Abstract:
There is provided a wind power installation having a component to be monitored and a crack detection unit. In that case the crack detection unit has at least one thread or fiber which is fastened directly on the component to be monitored. The crack detection unit further has a crack detector which serves to detect whether the thread or fiber is or is not cracked.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present invention concerns a wind power installation. 
         [0003]    2. Description of the Related Art 
         [0004]    Wind power installations convert the kinetic energy of the wind into electric energy. In that case the wind power installations are exposed to “wind and weather”, which leads to considerable loadings on the wind power installation and parts thereof. The stresses or loadings for the parts or components of the wind power installation can be very different. It is however necessary to ensure that the corresponding parts can withstand the loadings to be expected. In addition it is important to detect possible damage to the wind power installation as early as possible. 
       BRIEF SUMMARY 
       [0005]    One or more embodiments of the present invention is to provide a wind power installation which affords a simple and inexpensive possibility of quickly and reliably detecting damage to the wind power installation. 
         [0006]    Thus there is provided a wind power installation having a component to be monitored and a crack detection unit for detecting a crack in the component. In that case the crack detection unit has at least one thread or fiber which is fastened directly on an inner or outer surface or embedded in the component to be monitored. The crack detection unit further has a crack detector which serves to detect whether the thread or fiber is or is not cracked or torn. 
         [0007]    By virtue of direct fastening of the thread or fiber on or in the component to be monitored a crack in the component also leads directly to a crack in the thread. That crack can then be detected by the crack detector and control of the wind power installation can be suitably influenced. 
         [0008]    In an aspect of the invention the wind power installation has a control unit for controlling operation of the wind power installation. If the crack detector detects that the thread or fiber is cracked then the control unit can influence operation of the wind power installation. Such influence could provide for example that the mechanical loading on the monitored component is reduced (for example by reducing the rotary speed, changing the pitch angle, altering the azimuth position and so forth). 
         [0009]    In a further aspect of the invention the thread or fiber can be made from one or more materials that are electrically conducting or light-conducting. In that way crack detection can be effected either by electric or by optical checking. 
         [0010]    In an aspect of the invention the fiber can be in the form of a glass fiber or a carbon fiber. In the case of a glass fiber optical checking can be effected and in the case of a carbon fiber electric checking can be effected. 
         [0011]    In a further aspect of the invention it is possible to provide fibers or threads of differing lengths to permit the position of the crack to be more accurately determined. The fibers or threads can be straight, of a meander configuration or of a grid structure. 
         [0012]    The invention also concerns a method of monitoring components of a wind power installation. For that purpose threads or fibers are fastened directly on or in the component to be monitored. Then a crack detector is used to detect whether the thread or fiber is or is not cracked. 
         [0013]    The invention concerns the notion of providing a wind power installation which involves simple and effective crack detection on components of the wind power installation. Cracks occurring at crack-endangered locations of the wind power installation (for example rotor blades, castings, pylon, foundation and so forth) can be detected by means of crack detection. To implement crack detection, an interruptible thread or fiber is fastened, for example by adhesive, to the locations to be monitored (crack-endangered locations), or the thread or fiber is fitted in the component to be monitored. If a crack occurs at the respective component then that will also lead to an interruption in the thread of the crack detection system. That crack or the interruption in the thread or fiber can then be detected for example electrically or optically. If a crack in the fiber is detected that can result in the control system of the wind power installation being influenced, for example to reduce the mechanical loading on the cracked component. A reduction in the mechanical loading on the installation can be effected for example by control of the pitch angle of rotor blades or by control of the azimuth drive. 
         [0014]    The interruptible thread or fiber can be for example a light conductor, an optical waveguide, an electric conductor, a glass fiber, a carbon fiber or the like. The interruption in the thread can be detected for example electrically or by means of light. After an interruption has been detected the control system of the wind power installation can be influenced and the installation can possibly be stopped. 
         [0015]    The crack detection or crack monitoring system according to one embodiment of the invention can afford crack detection at an early stage so that suitable countermeasures (adapted control of the wind power installation or replacement of the cracked component) can be taken before really major damage can occur. 
         [0016]    According to one embodiment of the invention the thread can be fastened in a plurality of passes, in a meander shape and/or in the form of a grid structure, on the component to be monitored (such as for example a rotor blade, a steel rotor blade, a GRP rotor blade, a CRP rotor blade, castings of the installation (such as for example the rotor hub), a concrete or steel pylon or the foundation). 
         [0017]    Preferably the threads or fibers are fastened flat on one or more surfaces of the component to be monitored (in particular by adhesive). Gluing the threads or fibers in position flat on the component is advantageous as a crack can thus be relatively quickly detected. In particular it is possible thereby to avoid the thread or fiber stretching too long before it tears away. 
         [0018]    Further configurations of the invention are subject-matter of the appendant claims. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0019]    Advantages and embodiments by way of example of the invention are described in greater detail hereinafter with reference to the drawings. 
