A wind turbine

Abstract

A wind turbine comprising a hub assembly and a blade part coupled to the hub assembly, the blade part extending longitudinally in a spanwise direction between an inboard end and an outboard end; the wind turbine further comprising at least one detection apparatus comprising: an arm having a fixed end and a free end, the fixed end being attached to the blade part or the hub assembly; and a force sensor arranged between the free end of the arm and the other of the blade part or the hub assembly, the force sensor being configured for detecting a mechanical force applied between the free end of the arm and the respective blade part or hub assembly, such that the detection apparatus is arranged to detect relative movement between the blade part and the hub assembly.

Description

[0001] A wind turbine

[0002] Technical field

[0003] The present invention relates to a wind turbine and a detection apparatus for detecting relative movement between a blade part and a hub assembly.

[0004]

[0005] Wind turbines typically comprise a rotor having a plurality of wind turbine blades attached to a central hub. The blades may be attached to the hub in different ways, however, in modern megawatt wind turbines the blades are typically attached to the hub using mechanical fasteners, such as bolts. In some examples, mechanical fastening components may be integrated in a composite shell of a wind turbine blade.

[0006] It is important to inspect wind turbines regularly to ensure safe and efficient use of the turbine. In some cases it may be advantageous to monitor aspects of the wind turbine on an ongoing basis. However, inspecting and / or monitoring the attachment of a blade to the hub, for example by inspecting and / or monitoring the mechanical fasteners attaching a blade to a hub, can be challenging once the blade is in use and attached to an operational turbine. Inspection of fasteners integrated in a composite shell without damaging the composite shell, and thereby compromising the strength of the shell, is even more challenging.

[0007] It is against this background that the present invention has been developed.

[0008] Summary of Invention

[0009] According to the present invention there is provided a wind turbine comprising a hub assembly and a blade part coupled to the hub assembly, the blade part extending longitudinally in a spanwise direction between an inboard end and an outboard end; the wind turbine further comprising at least one detection apparatus comprising: an arm having a fixed end and a free end, the fixed end being attached to the blade part or the hub assembly; a force sensor arranged between the free end of the arm and the other of the blade part or the hub assembly, the force sensor being configured for detecting a mechanical force applied between the free end of the arm and the respective blade part or hub assembly, such that the detection apparatus is arranged to detect relative movement between the blade part and the hub assembly.The at least one detection apparatus provides a simple and accurate means for detecting relative movement between the blade part and the hub assembly. Relative movement between the blade part and the hub assembly may be the result of loose fasteners attaching the blade part to the hub assembly or loose inserts in the blade part which are also configured for attaching the blade part to the hub assembly. As described later in more detail, signals from the at least one detection apparatus indicating the detection of relative movement between the blade part and the hub assembly can be analysed to monitor relative movement between the blade part and hub assembly in use. For example, the wind turbine and at least one detection apparatus may be part of a wind farm monitoring and control system configured to perform turbine operations, such as halting the turbine, dependent on signals output from the at least one detection apparatus.

[0010] The relative movement between the blade part and the hub assembly may also be referred to as a displacement between the blade part and the hub assembly.

[0011] Relative movement between the blade part and the hub assembly may be detected by the at least one detection apparatus detecting a variation in the force measured by the force sensor. Such variation in the force, may be indicative of a variation in the position of the blade part relative to the hub assembly.

[0012] By continuously monitoring the forces and movements, maintenance can be scheduled more effectively. This predictive maintenance approach reduces downtime and maintenance costs, ensuring the wind turbine operates efficiently.

[0013] The force sensor may be in the form of a pressure pad which senses and measures pressure between the free end of the arm and the blade part or hub assembly. In an example, the force sensor, such as a pressure sensor may be a strain gauge. In other examples, the force sensor may be a piezoelectric sensor. The force sensor may produce an electrical signal depending on the force applied to the sensor, and this electrical signal may be sent to a controller.

