High-Voltage Vacuum Circuit Breaker a Feasibility Study

This study focuses on a compact vacuum circuit breaker for nominal voltage of 72.5 kV, nominal current of 2000 A and short circuit current of 31.5 kA. The dielectric conception of the vacuum interrupter (VI) is based on: - Standard dielectric criteria including the "area effect". - A multiple floating shield configuration which reduces risk of total breakdown due to partial breakdown between contacts and shield. - A maximum electrical field on the contact surface that points towards the floating shield hence reducing the effective area of the contacts facing each other. All tests have been performed on a specially designed single-phase circuit breaker pole-unit equipped with a low energy spring type mechanism. Interruption performance was confirmed in direct tests. The CB pole was proved to be restrike-free as defined for class C2. Dielectric tests in new condition and after interruption tests confirmed the announced ratings. These tests confirm the feasibility of this HV-CB with 25% more compact VI\´s based on the outlined dielectric conception