           [0020]      FIG. 1  shows a diagrammatic view of a wind power installation according to an embodiment of the invention, 
           [0021]      FIGS. 2A and 2B  show diagrammatic views of a rotor blade with a crack detection unit according to embodiments of the invention, 
           [0022]      FIGS. 3A and 3B  each show a diagrammatic view of a pylon of a wind power installation having a crack detection unit according to embodiments of the invention, and 
           [0023]      FIG. 4  shows a diagrammatic view of a part of a rotor blade of a wind power installation together with a crack detection unit. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIG. 1  shows a diagrammatic view of a wind power installation according to the invention. The wind power installation has a pylon  10  and a pod  20  on the pylon  10 . Azimuthal orientation of the pod can be altered by means of an azimuth drive  80  to adapt the orientation of the pod to the currently prevailing wind direction. The pod  20  has a rotatable rotor  70  with at least two and preferably three rotor blades  30 . The rotor blades  30  can be connected to a rotor hub  75  which in turn is connected to an electric generator  60  directly or by means of a gear arrangement (not shown). The rotor of the generator  60  is rotated by rotation of the rotor blades  30  and of the rotor  70  and that therefore provides for the generation of electric energy. 
         [0025]    The wind power installation further has a control unit  40  for controlling operation of the wind power installation. In addition an anemometer and/or a wind direction indictor  50  can be provided on the pod  20 . The control unit  40  can adjust the pitch angle of the rotor blades  30  by means of pitch drives  31 . In addition the control unit  40  can control the azimuthal orientation of the pod by means of the azimuth drive  80 . The electric energy generated by the generator  60  is passed to a power cabinet  90  for example in the base of the pylon  10 . A converter can be provided in the power cabinet  90 , and can deliver the electric power at a desired voltage and frequency to an energy supply network. 
         [0026]      FIG. 2A  shows a diagrammatic view of a rotor blade  30  of the wind power installation of  FIG. 1  together with a crack detection unit according to one embodiment. In this case the crack detection unit comprises at least one (interruptible) thread or fiber  110  provided in the rotor blade on the inside (or alternatively or additionally on the outside). That thread or fiber  110  is preferably glued to the inside surface of the rotor blade or fixed thereon in some other fashion. In one embodiment, the thread or fiber  110  is secured in a flat manner across a surface of the rotor blade. The thread  110  is an interruptible thread. If the material of the rotor blade  30  cracks then the thread or the fiber will also crack or tear. That is, as the material of the rotor blade  30  separates along a crack, the thread or fiber is also pulled apart. The thread or fiber may be suitably brittle to break apart in response to a particular sized crack to be monitored on the rotor blade. The interruption in the thread  110  in the case of a crack in the material of the rotor blade can be detected by a crack detector  41 . Detection of a crack or tear in the fiber  110  can be effected for example electrically or optically. In the case of electric detection, the thread  110  includes electrically conductive material. In the case of optical detection, the thread  110  is capable of conducting light. 
         [0027]    As will be clear to those of ordinary skill in the art, if electrical detection is used, the crack detector  41  may include an electronic device that is electrically coupled to the thread or fiber and configured to receive an electrical signal from the thread or fiber  110 . If the thread or fiber breaks apart due to a crack in the rotor blade  30 , the electrical signal received by the electronic device will be different than it was prior to the thread or fiber  110  breaking. For instance, after the thread or fiber  110  breaks, a current or voltage received by the electronic device may be zero. If optical detection is used, the crack detector  41  may include an optical device that is optically aligned with thread or fiber and configured to receive an optical signal therefrom. If the thread or fiber breaks apart due to a crack in the rotor blade  30 , the optical signal received by the optical device changes. 
         [0028]    The crack detector  41  can be part of the control unit  40  or can be connected thereto according to another embodiment of the invention. Upon detection of a crack, the control unit  40  can influence operation of the wind power installation (adjustment of the pitch angles, adjustment of the azimuth angle and so forth). In particular such influence can lead to a reduction in the mechanical loading on the rotor blade or also on other parts of the wind power installation to suitably protect the components. 
         [0029]      FIG. 2B  shows a diagrammatic view of a rotor blade on the wind power installation of  FIG. 1  with a crack detection unit. Threads  120  are provided within the rotor blade or at the inside surface of the rotor blade. In this case the threads are arranged in a grid structure while the threads  111  in  FIG. 2A  are oriented substantially in the longitudinal direction or in one direction. The advantage of a grid structure is that the precise position of the crack in the rotor blade can be better detected. The functioning of the crack detector  41  corresponds to that of the crack detector  41  in  FIG. 2A . 
         [0030]    Optionally the threads or fibers shown in  FIG. 2A  and  FIG. 2B  can also have a return line back to the detector  41 . 
