Structural Health Monitoring of Multi-MW-Scale Wind Turbines by Non-contact Optical Measurement Techniques: An Application on a 2.5-MW Wind Turbine

Abstract

AbstractOptical measurement systems utilizing photogrammetry and/or laser interferometry are introduced as cost-efficient alternatives to the conventional wind turbine/farm health-monitoring systems that are currently in use. The proposed techniques are proven to provide an accurate measurement of the dynamic behavior of a 2.5-MW, 80-m-diameter wind turbine. Several measurements are taken on the test turbine by using four CCD cameras and one laser vibrometer, and the response of the turbine is monitored from a distance of 220 m. The results of the infield tests show that photogrammetry (also can be called as computer vision technique) enables the 3-D deformations of the rotor to be measured at 33 different points simultaneously with an average accuracy of ±25 mm while the turbine is rotating. Several important turbine modes can also be extracted from the recorded data. Similarly, laser interferometry (used for the parked turbine) provides very valuable information on the dynamic properties of the turbine structure. Twelve different turbine modes can be identified from the obtained response data. The measurements enable the detection of even very small parameter variations that can be encountered due to the changes in operation conditions. Optical measurement systems are very easily applied on an existing turbine since they do not require any cable installations for power supply and data transfer in the structure. Placement of some reflective stickers on the blades is the only preparation that is necessary and can be completed within a few hours for a large-scale commercial wind turbine. Since all the measurement systems are located on the ground, a possible problem can be detected and solved easily. Optical measurement systems, which consist of several CCD cameras and/or one laser vibrometer, can be used for monitoring several turbines, which enables the monitoring costs of the wind farm to reduce significantly.KeywordsGlobal Position SystemWind TurbineWind FarmStructural Health MonitoringLaser Doppler VibrometerThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.