Probabilistic capacity assessment of single circuit transmission tower-line system subjected to strong winds

The safety and resilience of physical infrastructure of the power systems, including the transmission towers and lines for high-voltage transmission as well as the poles and wires for power distribution at a lower voltage level, is critical to avoid and recover from power outages under the extreme weather related loads such as strong winds from hurricanes, tornados, downbursts or isolated thunderstorms. In the current engineering practices, single circuit lattice steel towers linked by transmission lines are widely used to form power transmission systems. Failure of either a structural component (local failures, such as buckling of a local member or breakage of a single wire) or the entire structure (global failures, such as instability of the entire tower) could propagate to their adjacent structural members or systems (such as neighboring towers or lines). Therefore, there is a strong need to identify the root cause of the failure of the transmission tower-line system and identify the weakest link under various extreme weather scenarios. This study is to develop a probabilistic assessment approach for a typical transmission tower-line system subjected to strong wind loadings under synoptic winds (atmospheric boundary layer wind). Due to the complicated structural details and complex wind-structure interactions, wind tunnel experiments were carried out to obtain the static wind load coefficients for different panels of the transmission towers as well as for the transmission lines. Incremental dynamic analysis (IDA) is carried out to obtain the capacity curve for the transmission tower-line system. Uncertainties from the meteorological parameters are also considered in the analysis. The probabilities of failure for the two predefined limit state functions are obtained considering the meteorological uncertainties. Meanwhile, the probabilities of failure at different return periods are presented for a transmission tower-line system subjected to strong winds in a coastal region. Finally, the effects of the aerodynamic damping for the transmission lines on the dynamic responses of the tower-line system are discussed, as well.