Abstract
Electric breakdown form of the uniform electric field air gap is the spark discharge with a single channel. However, it was proven that pre breakdown phenomenon had been generated just before spark over discharge. In this paper, the pre- discharge of the ultraviolet radiation is defined as the following ULD By applying alternative impuls voltage to the sphere gap, this study investigated discharge form and incidence of ULD, and also effect of ULD on the spark discharge form by the combined use of standstill camera and ICCD camera with the high-speed gate. As the result, In the vertical sphere gap, it was proven that the negative half wave voltage was higher than the positive half wave voltage on the incidence of ULD in upper spherical electrode. Generally the linear spark discharge is observed in uniform electric field sphere gap at atmosphere. However, there is a case in which the bent shape of spark is sometimes observed. This discharge phenomenon was observed with a high sensitive camera. It was shown that this bent shape of spark discharge was caused by ULD.
