1. An aerodynamic rotor imbalance was detected in the course of a rotor imbalance measurement. The results for the blade angle correction carried out here were determined either by an optical blade angle measurement and/or by a so-called test pitch measurement.
A basis for the evaluation of the determined deviations is the "Guideline for the Certification of Wind Turbines" of Germanischer Lloyd (2010 edition). According to this, with regard to aerodynamic asymmetries, deviations of the blade pitch angle should not exceed ±0.3°. This means that the angular deviation of the rotor blades from each other in a blade set should not exceed 0.6°. However, experience shows that a significant aerodynamic imbalance can occur with a blade angle deviation of 0.3°, especially on larger rotors.
2. As part of a performance optimisation of this wind turbine, an optical blade angle measurement was carried out with determination of the absolute blade pitch angle. The measurement showed significant deviations from the nominal value. These deviations were corrected with a re-referencing of the blade pitch angles.
Easy to recognize markings were installed after the rotor blades have been readjusted. These markings can be used, for example, to readjust the blades after changing the pitch controller.