Asynchronous Control Method for Large-Capacity Generator Circuit Breaker With Vacuum Multi-Breakers in Parallel

Generator Circuit Breaker (GCB) is a key power switching equipment in the power plant. A single vacuum interrupter can't meet the rated current and short-circuit breaking requirements of large-capacity GCBs, and multiple VIs need to be connected in parallel. To address the problem of current-sharing, the current-sharing experimental platform of vacuum multi-breakers in parallel was constructed by taking two VIs in parallel as an example. The electromagnetic repulsion mechanisms were used to drive the VIs respectively, and current-sharing experiments with the peak current of 20kA were carried out. According to the arcing characteristics of each branch, the dynamic current-sharing process was divided into the first current-sharing stage and the second current-sharing stage. The current transfer at different stages was comparatively analyzed, and the influence mechanism of arc voltage on current-sharing was clarified. Next, the influence of different delay times on the dynamic current-sharing was studied in detail. An optimal asynchronous control strategy was proposed, which can effectively compensate for the defect of static current-sharing and suppress current spikes by flexibly using the arc voltage to drive current transfer. The experiments verified that the proposed method achieved better dynamic current-sharing with a current-sharing coefficient of 96.01%.