Lightning protection system

Abstract

A pitch-controlled wind turbine comprising a tower, a nacelle mounted on the tower, a hub rotatably mounted on the nacelle, and at least three wind turbine blades wherein each wind turbine blade extends between a root end and a tip end, the root end being connected to the hub via a pitch mechanism; the wind turbine further comprises at least three blade connection members, each blade connection member extending from a connection point on one wind turbine blade towards a connection point on an adjacent wind turbine blade, wherein the connection points on a given wind turbine blade are arranged at a distance from the root end of the wind turbine blade and at a distance from the tip end of the wind turbine blade; each wind turbine blade comprising an outboard portion extending the distance from a tip end of the wind turbine blade to the connection point, and an inboard portion extending the distance from a root end of the wind turbine blade to the connection point; wherein the wind turbine further comprises a lightning strike protection system, and each blade connection member has an electrically conductive material configured to conduct lightning current from an outboard portion of the wind turbine blade from which the connection member extends and along a path extending with the blade connection member towards the tower.

Description

Technical Field

[0001] This invention relates to a pitch-controlled wind turbine. Background Technology

[0002] Wind turbine blades are vulnerable to lightning strikes. To protect wind turbine blades, lightning protection systems connect the blades to the ground. Typically, a lightning protection system includes a lightning receiver and conductors that are electrically connected to the ground from the blade tip via the tower and nacelle. Additional devices conducting electricity to the ground may include surface protective layers, such as a metal mesh or foil surface protective layer incorporated into the blade shell at the outer surface of the blade and extending along at least a portion of the blade. The surface protective layer intercepts lightning strikes before they reach the conductive components of the blade and is typically connected to the lightning protection system at multiple points to ensure a good electrical connection with the surface protective layer. These systems are often integrated into or on the wind turbine blade itself, and any connections between components of the lightning protection system, as well as between blade segments of a modular blade, require careful design to ensure a continuous electrical path across the connections. Therefore, the design, manufacture, and maintenance of wind turbines with lightning protection systems present significant challenges.

[0003] In view of this background, the present invention has been designed. Summary of the Invention

[0004] A first aspect of the invention provides a pitch-controlled wind turbine, comprising a tower, a nacelle mounted on the tower, a hub rotatably mounted on the nacelle, and at least three wind turbine blades, wherein each wind turbine blade extends between a root end and a tip end, the root end being connected to the hub via a pitch mechanism; the wind turbine further comprises at least three blade connection members, each blade connection member extending from a connection point on one wind turbine blade toward a connection point on an adjacent wind turbine blade, wherein the connection point on a given wind turbine blade is arranged at a distance from the wind turbine blade. The wind turbine includes a distance from the root end of the blade and a distance from the tip of the wind turbine blade; each wind turbine blade includes an outer portion extending from the tip of the wind turbine blade to the connection point along the distance, and an inner portion extending from the root end of the wind turbine blade to the connection point along the distance; wherein the wind turbine also includes a lightning protection system, and each blade connection member has a conductive material configured to conduct lightning current from the outer portion of the connection member of the wind turbine blade and along a path extending toward the tower together with the blade connection member.

[0005] Optionally, the wind turbine also includes at least three pretensioning members, each pretensioning member being connected to one of the blade connection members and to the hub, each pretensioning member thereby providing pretension in the blade connection member to which it is connected, and wherein each pretensioning member has a conductive material that forms part of a lightning protection system and is configured to conduct lightning current from the blade connection member to which the pretensioning member is connected and along a path extending toward the tower together with the pretensioning member.

[0006] Optionally, the conductive material of the blade connecting member and / or pretensioning member is embedded in the corresponding blade connecting member or pretensioning member.

[0007] Optionally, the conductive material of the blade connection member and / or pretensioning member is attached to the outer surface of the respective blade connection member or pretensioning member.

[0008] The conductive material can be embedded within or attached to the outer surface of the corresponding blade connecting member or pretensioning member. A first portion of the conductive material can be embedded, while a second portion can be attached to the outer surface.

