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9. Maintenance
The maintenance operations are aimed at keeping the
apparatus in good working condition for as long as possible.
In accordance with what is specified in the IEC 61208 / DIN
31 051 Standards, the following operations must be carried
out.
Inspection:
Finding out the actual conditions
Overhauling: Measures to be taken to maintain the specific
conditions
Repairs:
Measures to be taken to restore the specific
conditions.
9.1.
General
The vacuum circuit-breakers are characterised by simple,
sturdy construction and a long life.
The operating mechanism requires maintenance and
functional inspections to reach the expected operating-life
(see par. 9.3.2.).
The vacuum interrupters are maintenance-free for their whole
operating life.
Vacuum interruption does not produce any harmful effects
even when there are frequent interruptions at the rated and
short-circuit current.
The interventions during service and their aim are determined
by the ambient conditions, by the sequence of operations and
by the short-circuit interruptions.
Note
Respect the following Standards for maintenance work:
– the relative specifications given in the chapter on "Standards and
Specifications";
– work safety regulations in the chapter on "Putting into service and
operations";
– standards and specifications of the country where the apparatus is installed.
The maintenance operations must only be carried out by
trained personnel and who follow all the safety regulations.
Furthermore, it is advisable to call on ABB personnel, at least
in cases for checking the performances in service and for
repairs.
Cut the power supply off and put the apparatus under safe
conditions during the maintenance operations.
Before carrying out any operations, check that the
circuit-breaker is open, with the spring discharged
and that it is not supplied (medium voltage circuit
and auxiliary circuits).
9.1.1. Operating life expectancy
The operating life expectancy for the VD4 circuit-breakers is
as follows:
– vacuum interrupters: up to 30,000 operations, according to
their type (see par. 7.2.3. Trip curves);
– switching device, actuator and transmission system: up
to 10,000 operations, under normal operating conditions,
according to the type of circuit-breaker and with regular
maintenance (see par. 9.3.2.);
– with operations correctly executed it is possible to carry out
up to 1000 racking-out/in operations (as prescribed in the
IEC 60271-200 Standards);
– the data regarding the operating life are basically applicable
to all the components which cannot be directly affected by
operator activity. The manually operated components (mov-
ing parts of isolatable parts, etc.) can vary their behaviour.
9.2.
Inspections and functionality tests
9.2.1. Interruption devices in general
– Check the conditions of the interruption devices with regular
inspections.
– Inspection at fixed intervals can be avoided when the
apparatus is permanently under the control of qualified
personnel.
– The checks must, first of all, include visual inspection
to check for any contamination, traces of corrosion or
electrical discharge phenomena.
– Carry out more frequent inspections when there are unusual
operating conditions (including severe climatic conditions)
and in the case of environmental pollution (e.g. high level of
contamination or an atmosphere with aggressive agents).
– Visual inspection of the isolating contacts.
It is recommended to turn the contact system alternately
in order to keep the internal surface of the contact areas
clean. The contact areas must be cleaned when there
are signs of overheating (discoloured surface) (also see
Repairs).
– In the case of abnormal conditions, take suitable
overhauling measures (see Overhauling par.).
9.2.2. Stored energy operating mechanism
Carry out the functional test of the operating mechanism
after 5,000 operations
or during ordinary maintenance
operations as specified in par. 9.2.1.
Before doing the test, open the circuit-breaker and carry out
the following operations:
– in the case of withdrawable circuit-breakers, take the
circuit-breaker to the isolated for test position
– in the case of fixed circuit-breakers: cut off the power
supply to the medium voltage circuit.
Note
Insulate the work area and make it safe, following the safety regulations
specified in the IEC/DIN VDE Standards.
Functional test
– With the circuit-breaker not connected to the load, carry out
a few opening and closing operations.
– If foreseen, cut the power supply to the spring charging
motor off. Discharge the spring by closing and opening
the circuit-breaker by means of the closing and opening
pushbuttons.
– Visually inspect the lubrication conditions of the tulip
isolating contacts, of the sliding surfaces, etc.
– Check correct electrical and mechanical operation of the
various devices, with particular attention to the interlocks.
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