Scaled 500A, 900V, Hardware Model Demonstrator of Mechanical DC CB with Current Injection

This paper reports on the development of laboratory-scale mechanical DC Circuit Breaker (DC CB) demonstrator of current injection type. A 500A, 900V DC CB is developed with around 4ms operating time. We have used 3 series connected commercially-available mechanical contactors, with appropriate grading circuits, as the main switch. The resonant circuit has been designed with 3kHz resonance frequency. The experimental tests show successful interruption of 500A current at 1000V DC voltage in both positive and negative direction. Further tests with high impedance faults show successful interruption of low fault current at 65 A. Some further analysis of impact of timing of current injection is shown.