[0009] Optionally, the conductive material is coupled to the corresponding blade connecting member or pretensioning member inside or outside the profile of the corresponding blade connecting member or pretensioning member.

[0010] Optionally, the conductive material is connected to the outside of the corresponding blade connecting member or pre-tensioning member via a support.

[0011] Alternatively, the conductive material may be formed as one or more strands, cables, or braided sleeves.

[0012] Alternatively, the conductive material is spirally wound along the corresponding blade connecting member or pre-tensioning member.

[0013] Optionally, in the first region of the corresponding blade connecting member or pretensioning member, the conductive material is spirally wound, and in the second region of the corresponding blade connecting member or pretensioning member, the conductive material extends coaxially with the longitudinal axis of the corresponding blade connecting member or pretensioning member.

[0014] Optionally, the conductive material is spirally wound on the first part of the corresponding blade connecting member or pretensioning member at a first pitch, and the conductive material is spirally wound on the second part of the corresponding blade connecting member or pretensioning member at a second pitch different from the first pitch.

[0015] Optionally, the blade connecting member and / or pretensioning member comprises a metallic material, and the metallic material is a conductive material of the blade connecting member and / or pretensioning member.

[0016] Optionally, the blade connecting components and / or pretensioning components comprise polymer materials.

[0017] Optionally, the outer and inner portions of each wind turbine blade are connected to each other at a split (segmented) location, wherein the connection points on the wind turbine blade are arranged at the split location.

[0018] Alternatively, the inner portion of each wind turbine blade has a reduced lightning current conduction capacity compared to the outer portion of the wind turbine blade.

[0019] Alternatively, the inner portion of each wind turbine blade is not configured to conduct lightning current from the outer portion of the wind turbine blade toward the tower. For example, the outer portion of each blade is provided with a down conductor extending from the tip of each blade to the corresponding connection point, and the inner portion of each blade is not provided with a down conductor. Attached Figure Description

[0020] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 A front view of a wind turbine based on the first example is shown; Figure 2 A side view of a wind turbine is shown; Figure 3 A wind turbine according to the second example is shown; Figure 4 This shows a segmented wind turbine blade; Figure 5 An exploded view of the connection joint between the blade sections is shown; Figure 6 A perspective view of the connection joint between the blade sections is shown; Figure 7 A lightning protection system according to the first example is shown; Figure 8 A lightning protection system according to the second example is shown; Figure 9 A set of conductive strands is shown embedded in a connecting member or pre-tensioned member; Figure 10 The cable attached within the outline of the connecting member or pre-tensioning member is shown; Figure 11 The cable is shown fixed to the outer surface of the connecting member or pre-tensioning member; Figure 12 The cable is shown being spaced apart from the outer surface of the connecting member by a support; Figure 13The diagram shows strands of wire spirally wound around a connecting member or pre-tensioned member; Figure 14 The diagram shows strands of wire wound helically at different pitches along the length of the connecting member or pre-tensioned member; Figure 15 It shows strands intermittently spirally wound between regions of non-spiral strands that extend coaxially with the longitudinal axis of the connecting member or pretensioning member; Figure 16 A braided sleeve is shown surrounding a connecting member or a pre-tensioned member. Detailed Implementation

[0021] In this specification, terms such as leading edge, trailing edge, pressure surface, suction surface, thickness, and chord are used. While these terms are well known and understood by those skilled in the art, definitions are provided below to avoid ambiguity.

[0022] The term leading edge is used to refer to the edge of a blade that will be located at the front of the blade when the blade rotates in the conventional direction of rotation of the wind turbine rotor.

[0023] The term trailing edge is used to refer to the edge of a wind turbine blade, which is located at the rear of the blade as the blade rotates in the conventional direction of rotation of the wind turbine rotor.

[0024] The chord of a blade is the straight-line distance from the leading edge to the trailing edge in a given cross section perpendicular to the blade's span. The term chord direction is used to refer to the direction from the leading edge to the trailing edge, or vice versa.

