Surface analyses of insulation materials eroded by partial discharges

Partial Discharges affect insulating materials, especially when the operating voltage exceeds the nominal voltage for short periods. Hence, there is a need for improving the surface erosion resistance resulting from partial discharge. The present work aims to characterize the erosion (depth, shape) of PEEK samples, either unfilled, filled with mineral fillers or glass fibers. PD resistance was evaluated using a rod-to-plane electrodes test cell with an air gap of 0.2 mm. The thickness of the samples tested was 1 mm. The material sheets were subjected to PD under 50 Hz AC voltage from one to several weeks. After PD exposures, the erosion was characterized by analysis of the surface's roughness and erosion depth using a profilometer. EDX measurements also helped to evaluate the filler quantity on the surface of the specimen exposed to PD. The evolutions of erosion with time and as a function of applied voltage are presented. Comparisons are made on the effect of various filler contents. The possibility of enhancing PD resistance through proper selection of filler contents is discussed.