DIRECT-CURRENT CIRCUIT BREAKER

A direct-current circuit breaker according to an embodiment comprises a mechanical breaking part, an arrester, and a commutation device. The mechanical breaking part lias at least one mechanical breaking unit. The at least one mechanical breaking unit has at least one unitized breaking part. Each of the at least one unitized breaking part has a mechanical contact section. All of the at least one unitized breaking part are connected in series to form a mechanical contact module. Both ends of the mechanical contact module are connected to a direct-current transmission system. The arrester is connected in parallel with the mechanical contact module. The commutation device has a commutation circuit. The commutation circuit is formed by connecting a reactor, a capacitor, and a closing device. The commutation circuit is connected in parallel with the mechanical contact module. The closing device is a high-speed closing device.