Effects of agglomeration of carbon particles in the semiconducting material on the dielectric strength of XLPE insulation

The relationship between the breakdown strength and the material structure of the order of a few micrometers near the interface between the polyethylene insulation and the semiconducting material is discussed. It was found that the agglomeration of the carbon particles in the semiconducting material ranges from about 100-300 nm. The autocorrelation function A(D) of the transmission electron microscope (TEM) photographs can represent some aspects of the agglomeration of the carbon particles. The characteristic distance D ₀ in the autocorrelation function ranges from about 100-300 nm, and corresponds closely to the size of the agglomeration of the carbon particles. It was found that the highest breakdown strength in terms of the Weibull 10% breakdown strength may be obtained when D₀ is around 200 nm. The thermal breakdown may explain the relationship between the breakdown strength and the agglomeration of the carbon particles