Analysis and Calculation of Typical Influencing Factors of Overhead Line Conductor Sag Under Vegetation Fire Condition

When a vegetation fire occurs under overhead transmission lines, high temperature leads to increased sag of the conductor, which leads to an increased trip risk of lines. To analyze the insulation strength of transmission lines under vegetation fire conditions, it is necessary to calculate the nonuniform temperature rise sag accurately. In this paper, a vegetation fire temperature measurement platform was established to obtain the fire temperature of pinus yunnanensis at different heights. Taking a 400m span and LGJ-500/65 conductor as examples, the effects of different vegetation types, number of fire spots and wind on maximum sag were analyzed. The simulation results show that the sag obtained considering the non-nonuniform temperature rise is more accurate than the existing piecewise calculation results. The highest flame temperature of pinus yunnanensis is 829°C, and its maximum sag can reach 15.82m. When the length of the conductor affected by flame is unchanged, the increase in the number of fire spots has little influence on the sag, and the maximum increase is only 2.51%. Under the transverse wind, the vertical height of the flame will be significantly reduced, so that the temperature at the conductor will be reduced, and the sag of the conductor will be reduced. The results can provide a reference for the accurate construction of the gap breakdown voltage prediction model under vegetation fire.