Temperature distribution along an outdoor insulator subjected to differentpollution levels

The appearance of dry bands on polluted insulator surfaces may cause the ig nition of electrical area, which in turn give rise to tracking and erosion, or may elongate until they bridge the electrodes causing flashover. Effici ent models able to predict the occurrence of such a severe problem is of pa ramount importance for the engineer involved in the design of power lines i nsulation. The present paper concerns the evaluation of the temperature dis tribution along the surface of an outdoor insulator subjected to pollution of different severity in order to predict dry band formation. The proposed numerical procedure, based on the joint solution of Maxwell equations in th eir quasi-static formulation and thermal equations, has been applied to stu dy the case of a suspension cap-and-pin glass insulator, covered with pollu tion layers of different conductivity and thickness. The dependence of the conductivity of the layer on the temperature has been taken into account pr operly. The influence of uniform and nonuniform pollution distribution on t he temperature profile is discussed for an applied sinusoidal power frequen cy voltage.