Apparatus for the current limiting interruption of currents at high voltages

Claim 1

In a circuit arrangement for the current-limiting interruption of high-voltage direct and alternating currents including a commutation switch connected in a high-voltage main, a residual current switch connected to said commutating switch, and a shunt path connected in parallel with said commutation switch with said shunt path including the series connection of a spark path and a temperature dependent resistor having a strongly positive temperature coefficient, the firing voltage of said spark path being such that said spark path responds after a predetermined arc voltage has been reached at said commutation switch upon opening thereof to cause the current to commutate to said shunt path, and said temperature dependent resistor being dimensioned so that in its cold state it can fully take over the maximum current of said commutation switch at said threshold value for the series-connected spark path and is heated to such an extent that, at maximum energy absorption, it reaches its highest permissible rise in resistance without being destroyed; the improvement comprising: a further commutation switch connected in series with said first mentioned commutation switch; a further shunt path connected in parallel with the series connection of said first mentioned commutation switch and said further commutation switch, said further shunt path including the series connection of a quenching spark path, with constitutes said residual current switch, and a further temperature dependent resistor having a strongly positive temperature coefficient; an auxiliary shunt path connected in parallel with said quenching spark path and including the series connection of another spark path and a capacitor; and said quenching spark path has a firing voltage which is substantially higher than that of said first mentioned spark path and that of said another spark path.