The grading rings of the high voltage capacitor voltage transformer play a key role in improving electric distribution and reducing the maximum electric field strength.In this paper

the 500kV capacitor voltage transformer was taken as researched object;the maximum electric field strength and asymmetric coefficient were selected as objective function;and the size and location of the grading rings were served as optimization variables respectively.Optimization design is performed by using the simulated annealing optimization strategy.Designing of the grading rings can be gained from the optimization result and a modern design method is presented in this paper.