Insulation property analysis of cross-linked polyethylene based on density functional theory

In recent years, molecular simulation technology, as the third mothed besides experiment and analysis, has been widely used in various fields. In the field of high voltage, molecular simulation is widely used in oilpaper and polymer insulation characteristics analysis, pyrolysis analysis and so on. In this paper, in order to clarify the electric aging mechanism of cross-linked polyethylene(XLPE), a simple XLPE molecular model is established with the ORCA package and the basic sets 3–21G, 6–31G and 6–311G(d, p) are utilized to optimize and get the most stable structure. We have chosen the band length, band gap and charge transfer within the molecule to characterize the XLPE molecule's status under electric field. The results show that the structural parameters and energy of the molecule present linear changes with electric strength. Especially, the band gap presents a downward trend, which means the insulation property of the material has decreased with the electric strength increases. These phenomena reveal the aging mechanism of XLPE molecule under electric field conditions, which is of great significance to the status evaluation of XLPE cable.