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8.5
Checking of Contact Erosion
The contact erosion is to be checked with the circuit-
breaker in the ON condition. Carry out steps 1 to 5 as in
clause 7.3 and close the breaker slowly as per clause 6.1.
Open the rear cover. The maximum permissible contact
erosion in vacuum interrupter is 3mm. It can be checked
by means of an indicator fitted on one side of each pole
support. In the 'as-supplied state' and with the breaker
closed, the contact erosion indicator (28) points to the
lower level of 3mm thick erosion scale (28.1). When the
breaker is in service, the degree of contact erosion can be
seen by the position of indicator relative the scale.
The breaker may only be operated as long as the erosion
indication remains with in the scale range.
8.6
Checking the Vacuum
Before putting the breaker in service, or if an interrupter
is suspected of leakage as a result of mechanical damage
check the vacuum as follows:
Steps 1 to 6 as in clause 7.3
Remove the bottom covers of the base frame.
Remove the circlip (P-15, Fig. 7) from the pin (P-16,
Fig. 7) use the handle in the closing direction to facilitate
removal of the pin.
When the pin is removed, the switching rod (P-6, Fig. 7)
will be suddenly pulled up due to the vacuum in the
healthy interrupter.
In the case of a loss of vacuum in the interrupter, if the
switching rod is pulled down it will not move back on its
own. This indicates that the vacuum interrupter has to be
replaced.
8.7
Cleaning
DANGER
Non-observance can result in death or
serious personal injury.
Terminals must not be touched if the power
supply is connected.
DANGER
Non-observance can result in personal injury.
All springs of the operating mechanism must be
discharged and the vacuum circuit-breaker be brought
into the open state, "Closing spring discharged"
indication visible.
To assure the insulating capacity, it is necessary that the
insulating components are clean. Insulating components
and external breaker part must be wiped with a damp
cloth. Use only warm water with the addition of a mild
liquid household detergent as cleaning agent.
8.8
Dielectric Test
Prior to commissioning the breaker or putting it back into
service after a maintenance outage, the circuit-breaker
should be checked for insulation resistance using a 5 kV
meggar kit.
1.
CB open between phase terminals
(2 readings)
2
CB open between top terminals and earth
(3 readings) and
3
CB closed between terminals and earth
(3 readings)
In each case the reading should be greater than
100 MOhm.
8.9
Accessories and standard spare parts
Owing to the fact that all parts of this breaker type have
been optimized to last the normal service life, there is no
need to recommend any particular spare parts for
keeping in stock.
Nevertheless, if you require spare parts, state the
following data when ordering them:
15
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