High-risk region of bird streamer flashover in high-voltage transmission lines

Bird-caused outages are more common and widespread than generally believed, and greatly threaten the safety of transmission lines. However, few reports are concerned with laboratory research of bird-caused faulting, especially in the case of long air gap insulators. This paper carried out experimental and simulation work on bird streamer flashover of 220 kV insulators. It was found that the radial distance from the insulator axis shows great influence on the bird streamer flashover. Significant is that we also found a high-risk region of bird streamer flashover which can be restricted in an elliptical region located at the center of 220 kV insulator string, the major and minor axes being 500 mm and 250 mm. The processes of flashover due to bird streamer are discussed in detail. Simulation work further demonstrates the existence of the elliptical region of high flashover risk, which is of significance for transmission line protection.