380 / 2017-04-20 10:45:55

Development of a 40.5 kV indoor Vacuum Circuit Breaker for Back-to-back Capacitor Bank Switching Duty

Vacuum Circuit Breaker,Vacuum Interrupter,Back-to-back capacitor bank,Inrush current

Capacitor banks are frequently switched for reactive compensation in power systems. Although vacuum technology is commonly used in medium voltage systems, challenges still exist for commercial vacuum circuit breakers (VCBs) to cope with requirements of back-to-back capacitor bank switching duty, especially at the rated voltage ≥ 24 kV. The main reason is that the inrush current can cause serious damages to the contact surfaces and further deteriorate the high voltage withstand ability of the vacuum gap. The objective of this paper is to develop a 40.5 kV indoor VCB which is exclusively used for back-to-back capacitor bank switching. The main circuit of this VCB adopted series vacuum interrupter technology, which adopted different contacts (CuW and CuCr), separated functions and specified operation sequence to deal with the challenges of high frequency inrush current and withstanding of (1-cos t) recovery voltage. In order to satisfy the frequent operation duty, permanent magnetic actuator and simplified linkage arrangements were used during mechanical designing. The type tests were successfully passed showing that no restrike or NSDD occurred during 1200 A back-to-back capacitor bank switching test. The mechanical life reached 30,000 cycles, and the short circuit current interrupting capability was 31.5 kA