Direct-current breaker for high power for connection into a direct-current carrying high-voltage line

A d.c. breaker for high power and for connection into a high-voltage d.c, line, and with a breaking member which comprises:

• a) a controllable semiconductor device,
• b) control members to control the semiconductor member such that a zero crossing of the current through the breaking member is obtained,
• and with a capacitor which is connected in parallel with the breaking member and to which the current in said line is commutated over to said capacitor after a zero crossing of the current through the breaking member,
• the breaking member comprises first and second normally closed electrically series-connected mechanical breaks traversed by the current in said line and opened for breaking of said current,
• the capacitor is in parallel with the series connection of the two breaks,
• the semiconductor member is connected in parallel with said first break,
• the breaker comprises an inductive member which is connected in a circuit with the capacitor and the first and second breaks for forming an oscillating circuit comprising the inductive member, the capacitor and the first and second breaks, and
• the control members, in connection with the opening of the series-connected breaks, control the semiconductor member periodically for generating a growing oscillation in the oscillating circuit and hence a zero crossing of the current through the second break.