Degradation effects and insulation diagnosis of HV polymeric insulating materials under accelerated aging conditions

Polymeric insulating materials for HV outdoor composite insulators were used for accelerated aging experiments to investigate their degradation effects due to the combined actions of ac electrical stress and salt fog contamination. Variations of leakage current were recorded and partial discharge patterns of the samples were monitored by a partial discharge (PD) computer measuring system. Besides, surface microstructures and chemical change of the silicone rubbers were analyzed by SEM and ESCA methods which also revealed evidence of aging, together with the measured contact angles. The loss and recovery of hydrophobicity on SR surfaces were taken into account to elucidate the obtained data. These results and techniques are valuable and useful for insulation monitoring and diagnosis of composite insulators and systems.