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 discharge 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 discharge 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 homopolar 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.