Influence of surface trap parameters on DC flashover in vacuum of epoxy composites

Surface flashover phenomena under dc voltage greatly limit the improvement of insulating strength, which has been a key problem restricting the miniaturization and the practicality of high voltage dc power equipment. This paper investigated the influences of surface trap parameters for electrons on dc flashover in vacuum of epoxy composites. Pure epoxy resin, three kinds of epoxy nanocomposites and two kinds of epoxy microcomposites were used. In this paper, the surface trap distributions were calculated by a model of the detrapping of surface trapped charges based on surface potential decay measurements, and the influences of different additives on trap parameters and dc flashover voltages were also discussed. Considered electron triggered polarity relaxation model and secondary electron emission avalanche model, the relationships between dc flashover voltages and surface trap parameters were analyzed. The results show that: the epoxy samples with single trap center, in which the shallow trap centers disappear, have higher flashover voltages; respectively for the epoxy samples with single trap center and two trap centers, dc flashover voltages increase linearly with deep trap densities on semi-logarithm coordinate system.