Dynamic potential distributions of surface discharge in silicone gel

Silicone gel is widely used to encapsulate power electronic circuits. It is known that the weakness of this insulation system is the surface discharges between gel and substrate. These discharges give rise to the growth of cavities in gel, which may lead to eventual failure of the insulation. Despite the fact, surface discharges in gel has not yet been studied enough. In order to clarify the nature of streamers in the cavity and relation between streamer propagation and charge accumulation at the interface of the cavity, the relation between apparent charge, light emission, motion of the cavities, and dynamic potential distribution of surface discharge in silicone gel was investigated. The results showed that conductive streamers initiate at the electrode, propagate through the cavity and accumulate charges on the cavity surface. In addition, it was confirmed that conductivity of the cavity surface is low.