Simulation of Interface Charge Behaviors in HVDC Cable Accessory Based on Bipolar Carrier Transportation Model

HVDC extruded cable is the key equipment of flexible DC transmission technology. However, the interface charge between different dielectrics is easy to accumulate in the HVDC cable accessories due to the discontinuity of conductivity and permittivity, which will threaten the safety of the HVDC cable system. The injection and transportation behaviors of space charge in ethylene propylene diene monomer (EPDM)/low-density polyethylene (LDPE) bi-layer dielectrics were simulated by using a bipolar charge transport model with different interface characteristics including the surface states, interface barrier and carrier mobility. The simulation results show that the interface charge density in HVDC cable accessory is dependent on the surface trap energy level, interface barrier and large carrier mobility difference. Decreased the EPDM’s surface trap depth and interface barrier of the bi-layered system are helpful to reduce the interface charge accumulation. Therefore, the insulation match in HVDC cable accessory can be improved by modifying the surface state distribution and decreasing the interface barrier.