Study on Stability of Transmission Tower-Line System under a Downburst

A downburst is one of the high-intensity winds that cause transmission tower failures. In recent years, downbursts have brought great disasters to the economies and lives of people all around the world. In this paper, the dynamic stability of the transmission tower-line system under a downburst is analyzed. The deterministic-random mixed model is used to generate the downburst wind field and ANSYS software is employed to establish the finite element model of the transmission tower-line system. The response characteristics of the transmission tower-line system in the downburst and the atmospheric boundary layer (ABL) wind fields are compared through time history analysis. The displacement response of the transmission tower is analyzed with different Z(max) values and attack angles. Based on the Budiansky-Roth criterion and dynamic incremental method, the dynamic stability of the transmission tower system under the action of the downburst wind field is studied, and the corresponding wind speed conditions when the transmission tower-line system is unstable are obtained. The results show that the top displacement of the tower-line system under the action of a downburst is 1.83 times that under the ABL wind. The tower top acceleration under the downburst is 1.57 times that under ABL wind. The most unfavorable wind attack angle for a transmission tower-line system is 90 degrees. When Z(max) is within the height range of the transmission tower, the influence on the displacement of the transmission tower increases with the increase in Z(max). When Z(max) exceeds the height range of the transmission tower, the influence on the displacement of the transmission tower decreases. Under the most unfavorable wind attack angle, the influence of the conductor on the stability of the transmission tower is obvious.