Simulation study on E-field distribution and corona characteristics of composite insulator with water droplets

Silicone rubber makes composite insulators show excellent moisture dirt performance because of its hydrophobicity. In the wet environment, separated water droplets instead of continuous water film will form on the surface of composite insulators, helping curb the occurrence of arc in high-strength field. However, separated water droplets will distort the electric field easily leading to the partial discharge such as corona. Long-term corona discharge on silicone rubber surface will lead to the aging and ablation of silicone rubber, and then water will get inside the insulator, causing slow corrosion on mandrel and eventually leading to fracture. Therefore, it is essential to investigate the electric field distribution when there are water droplets on the composite insulator surface. In this paper, a simple electrode system is established to study the impact of water droplets on electric field on the silicone rubber by using finite element analysis software ANSYS. The law of the electric field distribution with the water contact angle, number and spacing changing is summed up. A two-dimensional model of a composite insulator is established to conduct calculation with water on the surface, after analysis the law of the electric field distribution in the sheds and sheath area and along the insulator surface is summarized. Parametric design language is applied in ANSYS to model, calculate and analyze, and then MATLAB and ANSYS are combined to optimize grading ring of a composite insulator, using genetic algorithm. Optimization results are applied to three-dimensional composite insulators insulator model to calculate in two cases, one is that drops on the surface have constant radius 2mm and the other is that the radius varies from 1mm to 3mm. The law of the electric field distribution is summed up and compared to the results in two-dimensional case.