Assessing Fatigue in Metal Support Towers in Wind Power Plants

Abstract

This paper describes an overview assessment of the fatigue state of three identical 100 m metal support wind turbine towers in wind power plants (WPPs) that have been used for 12, 13, and 15 years. A nondestructive testing (NDT) technique, the magnetic coercive force method (CFM), was used to measure the magnetic characteristics of the metal, in particular, its coercive force. The weakest link of the structure is determined by the degree of fatigue, and its correlation with the individual characteristics of each wind turbine structure is shown. Based on the state of the structure’s weakest link, the residual service life of the wind turbine tower is predicted. Within the general aging process, each tower has its own state of metal characteristics, which individualizes the resource forecast. Through the assessment, it was determined that the amount of time worked is not a main deciding factor. Ways to improve the reliability of wind turbine towers during their manufacture are identified, as well as changes in structure design. CFM performed on the towers reveals maturing fatigue fractures and can be used to assess the holistic structure or its parts for priority maintenance based on the state of the metal.