Simulation analysis on the synergistic effect of vegetation ashes and charged particles on the gap electric field distortion

Hill fires, a sort of ultra-natural disaster that poses a severe threat to the safe and stable operation of transmission lines, have become more frequent in recent years. Currently, the modelling research on the transmission line gap electric field distortion under hill fire conditions does not consider the synergistic effect of charged particles and ash particles, which would lead to the imperfect gap electric field distortion mechanism. Herein, a coupled multi-physics field simulation model of electric, thermal, fluid, chemical field and particle motion was constructed to analyze the electric field distribution and particle motion. Compared to the related simulation models, this study improves the simulation accuracy by around 407% by optimizing the structure and parameters of the simulation model. The results show that the percentage of ash entering the examined region of the AC conductor was 34.1% higher, and the percentage of connected ash was 45% higher, increasing the likelihood of gap breakdown compared to the DC conductor; the charge of ash (10-14-10-11) is significantly less than the saturation charge of ash (≥10-3). Therefore, the charged particles change the motion characteristics of the ash primarily through the electric field force and dielectrophoresis force, while the ash-induced distortion of the electric field affects the spatial distribution of the charged particles, eventually, the background electric field undergoes significant distortion by the synergistic effect of the two. The results examine the inherent mechanism of gap electric field distortion at the microscopic level, which can provide theoretical support for understanding the transition phase of transmission line gaps from insulation to breakdown under hill fire conditions.