Circuit-breakers for medium-voltage DC grids

Advancements in power-electronic devices as well as the transition to new electrical power sources make the application of multiterminal medium voltage DC grids feasible. In order to selectively interrupt fault currents, DC circuit-breakers might be required for a safe grid operation. Since different DC breaking concepts for low, medium and high-voltage are available, this paper compares several concepts with respect to technical performance, reliability, conduction losses and relative investment costs. Evaluating the technical parameters like interruption speed, peak fault-current amplitudes or the reliability of the breaking concept, the solid-state DC breaker shows the best performance. However, it suffers from high losses due to power-electronic devices in the main conduction path. A good alternative with low conduction losses and marginal higher costs is the snubbered mechanical DC breaker.