[0014] In a preferred example, the fixed end of the arm is attached to the blade and the free end of the arm faces the hub assembly. The force sensor is sandwiched between the free end of the arm and the hub assembly. If the blade part moves, the arm attached to the blade part will also move and therefore the force applied by the arm to the force sensor will change. The force sensor may be fixedly attached to the hub assembly and / or the free end of the arm.In another example, the fixed end of the arm is attached to the hub and the free end of the arm faces the blade part. The force sensor is sandwiched between the free end of the arm and the blade part. A bracket may be provided on the blade part to support the force sensor.

[0015] The fixed end of the arm may be bonded (such as via adhesive) or mechanically fixed (such as via screws or bolts) to the blade part or hub assembly. It is important that the fixed end is securely fixed to the blade part or hub assembly such that it does not move relative to the part to which it is affixed.

[0016] Preferably the arm has a stiffness greater than 100 N / mm. This means that the relative movement between the blade part and the hub assembly will be transferred through the arm and to the force sensor.

[0017] Preferably the arm is formed from plastic, although it could also be formed from other materials such as metal. The arm may be formed in a single piece or may be provided as a multi-piece component.

[0018] When the detection apparatus is installed on the wind turbine, the free end of the arm may be arranged such that an initial force is applied to the force sensor. Then, as the wind turbine is operated, a change from the initial force can indicate a displacement between the blade part and the hub assembly.

[0019] A variation in the mechanical force detected by the force sensor may indicate relative movement between the blade part and the hub assembly.

[0020] The fixed end of the arm and the free end of the arm may be spaced from each other in the spanwise direction and in a direction perpendicular to the spanwise direction.

[0021] The direction perpendicular to the spanwise direction may also be seen as a chordwise direction of the blade part. By spacing the fixed end of the arm and the free end of the arm in the spanwise direction and in the direction perpendicular to the spanwise direction means that the arm acts as a lever on the force sensor. As such, small displacements of the blade part relative to the hub assembly are magnified at the free end of the arm so that the force sensor can detect such small displacementsThe arm may extend diagonally from the blade part to the hub assembly. Extending the arm diagonally from the blade part to the hub assembly provides a simple way of creating a lever arm so that the force sensor can detect small relative displacements between the blade part and the hub assembly

[0022] The hub assembly may comprise a pitch bearing, the blade part being attached to the pitch bearing, and wherein the force sensor is attached to the pitch bearing.

[0023] The blade part attached to the pitch bearing may be rotatable, for example rotatable about its longitudinal axis, relative to a hub main body. For example, the pitch bearing may comprise an inner bearing ring (i.e. inner bearing race) and an outer bearing ring (i.e. outer bearing race), where the inner and outer bearing rings are configured to rotate relative to one another. The blade part may be attached to one of the inner or outer bearing rings. In such examples, the arm of the at least one detection apparatus may extend between the blade part and the bearing ring to which the blade part is attached. The at least one detection apparatus may preferably be arranged to detect relative movement between the blade part and the respective bearing ring to which the blade part is attached.

[0024] The pitch bearing may comprise a stiffening plate, and wherein the force sensor is attached to the stiffening plate.

[0025] The stiffening plate may also be referred to as a bearing plate. For example, the stiffening plate may reinforce the pitch bearing. The stiffening plate may provide a particularly advantageous surface for attachment of the force sensor.

[0026] The blade part may comprise a composite shell and a plurality of inserts embedded in the composite shell, wherein the inserts are configured for attaching the blade part to the hub assembly.

[0027] The inserts may be metallic bushings with an internal thread. The bushings may receive a fastener, such as a stud bolt, for attaching the blade part to the hub assembly.

[0028] The blade part may be attached to the hub assembly via the inserts such that the blade part is cantilevered relative to the hub assembly. A moment of mass of the blade part may cause tensile and compressive loading of the composite shell. Such loading may cause relative movement between the blade part and the hub assembly which can be detected by the at least one detection apparatus.In some examples, the blade part may be a blade shell of a wind turbine blade. For example, the composite shell of the blade part may form substantially the entire blade shell of a wind turbine blade. An inboard end of the blade part may define a root end of the blade configured for attaching the blade part to the hub assembly. An outboard end of the blade part may define a tip end of the blade.

