High field degradation in n-hexane impregnated XLPE

Tree initiation voltage by ac stress in XLPE is drastically improved by insulating liquid impregnation. It is considered that liquid fills free volume of the polymer and removes space for electron to be accelerated to high energy. Recently, we found that XLPE well impregnated with n-hexane does not show degradation even when subjected to very high electric field. If the absorbed volume of n-hexane in XLPE was not enough, degradation was formed. The experimental results showed that inception voltage of degradation increases with absorbed n-hexane volume. These experimental results support that hot electron impact causes polymer degradation.