Experimental Study On Bird Streamer Flashover for V-Type Insulators of DC Transmission Line in High Altitude Area

In order to obtain the bird streamer flashover characteristics in high altitude areas, the discharge of DC V-type string insulators was studied in high-altitude test base at 4300 m in Tibet. The study results show that medium viscosity bird streamer is easy to form a continuous channel and cause flashover. The flashover probability of positive polarity transmission lines is slightly higher than that of negative. The conductivity of bird excrement almost has no effect on the flashover probability in the range of 1.9 similar to 20.9 mS/cm. To increase the vertical air gap distance can reduce bird streamer flashover probability. Based on the experiment results, the recommended vertical air gap distance values of +/- 400 kV DC transmission line were proposed. Considering the influence of wind and bird streamer falling angle, the protection radius was set 3.5 m at 3500 similar to 5000 m altitude area. Bird streamer flashover is a mixed discharge of air gap breakdown and the surface discharge along the bird streamer channel, at the altitude of 4300 m area, the minimum breakdown potential gradient is about 2.1 kV/cm, and the discharge between bird streamer and shielding ring can be approximately equivalent to rod-rod gap discharge.