Study on the Influence of Crosslinking By-Products on XLPE Breakdown Performance in XLPE Cables Based on the First-Principles and Band Gap Theory

When high voltage XLPE cables are cross-linked with dicumyl peroxide (DCP), the by-products generated by the decomposition of DCP can significantly reduce the intrinsic breakdown performance of XLPE dielectrics. To investigate the effect of crosslinking by-products on the breakdown performance of XLPE, the band gap of three typical crosslinking by-products, α-methylstyrene, acetophenone and benzenemethanol, was calculated based on the first-principles and band gap theory, and the resulting data were fitted and analyzed. The results show that in the calculated field strength range, the band gap of all three decreases with increasing electric field strength, but at different rates; and the threshold values of electric field strength when the band gap of acetophenone, α-methylstyrene, and benzenemethanol decreases to zero are 0.048, 0.065 and 0.068 a.u., respectively; at any electric field strength the band gap values of acetophenone are lower than the other two when the band gap decreases to zero, which has the greatest impact on breakdown and should be removed as a priority in the production process.