Low-Voltage Thyristor Based Multi-Port DC Breaker for Single-Source Multi-Loads System in Substation

Low-voltage direct current 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 (ACBs) in cooperation with inverse time-lag trip. However, due to the long response time of ACB (≥10 ms), 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 article are as follows: First, a novel thyristor based multiport dc breaker (T-MP-CB) with response time less than 1ms is proposed for the ±110 V single-source multiloads power supply system in substation. With special configuration of metal oxide varistor (MOV), transient interruption voltage can always be limited within ∼1.6 p.u., avoiding the potential degradation of MOV caused by leakage current. Second, it is proved by experimental data that extinguishing of thyristor is closely related with reverse recovery time (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t_r</i>) and uncertain zone of (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t_r</i>) 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.