Back-to-back capacitor bank switching performance of vacuum circuit breaker by series technology

Capacitive current switching is a frequency task for reactive compensation in power system. The IEC standard 62271-100 and the Chinese standard GB 1984 require a severe inrush current of 20 kA peak and 4250 Hz frequency in back-to-back capacitor bank switching tests. Challenges still exist for commercial vacuum interrupters (VIs) to cope with the class C2 requirement in the standards. The objective of this paper is to propose a vacuum circuit breaker (VCB) by two VIs in series for back-to-back capacitor bank switching, in which the two VIs have different contacts materials and different operation sequences. One of the VIs use contact material of CuW for making the inrush current, while the other VI use contact material of CuCr for interrupting the capacitive current and the VI with CuCr contact material is not responsible for making the inrush current. In the dielectric recovery period of the current interruption process, the two VIs were connected in series to withstand the recovery voltage. Type test results showed that the proposed VCB (40.5kV/2500A/31.5kA) successfully passed 24 times "O" BC1 rated test (150-600 A) and 80 times "CO" back-to-back capacitor bank BC2 rated test (1500A) without any restrikes, which met the class C2 requirement.