Temperature Dependent Space Charge and Breakdown Strength of Aromatic Amine Antioxidant Grafted Crosslinked Polyethylene

Space charge accumulation and electric field distortion in crosslinked polyethylene (XLPE) especially at a higher temperature are still urgent problems to be solved in the development of high voltage level XLPE insulated direct current (dc) cables. To improve the working temperature and transmission capacity of XLPE insulated dc cables, antioxidant N-(4-anilinophenyl) maleimide (MC) is grafted onto XLPE macromolecular chains in this article, and the space charge characteristics and dc breakdown strengths of the grafted XLPE at various temperatures are investigated. The experimental results show that the grafting modification of antioxidant MC can effectively suppress space charge accumulation and electric field distortion, and increase dc breakdown strength, especially at elevated temperatures. The immobile and dense deep traps introduced by the polar groups of antioxidant MC anchored on XLPE macromolecular chains can capture and scatter charge carriers to reduce the charge density and restrict the charge migration. At the same time, the grafted antioxidant MC is not easy to leach out of XLPE and maintains lasting antioxidative activity. Antioxidant MC grafted XLPE exhibits improved high-temperature electrical properties with the additional excellent thermal oxidation aging resistant performance and is suitable for application in the higher voltage level dc cable insulation.