Interface Charge Behaviors between XLPE and EPDM with Different Conductivity

The space charges accumulation between HVDC cable and accessory insulation will accelerate degradation and breakdown of the cable system, endanger the safety of the power grid. As is known that conductivity mismatch of cross-linked polyethylene (XLPE) and ethylene-propylene-diene terpolymer (EPDM) is the main reason for the charges accumulation in the interface. To investigate the influence of EPDM conductivity on the interface behaviors of XLPE/EPDM, In this paper, high field conductivity of two kind of EPDM and XLPE were tested at −5 kV/mm, −10 kV/mm, −20 kV/mm, −30 kV/mm, −40 kV/mm, −50 kV/mm and −60 kV/mm, and the space charges distribution of XLPE/EPDM interface was tested by pressure wave propagation (PWP) at −10kV/mm, −20kV/mm and −30kV/mm. It is shown that, when the conductivity of XLPE is lower than EPDM, the interface charge is positive; On the contrary, when the conductivity of XLPE is higher than EPDM, the interface charge is negative, and the interface charges density increases as the electric field rise. The experimental results are consistent with the interface charge density calculated based on the Maxwell-Wagner theory.