Blade deflection measurement with magnetostrictive sensor

Abstract

A measurement arrangement for measuring a deflection of a wind turbine rotor blade is provided. The measurement arrangement includes a magnetostrictive sensor, which includes a first sensor part and a second sensor part, a first support structure, which is adapted to be mounted to a first portion of the rotor, wherein the first sensor part is mounted to the first support structure, and a second support structure, which may be mounted to a second portion of the rotor, wherein the second sensor part is mounted to the second support structure and wherein either or both the first portion and the second portion is a portion of the blade. The magnetostrictive sensor measures the relative spatial position between the first sensor part and the second sensor part. A method for measuring a blade deflection and a wind turbine rotor which includes the described blade deflection measurement arrangement are also provided.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority of European Patent Office application No. 09015863.5 EP filed Dec. 22, 2009, which is incorporated by reference herein in its entirety.FIELD OF INVENTION[0002]The present invention relates to the technical field of measuring and controlling mechanical loads which are acting on a rotor blade of a wind turbine. Specifically, the present invention relates to a measurement arrangement and to a method for measuring a deflection of a blade of a rotor of a wind turbine. Further, the present invention relates to wind turbine rotor and to a wind turbine which comprise the described blade deflection measurement arrangement.ART BACKGROUND[0003]Rotor blades of wind turbine are exposed to large dynamic mechanical loads in particular when the wind turbine is operated in turbulent wind conditions or in conditions of flow distortion, e.g. high wind shear. Therefore, the rotor blades of wind turbines and the corresponding ...

AI Technical Summary

Benefits of technology

[0016]It is mentioned that it is not necessary that the magnetostrictive sensing element and the position determining magnet are in mechanical contact with each other. It is only necessary that the first magnetic field generated by the propagating current pulse and the second magnetic field generated by the position determining magnet can interact with each other in such a manner, that the described local mechanical deformation is generated. After the generation of this local mechanical deformation the deformation propagates or travels within the magnetostrictive sensing element. Therefore, the magnetostrictive sensor can operate in a contactless manner, which may guarantee a long sensor lifetime.

[0045]According to an embodiment of the invention the first portion of the rotor is a portion of the hub and the second portion of the rotor is a portion of the blade. This may provide the advantage that the surface of the first portion of the rotor and the surface of the second portion of the rotor can be oriented angularly, in particular at least approximately perpendicular, with respect to each other. This may allow for realizing the measurement arrangement with from a mechanical point of view comparatively simple support structures.

Problems solved by technology

Rotor blades of wind turbine are exposed to large dynamic mechanical loads in particular when the wind turbine is operated in turbulent wind conditions or in conditions of flow distortion, e.g. high wind shear.

The risk for damaging a rotor blade strongly depends on the fatigue the blade is currently suffering and on the fatigue life time, which the rotor blade has accumulated so far during its previous operation.

If the rotor blade has a large deflection the fatigue load in the root is relatively big.

However, continuing load cycles of rotor blades cause a big wear of such strain gauges resulting in a reduced lifetime of the respective strain gauges.

Another disadvantage of strain gauges is that they tend to drift over time and due to temperature changes.

Furthermore, maintenance of strain gauges is often tedious when the respective strain sensor is located in an outer radial portion of the rotor blade.

Further, when mounting a strain gauge at an outer radial rotor blade portion, for contacting the strain gauge electrical wires are necessary which run on or within the longitudinal extension of the blade and which make the rotor blade vulnerable to lighting strikes.

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