[0025] The pressure surface (or windward surface) of a wind turbine blade is the surface between the leading and trailing edges. When the blade is in use, this pressure surface has a higher pressure than the suction surface of the blade.

[0026] The suction side (or leeward side) of a wind turbine blade is the surface between the leading and trailing edges. When the blade is in use, this suction side will have a lower pressure acting on it than the pressure side.

[0027] The thickness of a wind turbine blade is measured perpendicular to the chord of the blade and is the maximum distance between the pressure and suction surfaces in a given cross section perpendicular to the blade spanwise direction.

[0028] The term spanwise refers to the direction from the root tip of a wind turbine blade to its tip, and vice versa. When wind turbine blades are mounted on a wind turbine hub, the spanwise and radial directions will be substantially the same.

[0029] The term sparsity cap (spar edge) is used to refer to a longitudinally extending, generally spanwise, reinforcing member of a blade. A sparsity cap can be embedded in the blade shell or attached to it. Sparsity caps on the windward and leeward sides of the blade can be connected by one or more shear webs extending through the internal hollow space of the blade. A blade can have more than one sparsity cap on each of its windward and leeward sides. A sparsity cap can form part of a longitudinally reinforcing spars or support member of the blade. In particular, a sparsity cap can form part of a load-bearing structure extending longitudinally to support the flapping bending load of the blade. A sparsity cap can include a portion of the sparsity cap on either side of a connection joint between portions of the blade.

[0030] The term "outer side" (end side) refers to the radial direction from the blade hub toward the blade tip. The term "inner side" (root side) refers to the radial direction from the tip toward the hub.

[0031] Figure 1 and Figure 2 A pitch-controlled wind turbine 1 according to the first example is shown. Figure 1 This is a front view of wind turbine 1. Figure 2 This is a side view of a wind turbine 1. The wind turbine 1 includes a tower 2 and a nacelle 3 mounted on the tower 2. A hub 4 is rotatably mounted on the nacelle 3 and carries three wind turbine blades 5 projecting outwards from the nacelle 3. Although Figure 1 and Figure 2 The example shown has three blades 5, but it should be understood that other numbers of blades 5 are possible.

[0032] When wind blows towards the wind turbine 1, the wind turbine blades 5 generate lift, which causes the generator (not shown) inside the nacelle 3 to generate electricity.

[0033] It should be understood that the wind turbine 1 depicted can be any suitable type of wind turbine 1. The wind turbine 1 shown is a headwind turbine, but it should be understood that the wind turbine 1 can also be a tailwind turbine. The wind turbine 1 can be an onshore wind turbine, such that the base is embedded in the ground, or the wind turbine 1 can be an offshore facility, in which case the base will be provided by a suitable offshore platform.

[0034] The three blade connecting members 6 interconnect adjacent wind turbine blades 5 (such as...) between connection points 7a and 7b on the wind turbine blades 5. Figure 6 (As shown in further detail below). The connecting member 6 is a cable, such as a metal cable (e.g., including steel) or a polymer (e.g., including high-density polyethylene-HDPE).

[0035] The pretensioning member 8 can extend between one of each blade connecting member 6 and a common point located at or near the hub 4. Figure 1 and Figure 2 In the example shown, the pretensioning member 8 extends to the hub 4. The pretensioning member 8 is configured to provide pretension in the blade connection member 6.

[0036] The pre-tensioned blade connecting member 6 enables the wind turbine blades 5 to support each other, and in this sense, the load on the wind turbine blades 5, especially the edge load and flapping load, is distributed among the wind turbine blades 5.

[0037] Figure 3 This is a side view of the pitch-controlled wind turbine 1 according to the second example. Figure 3 The wind turbine 1 is similar to Figure 1 and Figure 2 The same features will not be described in detail here.

