The optimization of arrester grading ring takes its pipe diameter

ring radius

and shielding depth as independent variables

and takes the maximal voltage distribution ratio and the maximal electrical field intensity on the surface of grading ring as dependent variables. The maximal voltage distribution ratio is set as the objective function

and the constraint condition is that the maximal electrical field intensity must be lower than the electrical field intensity for corona inception. The optimum parameters are difficult to be solved

but they are easy to be evaluated. Thus

differential evolution algorithm is combined with finite element method to optimize the grading ring for a 750 kV arrester. The results show that the homogeneous degree of voltage distribution ratios of the grading ring is significantly improved after optimization

the maximal voltage distribution ratio is reduced from1.429 to 1.108

and the maximal electrical field intensity is depressed from 2.555 kV/mm to 1.673 kV/mm

all satisfying the relevant standards.