Interrupting chamber for high-voltage circuit breaker with improved arc blow-out

An interrupting chamber for high-voltage circuit breaker, intended to break all currents of value less than or equal to the short circuit interrupting capacity of the circuit breaker, including asymmetric currents, the chamber comprising a pair of contacts, the pair of contacts comprising an arc contact and adapted to be separated apart during an arc breaking, an insulating arc blow-out nozzle comprising a neck, the arc blow-out nozzle being integral with the arc contact thereby constituting a moveable assembly, the interrupting chamber comprising an additional insulating component integral with the arc contact and the nozzle and arranged between an interior part of the nozzle upstream of the neck and the arc contact so as to define a first channel and a second channel, the first channel being defined between the nozzle and the additional insulating component and with the interrupting chamber having a cavity of variable volume, the volume of the cavity being variable under the action of a fixed blow-out piston, the blow-out piston being pierced with a through hole adapted to be closed by a main valve, with the main valve being closed when the overpressure exerted in the cavity is less than a predetermined value, the hole being in communication with the second channel defined between the additional insulating component and the arc contact, when the overpressure exerted in the cavity is greater than the predetermined value, the main valve loading being carried out so as to conserve a sufficiently high overpressure in the cavity for the entire range of currents to be broken.