Study on the Flashover characteristics of air gaps for San-Hu II ± 500kv double line transmission towers

Flashover characteristics of the upper frame air gaps for ±500 kV DC double line transmission towers are researched by impulse flashover test on real size simulation tower, and the test curves are presented. Tests about Flashover characteristics impacts of the lower crossbeam on the upper frame air gaps are carried out, the test curves are given in this paper under the precondition that the distance of upper line to upper crossbeam and tower body is 4.4 m and the distance of upper line to lower crossbeam is 2.7 m~4.2 m. Combined with the test result curves when the upper frame gaps have the same distance and the correction formula with different tower width, the curves of lower frame air gaps are also given in this paper. Based on the over-voltage and the switching impulse flashover characteristics on air gaps, the minimum clearances for the air gaps of upper and lower frame of ±500 kV DC double line transmission towers from the Three Gorges Hydropower Station to Shanghai are presented.