Development of HVDC Circuit Breaker Based on Hybrid Interruption Scheme

A hybrid interrupting unit (IU) has been examined which consists of a puffer type SF6 gas interrupting unit (GIU) and a vacuum interrupting unit (VIU) connected in series as the interrupting unit of HVDC circuit breaker (HVDC CB). Using the hybrid IU, a test of interrupting a dc current of 8 kA under a peak recovery voltage of 420 kV was conducted by means of a forced current injection method which superposes high frequency counter pulse current to dc current to produce a current zero point. Interrupting mechanism has been analyzed which applies to the transient recovery voltage period of the hybrid IU. A 250 kV -1,200 A gas insulated prototype HVDC CB has been manufactured and tested successfully.