Fractal characteristic of electrical tree grown in silicone rubber under environmental stress

Abstract

One of the degradations of insulation is in the form of electrical treeing in which classified as a pre-breakdown phenomenon of electrical insulation. The electrical tree is commonly forming in the shape of tree-like or root-like which may have fractal structures. Due to this fractal structure, electrical treeing formation and patterns are analysed via fractal dimension and lacunarity to study the self-similarity patterns of electrical treeing. Many types of research have been conducted to study the fractal dimension and lacunarity of electrical treeing to fully understand the electrical tree mechanism and characteristics. However, fractal and lacunarity structures of electrical trees in silicone rubber correlated with humidity influence are not fully understood. This research work involves the experiment set-up for obtaining the electrical trees in silicone rubber. The purpose of this research work is to investigate the correlation between the characterisation of tree growth in silicone rubber with respect to the humidity influence. The obtained electrical tree patterns were measured by using a box-counting method to analyse the fractal dimension and sliding box lacunarity. Obtained results show that the growth of tree structures changes with the different value of relative humidity, in which dry humidity brought higher fractal dimension and lacunarity compared to that of moisture condition. It was suggested that the vulcanization network in silicone rubber with relative humidity led to the effect on treeing patterns and lifespan of solid insulation.