Study on Influencing Factors of Insulators Flashover Characteristics on the 110 kV True Tower Under the Lightning Impulse

Lightning strike is the main reason for the transmission line tripping. Studies on the insulator flashover characteristics and the accurate flashover criteria under the lightning impulse are the basis for correctly evaluating the lightning resistance performance of the transmission line. In this paper, an experimental study on the flashover characteristics of the insulators with different materials was carried out on the 110-kV double-circuit transmission line tower. The insulators were hung on the umbrella-shaped tower and the drum-shaped tower in the test, and both the standard lightning impulse (1.2/ $50~\mu \text{s}$ ) and the short-tail lightning impulse (1/ $10~\mu \text{s}$ ) were used. The flashover test of a single composite insulator was also carried out for comparatively analyzing the influence of the true tower on the insulator flashover performance. According to the test results on the true tower, the lightning flashover criteria of the insulators with different materials are given. The influencing factors of the insulator flashover characteristics, including the impulse waveform, the insulator material, the tower type, and the insulator suspension position, were further compared and analyzed. Meanwhile, the results of the single insulator test proved that the true tower has great influence on the insulator flashover characteristics and that the flashover test on the true tower can reflect actual situation better and obtain more accurate results. In addition, based on the simulation analysis results of the electric-field distribution around the insulators, the difference of 50% impulse flashover voltage ( $U_{\mathrm {50\%}}$ ) of the insulators in different conditions was partly explained.