The Enhancement of Direct Current Electrical Performance of Cross‐Linked Polyethylene by Combined Grafting of Multi‐Functional Group Crosslinking Agents and Polar Small Molecules

ABSTRACT To solve the space charge accumulation and electric field reversal in the insulation layer of cross‐linked polyethylene (XLPE) high‐voltage direct current (HVDC) cables. The small molecule compound 3,4‐diacetyloxyethylene styrene (DAS) and the co‐crosslinking agent trimethylolpropane trimethylallyl trimethacrylate (TMPTMA) were grafted onto XLPE. Thermal stimulation current and quantum chemical calculations indicated that DAS and TMPTMA introduced high‐density deep traps in XLPE, which reduced mobility and suppressed charge injection by capturing carriers. The conductivity current and temperature sensitivity of modified XLPE were decreased significantly, the phenomenon of electric field reversal was suppressed considerably, the breakdown strength was increased substantially, and it exhibited reasonable space charge suppression characteristics. Among them, the conductive current of XLPE‐g‐(TMPTMA‐co‐DAS) is only 0.1% of that of unmodified XLPE, while the breakdown strength has increased by more than 34%. This provides theoretical support for the development of DC cable insulation materials with high voltage levels.