The stages of current interruption in high voltage Gas circuit breakers are shown in Figure:
- Initially the breaker is closed, with both main contacts and arcing contacts engaged. When the breaker opens, the main contacts separate first causing the current to commutate to the arcing contacts.
- As soon as the arcing contacts separate an arc is drawn between them .
- As the arcing contacts separate further, the auxiliary nozzle becomes exposed to arcing.
- When the arcing contacts separate further the main nozzle becomes subject to ablation.
- As the arcing contacts continue to separate, the aforementioned parts of the interrupter, i.e. arcing contacts, auxiliary nozzle and main nozzle continue to experience wear.
- until the arc is finally extinct.