Grading ring optimization for tension porcelain insulator string on Double Circuit Tension Tower in 1000 kV AC Transmission Lines

Porcelain insulator can provide electrical insulation and mechanical fixation. It is an important kind of power devices. In this paper, a full-scale 3D simulation model of strain tower was established. By using finite element method, the potential and electric field distribution of porcelain insulators were calculated. The comparison of calculation results between the two situations (with and without grading ring) is shown. The structure parameters of grading ring that affect the potential distribution such as shielding depth, ring diameter and tube diameter were compared and analyzed. Combined with engineering practice, a reasonable design and placement for grading ring was proposed. It can improve the voltage distribution of tension porcelain insulator string and reduce the electric field strength of grading ring. The conclusion has practical value for actual construction project.