Study on the various pollution performance of the post insulators in exceeding high voltage in high altitude area

The 750 kV alternating voltage of transmission lines plan to be built in the northwest of China, where the altitude is from 1800 m to 2800 m, and the climate is very serious. In the design of the lines, we contrast the ability against the pollution flashover of the post insulators. For three types of typical high intensity, big diameter post insulators, the artificial contamination tests are carried out in four pressure cases corresponding to the altitude from 0 m to 3000 m and in two typical kinds of equivalent salt deposit density (ESDD). The test results show that the flashover voltage of polluted insulators at high altitudes regularly decreases with the dropping of the air pressure. And there is certain relationship between voltage and the shed shape. Also, with a normal post insulator with RTV coating, the artificial contamination tests are carried out in the four pressure cases. The test shows, in the same ESDD and the same pressure condition, the ability to prevent the pollution flashover of the post insulator with RTV coating is much too stronger than that without RTV coating. And the rule that the flashover voltage decreases with the dropping of the air pressure is almost the same.