Frequency characteristics and switching, operating characteristics of Circuit breaker.

Rated frequency of circuit breaker:

Two frequencies are currently used throughout the world: 50 Hz in Europe and 60 Hz in America, a few countries use both frequencies. The rated frequency is either 50 Hz or 60 Hz.

The performance of a circuit breaker is same for both the frequencies 50HZ and 60HZ ac network. Same thermal effect and other performance for up to 60HZ of a circuit breaker. Special consideration is required for frequency above 60HZ.

Switching sequence & Operating sequence of circuit breaker:

We should not switch on or off a circuit breaker or operate a circuit arbitrarily, there is some specific standard for switching and operating sequence of a circuit breaker.

Switching sequence

Rated switching sequence of circuit breaker according to IEC(International Electrotechnical Commission), O – t – CO – t’ – CO. (cf: opposite diagram)
O : represents opening operation
CO : represents closing operation followed immediately by an opening operation.
So after opening the circuit breaker there should be some time gap, then closing operation. The the next time gap should be a little more. This is explained below.

Operating sequence

Three rated operating sequences exist:
v slow: 0 – 3 minute – CO – 3 minute – CO
v quick 1: O – 0.3 s – CO – 3 minute – CO
v quick 2: O – 0.3 s – CO – 15 s – CO

rated operating sequence of circuit breaker
rated operating sequence of circuit breaker

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