Disclosed is a DC circuit breaker capable of interrupting fault currents flowing in both forward and backward directions. The DC circuit breaker includes: a first mechanical switch for interrupting a current in a DC transmission line; a first diode connected in parallel with the first mechanical switch; a second mechanical switch, connected in series with the first mechanical switch, for interrupting a current in the DC transmission line; a second diode connected in parallel with the second mechanical switch; an LC circuit connected in parallel with the first and second mechanical switches and including a capacitor and a reactor connected in series to induce LC resonance; a first unidirectional switching device connected in parallel with the LC circuit and switching a current to induce LC resonance; and a bidirectional switching device connected in series with the LC circuit and switching currents flowing in both forward and backward directions.

A switch capable of easily accomplishing current cutoff roles required for a high-voltage switch, and which has a short breaking time. The switch includes pressure housings filled with an insulative medium, a plurality of contactors each including a contact, a plurality of operation units actuating the contacts, an insulative spacer dividing the interiors of the pressure housings into the same number of internal spaces as the number of contacts, and an electrode passing completely through the insulative spacer and fastened to the insulative spacer. The contactor is provided one by one for each internal space, and all contacts are electrically connected in series via the electrode, and the operation units actuate the corresponding contacts, respectively.

A switching device has a commutation flow path, a first isolating gap, and a second isolating gap. The first isolating gap and the second isolating gap form an electrical series circuit which is arranged parallel to the commutation flow path. The second isolating gap has a first contact, a second contact, and a third contact. The first contact is a moving contact. The first contact is mounted movably along a switching axis from a first galvanic contacting position with the second contact to a second galvanic contacting position with the third contact. In the second contacting position, a mechanical contact force acts between the first contact and the third contact in a radial direction.