In order to ensure the stability of arresters in substation

the maximum voltage distribution ratio of the in internal valve elements should be reduced as much as possible. The voltage distribution ratio can be reduced by changing the structure of grading rings. In view of the complex relationship between voltage distribution ratio and grading rings structure

it is difficult to establish an accurate mathematical model. Consequently

we established a support vector machine model for this relationship by using the simulation results of the two dimensional symmetric model of the arrester. Then based on support vector machine model

with the object of minimizing the maximum voltage distribution ratio and the constraint of the surface electrical field intensity

the optimal structure of the grading ring was obtained by differential evolution algorithm. The optimization results show that the maximum electric field strength of two grading rings are decreased by 43.24% and 32.21%

respectively

the maximum voltage distribution ratio of the internal valve elements is 1.088

so the working performance of the arrester is improved obviously. Finally

the validity of the proposed method is verified by comparison.