[0038] exist Figure 3 In this configuration, the pretensioning member 8 is not directly connected to the hub 4. Instead, the pretensioning member 8 is connected to the hub member 9 adjacent to the hub 4, and the hub member 9 extends from the hub 4 substantially along the direction defined by the axis of rotation of the hub 4. Therefore, the connection point of the pretensioning member 8 is more... Figure 1 and Figure 2 The example is further away from the hub 4, and thus further away from the location where the wind turbine blade 5 is connected to the hub 4. This has the result that the pretensioning member 8 can also pull the blade connecting member 6 away from the hub 4 and away from the tower 2. This may also cause the wind turbine blade 5 to be pulled in this direction, thereby further reducing the edge load and flapping load at the root of the wind turbine blade 5 and ensuring tower clearance (similar to the clearance obtained when the cone angle is introduced). Due to the use of the connecting member 6, it has been found that this tends to lead to an increase in stiffness in the inner part of the blade 5.

[0039] like Figure 4 As shown, the wind turbine blade 5 has a root end 11 near the hub 4 and a tail end 12 away from the hub 4, the root end 11 being adapted to be connected to the hub 4 via a pitch mechanism. The blade 5 includes a leading edge 13 and a trailing edge 14 extending between the respective root end 11 and tail end 12. The blade 5 includes a suction side 15 and a pressure side 16. The thickness dimension of the blade 5 extends between the suction side 15 and the pressure side 16.

[0040] like Figure 4As shown, each blade 5 may have a cross-section with a generally circular profile near the root tip 11. Moving outward from the root tip 11, the blade 5 may transition from a circular profile to an airfoil profile. The blade 5 may include a "shoulder" 28 outside the root tip 11, which is the widest portion of the blade 5 with its maximum chord. The blade 5 may have an airfoil profile with a gradually decreasing thickness in the outer portion of the blade. The gradually decreasing thickness may extend from the shoulder 28 to the tip 12.

[0041] Connection points 7a and 7b can be located between 10% and 60% of the length of the wind turbine blade 5 from root end 11 to end end 12 in the radial direction, but preferably located radially inside 50% of the length of the wind turbine blade 5 from root end 11 to end end 12, and more preferably located radially inside 45% of the length of the wind turbine blade 5 from root end 11 to end end 12, for example, around 35-40%.

[0042] Each blade 5 is a split blade formed by connecting a first blade portion 22 and an outer blade portion 24, such as... Figure 4 As shown. Each blade portion 22, 24 has a housing defining a corresponding leading edge 30a, 30b, trailing edge 32a, 32b, suction side 34a, 34b and pressure side 36a, 36b.

[0043] The inner portion 22 and the outer portion 24 of each blade 5 can be connected at a joint indicated by the connecting line 40. The connecting line 40 between the inner blade portion 22 and the outer blade portion 24 can be a spanwise split line, wherein the connecting line 40 is chordally oriented. The inner blade portion 22 extends from the blade root 11 to the connecting line 40. The outer blade portion 24 extends from the blade connecting line 40 to the blade tip 12.

[0044] It should be understood that the blade 5 may have any number of blade sections 22, 24, with corresponding connecting joints between them.

[0045] As described above, the inner blade portion 22 and the outer blade portion 24 are connected by a connection joint including a connector 41, such as... Figure 5 and Figure 6 As shown. Specifically, connector 41 connects the first blade end face 26 of the inner blade portion 22 to the second blade end face 27 of the outer blade portion 24. As explained in further detail below, the connection points 7a and 7b of the connecting member 6 are located on connector 41 at the connection joint.

[0046] The connector 41 is adapted to transmit a load between the inner blade portion 22 and the outer blade portion 24, and particularly between the first spar cap portion 23 of the inner blade portion 22 and the second spar cap portion of the outer blade portion 24.

[0047] Connector 41 is a cast metal assembly; however, it should be understood that connector 41 can be formed from any suitable material (e.g., composite material) and manufactured using any suitable manufacturing technique (e.g., machining, co-curing, or co-bonding). In this example, connector 41 is conductive and forms part of the electrical connection between the end 12 of the blade 5 and the connecting member 6. In the case where connector 41 is formed from a non-conductive or low-conductivity material, a separate electrical connection is formed between the end 12 and the connecting member 6 via the blade 5. Connector 41 is a single, integral connector assembly 43; however, it should be understood that in some examples, connector 41 can be formed from two or more assemblies.