[0029] In some examples, the blade part may be a blade module of a modular wind turbine blade. The blade part may be configured for connection to another blade module to form the modular wind turbine blade. The inboard end of the blade part may define the root end of the blade configured for attaching the blade part to the hub assembly, and the outboard end of the blade part may define a connection end configured for connecting the blade part to an outboard blade module.

[0030] Composite materials, such as glass fibre reinforced plastic (GFRP), can provide relatively high load bearing capacity at a relatively low component mass, whilst also facilitating strict control of load paths and mass distribution. Accordingly, the shell of the wind turbine blade part may be an advantageous application for composite materials. However, composite materials such as GFRP can be relatively brittle and concentrated loads can be detrimental to the longevity of a composite component. It follows that whilst composite materials may be advantageous for forming the shell of the blade part, such materials also present challenges for attaching the blade part to other wind turbine components, such as the hub assembly. The plurality of inserts are configured specifically for attaching the blade part to the hub assembly. Accordingly, the inclusion of a plurality of inserts in the composite shell provides a simple and robust means for attaching the blade part to the hub assembly.

[0031] In some preferred examples the inserts may be formed of a different material compared to the composite shell of the blade part. For example, the inserts may be formed of a material, such as steel, having a higher strength and stiffness than the composite shell in which they are embedded. Such materials also facilitate the use of a threaded fastener for attaching the blade part to the hub assembly.

[0032] The plurality of inserts embedded in the composite shell may be integrated with the composite material of the shell during manufacture of the blade part. As such, the inserts may be referred to as “integrated inserts”, i.e. integrated in the composite shell.In some examples, each insert embedded in the composite shell may be oriented to extend longitudinally in the spanwise direction of the blade part.

[0033] The blade part may define a root portion of a wind turbine blade, and wherein the inserts are distributed circumferentially around the root portion.

[0034] Distributing the inserts around the root portion may help to spread the loads transferred between the blade part and the hub assembly, in use. Accordingly, peak loads experienced by each insert and the respective portion of the composite shell surrounding said insert may be reduced, thereby increasing the longevity of the blade part.

[0035] The at least one detection apparatus may comprise a plurality of detection apparatuses, and wherein the detection apparatuses are distributed circumferentially around the root portion of the blade part.

[0036] Distributing the detection apparatuses around the root portion may help to facilitate accurate identification of any instances of relative movement between the blade part and the hub assembly. Assessment of signals output from the plurality of detection apparatuses may provide an accurate indication of the portion of the blade part experiencing movement relative to the hub assembly. Such an assessment may therefore be helpful for identifying loose inserts and / or fasteners attaching the blade part to the hub assembly.

[0037] In some examples, each detection apparatus may be aligned with an insert embedded in the composite shell of the blade part. Such an arrangement may be particularly advantageous for detecting any relative movement between the blade part and the hub assembly resulting from the inserts, such as loose or disbonded inserts in the composite shell. In particular, such an arrangement may help to accurately pinpoint the or each specific insert responsible for the relative movement. In some preferred examples the plurality of detection apparatuses may comprise at least one detection apparatus for each insert in the blade part.

[0038] The arms of the plurality of detection apparatuses may be provided in a continuous annular ring shape, with cutouts in the ring so as to form individual arms. This allows the arms to be mounted to the blade part in a single operation.

[0039] The plurality of detection apparatuses may comprise at least one detection apparatus positioned at each of a leading edge and an opposing trailing edge of the root portion, and atleast one detection apparatus positioned on each of a windward side and a leeward side of the root portion.

[0040] These regions of the root portion may be expected to experience the highest loads, in use. Accordingly, it may be expected that any relative movement between the blade part and the hub assembly would be most likely to occur in, or proximal to, these regions. Arranging detection apparatuses in each of these regions therefore improves the likelihood of detecting relative movement in the event that such movement may occur.

[0041] In some preferred examples, the plurality of detection apparatuses may additionally comprise at least one detection apparatus positioned on the windward side of the root portion between the trailing edge and a central position between the leading edge and the trailing edge.

[0042] The plurality of detection apparatuses may comprise a plurality of outer detection apparatuses attached to an outer surface of the blade part and a plurality of inner detection apparatuses attached to an inner surface of the blade part.

