An assessing framework for the structural functional states of transmission lines under wind loads

To quantitative analyze the structural function of transmission lines under wind and provide a research basis for the wind resistance resilient of them, an assessing framework is established. This framework includes four effects that wind has on the structural function of transmission lines and is applicable to the state parameters obtained under various wind conditions. Firstly, for each case, the performance function is established according to its critical parameter and safety factor. Then, the probabilistic density analysis is conducted on the acquired states parameters of transmission lines. Finally, the index values of functional state are calculated by the quantitative calculation method proposed based on performance functions and probability densities. To ensure accuracy in the analysis, plenty of dynamic wind fields should be applied to the investigated lines. The wind with long-duration can be divided into multiple wind with unit duration, which can improve the computational efficiency when transmission lines encounter various wind conditions. Based on the state results, weak positions of transmission lines can be identified. In this paper, a section of one 110 kV transmission line is selected for analysis. From the case study, it is evident that applying at least 50 random dynamic wind fields to this line is necessary for convergence of the results when the unit duration is 10 minutes and the time interval for obtaining state parameters is 0.1 seconds. Additionally, the span distances should be reasonably determined based on tower categories and wind-resistant capacity.