         [0031]      FIG. 3A  shows a diagrammatic view of a pylon  10  of a wind power installation of  FIG. 1  with a crack detection unit according to an embodiment of the invention. Provided at the inside surface of the pylon  10  is at least one thread (or fiber), preferably a plurality of threads (or fibers)  110 , in particular in one direction. The threads  110  are preferably glued or fastened in some way to the inside surface of the pylon (steel or concrete). If a crack occurs in the steel or concrete of the pylon then that crack will cause a crack or tear in one of the threads  110 . That crack or tear can be detected by the crack detector  41 . 
         [0032]    Optionally the crack detection unit of  FIG. 3A  can have threads or fibers which extend back to the detection unit  41  by way of a return line. 
         [0033]      FIG. 3B  shows a diagrammatic view of a pylon  10  of a wind power installation of  FIG. 1  with a crack detection unit according to another embodiment of the invention. The crack detection unit  100  has at least one thread  130  at the inside surface of the pylon  10 . In this embodiment, the thread  130  can be fastened to the inside surface of the pylon  10  in a meander shape. The thread  130  is coupled to a crack detector  41 . The functioning of the crack detector  41  corresponds in that respect to that of the crack detector in  FIG. 2A . 
         [0034]      FIG. 4  shows a diagrammatic view of a part of a rotor blade of the wind power installation of  FIG. 1  according to one embodiment of the invention. A thread or fiber  130  is provided in a meander shape at the inside surface  32  of the rotor blade  30 . The thread or fiber can be glued to the inside of the rotor blade. If a crack in the material of the rotor blade occurs, that will also lead to a crack or tear in the thread or fiber  130 . Such a crack or tear can be detected by a crack detector  41  (not shown) as already described hereinbefore. 
         [0035]    The crack detection unit according to the invention can also be provided for example on the rotor hub  75 . 
         [0036]    The crack detection unit according to the invention can be used in relation to all components of a wind power installation which is crack-endangered. For that purpose it is only necessary for threads or fibers of the crack detection unit to be fastened (for example glued) on surfaces of components to be monitored. 
         [0037]    The thread or fibers for crack detection can be fastened or glued on the component to be monitored, in point form or in flat areal relationship. Fastening of the thread or fiber to the component to be monitored must be such that, if a crack occurs in the component to be monitored, that also leads to a crack or tear in the thread or fiber so that the crack in the component can be suitably detected. 
         [0038]    In a further embodiment which can be based on the preceding embodiments, the threads or fibers can be fitted or fastened in the component to be monitored. That can be effected for example when casting the foundation. As an alternative thereto the fibers or threads can be provided for example between glass fiber mats upon production of a rotor blade. 
         [0039]    Detection of the exact crack or tear location on the thread or fiber is possible for example if the spacing of the tear location from the beginning of the thread or fiber can be determined by a reflection method. If the thread or fiber is for example electrically conducting, it is then possible to use reflection methods involving remote signaling technology. 
         [0040]    If the threads or fibers are glass fiber threads or fibers then a fault location can be determined to a precision of a few centimeters by means of the backscatter method. For that purpose a so-called optical time division reflectometer OTDR can be used. Such monitoring can be effected continuously by an optical switching device during operation of the wind power installation. As an alternative thereto the optical time division reflectometer can also be in the form of a portable device so that a service team can perform the monitoring procedure. 
         [0041]    If the threads or fibers have a return line then a change in damping can be detected by means thereof. One reason for a change in damping can represent for example a crack. 
         [0042]    Locating a crack can also be effected for example in the peripheral direction in the case of a meander-shape configuration for the detector if the meanders are distributed in the peripheral direction. 
         [0043]    In  FIGS. 2A ,  2 B and  3 A the end remote from the detector  41  can be connected to earth so that crack detection can be effected. 
         [0044]    The embodiments for crack detection shown in  FIGS. 2A ,  2 B and  3 A can be advantageous when permanent length monitoring is effected. That can optionally also be effected when the threads or fibers are disposed in or fastened in the component to be monitored (cast or laid internally therein, for example between glass fiber mats). Crack detection can respond upon an abrupt reduction in the line length. 
         [0045]    As an alternative thereto length monitoring can be successful when the thread or fiber has a return line back to the detector. That return line to the detector can also be glued on the surface of the rotor blade or fastened thereto in areal relationship and can also be used for crack detection. 
         [0046]    The crack detection unit according to the invention can be used in relation to all components of a wind power installation, which are at risk of cracking. In that respect the components can represent for example the foundation of the wind power installation, the pylon of the wind power installation (particularly in the case of a concrete pylon), all cast parts of the wind power installation (for example rotor hub) as well as the rotor blades. 
         [0047]    The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent application, foreign patents, foreign patent application and non-patent publications referred to in this specification and/or listed in the Application Data Sheet are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, application and publications to provide yet further embodiments. 
         [0048]    These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.