Abstract: The intermediate screen of LVQHB-500W2 500 kV composite insulation SF₆ inverted current transformer and the basin insulator are connected by bolts, and shield balls are installed on the bolts. When the shield balls at this position are loose or fall off, the bolts will be exposed, which will seriously affect the distribution of electric field and cause flashover and discharge on the surface of the basin insulator. By analyzing the fault phenomena, types and causes of this type of current transformer, this paper studies the influence of shielding balls on the local electric field strength of the basin insulator of this type of current transformer, and puts forward improvement measures and prevention strategies, which can provide reference for ensuring the scientific design and safe operation of this type and similar electrical equipment.