Wind Turbine Tower Deformation Measurement Using Terrestrial Laser Scanning on a 3.4 MW Wind Turbine

Abstract

Wind turbine plants have grown in size in recent years, making an efficient structural health monitoring of all of their structures ever more important. Wind turbine towers deform elastically under the loads applied to them by wind and inertial forces acting on the rotating rotor blades. In order to properly analyze these deformations, an earthbound system is desirable that can measure the tower’s movement in two directions from a large measurement working distance of over 150 m and a single location. To achieve this, a terrestrial laser scanner (TLS) in line-scanning mode with horizontal alignment was applied to measure the tower cross-section and to determine its axial (in the line-of-sight) and lateral (transverse to the line-of-sight) position with the help of a least-squares fit. As a result, the proposed measurement approach allowed for analyzing the tower’s deformation. The method was validated on a 3.4 MW wind turbine with a hub height of 128 m by comparing the measurement results to a reference video measurement, which recorded the nacelle movement from below and determined the nacelle movement with the help of point-tracking software. The measurements were compared in the time and frequency domain for different operating conditions, such as low/strong wind and start-up/braking of the turbine. There was a high correlation between the signals from the laser-based and the reference measurement in the time domain, and the same peak of the dominant tower oscillation was determined in the frequency domain. The proposed method was therefore an effective tool for the in-process structural health monitoring of tall wind turbine towers.

Dynamic optical deformation measurements on wind turbines

“…As shown in [6], a tower deformation measurement using a 2d terrestrial laser scanner using time-of-flight is possible. The laser scanner can either be aligned horizontally or vertically with regard to the tower.…”

Contactless Deformation Monitoring of Bridges with Spatio-Temporal Resolution: Profile Scanning and Microwave Interferometry

“…Furthermore, advanced processing algorithms are presented that enable the universal use of a profile scanner. Further publications on the subject of profile scanning also deal with bridges [ 14 , 15 , 16 , 17 ], noise barriers [ 18 ] and wind power plants [ 14 , 19 , 20 , 21 , 22 , 23 ]. In these publications, the sensor performance is regularly evaluated through comparisons with conventional sensors, such as LVDTs or accelerometers, proving that a profile scanner can be used reliably for a wide range of structures and applications.…”

Review on the Research and Applications of TLS in Ground Surface and Constructions Deformation Monitoring

“…In addition, some scholars have used not only TLS, but also combined it with other technologies to monitor the deformation of tall constructions. Based on the TLS technology, the video measurement was also used [ 70 ], with the camera placed face up at the bottom of the generator, video observation of the nacelle using point tracking software to measure the movement of the nacelle, and the laser scanner tilted upward to measure the deformation at the top end of the tower. The measurements were compared in time and frequency domains under different operating conditions, such as low/strong winds and turbine start/brake.…”