PURPOSE: To provide a high-tension direct-current breaker which cuts off direct current of an arbitrarily value through a combination of a technique of utilizing capacitor discharge and a technique of utilizing superconduction. CONSTITUTION: In the normal operation of a line, a breaker D is closed and a switch 1F is opened. A capacitor C is permanently charged by means of a resistor R from the upstream side of the line. If a trouble is caused in the line as indicated by a zigzag line E, a current flowing through the line suddenly rises up to its critical value to thereby transit superconductive windings 7 and 8 and thus excessively increase their resistance. As a result, a higher voltage is generated across the terminals of a varistor V to absorb most electromagnetic energy into the varistor V, and residual currents in the windings are easily cut off by the breaker D. In that case the capacitor is not discharged. The line is thus promptly protected with no high-speed troubleshooting.