Development of Hybrid Fault Current Limiting Circuit Breaker with Environmentally Benign Gases

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In the present study, a current-interruption experiment was performed to examine the interrupting capability for a hybrid circuit-breaker consisting of a load-break switch filled with H_2 and an air contactor connected in series. As far as the present experimental conditions are concerned, it is found that the hybrid model is capable of breaking a current with a peak value of 950 A. Compared with a double-switch model using Air in both quenching media which can interrupt a current with a peak value of 600 A, the current interrupting capability of the hybrid circuit-breaker was proved to be higher than that of the double-switch Air circuit-breaker due to the difference of the thermal and electrical conductivity between H_2 and Air. In other words, the hybrid model using Air and H_2 as arc-quenching media improves the interrupting performance. Furthermore, we have proposed a hybrid system in which a fault current limiter (FCL) and a circuit breaker (CB) are combined in' series. The present study describes the breaking ability of a small model of a hybrid fault current limiting circuit breaker (hybrid FCLCB), which consists of an air relay unit and a flux flow resistive type of a superconducting FCL unit with a high Tc B2223 bulk. We took two Bi2223 elements connected in series as the minimum configuration of the flux flow resistive type of the FCL and investigated the generation process of the flux flow resistance and the contact resistance. The current limiting breaking performance was investigated for the small model of the hybrid FCLCB that was constructed by connecting the minimum unit of the FCL to the relay contactor. The hybrid FCLCB for the 6.6 kV power distribution system was designed from the experimentally obtained results in the small model.