Checks With Secondary Values
281
7SS52 V4 Manual
C53000-G1176-C182-3
On the trip characteristic is valid | I
2
− I
1
| = k [| I
1
| + | I
2
|]
Because the currents I
1
and I
2
have a phase displacement of 180°, you have
I
2
(1 − k) = I
1
(1 + k) or. I
2
= I
1
(1 + k) / (1 − k) and
I
2
= 9 × I
1
, if k = 0,8
Repeat the checking with a different constant current I
1
. The Trip characteristic
graph is shown in Figure 7-12, page 281.
After the checking, switch on the differential current supervision again with the pa-
rameter DIFF SUPERV (6306/CU).
Figure 7-12 Trip characteristic of the busbar protection
7.4.2.2 Check Zone
Alternatively, the decision to trigger by the checkzone can be requested via the mes-
sage "Trip L1 CZ" (FNo. 10457 to 10459/CU) as a phase selection. This enables
a check which is independent of the selected bus protection.
Example You want to set the trip characteristic for the check zone with the parameters for the
differential current threshold Id> CZ (6104/CU) = 2,0 I
no
and the stabilizing factor
STAB FAC:CZ (6103/CU) = 0.8.
You want to set the busbar-selective protection the parameters Id> BZ (6102/CU) to
0,5 I
no
and the stabilizing factor STAB FAC:BZ (6101/CU) to 0.5.
Test setup
For the test setup use three bays with the same normalizing factor. Sectionalizers,
or bus couplers must not be used for testing.
Connect the bays 1 and 2 to the same bus zone.
Connect the current inputs of these bay units back to back (see Figure 7-13, page
282). Connect bay 3 to a different bus.
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