Section 2 1MRK 505 351-UEN
Commissioning
12 Commissioning Manual
Distributed busbar protection REB500
Check that the correct circuit-breaker tripping coil is tripped by the
correspondingly configured tripping output. Repeat the procedure for the separate
alarm contacts.
2.2.8 Checking protection stability
The stability check verifies that all CTs are connected with the correct polarity and
have the correct ratio. All feeder and bus-tie breaker CTs must be connected,
otherwise the correct operation of the protection cannot be guaranteed.
Wherever possible the stability should be checked before the busbar is energized,
because the risk of a busbar fault is especially high when it is being energized for
the first time (flashovers, grounding isolators still closed etc.).
2.2.8.1 Checking through-fault stability with de-energized busbars
Inject a current from a primary injection test set (25 % of the CT rated current is
recommended) into two feeders (a reference feeder and one other feeder). Any
feeder can be used as reference. Compare each of the other feeders and bus-tie
breaker with the reference feeder.
Figure 2 Through-fault stability by primary injection (two feeders)
If a bus-tie breaker is only equipped with one set of CTs, note that they are used by
two busbar sections.
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