Integrated sensor system for structural integrity and load monitoring of wind turbines

The development and laboratory scale testing of a Fiber Bragg Grating (FBG) based distributed strain sensor system for structural health monitoring (SHM) and real time load monitoring of a wind turbine is reported. The key objective of the study is to characterize the performance of the sensor system under various loading conditions in order to determine its effectiveness for such applications. Loading conditions considered in this study include quasi-static loading, vibrations and wind flow from wind tunnel. For quasi-static loading condition a single instrumented blade was tested under various loading levels, and the strains measured using FBG system were compared with conventional strain gages. Both free and forced vibration studies were conducted on an instrumented single blade. The obtained dynamic response in terms of natural frequencies and mode shapes were compared with those obtained from numerical models. Finally, a 1.828 meters wind turbine rotor with three instrumented blades was tested under the wind flow generated from a wind tunnel. The sensor data transmitted wirelessly were analyzed for dominant frequencies and correlated with other information collected using other methods, such as accelerometers on the tower. The results from the present study demonstrate that the FBG based strain sensor system has high potential to be used as SHM and real time load monitoring systems.