A method of determining a blade clearance during operation of a wind turbine is provided, the blade clearance corresponding to a distance between a rotor blade and a tower of the wind turbine. The method includes (a) detecting a rotor blade velocity, (b) emitting a first signal from an observer location, the first signal having a first frequency, (c) receiving a second signal at the observer location, the second signal being reflected from the rotor blade when the first signal impinges on the rotor blade, (d) determining a Doppler shift of the second signal relative to the first signal, and (e) determining the blade clearance based on the first frequency, the Doppler shift, the observer location, and the rotor blade velocity, wherein the step of determining the blade clearance utilizes a mathematical model. A corre-sponding system and a wind turbine comprising such a system are also provided.

A method for operating a wind turbine, in particular at a location characterized by a cold climate is provided. The method includes, specifying an air density at a location of the wind turbine, setting a blade angle of an adjustable rotor blade based on an output power, torque and/or rotor speed. The method includes setting the blade angle as a function of a at pitch characteristic curve which specifies the blade angle as a function of the output power, the torque and/or the rotor speed and as a function of the air density. According to the pitch characteristic curve, the blade angle has a minimum as a function of the air density in a region of a reference density of an atmosphere at the location which is characterized by a cold climate.

Described is a system for monitoring deflection of turbine blades of a wind turbine comprising a tower. The system comprises a position detecting apparatus mounted to the wind turbine, the position detection apparatus comprising position detection components each detecting a presence or absence of a corresponding one of the segments of the turbine blades; and a deflection controller configured to receive the presence or absence detection and to use the presence or absence detection to determine a distance of each of the segments of the turbine blades relative to the tower, whereby the distance of each of the segments of the turbine blades relative to the tower is representative of the deflection of the turbine blades.

An apparatus including a leaky feeder arrangement including a plurality of parallel leaky feeders, a transmitter coupled to the leaky feeder arrangement and configured to supply individual first radar signals to a group of leaky feeders in the leaky feeder arrangement, the first radar signals being configured to form a first radar signal beam in a predetermined direction relative to the leaky feeder arrangement, a receiver coupled to the leaky feeder arrangement and configured to receive a second radar signal from the leaky feeder arrangement, wherein the second radar signal is reflected from the target object when the first radar signal beam hits the target object, and a processing unit configured to analyse a first signal corresponding to the first radar signals and a second signal corresponding to the second radar signal to determine the properties of the moving object. A wind turbine and a method are also provided.

A measuring arrangement for detecting deformations, in particular bending of the outer surface, of a wind turbine structural element, includes: at least two measurement sites on the structural element spaced apart from one another toward a structural element extension, each having at least one acceleration sensor, that can be communication-connected—preferably via a wireless interface—to an evaluation device. The measuring arrangement—has at least two speed sensors, in particular angular speed sensors, on the structural element and spaced apart from one another toward a structural element extension, preferably the longitudinal extension, and/or the measuring arrangement has at least two position sensors, in particular magnetic field sensors, on the structural element and spaced apart from one another toward a structural element extension, preferably the longitudinal extension. The speed sensors and/or the position sensors can be communication-connected to the evaluation device—preferably via a wireless interface.

A method of controlling at least one adaptable airflow regulating system, in particular spoiler and/or flap, of at least one rotor blade of a wind turbine having a wind turbine tower includes: determining a quantity related to a distance between the rotor blade and the wind turbine tower; controlling the airflow regulating system based on the quantity.

The present disclosure relates to methods and systems for measuring deflection of blades of a wind turbine. Examples include a light emitting and collection device mounted to the nacelle and configured to emit light in a direction within a substantially vertical plane. Examples include a method for operating a wind turbine including emitting light above a hub, receiving the light when reflected by a blade of the wind turbine, and, if the level of blade deflection is above a threshold, reducing blade loading of the blade before the blade reaches a vertically downward position. Examples include a method for monitoring deflection of a rotor blade of a wind turbine comprising emitting a light sheet, collecting reflections of the emitted light, and determining deflection of the rotor blade by determining a time during which the blade reflects the emitted light sheet.

Described is a system for monitoring deflection of turbine blades of a wind turbine comprising a tower. The system comprises a position detecting apparatus mounted to the wind turbine, the position detection apparatus comprising position detection components each detecting a presence or absence of a corresponding one of the segments of the turbine blades; and a deflection controller configured to receive the presence or absence detection and to use the presence or absence detection to determine a distance of each of the segments of the turbine blades relative to the tower, whereby the distance of each of the segments of the turbine blades relative to the tower is representative of the deflection of the turbine blades.

Provided is a method for detecting a wind gust that affects a wind turbine, wherein the wind turbine includes two or more blades which are coupled to a connection means so that the blades are essentially arranged in a common plane. The method including: i) measuring an event that at least one blade is at least partially out of the plane to obtain a measurement signal, ii) providing the measurement signal as a measurement input signal to an evaluation algorithm, iii) elaborating a detection result from the measurement input signal using the evaluation algorithm, and iv) comparing the detection result with a predefined wind gust threshold value (h) to determine, if a wind gust is detected. Furthermore, a wind gust detection system, a wind turbine that includes the system, and a wind turbine operating method are provided.

A method and device for determining a tower clearance of a wind turbine. The method includes: acquiring an image of a wind turbine in operation (S10), the image comprising the tips of blades (2) and a tower (1) of the wind turbine; determining the positions of the tips of the blades (2) of the wind turbine in the image acquired (S20); identifying the edges of the tower (1) in the image acquired (30); and calculating, on the basis of the positions of the tips of the blades (2) and the edges of the tower (1) that have been determined, the distance from the tips (2) of the blades (2) to the edges of the tower (1) to acquire a tower clearance (S40).