Calculation of electric field and voltage distribution along glass insulator string and optimum design of its grading rings for 1000kV a.c. UHV transmission lines

Three-dimensional finite element method has been used to calculate the electric field and voltage distribution along glass insulator string for 1000 kV a.c. UHV transmission lines. Compared with the test results, it is verified that the calculation results are accurate. Various parametric designs of the grading rings of the glass insulator string have been analyzed. Based on the designs, the orthogonal experimental method has been employed to propose several optimum designs of the grading ring for reducing voltage distribution ratio along the glass insulator string. The optimization of grading rings indicates that the grading effect is preferable when tube diameter r equals to 60 mm, ring diameter R 550 mm, height H 350 mm and the number of insulators n 52.