Study on Tree-wire Critical Breakdown Distance of 500kV Transmission Lines

Abstract

Flashover fault is an important cause of trip or even outage of transmission lines. In order to reduce the occurrence of tree flashover failure and strengthen the management of tree growth in the transmission line corridor, it is necessary to study electric field and potential distribution characteristics of trees below transmission lines. Firstly, the influence of tree dielectric constant and conductivity on 3D modelling is analysed. Then the actual 3D simulation model is established. The spatial electric field and potential variation of trees with different shape crowns and different heights and horizontal distances are studied. The starting field strength of flow is used as the gap breakdown criterion, and the critical breakdown distance under different power supply phase angles is calculated. Conclusion shows that the critical distance of tree flashover of 500kV transmission line is 1.76m. In practical applications, trees should be avoided too close to the wire.