'(& )( )'& &) ( &!& ")& &$(( $# Ć %&( $# #)" &&#$
4 - 25
Siemens AG ⋅ May 1998
feeder curĆ
rent
TRIP by internal
busbar protection
P >CBF
DA 67xx/ZE
&
P T-CBF
DA 6204/ZE
transfer trip command for
CB-initiating feeder
t
1
(feeder-selective)
4.6.3 Failure of the bus coupler circuit breaker
If with closed bus coupler a busbar short-circuit ocĆ
curs (refer to figure 4.22), then a TRIP command is
issued to all related feeders of this zone and to both
coupling bay units.
Thus bus zone BBA is isolated and the healthy bus
zone BBB stays in service.
In the event of a failure of the bus coupler circuit
breaker, the busbar protection has to disconnect bus
zone BBB, too.
If the current persists in the coupler bay units after
the time T-CBF (DA 6204/ZE) has elapsed, then
breaker failure is assumed .
This results in unbalancing of the coupler bay current.
The trip criterion is thus fulfilled and bus zone BBB is
isolated, too..
BBA
BBB
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