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 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.