Study on AC Contamination Performance and its Altitude Correction Factor of Long String Insulators

In order to provide a scientific reference for the constructions of AC transmission lines in high altitude areas, studying the contamination flashover performance of long string insulators at different altitude is necessary. In this paper, artificial pollution tests for double sheds porcelain insulator (XWP₂-300) at simulated high altitude were performed in large artificial climate laboratory. Solid layer method was used and 50 % withstand voltage (U₅₀%) were determined by the up-and-down method, then the flashover performance and the altitude correction factor of flashover voltage are obtained. The flashover performance of insulator at simulated high altitude is analyzed. It is shown that the relationship between U₅₀% and SDD at different high altitudes can be expressed with the same equation, U₅₀% as a function of insulator length is nonlinear when the length exceeds 5m, and U₅₀% flashover strength is almost the same for different string configurations. The influences of SDD, insulator length, and string configuration on altitude correction factor were analysed. It is shown that altitude correction factor will be smaller with the increase of SDD, the altitude correction factors of different insulator length are approximately the same, and the value of exponent n for horizontal is smaller than that for I-String.