GE P742

Operation
P74x/EN OP/N
a7
MiCOM P741, P742, P743
(OP) 5-
21
OP
P3739ENa
>1
>1
>1
DDB Ext. CB Fail
DDB O/C Protection
DDB Ext. 3ph Trip
DDB External Trip A
DDB External Trip B
DDB External Trip C
1
2
3
>1
>1
>1
DDB CB Aux. 3ph (52a)
DDB CB Aux. A (52a)
DDB CB Aux. B (52a)
DDB CB Aux. C (52a)
4
5
6
7
Trip signal from CU
8
12
13
>1
DDB CBF Int Backtrip
DDB CBF Ext Backtrip
DDB Int Retrip 3ph
9
10
11
DDB Ext. Retrip ph A
DDB Ext. Retrip ph B
DDB Ext. Retrip ph C
DDB BF Trip Request
Trip signal towards CU
CB Fail
Logic
(See Fig 9)
FIGURE 9: CB FAIL LOGIC (DDB INPUTS & OUTPUTS)
1.3.3.2.6 Internally Initiated CBF i.e.
Tripping from the Differential Element 87BB issued by the Central Unit
When a tripping order is generated by the busbar protection (87BB or 50BF) but not
executed due to a circuit breaker failure condition, the following circuit breakers are required
to be tripped instead:
All the circuit breakers in the adjacent busbar zone if the faulty circuit breaker is that of a bus
coupler or bus section.
Optional: The remote end circuit breaker if the faulty circuit breaker is that of a feeder (line or
transformer). This intertripping is done via PSL and may not be required on feeders, which
may be serviced automatically via the distance or other line protection.
The tripping order from the busbar protection is referenced as Tp
ABC
, it is always three-phase
and initiates timers tBF1 and tBF2. The first timer is associated with the local re-trip function
while the second timer is associated with the conveyance of the signal to the central unit for
tripping of the adjacent zone in the cases of bus coupler/bus section circuit breaker failure.