Existing high impedance ground fault (HIF) models face challenges in simulating the gradual variation characteristics of fault resistance during tree-contact single- phase-to-ground faults (TSF). To address this issue

this paper proposes a multi-physics coupling TSF model. The binary relationships between wood conductivity

temperature

and moisture content are experimentally determined

and the accuracy of the model is validated through full-scale tree tests. The model effectively characterizes the long-term gradual variation of fault current before visible flames emerge

particularly capturing the transition characteristics of the first current peak. It quantifies the influence of trunk dimensions (height and radius)

moisture content

and other parameters on the amplitude of the first peak. Large-sample simulations are conducted to analyze the challenges of TSF detection in Guangxi Zhuang Autonomous Region and Heilongjiang Province. The results demonstrate that variations in trunk height

radius

and moisture content significantly affect the peak current. Vegetation pruning must adhere to a hyperbolic safety space criterion. Seasonal differences impact both the first peak current and the temporal evolution of faults: the fault detection rate in summer is 5%~10% higher than in winter

while the fault development process in winter is prolonged by thousands of seconds compared to summer.