End Fault Protection
135
7SS52 V4 Manual
C53000-G1176-C182-3
5.4
End Fault Protection
The function of the end fault protection is to protect the zone between the current
transformer and the circuit breaker when the circuit breaker is open.
5.4.1
End Fault Protection in the Feeder
Bus-side
current transform-
ers
With bus-side current transformers (Figure 5-28, page 136, 1a) the zone protected by
the busbar protection is normally delimited by the location of the current transformer.
The end fault protection allows to extend this zone as far as the circuit breaker. In case
of a fault the busbar protection can issue a trip command in very short time. Without
end fault protection, the feeder protection would detect a fault, but issue no trip com-
mand. The fault could only be cleared by the circuit breaker failure protection func-
tions, with the resulting time delay.
Line-side
current transform-
ers
With line-side current transformers (Figure 5-28, page 136, 1b) and 2), the end fault
protection helps to avoid an overfunction of the busbar protection. If a data transmis-
sion feature is provided, it can also issue a transfer trip command to the circuit breaker
at the remote end ”
End-Flt. Trip
” (
FNo. 7644/BU
). The feeder protection would
interpret such a situation as a fault in reverse direction and trip with the resulting delay.
Without any transmission channels, the fault is only cleared with a distance-dependent
time offset by the remote end.
The logic of the end fault protection is shown in Figure 5-29, page 136. A prerequisite
for activating the end fault protection is that the circuit breaker is open
(”
>CB OFF
” (
FNo. 7617/BU
) marshalled to a binary input). Before the circuit breaker
is closed and the feeder current is integrated into the busbar measurement again, the
end fault protection must be blocked. Therefore the leading information of the
CB CLOSE
command is evaluated (”
>CB man.close
” (
FNo. 7618/BU
) marshalled
to a binary input).
The end fault protection is blocked if the monitoring of the switching status feedback
(Chapter 5.5.1.10, page 151) has detected a fault.
This function is only available for the bay type ”feeder bay”; it can be activated and
deactivated per feeder with the parameter
XX29/CU
).
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