Siemens SIPROTEC 7SS522 V4.6, Manual

Page: 302 / 440

Installation and Commissioning
286
7SS52 V4 Manual
C53000-G1176-C182-3
Test steps ‰ To prevent the differential current supervision from blocking the protection during
checking switch it off with the parameter
DIFF SUPERV
(
6306
/
CU
).
‰ Set the supervision of the breaker failure protection triggering inputs with the pa-
rameter
BF BI MODE
(
XX14/CU
) to
1-ch w/o sup
or
2-ch w/o sup
.
‰ Configure the feeder-selective parameter to
BF OP MODE
(
XX15/CU
)
BZ unbal-
ance
.
‰ Set the parameters for the differential current threshold I> BF ( XX18/CU ) and the
stabilizing factor
STAB FAC:BF
(
6201/CU
) to the desired value.
‰ Set the isolators so that bay 1 and 2 are connected to the same bus zone.
‰ The test currents I
1
and I
2
must have a phase displacement of 180°. To find out the
phase angle, check the feeders 1 and 2 each with the same current (0,5 I
N
).
‰ If the differential current is not zero reverse the polarity in a feeder.
‰ Apply to the bays 1 and 2 though the test equipment a constant current I
1
. After the
start by the feeder protection (TRIP command) in feeder 2 the protection system
permanently unbalances the measuring value of feeder 2.
‰ If the connection is correct there must be a differential current and the stabilizing
current must be twice the supply current.
‰ Slowly increase the current in feeder 2 until the protection trips.
‰ The differential current must then be | I
1
+
I
2
| and the stabilizing current must be |
I
1
|
+
| I
2
|. The stabilizing factor must be the ratio of differential current to stabilizing
current k = | I
1
+
I
2
| / | I
1
|
+
| I
2
|.
7.4.5.2 Delay Time at Operating Mode “Unbalancing” and “I
>
Query”
Test setup The test setup for the measuring of the time delay is shown in Figure 7-14, page 285.
Test steps ‰ Set the two feeders to the same normalizing factor i.e.to the same CT transforma-
tion ratio.
‰ Set the CT polarity in such a way that the current flow (approx. 2 I
N
) before the un-
balancing corresponds to an external short-circuit (flowing through current). The dif-
ferential current is approx. zero.
‰ Apply for the test to one bay unit twice the current set in parameter
I> BF
(
XX18/
CU
).
‰ Simulate the TRIP command from the feeder protection for feeder 2 and start the
time measuring.
‰ Stop the time measuring device with the TRIP command of the busbar protection.
The value displayed by the measuring device corresponds to the set delay time plus
the tripping time of the protection.
7.4.6 Finishing the Tests with Secondary Values.
‰ Remove all devices for the tests with secondary values and re-establish the original
status (switching off the test switch,...).
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