Checks With Secondary Values
279
7SS52 V4 Manual
C53000-G1176-C182-3
During all checks it is important that the corresponding annunciations are for remote
signaling transmitted to the LEDs and are passed on via the alarm relays.
Before you start the checks with the secondary values:
Read out the isolator replica with DIGSI Plant Visualization. The output corre-
sponds to the plant status.
Check whether the assignment of the switching devices in the plant visualization is
correct.
7.4.2
Trip Characteristic of the Busbar Protection
Connect the test currents directly to the measuring inputs of the bay units. Depending
on the model the rated current of the bay unit is 1 A or. 5 A.
The test setup for the zone-selective protection is shown in Figure 7-11, page 280. By
the TRIP commands of the feeders the test equipment is switched off.
The test setup for the check zone is shown in Figure 7-13, page 282. When the bus
selectivity is checked switch one or more bays on a second bus (possibly by a feeder
position simulation)
7.4.2.1
busbar-selective Protection
To check the busbar-selective protection the check zone must be set more sensitive
than the bus -zone selective protection. By this, the release of the check zone is grant-
ed before the release of the busbar-selective protection.
Example
You can set the Trip characteristic for the busbar-selective protection shall be set with
the parameters
CU
) =
2,0
I
no
and the stabilizing factor
(
CU
) =
0,8
.
For the check zone the parameters for the differential current threshold is assumed to
be set
(
CU
) to
0,5
I
no
and the stabilizing factor
/
CU
) to
0,5
.
Test setup
For the test use 2 bays (no sectionalizers, no bus couplers) with the same normal-
ization factor (CT-transformation ratio).
Connect both bays to the same busbar.
Note
The measuring accuracy depends on the electric data of the test source used. The
accuracy given in Chapter 9, page 311 “Technical data” Test can only be expected
when following the reference conditions corresponding to
DIN VDE 0435/Teil 303 or IEC 255 and using precision measuring instruments.
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