A circuit breaker comprising, for each pole, at least one interrupting chamber having fixed contacts and moving equipment including a moving contacts, and in parallel with each interrupting chamber series circuit comprising a varistor and a switch, said switch being open when the circuit breaker is disengaged and being closed when the circuit breaker is engaged. The switch comprises a moving contact driven by the moving equipment when the circuit breaker is performing an engagement operation, with the moving contact being constrained to follow the movement of the moving equipment when the circuit breaker performs a disengagement operation, but with a certain delay.