Investigation on simulation method of gaps discharge characteristic under forest fire conditions

Abstract

The insulation of transmission lines phase-ground and phase-phase air gaps decrease significantly under forest fire condition, which causing transmission lines trip and threatening the operation safety of EHV and UHV transmission lines. In order to attain a simulation method to test the gaps discharge characteristics under forest fire condition, wooden cribs were applied to study the flame heights and discharge characteristics under different scale of cribs and also the leakage currents and discharge voltages of gaps under typical vegetation fire conditions were tested. Test results show that the flame of different scale of wooden cribs were stability and flame heights were separately 62 cm, 90 cm and 140 cm, the flame temperature was between 810 ~ 900 °C.The breakdown voltage gradient under three scale wooden cribs flames were in the range of 81.7 ~ 87.8 kV/m, and breakdown voltage gradient under the flames of typical vegetation were respectively 30 kV/m, 38 kV/m and 60 kV/m, which were far less than the breakdown voltage levels under the condition of wood crib fires. Besides flame temperature, flame conductivity and flying ash particles has important effect on breakdown voltage of gap clearance. So, the simulation gap discharge test under forest fire condition must consider the flame conductivity, temperature and flying ash particles effects on the discharge under forest fire condition.