<i>In Situ</i> Blade Deflection Monitoring of a Wind Turbine Using a Wireless Laser Displacement Sensor Device within the Tower

Abstract

With commercially viable global wind power potential, wind energy penetration is further expected to rise, as will the related problems. One issue is the collision of wind turbine blades with the tower during operation. Structured 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. Large numbers of sensors such as fiber Bragg grating and piezoelectric devices have been attached to the structure, a design that is uneconomical and impractical for use in large wind turbines. This study proposes a single laser displacement sensor (LDS) system in which all of the rotating blades could be cost-effectively evaluated. Contrary 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 installation in the tower will enable various approaches for wind turbine structural health monitoring. Blade bolt loosening causes deflection in the affected blade. Similarly, nacelle tilt or mass loss damage in the blade will result in changes in blade deflection, but the proposed system can identify such problems with ease. With the need of more energy, the sizes of wind blades are getting bigger and bigger. Due to the large size of wind turbine, nowadays wind turbines are installed very high above the ground or water level. It is impractical to monitor the results from LDS through wired connection in these cases. Hence, the wired connection of LDS to base (monitoring) station must be replaced by a wireless solution. This wireless solution is achieved using Zigbee technology. Zigbee operates in the industrial, scientific and medical (ISM) radio bands, typically 2.4 GHz, 915 MHz and 868 MHz. The output from the LDS is fed to the microcontroller which acts as an analog to digital converter. The output from the microcontroller is connected to the Zigbee transceiver module, which transmits the data and at the other end, the zigbee reads the data and displays on the PC from where user can monitor the condition of wind blades.