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Installation and Commissioning
7.2.1
Checking the connection circuit
7.2.1.1
Infeed circuits of the protection
Trip circuits
Isolator status
feedback signals
Isolator replica
Current
transformer
circuits
7-6
The busbar protection is delivered in individual components. The configuration, wiring
and testing of the system has to be made specifically to match the station conditions.
Note:
The wiring of the relays on the individual peripheral modules depends on the polarity.
Therefore, the wiring must be checked against the block circuit diagrams in Appendix
A.3.
In particular, it is recommended to check by a continuity test the status of the connect-
ing leads to the current transformers, to the input or summation current and matching
transformers (where required, if the modules are installed outside the cubicle or cubi-
cles), and to the station battery, the circuit breakers, the isolator auxiliary contacts and
any connected signalling equipment. The applicable plans for the power system must
be observed.
Before switching on the station battery, the correctness of the rated voltages and of
the polarity must be checked.
q
Check the trip circuits for controlling the circuit breakers. Where service conditions
do not allow to trip a circuit breaker, you can proceed e.g. by switching off the
breaker control voltage and checking the trip function as far as the circuit breaker
coil.
q
Check that isolator states are correctly detected. To do so, perform an isolator
switching operation and check the feedback signal in OPEN position. If there is no
checkback signal (because of wire break or auxiliary power outage), the isolator is
assumed to be CLOSED, so that instabilities of the measuring system when a cur-
rent flows are efficiently counteracted.
q
Check the correct allocation of the feeder currents to the measuring system (isolator
replica) using load currents or secondary test equipment.
In this context, it must be checked that the busbar protection is "normalized", i.e. that
it provides a uniform transformation ratio in all output circuits. Where current trans-
formers have different transformation ratios, the primary rated current is set to a value
between 70 and 100% of the rated maximum primary current of the existing current
transformers by means of suitable matching or summation current matching trans-
formers.
For the check of the connection circuits, the currents that are fed by the CTs onto the
protection are short-circuited at the terminals of the protection. They are proportional
to the respective primary-side currents. The equivalent of the normalized primary rat-
ed on the secondary side of the matching or summation current transformers is a cur-
rent of 100 mA. The correct current ratio must be checked by measurements in each
feeder or coupler bay with a primary current that should be at least 20 % of the nor-
malized rated current.
7SS60 Manual
E50417-G1176-C132-A1
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Troubleshooting
