Design, Modeling and Control of Hybrid DC Circuit Breaker Based on Fast Thyristors

Abstract

This paper presents a systematic study on designing a hybrid direct current (dc) circuit breaker (CB) based on fast thyristors. As an illustration, the dc CB main parameters are calculated for a 120 kV, 1.5 kA test breaker with an interrupting current of 10 kA. The studies indicate that the opening time of 2.3 ms can be achieved only if fast thyristors are employed. It is further illustrated that there is a design tradeoff between minimum interrupting current capability and discharge time for the internal capacitors (reclosing speed). The dc CB control system for opening and closing is presented based on different levels of protection and the self-protection. The dc CB is modeled in PSCAD and simulation results are used to evaluate the breaker performance under different operating conditions. It is concluded that the model represents well the dc CB and can be employed for dc grid protection studies. It is further shown that the opening time becomes longer as interrupting current reduces, and it is very long in the case of load current interruption.