[0048] exist Figure 5 In the example shown, connector 41 includes a first branch 54 for connecting the inner blade portion 22 and the outer blade portion 24 via a suction side 15, and a second branch 55 for connecting the first blade portion 22 and the second blade portion 24 via a pressure side 16. The first branch 54 and the second branch 55 can be connected via a first link 56 positioned toward the leading edge 13 of the blade 5, and via a second link 57 positioned toward the trailing edge 14 of the blade 5. In this way, the first branch 54, the second branch 55, the first link 56, and the second link 57 form an annular shape. The first branch 54 and the second branch 55 can be integrally formed with the first link 56 and the second link 57; however, it should be understood that the first branch 54 and the second branch 55 can be separate components from each other, and / or separate components from the first link 56 and the second link 57. It should be understood that connector 41 can take other forms.

[0049] Connector 41 may extend across substantially the entire chord of the wind turbine blade 5, although preferably connector 41 extends only a portion of the chord across the wind turbine blade, such as Figure 5 As shown in the diagram. This helps reduce the weight of connector 41 while allowing connector 41 to be positioned adjacent to the spar cap portion 23 of the blade portions 22, 24, which typically bear most of the load.

[0050] Connector 41 can extend across any chordal portion of the adjacent spar cap portion 23 of blade 5, but... Figure 5 The example shown extends upward to the leading edge 13 of blade 5.

[0051] The leading edge extension 42 may extend in front of the leading edge 13 of the blade 5. The leading edge extension 42 is integrally formed with the connector 41, but it should be understood that, in alternative examples, the leading edge extension 42 may be a component separate from the connector 41.

[0052] The leading edge extension 42 includes connection points 7a, 7b attached to the connecting member 6. In this example, the leading edge extension 42 includes a first connection point 7a and a second connection point 7b, but in alternative examples, the leading edge extension 42 may include any suitable number of connection points. The first connection point 7a and the second connection point 7b may be arranged in front of the leading edge 13 and adjacent to the pressure side 16, such as... Figure 5 As shown, this provides additional clearance for the connecting member 6 when the wind turbine blade 5 rotates around the nacelle 3 together with the hub 4. In particular, sufficient clearance is provided between the connecting member 6 and the inner blade portion 22 when the blade 5 pitches between approximately -5 degrees and approximately +95 degrees.

[0053] It should be understood that connection points 7a and 7b may be adjacent to each other on the leading edge extension 42. Alternatively, connection points 7a and 7b may be spaced apart from each other. For example, the second connection point 7b may be positioned further toward the pressure side 16 than the first connection point 7a, for example, the second connection point 7b may be closer to the pressure side spar cap 23, while the first connection point may remain adjacent to the leading edge 13.

[0054] In some examples, connector 41 may include a plurality of leading edge extensions 42 integrally formed with connector 41. The leading edge extensions may be spaced apart from each other, for example, one may be positioned more toward the pressure side 16 than another, wherein each leading edge extension 42 has a corresponding connection point 7a, 7b.

[0055] Connection points 7a and 7b allow the connecting member 6 at at least some degrees of freedom of movement at its respective connection points 7a and 7b. Figure 6 In the example shown, connection points 7a and 7b allow each blade connection member 6 to rotate about the corresponding connection points 7a and 7b with two orthogonal rotational degrees of freedom. This allows each connection member 6 to move independently of each other, thereby reducing constraints on the wind turbine 1.

[0056] In addition to “sharing” the load between the wind turbine blades 5, the connecting member 6 and the pretensioning member 8 can also form part of a lightning protection system, as will be discussed below.

[0057] The lightning protection system may include a down conductor 70, such as a down conductor cable, which extends along the length of the blade 5 from the end 12 to the connector 41. Figure 7 In the example shown, the downlead 70 extends only from the end 12 of the blade 5 to the connector 41, such that no downlead extends through the blade inside the connector 41. In other examples, instead of a cable or in addition to a cable, the downlead may include a surface protective layer.

