The Impact of Partial Discharges on Their Inception Voltage on the Surface of Silicone Rubber

In humid conditions, silicone insulators lose hydrophobicity because of surface partial discharges between water droplets. There are two positive feedback loops that accelerate the degradation process: 1) the damaged surface retains more water and 2) the partial-discharge inception voltage decreases. The present work assesses how quickly and how much the inception voltage can decrease due to the effect of weak surface discharges when each transferring tens of nanocoulombs. The experimental set-up used in the study allows simultaneous discharge generation and inception voltage measurement. It has been found that the streamer inception voltage drops by almost 50% and then recovers only partially. Moreover, the inception voltage recovery takes more time than that of hydrophobicity.