[0043] In use, the blade part attached to the hub assembly may experience both tensile and compressive loading. In particular, the outer surface may experience tensile loading whilst the inner surface experiences compressive loading, and similarly the outer surface may experience compressive loading whilst the inner surface experiences tensile loading. Due to the different loading conditions of the inner and outer surfaces of the blade part, relative movement between the blade part and the hub assembly may be more easily detected at either one of the inner surface or the outer surface in different situations. Positioning a plurality of detection apparatuses on each of the inner surface and the outer surface of the blade part may therefore increase the likelihood of detecting relative movement in the event that such movement may occur.

[0044] In some examples, each inner detection apparatus may be aligned with a corresponding outer detection apparatus. For example, the blade part may comprise a composite shell, and each inner detection apparatus may be separated from the corresponding detection apparatus by the composite shell. A pair of detection apparatuses may be arranged back-to-back and separated by a portion of the composite shell. Such an arrangement facilitates an accurate analysis of the movement of each respective portion of the blade part relative to the hub assembly. Further, the inner and outer surfaces of the portion of the composite shell may experience different loading dependent on the integrity of the composite shell, one ormore inserts embedded in the composite shell, and the bond between the inserts and the composite shell. Aligning an inner detection apparatus with a corresponding outer detection apparatus may facilitate improved monitoring and / or inspection of the wind turbine blade.

[0045] In some examples, the at least one detection apparatus may be temporarily attached to the blade part or hub assembly, for example during a service or monitoring procedure. The at least one detection apparatus may be configured to be removed from the blade part or hub assembly for normal operation of the wind turbine.

[0046] Alternatively, the at least one detection apparatus may be configured to remain in the wind turbine during normal use. Such a configuration may facilitate continuous monitoring of the wind turbine in use. The wind turbine and the at least one detection apparatus may be part of a wind farm monitoring and control system.

[0047] A wind turbine monitoring and control system may be provided comprising a system controller and the wind turbine as described above, the wind turbine further comprising a wind turbine controller; wherein the system controller is communicably coupled to the at least one detection apparatus to receive output signals from the at least one detection apparatus indicative of detected relative movement between the blade part and the hub assembly; and wherein the system controller is communicably coupled to the wind turbine controller and configured to instruct the wind turbine controller to perform a turbine operation dependent on the output signals received from the at least one detection apparatus.

[0048] As used herein, the term “communicably coupled” may refer to any example of facilitating communication between the respective controller and the at least one detection apparatus. For example, communicably coupled may refer to physical wired connections or to wireless communication, such as WiFi communication.

[0049] In some examples, the system controller may be configured to instruct the wind turbine controller to perform a turbine operation when the output signals received from the at least one detection apparatus indicate a variation in relative displacement between the blade part and hub assembly which exceeds a predetermined relative displacement threshold. In some examples, the predetermined displacement threshold may be 1 mm, or preferably 0.5 mm. The system controller may be configured to instruct the wind turbine controller to perform a turbine operation when the output signals received from the at least one detection apparatus indicate a variation of 1 mm, or preferably 0.5 mm, in the relative displacement between the blade part and hub assembly.In some examples, the turbine operation may comprise pitching a wind turbine blade, i.e. varying an angle of attack of the blade, reducing the speed and / or power of the wind turbine, or changing a yaw angle of the turbine. In some other examples the turbine operation may comprise halting operation of the turbine. For example, halting operation of the turbine may comprise one or more of activating a rotor brake or feathering the wind turbine blade.

[0050] Brief description of the drawings

[0051] Examples of the present invention will now be described by way of non-limiting example only, with reference to the accompanying figures, in which:

[0052] Figure 1 is a schematic view of a wind turbine comprising a hub assembly and a blade part; Figure 2 is a schematic perspective view of the blade part;

[0053] Figure 3 is a schematic cross-sectional view of a detection apparatus attached to the blade part;

[0054] Figure 4 is a schematic end view of the blade part showing a plurality of detection apparatuses attached to the blade part;

[0055] Figure 5 is a schematic diagram of a wind farm monitoring and control system;

[0056] Figure 6 illustrates a process for controlling a wind turbine based on output signals from the detection apparatuses;

[0057] Figure 7 is a schematic cross-sectional view of a detection apparatus attached to the blade part; and

[0058] Figures 8a and 8b are schematic views of a strip of force sensors.

