Due to the special structure of the long-rod porcelain insulator string

its voltage distribution is more uneven than that of normal disk ceramic insulator. The shielding ring of the long-rod porcelain insulator string ought to be optimized. In this paper

a three-dimensional model of the long-rod porcelain insulator string on 500 kV transmission line is established in the finite element software Ansys to simulate the influences of shielding ring’s structure on the electric field and potential distributions along the insulator string

and hence to optimize the structure parameters of the shielding ring. Simulation results show that the optimum structure parameters of the shielding ring are as follows: cover depth is 300 mm

ring diameter is 1 000 mm

and pipe diameter is 125 mm. The optimum structure parameters can help reduce the maximum peak electric field strength of shielding ring to 743.77 kV·m-1

and improve the voltage division ratio of three-insulator string from 2:1:1 to 1.4:1:1. Calculation results prove that the optimized shielding ring significantly improves the electric field and potential distributions along the long-rod porcelain insulator string

reduces the maximum voltage on single insulator

and lowers its maximum peak strength of electric field.