Aerodynamic Sensitivity Analysis of Rotor Imbalance and Shear Web Disbond Detection Strategies for Offshore Structural Health Prognostics Management of Wind Turbine Blades

Operations and maintenance costs for offshore wind plants are projected to be considerably higher than the current costs for land-based wind plants. One way to reduce these costs would be to implement a structural health and prognostic management (SHPM) system as part of a condition based maintenance paradigm with smart load management. To facilitate the development of such a system a multiscale modeling approach has been developed to identify how the underlying physics of the system are affected by the presence of damage and faults, and how these changes manifest themselves in the operational response of a full turbine. This methodology was used to perform a sensitivity analysis, investigating several inflow conditions in an effort to further evaluate the maturity of rotor imbalance and shear web disbond detection strategies developed in past efforts under variable inflow conditions as would be experienced in actual operation. Based on an aerodynamic sensitivity analysis of the model, the operational measurements used for the pilot study in the detection of pitch error, mass imbalance, and shear web disbond were utilized to confirm the validity of the detection strategies for all three damage/fault cases. Detection strategies were refined for these fault mechanisms and probabilities of detection (POD) were calculated. For all three fault mechanisms, the probability of detecting each fault was 96% or higher for the optimized wind speed ranges of the laminar, 30% horizontal shear, and 60% horizontal shear wind profiles. This aerodynamic sensitivity study contributes to the evaluation of structural health monitoring information with the goal to reduce operations and maintenance costs for an offshore wind farm while increasing turbine availability and overall profit.