Study On The Mechanical And Electrical Properties Of Transmission Lines After Wildfires

Transmission lines are important equipment for power transmission.In recent years,wildfires occur frequently in China,which seriously affects the safety of transmission lines exposed in the wildfires.Therefore,it is particularly important to study the mechanical and electrical properties of the transmission lines after wildfires.In this paper,the commonly used overhead transmission line(ACSR:aluminum conductor steel reinforced)was taken as an study object,the wildfire simulation experiments were used to study the relationship between the temperature and the tensile strength,the current carrying capacity of the transmission lines.The finite element analysis was used to simulate the total length,the maximum sag and the stress of the transmission lines when the wildfire taking place.(1)Firewood burning transmission lines and pipe resistance furnace heating lines to simulate wildfire burning lines,which studied the relationship between the temperature and the tensile strength.The results show that,after firewood,the maximum breaking force of the whole transmission line or single strand line gradually reduced with the increase of the degree of fire burning.After the pipe resistance furnace heating transmission lines,the maximum breaking force of the single strand line or steel reinforced decreased,the elongation of single strand aluminum line increased,and the elongation of single strand steel reinforced decreased with the increase of the temperature.Wildfires has a deep influence on the outer layer of the transmission line,and has no influence on the middle and the inner layer.(2)The direct-current resistance(DC resistance)of the transmission line with different heated temperature was measured,and the current carrying capacity is calculated.The relationship between the current carrying capacity of the transmission line and the heating temperature was obtained.The results show that,when the transmission line is not broken,with the increase of heating temperature,the current carrying capacity of the transmission line slightly increased,the increase rate less than 3%.In the case of line broken,after the different temperature heating,the reduction ratio of the current carrying capacity of the transmission line is equal when the broken strand is equal.(3)The software ANSYS-CFX was adopted in this paper to simulate wildfires,and the temperature field of the transmission line was obtained,and based on the temperature filed,the changes of total length,maximum sag and tensile stress of the transmission line were figured out and analyzed.The same temperature was applied on the transmission line for static analysis in ABAQUS,and the relationship between the temperature and the length,the maximum sag,tensile stress of the lines was obtained.The results show that,for a certain span line,after the wildfires,the total length and the maximum sag of the lines increased,and the tensile stress of the line decreases with the increase of the temperature.The above conclusions provide the experimental and analytical reference to determine whether the transmission lines can continue work normally.