After making breaker(on load switch) off, isolator switch (offload switch) on both side of breaker are made off,, first on source side, and then on load side are made open and grounded. If breaker is opened perfectly, no sparking will take place while isolating.
The need for preventative maintenance of molded case circuit breakers will vary depending on operating conditions. Where heavy dust conditions exist, for instance, and the circuit breakers are not called upon to operate, an accumulation of dust on the latch surfaces may affect the operation of the breaker slightly. Dust accumulation can usually be cleared from the latch by occasionally manually turning the breaker “OFF” and “ON,” thus exercising the circuit breaker. When normal maintenance inspection and cleaning of bus connections, relays, lug connections, and other parts of the distribution system is being made, it is advisable to operate and check the circuit breaker operation.
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