[0059] Detailed description

[0060] Figure 1 shows a schematic perspective view of a wind turbine 10. The wind turbine 10 includes a rotor 12 which is rotatably coupled to a nacelle 14. The rotor 12 includes a hub assembly 16 and a blade part 18 which is rotatably coupled to the hub assembly 16. For example, the blade part 18 may be a blade shell of a wind turbine blade 20, as shown in the example of Figure 1. The blade part 18 extends longitudinally in a spanwise direction (S), between an inboard end 22 and an outboard end 24. The inboard end 22 may be coupled to the hub assembly 16. As shown in more detail in Figure 2, the blade part 18 may comprise a plurality of inserts 26 and the blade part 18 may be attached to the hub assembly 16 via the inserts 26. For example, the blade part 18 may therefore define a root portion 28 of a wind turbine blade 20With reference now to Figure 2, the blade part 18 may comprise a composite shell 30 and the plurality of inserts 26 may be embedded in the composite shell 30. For example, the inserts 26 may be integrated in the composite shell 30 during manufacture of the shell, which may be made in a moulding process such as vacuum assisted resin transfer moulding (VARTM). As shown in Figure 2, the inserts 26 may be distributed circumferentially around the root portion 28. This may help to distribute and transfer loads experienced by the blade part 18 to the hub assembly 16 in use.

[0061] As described by way of background, inspecting and / or monitoring a wind turbine 10 is important to ensure continued safe and efficient use of the turbine 10. In particular, it is advantageous to inspect and / or monitor the attachment of the blade part 18 to the hub assembly 16. Inspecting fastenings such as inserts 26 integrated in the composite shell 30 may be challenging, particularly once the blade part 18 is in use and attached to the hub assembly 16 of the wind turbine 10. Accordingly, in some examples the wind turbine 10 may be configured to facilitate inspection and / or monitoring of the attachment of the blade part 18 without necessarily requiring direct inspection and assessment of fastenings, such as the inserts 26.

[0062] Figure 3 shows the blade part 18 attached to a hub assembly 16. The hub assembly 16 may comprise a pitch bearing 40 having a stationary bearing ring 42 and a rotating bearing ring 44. The stationary ring is fixed to a hub main body 45. The rotating bearing ring 44 is connected to the inserts 26 via fasteners (e.g. bolts) 46. A stiffening plate 48 may extend across the pitch bearing 40, fixedly connected to the rotating bearing ring 44.

[0063] The wind turbine 10 includes at least one detection apparatus 50. The detection apparatus comprises an arm 52. The arm has a fixed end and a free end. In the example in Figure 3, a fixed end 54 is attached to the blade 18 and a free end 56 faces the stiffening plate 48 of the hub assembly 16. The detection apparatus 50 further comprises a force sensor 58 arranged between the free end 56 of the arm 50 and the stiffening plate 48.

[0064] The force sensor 58 can detect a mechanical force applied between the free end 56 of the arm 50 and the hub assembly 16, e.g. the stiffening plate. If the blade part 18 experiences relative movement with respect to the hub assembly 16, for example if the blade part moves in a spanwise direction relative the hub assembly, then the mechanical force detected by the force sensor will change. Therefore, by measurement of the mechanical force, relative movement between the blade part and the hub assembly can be detected. If there is relativemovement between the blade part 18 and the hub assembly 16, the free end of the arm will apply a different bending moment loads to the force sensor.

[0065] With reference still to Figure 3, but with additional reference to the end view of the blade part in Figure 4, in examples where the blade part 18 comprises a plurality of inserts 26 embedded in the composite shell 30, a plurality of detection apparatuses 50 may be attached to the blade part 18 and aligned with an insert 26. This may be particularly beneficial for detecting movement of the blade part 18 relative to the hub assembly 16 resulting from loose or disbonded inserts 26.

