Design and Implementation of an Auto-Oriented Bidirectional ZCS Hybrid Circuit Breaker

To protect power systems from severe short circuit faults, the zero-current switching (ZCS) technique is widely accepted due to its fast interruption speed. However, the traditional ZCS technique is more complicated in bidirectional switching, which limits its wide application, especially in AC power systems. Therefore, a novel auto-oriented bidirectional ZCS hybrid circuit breaker is proposed to simplify the overall topology of the circuit breaker. The design of the ZCS hybrid circuit breaker is based on the idea of diverting the pulse current toward the reverse direction of the fault current by the arcing voltage itself. The proposed scheme can interrupt bidirectional faults with just one ZCS circuit, without detecting fault current direction. Firstly in the paper, the topology and operating principles of the proposed bidirectional ZCS hybrid circuit breaker are introduced. Moreover, the key parameters are optimized to make the hybrid circuit breaker capable of bidirectional interruption automatically. Furthermore, dielectric recovery characteristics of the vacuum interrupter under special conditions are also measured to determine the design parameters. The proposed topology of the bidirectional ZCS hybrid circuit breaker is validated using a 450VAC/630A prototype. Short circuit breaking tests of the prototype are conducted without detecting fault current direction in advance. Experimental results show that the breaking time of the prototype is less than 1 ms in clearing either direction of fault current with a prospective value of 20 kA and
$\text{d}i/\text{d}t$
of 8 A/
$\mu \text{s}$
. The feasibility of the proposed scheme is verified with these test results.