Abstract: A high-voltage circuit-breaker has an interrupting chamber comprising a gas-tight cylindrical casing filled with a gas having good insulative properties such as sulfur hexafluoride. The casing contains a fixed permanent contact, a fixed arc contact and a mobile assembly comprising permanent contacts and arc contacts and associated with a gas blast assembly. The chamber also contains a carbon-based resistor having a resistance of approximately 500 ohms connected in parallel with the circuit-breaker contacts when the arc contacts are opened by an auxiliary switch. This resistor is connected in series with an arrangement of varistors, the resulting combination being disposed inside the casing and connected in series with the auxiliary switch. Opening of the auxiliary switch is effected by opening of the circuit-breaker. The volume of the resistor is greater than that of the arrangement of varistors by a factor of at least five.