[0066] For example, with reference to the end view in Figure 4 the plurality of detection apparatuses 50 may be attached to the blade part 18 and distributed circumferentially around the root portion 28. For example, the detection apparatuses 50 may include at least one detection apparatus 50 positioned at each of a leading edge 60 and an opposing trailing edge 62 of the root portion 28, and at least one detection apparatus 50 positioned on each of a windward side 64 and a leeward side 66 of the root portion 28. In some preferred examples the plurality of detection apparatuses 50 may be distributed evenly, i.e. spaced evenly, around the root portion 28.

[0067] In the example shown in Figures 3 and 4, the detection apparatuses 50 are arranged at an inner surface of the blade part 18. This may help to protect the detection apparatuses 50 from adverse weather conditions. Conversely, in some other examples (not shown) the wind turbine 10 may include detection apparatuses 50 arranged at an outer surface of the blade part 18. In some examples it may be easier to detect and measure movement of the blade part 18 relative to the hub assembly 16 at the outer surface of the blade part 18.

[0068] In some examples the detection apparatuses 50 may be provided at an outer surface 67 of the blade part 18 and at an inner surface 68 of the blade part 18. In such an example, each outer detection apparatus may be aligned with a corresponding inner detection apparatus 50. Such an arrangement may enable measurement and monitoring of the independent movement of the inner and outer surfaces of the blade part 18 in response to an applied load. This may also be useful for assessing the integrity of fastenings, such as the inserts 26, and associated portions of the composite shell 30.

[0069] In some examples the plurality of detection apparatuses 50 may be connected together in series. The connected detection apparatuses 50 may form a daisy chained array. A windturbine 10 in a wind farm monitoring and control system 70 may be a suitable application for such a daisy chained sensor array.

[0070] Figure 5 shows a schematic diagram of a wind farm monitoring and control system 70 which includes a wind turbine 10 as described in any of the examples herein. The turbine 10 may additionally include a wind turbine controller 72, and the wind farm monitoring and control system 70 may include a system controller 74. The system controller 74 may be communicably coupled to at least one detection apparatus 50 of the wind turbine 10 to receive output signals 76 from the at least one detection apparatus 50. For example, the system controller 74 may be communicably coupled to the least one detection apparatus 50 to receive output signals 76 via the wind turbine controller 72, in some examples. As indicated in Figure 5, the system controller 74 may receive output signals 76 from the at least one detection apparatus 50 via wireless communication. The output signals 76 may be indicative of detected relative movement between the blade part 18 and the hub assembly 16.

[0071] The system controller 74 may be communicably coupled to the wind turbine controller 72. For example, the system controller 74 may be configured to instruct the wind turbine controller 72 to perform a turbine operation dependent on the output signals 76 received from the at least one detection apparatus 50. In some examples the system controller 74 may therefore be configured to instruct the wind turbine controller 72 to perform a turbine operation when the output signals 76 received from the at least one detection apparatus 50 indicates a variation in relative displacement between the blade part 18 and hub assembly 16 which exceeds a predetermined relative displacement threshold.

[0072] Figure 6 shows an example of a process 78 in which the system controller 74 instructs the wind turbine controller 72 based on output signals 76 received from the at least one detection apparatus 50. For example, in step 80 the wind turbine 10 may be running in a normal operating mode. In step 82 the at least one detection apparatus 50 may measure or detect movement of the blade part 18 relative to the hub assembly 16. In step 84 the system controller 74 may receive an output signal 76 from the at least one detection apparatus 50. It should be appreciated that steps 82 and 84 may be repeated throughout operation of the turbine 10 as part of a monitoring operation. In step 86, the system controller 74 may determine whether the output signals 76 received from the at least one detection apparatus 50 indicate a variation in relative displacement which exceeds a predetermined relative displacement threshold. If such a threshold is exceeded, in step 88 the system controller 74may proceed to instruct the wind turbine controller 72 to perform a turbine operation. For example, the turbine operation may comprise halting operation of the turbine 10.

