Abstract: A first puffer chamber is formed by a puffer cylinder having a substantially cylindrical flange portion and a shaft portion, and a fixedly disposed piston. The piston is formed in a cylindrical shape sealed with respect to an external space, and is constituted to be accommodated in the flange portion of the puffer cylinder at the circuit breaking position of the circuit breaking unit. The internal space of the piston is constituted as a second puffer chamber which is designed to communicate with the first puffer chamber. The gas accumulated in the second puffer chamber is continuously blown out toward between the electrodes, thereby prolonging an effective interruptable arc time span without increasing the size of the circuit interrupting unit and operating unit.

Abstract: A line voltage charging type DC circuit breaker for use in DC transmission, having a series circuit connected in parallel with a commutation breaker, the series circuit being constituted by a capacitor to be charged by a line voltage, a reactor, and a circuit-closing means connected in series with each other, the DC circuit breaker comprising a circuit for charging the capacitor, the charging circuit including a current direction restricting circuit for restricting a current flowing through the restricting circuit only in one direction and a reverse control circuit for controlling the current direction restricting circuit to reverse the direction of a current for charging the capacitor in accordance with the power flow reversal control of the DC transmission.

Abstract: There is disclosed a high-voltage DC circuit breaker apparatus with reverse current insertion system by line voltage charge, which comprises a commutation switch, a series circuit of a capacitor, a reactor and a switch connected in parallel with the commutation switch, a resistor connected so as to charge the capacitor by a line voltage. The charging time constant of the capacitor determined by the capacity of the capacitor and the resistor is used as a reference in a manner so that the rise time constant of the line voltage is smaller than the charging time constant of the capacitor, and the rise time constant of the line current is larger than the charging time constant of the capacitor, thereby interrupting the fault current without fail.

Abstract: A capacitor and an inductance are connected in parallel with an interruptor disposed in a d-c circuit before the interruptor is mechanically opened. An oscillating current i.sub.o occurs in a circuit composed of the interruptor, the capacitor having a predetermined capacitance and the inductance having a predetermined amount of inductance when the interruptor is mechanically opened. The amplitude of the oscillating current i.sub.o is gradually increased and is superposed on a d-c current I. The interruptor breaks itself when the sum of the d-c current I and the oscillating current i.sub.o across the interruptor reaches zero.

Abstract: A circuit breaker comprising an interrupting unit mounted in a vessel filled with a charge of arc extinguishing gas of uniform pressure and operating such that when the circuit is broken the arc extinguishing gas is compressed to increase its pressure, so that the high pressure gas will be blown against an electric arc established between the contacts to extinguish the same. The circuit breaker is formed therein with two paths for the high pressure gas blown against the arc, each path having an insulating nozzle mounted in it.