Capacitor core-SF6 insulated bushings are widely applied in ultra-high voltage engineering. Within the electric field dominated by the normal component

the multi-layer insulation interfaces of the bushing are prone to accumulating charge. The charge distorts the nearby electric field

which can provoke flashover accidents

posing a threat to the safe and reliable operation of the bushing. This paper designs an epoxy core-gas insulated bushing model and establishes a platform to measure the surface potential of the model. The surface potential distribution on the surface of the capacitor core and the inner wall of the epoxy glass tube under various voltages and polarization times is tested. Based on this

the surface potential data are aligned in time scale and denoised

and the surface charge distribution is derived through inversion algorithms. It is concluded that negative charge accumulates on the surface of the capacitor core primarily

indicating solid side charge conduction is the primary source. Due to material heterogeneity

discrete positive charge aggregates on the surface. A helical accumulation of positive and negative charge exists on the inner wall surface of the epoxy glass tube

accompanied by charge patches formed by gas ionization

leading to local electric field distortion and insulation weak points. The negative charge at the end of the core and the positive charge on the epoxy glass tube enhance the pressure of gas insulation

resulting in radial electric field distort ion. This research provides experimental evidence and a theoretical basis for potential safety hazards that may exist in the operation of actual full-scale bushing.