Partial discharge features and parameters characterization under typical defect geometries in oil-paper insulation: Considering the aging states

The oil-paper insulation has been widely used in large power equipment, and thermal and electrical stresses are the two main origins causing the deterioration and failure of oil-paper insulation system. In this paper, accelerated aging experiments of oil impregnated paper are conducted and partial discharge (PD) measurement are performed under typical defect models, i.e. protrusion, surface discharge and cavity inside the oil-immersed paper. The PD experimental results of three typical defects indicate that discharges initiated from a protrusion in oil have the similarity with that in air but with a limited apparent charge. The surface discharge are much more disruptive for oil-paper insulation. The intervals between consecutive discharges has the good tendency of decrease in the whole discharge events.