Impact of temperature and tree moisture content on evolution characteristics of transition resistance of tree-contact single-phase-to-ground fault in distribution network

The occurrence of tree-contact single-phase-to-ground fault (TSF) poses a potential threat to the stable operation of power lines, and in severe cases, may result in wild fire. The development of TSF is influenced by crucial factors such as temperature and moisture content; however, the precise process and mechanism through which they impact failure remain unclear. This paper takes naturally growing pine trees as the experimental object and conducts a TSF experimental study. Based on the experimental data, it analyzes the impact of temperature and tree moisture content on the transition resistance of trees during TSF, and establishes an equivalent model of TSF transition resistance that takes into account the temperature and the moisture content of trees. The average relative error between model prediction and experimental measurement is less than 10%, validating the effectiveness of the model. The results show that the current heating of TSF will cause the water vapor inside the branches to evaporate into the interlayer between the bark and the trunk, which in turn affects the leakage current flow path and forms a carbonization channel on the interlayer. The distribution of moisture content caused by local heating and water vapor evaporation in the current channel is the main factor affecting the leakage current and transition resistance changes of TSF. The refined model diminishes its reliance on traditional empirical parameters and boasts enhanced alignment with experimental measurement data, offering valuable insight into the mechanisms underlying fault progression.