CSUR
input. The duration of the
CSUR
input signal can be prolonged by the
Carrier Min Dur setting to ensure a sufficient
duration of the
CS_PRM
signal.
In case of parallel feeders, when the external current reversal logic
(RCRWPSCH) is enabled, the
CS_PRM
signal is not prolonged and the
value of
Carrier Min Dur is set to zero to secure correct operation.
In the permissive overreach scheme, the received signal
CR_PRM
or
CRL
, if
the unblocking function is enabled, is used to allow the overreaching residual
overcurrent function DEFLPDEF 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.
The
CS_PRM
signal is also generated if the
CR_PRM
signal is received and the local
carrier acceleration signal
CACC
is active.
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.
~ ~
DEFH_START
CB_A
CB_B
Z2_START DEFL_START
TRIP_CB_A
TRIP_CB_B
Bus A
Bus B
3 3
Figure 713: 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
1MRS759142 F Protection related functions
REX640
Technical Manual
1255