Wind Speed Estimation Method for Snow Resistance Design Based on Axial Forces of Transmission Tower

In the snow resistance design of transmission towers, the weight of snow accretion on power lines and the wind loads that occur during snow accretion should be carefully evaluated. To determine the optimized design loads, we performed extreme value analyses of the axial forces of the tower members for 50 winter seasons spanning 1970-2020. In addition, the ‘required wind speed’ was calculated, which must act simultaneously with the design snow thickness specified in JEC-5101: 2022 to determine the extreme values of the axial forces. Sensitivity analyses of the required wind speeds with respect to tower specifications were performed using three tower models typically used in Kansai Transmission and Distribution. We found that the required wind speed increases as the relative contribution of the wind load exceeds that of the snow accretion load. In the supply area of Kansai Transmission and Distribution, the most conservative wind speeds derived using this method are significantly lower than the values specified in JEC-5101: 2022. Furthermore, the main posts of the transmission tower tend to experience their quite heavy axial forces during light snow accretion periods accompanied by strong winds and not during heavy snow accretion periods.