Solid-state circuit breakers and current-limiting devices for medium-voltage systems

Abstract

State-of-the-art mechanical circuit breakers in medium-voltage systems only allow handling of short-circuits if the short circuit power of the grid is limited. Using delayed turn-off times, the circuit breaker can be coordinated with lower level protection gear. Hence, a high availability of the grid can be guaranteed. However, during a short-circuit a significant voltage sag can be noticed locally in the medium voltage grid. Sensitive loads such as computers will fail even when voltage returns within a few seconds. The proposed semiconductor circuit breaker is able to switch fast enough to keep voltage disturbance within acceptable limits. The realization of the switch with state-of-the-art semiconductors and its impact on the grid is analyzed in this paper.