Surface Charge Characteristics On Insulators In Vacuum Under Nanosecond Pulse Excitation

Investigations have been carried out on an organic and a polyethylene insulatormaterials in vacuum under impulse voltage (rise time 50ns, halfwidth 350ns and 3us)excitation to study the surface charging distribution and pre-flashover phenomena.According to the experiment results, a pre-flashover current may be observed nearthe peak voltage, or the tail of voltage, or even voltage close to zero. Pre-flashover is thebasic reason that leading to surface charge under nanosecond pulse excitation. Positivesurface charge always been measured under negative (positive) long and short pulse ifpre-flashover happen, and the distribution near cathode is more than that near anodebecause electron emission began from cathode. Pre-flashover and surface charge onorganic is easy been observed than on polyethylene. Surface charge is related with thepre-flashover events , surface charge density increase with pre-flashover current.