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1MRK511447-UEN Rev. E
10.2.2.6
Trip circuit check
When the protection IED undergoes an operational check, a tripping pulse is normally obtained on
one or more of the output contacts and preferably on the test switch. The healthy circuit is of utmost
importance for the protection operation. If the circuit is not provided with a continuous trip-circuit
supervision, it is possible to check that circuit is really closed when the test-plug handle has been
removed by using a high-ohmic voltmeter and measuring between the plus and the trip output on the
panel. The measurement is then done through the trip coil of the circuit breaker and therefore the
complete trip circuit is checked.
Trip circuit from trip IEDs to circuit breaker is often supervised by trip-circuit supervision. It can then
be checked that a circuit is healthy by opening tripping output terminals in the cubicle. When the
terminal is opened, an alarm shall be achieved on the signal system after a delay of some seconds.
10.2.2.7
Restoring
Maintenance is very important to improve the availability of the protection system by detecting
failures before the protection is required to operate. There is however little point in testing healthy
equipment and then putting it back into service with an open terminal, with a removed fuse or open
miniature circuit breaker with an open connection, wrong setting, and so on.
Thus a list should be prepared of all items disturbed during test so that all can be put back into
service quickly and without overlooking something. It should be put back into service item by item
and signed by the responsible engineer.
Switchgear control unit SAM600-IO
Commissioning manual
Note that the breaker must be closed.
Please observe that the test system does not provide built-in security during this test. If
the instrument should be set on Amp instead of Volts, the circuit breaker naturally is
tripped, therefore, great care is necessary.
Remember to close the circuit directly after the test and tighten the terminal carefully.
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Commissioning and maintenance of the fault clearing system
Section 10
SEMOD56528-26 v5
SEMOD56528-36 v2
57
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