Environmental effects on the critical breakdown distance for trees in proximity to transmission lines

The transmission corridor is often rich in vegetation, including tall and flammable tree species such as arbors. When the clearance between vegetation and transmission lines is less than the insulation safety distance, discharge faults between vegetation and the lines can easily occur. In forested areas with abundant combustible materials, such incidents may initiate wildfires—particularly in the western Sichuan plateau region, where lower atmospheric pressure further increases the susceptibility to tree-conductor faults. To investigate the critical breakdown distance between trees and transmission lines under multiple environmental factors, a three-dimensional finite element model of the tree-conductor system was developed. This model was used to analyze the critical breakdown distance under various atmospheric pressure and humidity conditions, and its accuracy was experimentally validated. Data analysis revealed that the maximum critical breakdown distance between the trees and the transmission line—0.217 m—occurred at an atmospheric pressure of 50 kPa and 0% relative humidity. As pressure decreases, the critical breakdown distance increases. Conversely, when relative humidity increases (below the condensation level), the critical breakdown distance decreases. The error between simulation and experimental results remained within 10%.