Analysis of the influence of RC buffer on DC solid-state circuit breaker

Abstract

The DC solid state circuit breaker (SSCB) is the key equipment to construct the DC distribution network. In this paper, an improved topological scheme of RC buffer and metal oxide arrester (MOA) in parallel is proposed, which can not only improve the capacity of circuit breaker to cut off large current, but also reduce the pressure of MOA absorbing energy and shorten the time of fault clearing. A 10kV DC SSCB is designed based on the proposed topology, and a model of the influence of different RC buffer parameters on MOA and DC SSCB is built in PSCAD. The simulation results show that the energy absorbed by MOA is linearly decreasing with buffer capacitance Cs and total inductance L of the system. As the buffer resistance Rs increases, the energy absorbed by the MOA decreases first and then increases. Too small snubber resistance will cause the DC SSCB breaking overvoltage and fault current to oscillate; excessive snubber capacitor will cause the DC SSCB breaking overvoltage to be too high. Therefore, it is necessary to select the optimal RC parameters under different fault currents, which can not only reduce the pressure of MOA, but also improve the shutdown capability of DC SSCB.