O-0.3sec-CO-3min-CO shows the operating duty of the circuit breaker. If the breaker is closed, it can be opened immediately. There should be a pause of 0.3 seconds for closing the breaker. After that one opening sequence can be performed without a time pause. After opening the breaker there should be a time gap of 3 min for closing the breaker. After closing, the breaker can be switched off immediately.
If we see the operating cycle the breaker must be closed after 0.3 sec the first time and after performing this the second closing is done after 3 minutes. The time gap is made to rebuild the insulation level after arc quenching during circuit interruption.