Investigation on the recovery behavior of the mechanical switching path of DC hybrid circuit breakers

The number of DC grids are increasing due to a higher efficiency and a simplified integration of renewable energy sources. However, this increases the challenges for the switching device to perform satisfactorily. Hybrid circuit breakers can provide the needed performance as they offer fast and reliable switching under all load conditions. Depending on the used topology, the switch-off speed of a hybrid circuit breaker heavily depends on the recovery of the mechanical switch after contact separation. The state of recovery can be estimated by measuring the conductance of the switching path. Therefore, a test setup was developed and the recovering behavior investigated. It reproduces parts of the hybrid switch-off process including the reignition. The load current, recovering time, contact distance and switch-off overvoltage are independently adjustable. Therefore, the recovering behavior can be investigated reproducing many possible switch-off conditions, allowing an identification of the influence of each parameter. In this paper, the test setup and some results of initial experiments will be presented. The method and future investigations will be discussed.