Optical observation on forms of vacuum switching arc in short-gap

Vacuum arc, as the key element of vacuum circuit breakers, is one of the important subjects in the field of high voltage apparatus. The forms of vacuum arc have great influence on the breaking capacity and reliability of vacuum circuit breakers. In this paper an experimental set-up of vacuum arc was designed for getting dynamic images of vacuum arc in short gap. At the same time a vacuum arc mode was modeled to analysis the relationship between voltage and vacuum forms. By using a high speed CMOS digital video camera, images of vacuum arc could be observed when vacuum arc is ignited. From the results we can get the arc characteristics such as diffused forms, constricted forms and the regularity of change between them, at the same time, the cathode spots can be watched with the images collection. The results also indicate that the relationship between voltage and current of the arc is direct ratio; the life time of the vacuum arc is about 10 ms. According to the mode, controlling on the vacuum arc is very necessary to improve the breaking capacity.