84
6 Maintenance
6.4
Remedies for any operating anomalies vacuum circuit breaker
Anomalies
Possible causes
Checke and remedies
Shunt opening/
closing release remains
energized
Operating or accept contacts locked
closed
Check the state of contacts in series
with the release
Faulty switching circuit
Check connections, fuses, protection
switches and accept contacts
Shunt opening/closing
and/or under-voltage
release not sufficiently
energized
Supply voltage of the auxiliary circuits
too low
Measure the voltage: it must not be
lower than 85% of the rated voltage
Faulty switching circuit
Check connections, fuses, protection
switches and accept contacts
Under-voltage release
is not able to open the
circuit-breaker or it closes
but immediately opens
Supply voltage of the auxiliary circuits
too low
Measure the voltage: it must not be
lower than 85% of the rated voltage
Operating or accept contacts locked
closed
Check the state of contacts in series
with the release
Supply voltage different from the one
indicated on nameplate for these releases
Check the voltage indicated on the
nameplate of the releases
Faulty switching circuit
Check connections, fuses, protection
switches and accept contacts
Loose wire clamping screws
Check tightness of the screws
Incorrect electrical connections in the
power supply circuit
Check the connections with the
relevant diagram
Circuit-breaker
does not open
Supply voltage of the auxiliary circuits
too low
Measure the voltage: it must not be
lower than 85% of the rated voltage
Operating or accept contacts locked
closed
Check the state of contacts
in series with the release
Supply voltage different from the one
indicated on nameplate for these releases
Check the voltage indicated
on the nameplate of the releases
Faulty switching circuit
Check connections, fuses, protection
switches and accept contacts
Incorrect electrical connections in the
power supply circuit
Check the connections with the
relevant diagram
Release coils interrupted
Replace the coils
Operating mechanism locked
Operate manually;
contact SEL if the fault persists
Содержание QMT Series
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