Effect of XLPE/EPDM Interface on Space Charge Behavior in Cable Accessory

Space charges accumulate easily at insulation interface of cable accessories, which cause different electric field distribution and aging characteristics compared to single-layered cable. To explore the space charge behavior in double-layered insulation of cable accessories, a one-dimensional (1D) axisymmetric model for bipolar charge transport is built in this work, in which the effects of temperature gradient and electric field gradient in the radial direction are considered. Then the influences of electric field/temperature gradient and interface position on transport behavior of space charges are investigated. The simulation results suggest that the charges accumulate easily at the interface, which severely reduce the electric field in the inner layer of insulation and further inhibit the injection and migration processes of charges. The charge density at the interface increases with temperature and voltage, which accelerates the decay of the charge injection, furthers the interface charges to reach the dynamic equilibrium state quickly. The charge density at the interface and the electric field distribution are closely related to the interface position, and the electric field is more uniform when XLPE occupies the 1/3 to 1/2 inner part of the whole insulation.