Electrical Field Change of an XLPE Bounded Air-filled Spherical Cavity during DC Voltage Decreasing and Voltage Polarity Reversal

Partial discharge testing under DC voltage can be used to detect possible insulation defect of extruded HVDC cable system. And electric field distribution and field change at the defect is a decisive factor of partial discharge. An XLPE bounded spherical air cavity model was established in this paper, and electrical field change during applied DC voltage decreasing and polarity reversal were studied. The influence of field coefficient of XLPE conductivity was considered during the simulation. The obtained results predicted partial discharge with polarity opposite to the initial applied DC voltage. And this deduction accords with reported experimental results.