Abstract: The present disclosure is related to methods (400; 500; 600) configured for detecting the state of a wind turbine blade (22). The methods (400; 500; 600) comprising receiving (401; 501) load signals from a wind turbine blade (22), determining (402; 503) an energy of the load signal in a first and second frequency and comparing (403; 504) said energy to generate a flag signal if the energy in the first frequency is smaller than the energy in the second frequency. A control system (600) suitable to detect the state of a wind turbine blade (22) is also provided, as well as wind turbines (10) including such a control system (600).

Abstract: A method for operating a wind turbine determines reliability of an azimuth measurement system by measuring loads with load sensors during operation of the wind turbine. Based on the measured loads, in-plane moments generated on the blades at a rotational speed frequency of the rotor are determined. The azimuth measurement system has reduced reliability if the angular phase of the in-plane moments at the rotor rotational speed frequency of the rotor deviates from an angular phase measured by the azimuth measurement system by more than a first threshold value. The method generates a warning signal or changes operation of the wind turbine when it is determined that the azimuth measurement system has reduced reliability.

Abstract: The present disclosure relates to a method for determining reliability of one or more load sensors in a wind turbine. The method comprises measuring loads with the load sensors during operation of the wind turbine; determining in-plane moments based on the measured loads; selecting the in-plane moments with 1 p frequency; and comparing the selected in-plane moments with theoretical in-plane moments due to a mass of the blade. The method then comprises determining that the load sensors have reduced reliability if the selected in-plane moments deviate from the theoretical in-plane moments by more than a first threshold value. The present disclosure also relates to wind turbine systems incorporating load sensors and methods for on-line determination of correct functioning of load sensors mounted on a wind turbine blade.

Abstract: The present disclosure relates to methods for determining reliability of an azimuth measurement system in a wind turbine. The methods comprise measuring loads with load sensors during operation and determining in-plane moments with rotor rotational speed frequency of one or more blades based on the measured loads. The methods further comprise measuring an azimuthal position of a wind turbine rotor. The method also comprises determining that the azimuth measurement system has reduced reliability if an angular phase of the in-plane moments deviates from the measured azimuthal position by more than a first threshold value. The present disclosure also relates to wind turbine systems incorporating azimuth measurements and methods for on-line determination of correct functioning of azimuth sensors.

Abstract: The present disclosure relates to a method for determining reliability of one or more load sensors in a wind turbine. The method comprises measuring loads with the load sensors during operation of the wind turbine; determining in-plane moments based on the measured loads; selecting the in-plane moments with 1 p frequency; and comparing the selected in-plane moments with theoretical in-plane moments due to a mass of the blade. The method then comprises determining that the load sensors have reduced reliability if the selected in-plane moments deviate from the theoretical in-plane moments by more than a first threshold value. The present disclosure also relates to wind turbine systems incorporating load sensors and methods for on-line determination of correct functioning of load sensors mounted on a wind turbine blade.