Abstract: A circuit arrangement for the current-limiting interruption of high-voltage direct and alternating currents including a commutation switch connected in the high-voltage main, a residual current switch connected to the commutation switch and a shunt path connected in parallel with the commutation switch and including a temperature dependent resistor with a strongly positive temperature coefficient and a spark path connected in series with the resistor. The firing voltage of the spark path is such that the spark path responds after a predetermined arc voltage has been reached at the commutation switch to cause the current to commutate to the shunt path.

Abstract: In a circuit for the simulated testing of a high voltage direct current switch, which arrangement includes a first direct voltage source producing a high current and low voltage output, a first auxiliary switch and a first inductance both connected in series with the source and arranged to be connected to the switch to be tested, an auxiliary voltage source having a low current and high voltage output and arranged to be connected to the switch for stressing it to its voltage breakdown level, the simulation produced by such circuit is improved by the provision of a second inductance connected to the auxiliary voltage source and arranged to be connected in series between the auxiliary source and the switch to be tested, and a second auxiliary switch connected in series with the auxiliary voltage source and arranged for operatively connecting the auxiliary source across the switch to be tested at a time after the opening of such switch and before the current through the switch, produced by the first voltage sour