Supervisory Functions
153
7SS52 V4 Manual
C53000-G1176-C182-1
DIF SUP mode CZ The parameter DIF SUP mode CZ (6311/CU) is used to set the response of the pro-
tection after pickup of the differential current supervision.
With setting alarm only a pickup of the differential current supervision causes only
an alarm and not a blocking of the protection. You should select this setting if you want
to set the protection to maximum selectivity.
With setting block./release the protection will be blocked for the duration of the
malfunction.
If a malfunction occurs in the check zone, the corresponding phase of the protection
is blocked completely. The blocking is released as soon as the value that initiated it
drops below the pickup threshold.
With setting blocking the blocking of the affected phase and zone is treated as with
block./release. It differs from the setting block./release in that the protection
is released by an operator input ”Reset Id-Block” or via a binary input ”>Reset
Id-Block” (BI FNo. 6/CU) as soon as the malfunction is eliminated.
ZERO CR SUPERV When an external fault is tripped by an external protection device, linearized current
transformers with TPZ cores may carry during the demagnetizing phase a DC compo-
nent that mimicks a fault in the protection zone.
In order to avoid spurious tripping, the differential current may be monitored for the
presence of a pure DC component. For this purpose the zero crossing supervi-
sionZERO CR SUPERV (6312A/CU) must be activated.
With setting ON the zero crossing supervision will be activated.
With setting OFF the zero crossing supervision will be deactivated.
I> ZERO CR The parameter I> ZERO CR (6313A/CU) is used to set the threshold of the differential
current for the zero crossing supervision.
Set this limit value to 50% of the corresponding limit value for the differential current
in the parameters Id> BZ (6102/CU) and Id> CZ (6104/CU), or Id> BZ - EF
(6109A/CU) or Id> CZ - EF (6111A/CU), using the earth fault characteristic.
The DC component monitoring is performed for each measuring system. The differen-
tial current of the selective protection zones and of the check zone is compared with
the set threshold.
f 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 assumes a DC current and issues a selec-
tive blocking command to the protection. The blocking is maintained until the current
drops below the threshold again.
ISOL TIME The parameter ISOL TIME (6301/CU) is used to set the threshold for the isolator
runtime monitoring. If no final position checkback signal is received for an isolator after
this time, the protection assumes the isolator to be faulty and issues an alarm.
This threshold is determined by the longest isolator runtime to be expected.
ISOL DC FAIL The parameter ISOL DC FAIL (6303/CU) is used to choose the isolator status which
will be assumed by the isolator replica if the auxiliary voltage for the isolator status
checkback signal has failed.
With setting OLD the old status will be assumed.
With setting ON the isolator will be assumed to be CLOSED.
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