Famos 4 Wind a New Method for the Fatigue Monitoring of Wind Energy Plants

Abstract

Modern state-of-the-art fatigue monitoring approaches gain in importance in the context of renewables such as wind power plants. Fatigue is of utmost importance in terms of potential damage mechanisms and in the perspective of scheduled plant lifetime periods of 20 years. A qualified fatigue monitoring approach considering the real loads provides-the best possible knowledge of the state of the plant (protection of investment)-the basis for long term operation projects and-the basis for a load ranking within a wind park in case of partial load operation.It is the aim to ensure a constant damage accumulation across the wind park. AREVA disposes of a long tradition in the development of fatigue and structural health monitoring solutions. The methodology established for power plant applications is transferred to mechanical loading conditions of components of wind energy plants. The core challenge is the identification and qualified processing of realistic load-time histories. The related methodological requirements will be explained in detail. In terms of components of wind energy plants the wind loads are producing inner structural loads (forces and moments). Hence, the main target is gaining knowledge about the histories of these inner load series. The approach is based on a modern standard acceleration measurement at specific positions on the wind turbine tower. The fatigue monitoring process is as follows:1.Measurement of the tower acceleration with modern acceleration measurement equipment;2.Evaluation of displacement histories based on the acceleration measurements using double integration functions;3.Calculation of internal loads histories based on the equation of motion and the knowledge of towers stiffness;4.Scaling and superposition of elementary stress responses for getting component stress histories and5.Evaluation of fatigue accumulation based on stress histories and the Palmgren-Miner rule.