Development of a HVDC prototype breaker. Final report

The significant design features of a high-voltage dc (HVDC) circuit breaker based on the commutation concept were developed. Tests of components indicate the breaker is capable of interrupting a fault current of 10 kA on a 400 kV system and absorbing up to 10 MJ of system energy without generating more than 1.6 per unit (P.U.) voltage of the system. Interactions of the breaker with a three-terminal network were studied, using a system simulator. An ultrafast hydraulic actuator system was developed for this program which enables the breaker to initiate the current limiting process within 5 ms after receipt of a trip signal. A new hydraulic valve, operated by a repulsion coil, minimizes the delay before motion begins. Interruption will occur in series-connected vacuum interrupters. A 400 kV circuit breaker is estimated to require eight breaks in series. Only a single break was tested as part of this program because of the scale and cost required for multibreak tests. System energy will be absorbed by zinc-oxide-based surge suppressors included as an integral part of the breaker. The overall design is envisioned as a dead tank type using pressurized SF/sub 6/ gas as a dielectric medium. The actuator and all control functions are located at ground potential, with easy access for inspection or adjustment. Operational specifications have been carried over from NEMA standards for ac power circuit breakers where applicable. The cost of one pole of this circuit breaker, when in regular production, has been estimated as two times the cost of a three-phase 500 kV ac circuit breaker