Study On Pollution Classification And Insulation Configuration Of ±1100kV UHV DC Transmission Line

Domestic and foreign operating experience shows that insulator pollution flashover seriously threatens the safely operation of transmission line. Appropriate determination of pollution levels along the proposed lines and the external insulation configuration applied in different pollution areas not only directly determine the result of the transmission line from engineering design perspective and affect the cost of the project, but also relates to the safety and reliability of transmission lines operation.The proposed Zhundong-Huadong ±1100kV UHV DC line is considered as the highest voltage level DC line in the world, which walks through areas with special environment conditions, i.e., heavy pollution, heavy ice, high altitude, saline desert, Gobi desert, and etc. A systematic and comprehensive research has been carried out regarding the fouling and moisture characteristics of the UHV DC line, AC and DC transmission lines operation in the nearby areas and the measurement results of site contamination degree over the years with respect to insulators in DC or AC lines. Besides, the salinity of saline soil and sizes of the particles on the surface of insulators along UHV DC line have been measured. Based on the comprehensive analysis and calculation, the pollution distribution of the UHV DC line has been determined, of which, the light, medium and heavy polluted areas accounted for 11.4%,50.9% and 37.7% respectively to the overall length. Also, the measurement and analysis of the chemical composition of the filthy soluble content on the surface of the insulator along the UHV DC line was carried out, based on which we reach the conclusion that the valid ESDD coefficients of the south and north areas were 0.8 and 0.7, respectively. Apart from that, on the basis of the statistics and analysis on the ratio of NSDD to ESDD and the ratio of ESDD on bottom surface to that on top surface for insulators along the UHV DC line, we obtained the above-mentioned ratios in various areas. The pollution flashover characteristics test of porcelain insulators with different string length under ±1100kV voltage were carried out, and the linear relationship between the length of the porcelain insulator string and the flashover voltage were verified. What’s more, the pollution flashover performance of large-tonnage insulators for ±1100kV line was tested, and the characteristic curves of pollution flashover were completed. Therefore, different configurations of the insulators should be applied in various pollution areas, on the basis of the artificial pollution withstand voltage method and the pollution distribution along the UHV DC line.