Influence of applied voltage on space charge formation and accumulation characteristics of low density polyethylene

Abstract

Low density polyethylene (LDPE) has been widely applied on high voltage transmission cables due to its excellent insulating properties, good processability and chemical stability. Large numbers of experimental and theoretical studies have shown that space charge plays an important role in aging and breakdown in LDPE, and the applied voltage can significantly impact charge transport characteristic and space charge formation and accumulation in LDPE. By solving Schottky thermal emission equation, charge continuity equation and Poisson's equation, simulate space charge injection and accumulation phenomenon in LDPE under different applied voltages (0.4 kV-8 kV). The results show that: in a 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> m LDPE sample, space charge accumulation starts at the applied voltage of about 2 kV. The number of trapped electrons, free electrons and total amount of electrons all increase as the applied voltage goes higher. The higher the applied voltage, the faster the trapped electrons and total amount of electrons reach their stability. The space charge accumulation rate is fast before the injected electrons reach the anode, and slows down significantly after injected into the anode. The model has an important significance for in-depth studies to research and assess the LDPE insulating properties.