Post-mortem study on structural failure of a wind farm impacted by super typhoon Usagi

Super typhoon Usagi, which was on category 4 according to the Saffir-Simpson hurricane intensity scale [1], impacted a wind farm near Shanwei city on the southeast coast of China in 2013, see Figure 1. During typhoon impact, the wind farm experienced a dramatic change of wind direction and a maximum wind speed (3s average) of 57 m/s at a 10-m elevation. As a result of this super typhoon, eight turbine towers collapsed, eleven rotor blades broke off and three turbines were burned, leading to an approximate $16 million loss to the wind farm. Authors of this paper carried out a post-mortem study on the wind farm with particular focus on the tower collapse and blade failure. A systematic procedure was developed for this endeavor by integrating both aerodynamic analysis for wind characterization and structural analysis for towers and blades. To provide necessary input for the procedure, data of local wind record, terrain topography and turbine status were collected, analyzed and assessed together with field investigation and user inquiry. Through this study, plausible root-causes of structural failure of the wind farm were indentified. This paper summarized the process and key findings of structural failure investigation on the wind farm impacted by super typhoon Usagi. It is expected that insights gained from this study could assist structural failure mitigation of wind farms under extreme wind conditions.