Experimental Evaluation of 5kV, 2kA, DC Circuit Breaker with Parallel Capacitor

This article describes design, operation and experimental testing of a mechanical DC CB (Circuit Breaker) with parallel capacitors. The topology resembles hybrid DC CB but there are possible advantages in the costs since the main semiconductor valve is replaced with capacitors and in performance since this breaker inserts counter voltage earlier. A detailed PSCAD model is employed to support DC CB design and to analyse operating principles. A 5 kV, 2 kA hardware demonstrator with 1.5 ms disconnector opening time is developed in the university laboratory. The test results demonstrate successful breaking of DC currents, with the measured time for insertion of capacitor voltage of around 290 s. Further experimental analysis evaluates stresses on the key components, optimal timing for opening of LCS (Load Commutation Switch) and the margins for successful current interruption.