Feasibility of in situ blade deflection monitoring of a wind turbine using a laser displacement sensor within the tower

Abstract

With the potential of commercially viable global wind power, the use of wind energy is expected to rise further, along with related problems. One issue is collision of the wind turbine blades with the tower during operation. Structural health monitoring is required to improve operational safety, minimize the risk of sudden failure or total breakdown, ensure reliable power generation, and reduce wind turbine life cycle costs. To this end, large numbers of sensors such as fiber Bragg grating and piezoelectric devices have been attached to the structure, which is uneconomical and impractical for large wind turbines. This study proposes a single laser displacement sensor (LDS) system in which all of the rotating blades can be cost-effectively evaluated. In contrast to the approach of blade sensor installation, the LDS system is installed in the tower to enable noncontact blade displacement monitoring. The concept of a noncontact sensor and actuator and their energy delivery device installed in the tower will enable various approaches for wind turbine structural health monitoring. Blade bolt loosening can cause deflection in an affected blade. Similarly, nacelle tilt or mass loss damage in a blade can result in changes in blade deflection, but the proposed system can detect such problems early on.