Monitoring of Wind Turbine Blades Using Radar Technology: Results from a Field Study at a 2MW Wind Turbine

Abstract

Millimeter-wave and terahertz technology have been used successfully in nondestructive testing (NDT) applications for material defects identification. Such systems were recently proposed for structural health monitoring (SHM) to identify defects online during operation. One interesting application field is the monitoring of wind turbine blades that have large dimensions and a heterogeneous material system. Millimeterwaves are able to penetrate the dielectric components of the blade and sensitively interact with material defects such as cracks, delaminations and debondings. This paper presents results from a field study at a 2 MW wind turbine. The focus of this work is on the analysis of radar signatures at different parameters of the wind turbine such as variations of the azimuthal position of the nacelle. Therefore, consecutive radar signals are processed in a dedicated way to identify relative changes between different rotor blades. In addition, a methodology will be presented on how to apply an artificial damage on the surface of the rotor blade. Therefore, a remotecontrolled car (called Blade Rover) was modified so that it could spray shaving foam onto the rotor blade at a defined location. The shaving foam serves here as a reversible damage model, because it has a significant dielectric contrast due to its water content.