The study of surface discharges on the air- insulation interface.

Abstract

Surface partial discharges may degrade the electrical insulation in time. Analysis of their parameters, charge and phase distribution in a needle-cylinder electrode configuration at various insulation materials were done. The surface PDs were observed between the zero cross and the peak of an applied voltage and also before the zero cross due to the surface charges. The measurements on the different types of insulating materials and on transformer pressboard with various humidity resulted, that the surface discharges are influenced by the surface conductivity of material. The negative corona discharge was observed when the distance between the needle tip and the surface insulation increased.