Method for measuring imbalances in wind turbine rotors

A method for determining a torsion of a rotor blade of a rotor rotating around a rotor axis is determined as angles between two lines;

• wherein, by contactless distance measurement by a measuring device located a distance from the rotor on at least two measurement sections generated by at least two laser beams of the measuring device, which at least two measurement sections are not parallel to the rotor axis and which are oriented so that the at least two measurement sections are at least also simultaneously swept by a rotor blade, at least during the sweep of the rotor blade through the measurement sections on each measurement section, at least twenty distance measurement values are measured by the laser beams of the measuring device, wherein the angles between the measurement sections and the horizontal are measured, and wherein at least a first and a second connection line are determined by the measuring device in each case between at least two interpolation points which are given in each case by a measurement point or point on an interpolation of the measurement points of a measurement line, wherein the interpolation points lie at least on two different measurement lines, and wherein the measurement lines in each case are given by the measuring device connecting the measurement points at which the measurement values of a respective measurement section on the rotor blade were obtained, wherein, the first laser beam and the second laser beam are arranged in such a way that the first measurement section and the second measurement section are oriented such that, between the sweep of the interpolation points of a connection line through the measurement sections, there is a maximum temporal spacing of ⅕ s or a maximum temporal spacing in which the rotor is rotated maximally by 0.5° around the rotor axis;
• which two lines in each case extend parallel to a linking line from a leading edge to a trailing edge of the rotor blade or which extend perpendicularly to an edge of the rotor blade or perpendicularly to at least a first or a second connection line;
• and
• wherein the lines intersect the first and a second connection line or extends perpendicularly thereto, wherein the first laser beam and the second laser beam are arranged in such a way that the first measurement section and the second measurement section are oriented such that the interpolation points between which the first connection line extends have a maximum temporal spacing of ½ s or a maximum temporal spacing in which the rotor is rotated maximally by 1° around the rotor axis, from the leading edge of the rotor blade;
• and
• the measurement points between which the second connection line extends have a maximum temporal spacing of ½ s or a maximum temporal spacing in which the rotor is rotated maximally by 1° around the rotor axis, from the trailing edge of the rotor blade, are defined;
• wherein the first line lies between interpolation points of a first measurement line and a second measurement line, and the second line lies between interpolation points of a third measurement line and the second measurement line or of the third measurement line and a fourth measurement line, wherein, with respect to the horizontal, the inclination angle of the measurement section of the first measurement line is smaller than that of the second measurement line, which is smaller than that of the third measurement line, or, with respect to the horizontal, the inclination angle of the measurement section of the first measurement line is smaller than that of the second measurement line, which is smaller than that of the third measurement line, which is smaller than that of the fourth measurement line.

A method for determining an imbalance or an eccentric moment of inertia of a rotor of a wind turbine, wherein the rotor rotates around a rotor axis and includes at least two rotor blades, wherein the method comprises:

• positioning a measuring device a distance away from a base of a tower of the wind turbine,
• directing a first laser beam from the measuring device towards the rotor, wherein the directed first laser beam comprises a first measurement section;
• rotating the at least two rotor blades about the rotor axis;
• sweeping the at least two rotor blades through the first measurement section during rotation;
• detecting, with the first laser beam, the sweep of a first rotor blade of the at least two rotor blades through the first measurement section;
• detecting, with the first laser beam, the sweep of a successive rotor blade of the at least two rotor blades through the first measurement section;
• determining, with the measuring device, a first time span between when the first rotor blade sweeps the first measurement section and when the successive rotor blade sweeps the first measurement section;
• repeatedly sweeping the first measurement section with the first rotor blade and the successive rotor blade as the rotor continues to rotate;
• determining, with the measuring device, a successive time span for each time the first rotor blade and the successive rotor blade sweep the first measurement section;
• calculating a difference between the first time span and the successive time span;
• and
• determining an imbalance in the rotor or an eccentric moment of inertia of the rotor when the first time span differs from the successive time span.