Abstract
A new method for measuring the transient potential distribution of insulating material surface on which surface discharge propagates is developed. The measuring system consists of a BGO Pockels crystal, an Ar ion laser, a beam expander, a streak camera and a CCD camera. The potential profile on the BGO crystal plate along a linear path of 50mm in maximum length is measured with high space and time resolution: 50μm and 2ns in minimum resolution. From the measured potential profiles together with the electric field computation, the charge density of a surface discharge can be estimated. The experimental results obtained from the potential distribution measurement of positive surface discharge are summarized as follows: The propagating direction component of electric field in the stem of a positive surface streamer is 8-9kV/cm. The developing velocity of the streamer initially reaches 108cm/s just after its inception and decreases down to 107cm/s while propagating.
