Design optimization of corona ring and grading ring for a 400kV Tension insulator

Abstract

The design of polymer insulator depends on the surface electric field gradient. Increased electric field distribution generates corona discharge and leads to breakdown. Corona discharge has become an important factor not only because of corona losses but also due to electromagnetic interferences. Hence proper design optimization is necessary while designing the corona ring and grading ring which is employed at the critical region of the insulator to reduce the corona discharge. In this paper, optimized ring designs are identified for a 400kV tension type insulator. Three phase tension insulator along with the tower model is selected and its electric field distribution is calculated using finite element analysis. A 3D model design is developed using FEM based software. Seven structure parameters of the corona and grading rings are varied and the electric field is calculated. The optimized ring design is then achieved using multi-objective genetic algorithm. The obtained corona ring and grading ring parameters are compared with the simulated values and the error is less than 3%. Hence the proposed methodology can be used for prediction of corona ring and grading ring design, as the electric field is below the critical value.