HIGH VOLTAGE DIRECT CURRENT CIRCUIT BREAKERS

Abstract

Adequate protection of the power system is based on the provision of breaking the circuit at the current zero, occurring twice per cycle in the case of a.c. vhereaa in the case of d.c. there is no current zero. In the conventional method of breaking d.c. • circuits, it requires the are that has been drawn between the contactors of the circuit breaker, to be aiff ioiently extended. By greatly extending the are and using an efficient method of cooling, say by air blast or forced liquid, to obtain a large voltag gradientin the arc, it requires the are to be extended by five meters to break 100 KV, with 200 V/em voltage gradiont. This much lengthening of the are becomes impracticable in large HVDC system,