Influences of typical forest vegetation combustion processes on breakdown characteristics and mechanisms of wire-wire air gaps

Abstract

Worldwide, high voltage transmission lines have been suffering from frequent tripping accidents caused by wildfires. To further investigates the impacts of wildfire on breakdown characteristics and mechanisms of wire-wire air gaps, three typical forest vegetation samples were used as simulated fire sources in this work. Two segments of aluminum conductors steel reinforced (ACSR) were used as electrodes. The main flame characteristics, mass loss rate (MLR), and heat release rate (HRR) of the vegetation, main discharge breakdown characteristics of the wire-wire gap distances (5.0–25.0 cm) with fire, and the arc evolution processes under flame conditions were measured and analyzed. Results show that fir has the highest combustion intensity. In both flame zones, the wire-wire air gaps of fir are all the most prone to discharge breakdowns, except for a 5 cm gap in oscillating flame zone. Eucalyptus always shows a medium difficulty. The mean breakdown field strengths of eucalyptus, thatch and fir in continuous and oscillating flame zones decrease sequentially by 78.02 %–84.67 % and 46.51 %–53.67 % respectively compared to that in pure air. Mechanism analyses indicate that high temperatures, ionized particles, thermal convection, radiation, flame zones and electric field interactions are the primary driving forces, reducing gap insulation, and ultimately leading to breakdown.