±550 kV直流GIS海缆终端气固界面暂/稳态电场分布与起始放电电压评估OA

With the rapid development of deep-sea wind power,higher reliability requirements are imposed on GIS cable terminations in offshore converter platforms.Calculation of transient-and steady-state electric field distribution and dis-charge evaluation at the gas-solid interface has become a key issue in the insulation design of HVDC cable terminations.Therefore,considering bulk current,surface current,and gas-side current,we established a charge accumulation model for the gas-solid interface of DC cable terminations.The characteristics of charge accumulation and transient/steady-state electric field distribution under different temperature gradients were analyzed,and the initial discharge voltage of the gas-solid interface was evaluated using an improved calculation method.The results show that,under DC steady-state conditions,positive charge accumulation dominates at the gas-solid interface,bulk conduction is the primary mechanism,and severe field distortion occurs at the upper chamfer and belly of the epoxy insulator,which become the initial dis-charge positions.After polarity reversal,the surface charge distribution remains essentially unchanged,but the maximum field shifts to the triple junction on the HV side;shorter reversal times lead to more severe distortion,with the maximum field magnitude increasing by about 7％.Under impulse voltage,due to the distribution of positive surface charges and the structural features of the termination,the electric field exhibits a pronounced homopolar effect,and superimposed homo-polar pulses intensify the field distortion.Temperature gradients further alter the gas density and reduce the dielectric strength of the gas-solid interface,thereby lowering the initial discharge voltage.