POWER HV CIRCUIT-BREAKERS WITH SEVERE CAPACITIVE SWITCHING DUTY

The analysis and control of temporary overvoltages at the ac busbars of an HVDC converter station has been treated in great detail [1], [2], [3], [4]. Often it has been found necessary to operate circuit breakers to disconnect a major capacitive load from the main ac buses under severe transient overvoltage conditions. This paper describes results of tests made on a conventional puffer breaker aimed at gaining knowledge of the consequences of a restrike on the breaker itself. The paper also proposes a method to reduce the transient recovery voltage (TRV) requirements imposed on power circuit breakers in order to be able, in most of the cases, to use standard devices for capacitive breaking. The method is based on application of metal-oxide resistors in parallel with the breaker contacts. The phenomena described in this paper are in all aspects valid for any power system which can have the cases here presented. Therefore this paper is not particular only for HVDC converter stations.