Assessing the rotor blade deformation and tower–blade tip clearance of a 3.4 MW wind turbine with terrestrial laser scanning

Abstract

Abstract. Wind turbines have grown in size in recent years, making efficient structural health monitoring of all of their structures even more important. Wind turbine blades 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 blade deformation, as well as the tower–blade tip clearance 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 vertical alignment is used to measure the distance to passing blades and the tower for different wind loads over time. In detail, the blade deformations for two different wind load categories are evaluated and compared. Additionally, the tower–blade tip clearance is calculated and analyzed with regard to the rotor speed. Using a Monte Carlo simulation, the measurement uncertainty is determined to be in the millimeter range for both the blade deformation analysis and the tower–blade tip clearance. The in-process applicable measurement methods are applied and validated on a 3.4 MW wind turbine with a hub height of 128 m. The deformation of the blade increases with higher wind speed in the wind direction, while the tower–blade tip clearance decreases with higher wind speed. Both relations are measured not only qualitatively but also quantitatively. Furthermore, no difference between the three rotor blades is observed, and each of the three blades is shown to be separately measurable. The tower–blade tip clearance is compared to a reference video measurement, which recorded the tower–blade tip clearance from the side, validating the novel measurement approach. Therefore, the proposed setup and methods are proven to be effective tools for the in-process structural health monitoring of wind turbine blades.

Dynamic displacement measurement of a wind turbine tower using accelerometers: tilt error compensation and validation

“…The significantly higher noise level of the contactless TLS-based measurements makes them well-suited for applications where large displacements occur and where the attachment of a sensor to the measurement object is undesirable. This is particularly true, e.g., for measuring the low frequency displacements, such as those that occur at rotor blades (Helming et al, 2023). In contrast, accelerometers are preferable for monitoring wind turbine tower dynamics as they have a much lower noise level in the range of the first bending natural frequency and at higher frequencies.…”

“…to detect tower and rotor blade deformations are published inHelming et al (2021) andHelming et al (2023), respectively.…”

Development of a Procedure for Torsion Measurement Using a Fan-Shaped Distance Meter System

“…By determining the position of rotor blades using a camera system and tracking the laser doppler vibrometer with a pan-tilt head, a continuous measurement can be made at the same position. A similar method using a laser scanner in 2D mode and a camera is described in [32,33]. In [34], different approaches for optimisation and ground-based monitoring of turbines are presented.…”

“…Sensors 2023, 23, x FOR PEER REVIEW 3 of 16 laser scanner in 2D mode and a camera is described in [32,33]. In [34], different approaches for optimisation and ground-based monitoring of turbines are presented.…”