Dynamic current-sharing of parallel vacuum multi-breakers in large-capacity generator circuit breakers

Abstract

Large-capacity generator circuit breaker (GCB) is the key power equipment of the power system, and its short-circuit current is far beyond the breaking capacity of a single vacuum interrupter(VI). Multiple VIs need to be connected in parallel. However, there is a lack of research on the dynamic current-sharing of vacuum multi-breakers in parallel. Firstly, focusing on the volt-ampere characteristics of the vacuum arc, the arcing experiments were carried out based on a detachable vacuum chamber, and the arc morphology was photographed simultaneously by a high-speed camera. The volt-ampere characteristics curve of the vacuum arc shows the shape of the number "7″, and according to the geometric features, the arcing process was divided into three stages. The impacts of arc morphology and current on the volt-ampere characteristics in different arcing stages were analyzed. In addition, we found that the voltage of the vacuum arc had uncertainty, and the influence mechanisms of the arcing process and current on the arc voltage uncertainty were revealed. Afterward, the dynamic current-sharing was analyzed in detail. According to the arc starting characteristics of each branch, the stages of current-sharing were divided, and the law of current transfer in different stages was revealed. Further, the effects of arc-starting synchronicity and current level on the dynamic current-sharing were investigated, and the optimal arc-starting strategy was proposed. Finally, a prototype of the large-capacity GCB was proposed. The current-sharing experiments were carried out with peak currents of 116 kA and 564 kA, and better current-sharing effects were successfully achieved.