Functions
146
7SS52 V4 Manual
C53000-G1176-C182-3
Zero current
supervision
When the primary current is interrupted, a current continues to flow in the CT circuit
on the secondary side. The busbar protection cannot distinguish this current from a
differential current. At first, erroneous tripping is prevented by the stabilizing current.
The stabilizing current decays according to an e-function with a time constant of
64 ms. The zero current monitoring prevents spurious tripping after the stabilizing cur-
rent has decayed. If the zero crossings of the current do not recur at the latest after
32 ms (f
N
= 50 Hz) or 27 ms (f
N
= 60 Hz), the measuring system detects a DC current
and issues a selective blocking command to the protection ”
Block ZeroCross
”
(
FNo. 10444/CU
)
. The blocking is maintained until the current drops below the zero
current monitoring threshold again.
The zero current monitoring can be activated and deactivated with the parameter
CU
).
5.5.1.9
Isolator Status Supervision
Preferential treat-
ment for busbar
coupling
If two busbars are solidly linked via the isolators of one feeder, all feeders which are
connected to the linked busbars are allocated to a preferred busbar protection meas-
uring system. In any case, the bus zone with the lowest configured number is consid-
ered to be preferred. At the same time, the coupler bay is taken out of the allocation
list with respect to the currents.
Isolator statuses
The isolator positions “
OPEN
”, “
CLOSED
”, “Intermediate Position” are issued in the
following indications in function of the status (
FNo. 176.1110/CU
),
(
FNo. 176.1115/CU
), (
FNo. 176.1120/CU
), (
FNo. 176.1125/CU
) and
(
FNo. 176.1130/CU
). Here, 1-1 intermediate position and 0-0 running position are
combined.
Isolator running
status
If an isolator changes position, for instance from the OPEN position, it needs a certain
time (isolator running time) to reach the other position. During this running time, the
isolator is considered to be in the CLOSED position. This intermediate status is mon-
itored. If after a set isolator running time
) no checkback signal
is given, the isolator assumes faulty status and an alarm is created by the central unit
per isolator ("
FltR $01 $02
" (
FNo. 176.1122/CU
); e.g. for isolator 3 in bay
Fxx
).
In addition, the indication
"
Isol flt alarm
" (
FNo. 10425/CU
) i
s issued after the
isolator running time has elapsed
.
Behavior in the
case of an isolator
intermediate status
The parameter
ISOL ST 1/1
(
6304/CU
) is used to specify whether the isolator
status is assumed to be “CLOSED” or the “old isolator status” if the isolator position is
not plausible (“OPEN” and “CLOSED” at the same time). If the isolator is in
intermediate position, the isolator will be reported as faulty after the time set in
parameter
6301/CU
) has elapsed indicating
"
FltP $01 $02
" (
FNo.
176.1113/CU
), (
FNo. 176.1118/CU
), (
FNo. 176.1123/CU
), (
FNo. 176.1128/
CU
) and (
FNo. 176.1133/CU
). In addition, the indication
"
Isol flt alarm
" (
FNo.
10425/CU
)
is issued after the isolator running time has elapsed
.
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