Stepwise electric field induced charging current and its correlation with space charge formation in LDPE/ZnO nanocomposite

This study intends to establish the correlation between charging current under stepwise increased electric field and space charge formation in low density polyethylene (LDPE) and LDPE/ZnO nanocomposites. By applying stepwise increased electric field, the charging current and space charge distribution were measured as a function of time under 10, 30 and 50 kV/mm, respectively. The results show that homopolar space charge formation induces increasing charging current with time, while heteropolar space charge formation induces decaying charging current and excellent space charge suppression is accompanied by constant charging current with time. The abundant deep trapping states introduced by nanofillers dominate both the lower steady charging current and space charge suppression in the nanocomposite. The results indicate that charging current behavior induced by stepwise increased electric field is extremely informative and is feasible to be a direct method for rough estimation of space charge formation and suppression in polymer dielectrics. Addition of ZnO nanofillers suppresses space charge accumulation in LDPE, indicating LDPE/ZnO nanocomposite is a potential insulation material for high voltage direction current cables.