Ageing kinetics of solid insulating materials submitted to partial discharges

An attempt is made to correlate the characteristics of the electrical signals due to partial discharges (PDs) with the ageing kinetics of the insulating material subjected to these discharges. The light emitted by a single PD and the corresponding electrical pulses have been recorded using a high-speed camera and a computerized signal acquisition system. The discharge development both in time and space is related to the electrical pulse shape, i.e., the amplitude of each frequency component of the electrical signal, and can be related to the ageing of the insulating material. Several steps of insulation ageing appear. The surface wettability and thus surface conductivity increase at the very beginning of exposure to PD