Abstract: Aiming at ignition and penetration of single-phase tree-contract in distribution lines, a full-scale test platform is designed to analyze the spreading characteristics of tree-contract carbonization. First, the evolution of single-phase lap trunk ignition vegetation and its leakage current, voltage, impedance and temperature characteristics are analyzed, and the four development phases of initial lap, water evaporation, open flame spreading, and combustion penetration are defined. Then, the test found that the flame was formed on charring traces, and then analyzed the influence law of the charring spreading penetration rate on the impedance and current changes. Finally, considering the thickness of naturally growing vegetation, it was obtained that the spread rate increased by 119% when the diameter of Camellia sinensis was reduced from 52.77 mm to 30.17 mm; further, the mechanism of negative correlation between size and spread rate was revealed from the electrical properties of wood (breakdown field strength) and heat conduction angle (heat capacity).

Key words: single-phase tree-contract, evolutionary process, leakage current, equivalent impedance, charring spread, charring trace