Monitoring of Wind Turbine Structures using Stationary Sensors and Short-term Optical Techniques

Abstract

This research deals with monitoring of a large onshore wind turbine (3 MW, 142.5 m hub height) with a hybrid (steel/concrete) tower design. The structural dynamics of the tower are monitored by stationary sensors installed inside the tower and short-term optical techniques. The insights are used to calibrate a detailed finite element model of the tower. Combining measurement data and a finite element model, the overall objective of the project can be reached, which is to detect defects and fatigue and to estimate the remaining service-life of the wind turbine support structure. Modal parameters of the structure including uncertainties were obtained by operational modal analysis of 244 10-min. vibration monitoring datasets. The resulting first and second order bending eigenfrequencies (0.27 Hz and 1.17 Hz) were deployed for validating and improving a finite element model by adding initial displacement stiffness. Besides validation using modal parameters a comparison of the structural response from field measurements and FE model is scheduled. Therefore tower displacement is determined from acceleration and digital image correlation of video data. Test measurements at the full-size test wind turbine were carried out providing coinciding displacement values