32
20 Nm
20 Nm
fig. 26
Checking screw tightening
5.2.4. inspections and functional tests
interruption devices in general
– Carry out regular inspections to check that the interruption
devices are in good condition.
– Inspection at fixed intervals can be waived when the
apparatus is permanently monitored by qualified personnel.
– Above all, the checks must include a visual inspection
to check for any contamination, traces of corrosion and
electrical discharge phenomena.
– Carry out more frequent inspections when there are unusual
operating conditions (including adverse climatic conditions)
and in the case of environmental pollution (e.g. heavy
contamination or an atmosphere with aggressive agents).
– Visual examination of the isolating contacts.
Turning the system of contacts alternately is recommended,
in order to keep the internal surface of the contact areas
clean. The contact areas must be cleaned if there are signs
of overheating (discoloured surface) (also see the paragraph
on “Repairs”).
– If any anomalous conditions are found, appropriate
servicing measures must be taken (see the paragraph on
“Servicing).
functional test
– Make the circuit-breaker safe by discharging the closing
springs (close and open the circuitbreaker by means of the
closing and opening pushbuttons).
– with the circuit-breaker in the test position, carry out a
few opening and closing operations by means of the shunt
opening and closing releases.
– The nuts and screws are tightened in the factory and
correct tightening is marked with a coloured sign. Further
tightening operations during the operating life of the circuit-
breaker are not foreseen. However, if it should be necessary
to tighten the nuts or screws again following any trips, the
values indicated in fig. 26 must be respected.
Stored energy operating mechanism Carry out the functional
test of the operating mechanism every 5,000 operations or
every 4 years. before doing the test, open the circuit-breaker
and carry out the following operations:
– for withdrawable circuit-breakers, take the circuit-breaker to
the test position
– for fixed circuit-breakers: cut off the voltage to the medium
voltage circuit.
note
Insulate the working area and make it safe, following the
safety regulations specified in the ANSI C37.04 – C37.54 –
C37.09 – C37.55 VDE Standards.