[0073] Figure 7 shows another example of the detection apparatus 50. In this example, the arm 52 is formed from multiple parts. In particular, the arm 52 has an L-shaped bracket part and a bolt arrangement which extends from the bracket to the force sensor 58. One end of the bolt arrangement is connected to the bracket via nuts, such that the position of the bolt arrangement can be adjusted in the spanwise direction. The other end of the bolt arrangement forms the free end 56 of the arm that interacts with the force sensor 58.

[0074] Figure 8a shows a pitch bearing 40 isolated from the hub main body 45 and the blade part 18. As discussed above, the pitch bearing may comprise a stationary ring 42 and a rotating ring 44. The pitch bearing may also comprise a stiffening plate 48 extending across the rotating ring as shown. In this example, a plurality of force sensors 58 are provided on the stiffening plate. The force sensors are provided in a ring 90, as shown in this example, to face the arms that project from the blade part. The force sensors 58 may be in the form of pressure pads which are provided in a continuous strip 90 formed into a ring shape. Figure 8b shows schematically how the pressure pads may be provided in a strip 90 which is connected via a cable, or a plurality of cables to a control unit 92 The strip of pressure pads maybe adhesively bonded to the stiffening plate.

[0075] The description provided herein serves to demonstrate a plurality of possible examples of the present invention. Features described in relation to any of the examples above may be readily combined with any other features described with reference to different examples without departing from the scope of the invention as defined in the appended claims.

Claims

Claims1. A wind turbine comprising a hub assembly and a blade part coupled to the hub assembly, the blade part extending longitudinally in a spanwise direction between an inboard end and an outboard end;the wind turbine further comprising at least one detection apparatus comprising:an arm having a fixed end and a free end, the fixed end being attached to the blade part or the hub assembly; anda force sensor arranged between the free end of the arm and the other of the blade part or the hub assembly, the force sensor being configured for detecting a mechanical force applied between the free end of the arm and the respective blade part or hub assembly, such that the detection apparatus is arranged to detect relative movement between the blade part and the hub assembly.

2. A wind turbine according to claim 1, wherein a variation in the mechanical force detected by the force sensor indicates relative movement between the blade part and the hub assembly.

3. A wind turbine according to claim 1 or claim 2, wherein the fixed end of the arm and the free end of the arm are spaced from each other in the spanwise direction and in a direction perpendicular to the spanwise direction.

4. A wind turbine according to any of the preceding claims, wherein the arm extends diagonally from the blade part to the hub assembly5. A wind turbine according to any one of the preceding claims, wherein the hub assembly comprises a pitch bearing, the blade part being attached to the pitch bearing, and wherein the force sensor is attached to the pitch bearing.

6. A wind turbine according to claim 5, wherein the pitch bearing comprises a stiffening plate, and wherein the force sensor is attached to the stiffening plate.

7. A wind turbine according to any preceding claim, wherein the blade part comprises a composite shell and a plurality of inserts embedded in the composite shell, wherein the inserts are configured for attaching the blade part to the hub assembly.

8. A wind turbine according to claim 7, wherein the blade part defines a root portion of a wind turbine blade, and wherein the inserts are distributed circumferentially around the root portion.

9. A wind turbine according to claim 8, wherein the at least one detection apparatus comprises a plurality of detection apparatuses, and wherein the detection apparatuses are distributed circumferentially around the root portion of the blade part.

10. A wind turbine according to claim 9, wherein the plurality of detection apparatuses comprises at least one detection apparatus positioned at each of a leading edge and an opposing trailing edge of the root portion, and at least one detection apparatus positioned on each of a windward side and a leeward side of the root portion.

11. A wind turbine according to claim 9 or claim 10, wherein the plurality of detection apparatuses comprises a plurality of outer detection apparatuses attached to an outer surface of the blade part and a plurality of inner detection apparatuses attached to an inner surface of the blade part.

12. A wind turbine monitoring and control system comprising a system controller and the wind turbine of any preceding claim, the wind turbine further comprising a wind turbine controller;wherein the system controller is communicably coupled to the at least one detection apparatus to receive output signals from the at least one detection apparatus indicative of detected relative movement between the blade part and the hub assembly; and wherein the system controller is communicably coupled to the wind turbine controller and configured to instruct the wind turbine controller to perform a turbine operation dependent on the output signals received from the at least one detection apparatus.

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