A Galerkin model to study the field distribution in electrical components employing nonlinear stress grading materials

An effective model is presented for the evaluation of the electric field dy namics inside electrical components, using nonlinear stress grading materia ls. The model, implemented in a numerical procedure, permits the solution o f the Laplace equation and the diffusion equation by adopting the Galerkin method. Two-dimensional domains, even of very complex shapes and the finite thickness of the grading materials are properly taken into account, allowi ng an accurate evaluation of the electric field distribution and a sound un derstanding of the influence of the different types of nonlinearities on th e stress grading efficiency. The proposed technique has been applied to stu dy the field distributions inside a cable termination equipped with a stres s control tube and in a suspension cap-and-pin glass insulator covered with an anti-corona layer. Numerical results for sinusoidal power frequency and standard impulse voltages elucidate the different role of resistive and ca pacitive contributions in determining the overall potential maps.