Finite Element Analysis Of Electric Field Of Outdoor Insulator Under Pollution Un-Uniform Distribution

In recent years the pollution flashover accident of outdoor running insulator seriously increases with the transmission line voltage levels improving. Researching on pollution flashover especially the mechanization of pollution flashover is significant for preventing flashover. Arc forming on insulator surface is the premise condition of pollution flashover. The key factors of the emergence and development of arc is dry band appearing on the insulator surface. It is because the dry bands undertake large voltage and lead to huge change of electric field. Therefore, it is necessary to research the electric field and potential distribution along the surface of insulator with dry band.In this paper, the quasi-static harmonic method is used to analysis the electric field distribution of insulator with wet pollution and dry band. The electric field and potential and current density of insulator are calculated under the pollution uniform distribution. The leakage current is calculated by the current density distribution under different equivalent salt deposit density (ESDD). The reliability of electric field calculating model is verified by the results of artificial pollution test. The influence of dry band on single insulator to the electric field distribution is analyzed. The influence of position and width and number of dry band are considered. The dry band forming near the side of the two electrodes on porcelain surface has greater influence to electric field distribution than the dry band forming near the side of porcelain has. The dry band appears on the down surface near high voltage electrode of insulator has the greatest influence to the electric field distribution. The maximum electric field intensity decreases with the dry band width and number increasing. When the dry bands appear on the same shape of glass insulator and porcelain insulator, the maximum electric field intensity of glass insulator is larger than that of porcelain insulator.Based on the influence of dry band on single insulator to electric field distribution and considering the suspended conductor, the influence of dry band to the electric field distribution of the insulator string formed with 25 pieces of XP-160 insulator is calculated. According to the simulation results, dry bands appearing on different insulators have different influence to the electric field distribution of insulator string. Dry band appearing on middle position insulator has smaller influence to the electric field distribution than that appearing on the insulator near the two electrodes. When the dry band appears on different positions of the same insulator, it on the down surface near the steel foot has the largest influence to the electric field distribution. When many dry bands appear on insulator string, the maximum electric field of dry band appearing on the same insulator is larger than that appearing on different insulators.