Observation of Electrical Treeing Processes in Silicon Insulation Samples Using of Transformed PD Phase-Resolved Patterns

Under certain conditions, in the presence of a local strong electric field, an electrical treeing process can be initiated in polymeric insulation. The development of this process over time can lead to permanent damage of the insulation system. The paper presents the results of laboratory experiments during which electrical trees formed in optically transparent silicone insulation were observed by means of optical and electrical methods. Electrical trees were initiated in needle-plane electrode systems, using needles with different radii of curvature. Optical microscopic observations of electrical trees in silicone were made using a high resolution CCD camera and lenses system with fixed magnification. Electrical observations of the development of electrical trees were based on the acquisition of phase-resolved partial discharge (PD) patterns and their transformations to modified ones, with extended information on PD pulses energy.