Résumé
The effect of resistive field grading coatings on the electric field distribution in a medium voltage bushing has been studied. A typical coating is obtained by applying a commercial resistive field grading material and a conductive varnish that we both have previously electrically characterized. The electric field distribution over the bushing surface was computed and analyzed using a finite element method software (Flux 2D). The electric field enhancements at its critical points with and without field grading material were considered and confronted with experimental partial discharge detection. The complementary between the field grading material and the conductive varnish is highlighted: a special care of the true capability of the conductive layer to withdraw the electrical charges is stressed out.