TB MRI(K)3-C 03.02 E
35
5.7
Control functions
5.7.1 Block/Trip-time
The block/trip serves for recognising a CB failure pro-
tection by rear interlocking. Setting of the blocking input
will activate the blocking function and block the config-
ured protection functions. (refer to chapter 5.11.1) If the
block/trip time is not set to EXIT but to an adjustable
time (0.1 – 2.00s), the blocking function is cancelled
again after this time has expired. If trip blocking was set
to protection blocking PR_B, protection excitation with
subsequent tripping will take place after expiration of
the set time when blocking is cancelled on expiration of
the block/trip time. If blocking is set to trip blocking
TR_B, there will be immediate tripping after blocking has
been cancelled following expiration of the block/trip
time if the set time of the responding protection step has
already expired.
I>
+
+
+
tI>
tI>
t
1
0
I>
Block/
Trip time
t
1
0
Protection Block
Trip
Block
t
1
0
Figure 5.3:
5.7.2 Time delay for ext. Trip
Via a digital input a external trip with settable time is set-
table. The trip take place by the means of o high volt-
age level at the input for the setet time. It is possibe to
assign this in out function to the output relay. Also it can
assign to the alarm relay.
5.7.3 Dead time for Trip/Restore
This function fullfil the requirements for a manual switch
ON operation. When a high level at the assigned digi-
tal input take place, the relay trips immediately. When
the digital input is reset to low level a counter starts and
after the selectable delay time (0,1s – 300s) the relay
switch ON the CB.
Figure 5.4:
5.7.4 CB failure protection
The CB failure protection is based on supervision of
phase currents during tripping events. Only after tripping
this protective function becomes active. The test criterion
is whether all phase currents are dropped to <1% x I
N
within t
CBFP
(Circuit Breaker Failure Protection - adjustable
between 0.1 - 2.0 s). If not all of the phase currents
have dropped to <1%xI
N
within this time, CB failure is
detected and the related relay activated. The CB failure
protection function is deactivated again as soon as the
phase currents have dropped to 0 within t
CBFP
.