| CPC F03D 7/0288 (2013.01) [F05B 2270/17 (2013.01); F05B 2270/33 (2013.01); F05B 2270/802 (2013.01); F05B 2270/808 (2013.01)] | 13 Claims |

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1. A method of determining a distance between a rotor blade tip and a tower of a wind turbine, the method comprising:
estimating the distance based on a strain measurement;
measuring the distance;
correcting an estimation procedure based on the estimated distance and the measured distance; deriving a corrected distance based on the corrected estimation procedure; and
changing a blade pitch angle to reduce lift when the corrected distance is not in an allowed range,
wherein correcting the estimation procedure comprises:
forming a ratio of the estimated distance and the measured distance; and
calculating at least one correction parameter based on the ratio.
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