Computation of ac and dc electric field around a wet polluted insulator

Insulators in actual service conditions are polluted due to ambient operating conditions. Due to leakage currents dry bands can be formed on the surface of the insulator. Distortion of the potential distributions would occur by the existence of both a wet polluted band and a dry band in the presence of air. In our previous paper, a benchmark problem for the dc case of a cylindrical insulator with a wet and dry band was formulated. Substantial agreement was found between our finite-difference numerical results, the analytic solution, and the commercially available finite element package. In the present paper, the commercially available package is used to extend the calculations to include ac effects. Two configurations are considered. In one, the dry band is maintained next to the upper high voltage electrode; in the other, the dry band is next to the grounded low voltage electrode. The dry band length is varied as a percentage ratio of the length of the insulator.