The Influence of Water Permeation on the Chalking of HTV Silicone Rubber Composites

Chalking is a typical aging feature of the widely used silicone rubber based composite insulators, which could seriously damage the surface flashover performance. Based on the operation experience and experimental results, the chalking of silicone rubber is closely related to high temperature and high humidity. However, previous research focuses mainly on the water permeation process at room temperature, in which no obvious chalking phenomenon is identified, leaving the influence of temperature unrevealed. Considering that the evolution of water permeation is very slow in actual conditions, the samples are heated in water bath to accelerate the process in this research. The evolution of weight during the immersion and dehydration is measured, which illustrates that liquid immersion plays the major role in chalking. Also, the composition and microstructure of chalking layers are investigated, indicating that after exposure to severe conditions for sufficient time, samples of different formulas would become chalked in a similar way.