Low-voltage Thyristor Based Multi-port DC Breaker for Single-Source Multi-Loads System in Substation

Low-voltage direct current (LVDC) power supply system for secondary measuring and controlling devices in substation is a typical single-source multi-loads system, which is protected by air circuit breakers (ACB) in cooperation with inverse time-lag trip. However, due to the long response time of ACB (≥10ms), the selectivity of ACB cannot be ensured, enlarging the blackout scope and threatening the reliability of whole substation. To solve this problem, contributions of this paper are: (1) a novel thyristor based multi-port DC breaker (T-MP-CB) with response time less than 1ms is proposed for the ±110V single-source multi-loads power supply system in substation. With special configuration of metal oxide varistor (mov), transient interruption voltage (TIV) can always be limited within ∼1.6p.u., avoiding the potential degradation of mov caused by leakage current. (2) It is proved by experimental data that extinguishing of thyristor is closely related with reverse recovery time (tr) and uncertain zone of (tr) exists; by taking both reliable extinguishing of thyristor and economic performance into consideration, parameter optimization design method for T-MP-CB is proposed. Simulation and experiments validate the proposed T-MP-CB.