Effect of Polycyclic Aromatic Compounds on Electrical Treeing Growth in XLPE Insulation

This article focuses on the effect of polycyclic aromatic compounds (PACs) on the electrical tree of cross-linked polyethylene (XLPE) insulation for high-voltage (HV) cables. The XLPE insulation samples with or without PACs are prepared for electrical treeing degradation at constant and cyclic temperatures. The results show that the growth of the electrical tree within the XLPE/PACs insulation is retarded. The partial discharge (PD) amplitudes of XLPE/PACs insulation are significantly decreased during the treeing process compared to XLPE insulation. Furthermore, under cyclic temperature conditions, the tree growth of XLPE/PACs composites stagnates as the temperature decreases from 90 °C to 25 °C. Even when it rebounds to 90 °C, the treeing degradation of XLPE/PACs insulation is still retarded, resulting from a significant weakness of PD. The results show that the XLPE/PACs composites exhibit a greater electrical treeing resistance. Based on density functional theory (DFT), analysis of the excitation characteristics and density of states (DoS) reveals that the PACs absorb photon energy to prevent damage to insulation. In contrast, the excited PACs result in a cross-linking reaction to XLPE and introduce electron and hole traps, which capture hot electrons. The cross-linking product acts as localized states of electron traps and hole traps, which capture the high energy carriers during treeing. In summary, the PACs retard the growth of electrical trees and improve the insulation performance.