Circuit breaker containing a gas escape hood with sealable opening

A medium-, high-, or very high-voltage circuit breaker, comprising at least one arc-control chamber and an outer casing defining a space in which the arc-control chamber is arranged, said arc-control chamber comprising:

• a first set of electrical contacts and a second set of electrical contacts, at least one of the first and second sets being movable in such a manner as to enable closing and opening operations of the circuit breaker;
• an arc blast nozzle;
• and
• a discharge cap situated in the space and comprising an end wall and a side wall internally defining a gas-flow chamber situated at least in part downstream from the blast nozzle, the discharge cap including at least one opening for discharging gas;
• the circuit breaker including sealing means for sealing said opening, said sealing means being movable between a sealing position in which said sealing means prevent the gas from passing through the opening, and a retracted position in which said sealing means allow passage therethrough, the circuit breaker being configured in such a manner that in a closed position, said sealing means are in the retracted position, and in such a manner that passage from the retracted position to the sealing position takes place during an operation of opening the circuit breaker.