Current Zero Missing Phenomena caused by D.C. Current which Flows from Shunt Reactor at the Ground Fault and its Interruption

At substations where shunt reactors are installed, when a ground fault occurs near the reactor, d.c. current flows from the reactor to the fault point. There are cases where circuit breakers installed near the reactor interrupt only the d.c. current from the reactor with long arcing times. In those cases, attention should be paid to the damage of the contacts.This paper shows the investigation of the d.c. current interrupting performance for the 550kV one-break SF6 gas circuit breaker. In the range of some hundreds amperes, the d.c. arc voltages with long arcing times of the 550kV one-break circuit breaker were measured. The d.c. current waveform and arcing time at the d.c. current interruption by 550kV one-break circuit breaker in the 500kV cable system were calculated. Interrupting test circuit for the d.c. current interruption was constructed in the high power laboratory. From the interrupting test results, it was made clear that the circuit breaker had a good interrupting performance after the d.c. current interruptions.