[0058] The lightning protection system is grounded via hub 4 and a suitable energy handling mechanism (not shown). The lightning path from down conductor 70 toward tower 2 is achieved via at least one of the aforementioned connecting members 6 and / or via at least one of the pre-tensioning members 8. For example, the lightning path can extend from the outer portion 24 of the connecting member 6 of the wind turbine blade 5 and along a path extending toward hub 4 together with the blade connecting member 6, forming part of the lightning protection system of wind turbine 1.

[0059] In particular, such as Figures 9 to 16 As shown, the connecting member 6 and / or the pretensioning member 8 have conductive materials that form part of the lightning protection system and are configured to conduct lightning current. The connecting member 6 and the pretensioning member 8 may include a primary load-bearing material 80, such as a polymer material or a metallic material. The conductive material is arranged with a substantially non-load-bearing capacity such that it carries a minimal load compared to the primary load-bearing material 80. The conductive material can be any suitable material, such as a metal like copper or aluminum. The conductive material may be provided in the form of multiple conductive strands 81, cables 82, or braided sleeves 83.

[0060] In this way, the connecting member 6 and / or the pretensioning member 8 facilitate the distribution of load between the blades 5, while also eliminating or reducing any requirements for lightning protection in the portion of the blades 5 inside the connection points 7a, 7b of the connecting member 6. This is especially important in the inner blade portions (such as...) Figure 7 The inner blade portion 22 shown offers several benefits in terms of quality, cost, and manufacturability because it eliminates the need to bond a surface protective layer (SPL) to the outer surface of the blade 5, or to focus efforts on successfully transferring current through the connector 41 to the inner blade portion 22.

[0061] Figure 7 An example is shown where the inner blade portion 22 does not form part of a lightning protection system. In other words, the inner blade portion 22 is not designed to carry lightning current. Therefore, the inner blade portion 22 does not form part of a lightning protection system.

[0062] In an alternative example, the inner blade portion 22 may form part of a lightning protection system, but with reduced capability. For example, the inner portion of each wind turbine blade 5 may have part of a lightning protection system configured to conduct reduced lightning current compared to the portion of the lightning protection system on the outer blade portion 24, which is configured to conduct lightning current. Figure 8An example is shown where a second down conductor 70a (e.g., a down conductor cable) extends from connector 41 through inner blade portion 22 to hub 4. The second down conductor 70a has a greater impedance than the first down conductor 70. This may cause the majority of the lightning current to be conducted via the conductive material of connecting member 6 rather than via the second down conductor 70a. This can provide significant benefits in terms of reduced mass and cost of inner blade portion 22, as well as reduced manufacturing costs (which may occur while ensuring the second down conductor 70a is capable of conducting any lightning current), due to the wider range of suitable materials that can be used.

[0063] Figure 9 An example is shown in which the connecting member 6 or pretensioning member 8 includes a plurality of conductive strands 81 formed as embedded within the main load support material 80. The main load support material 80 may be a polymer material.

[0064] Figure 10 Alternative examples are shown in which the conductive material formed as cable 82 is attached to or embedded within the main load-bearing material 80 of the connecting member 6 or pre-tensioning member 8. The main load-bearing material 80 may be a polymer material. Cable 82 is shown adjacent to the outer surface 6a of the connecting member 6; however, it should be understood that cable 82 may be embedded anywhere within the connecting member 6.

[0065] In this case, the embedded strands 81 or cables 82 of the electrical material can be attached to the main load support material 80 so as to experience the same axial strain, but it should be understood that the strands 81 and cables 82 can move axially relative to the main load support material 80.

[0066] In these examples, the conductive material is coupled within the outline of the load support material 80 of the connecting member 6 or the pretensioning member 8. However, the conductive material may be coupled outside the outline of the load support material 80 of the connecting member 6 or the pretensioning member 8, for example, to isolate the conductive material from the load of the connecting member 6 or the pretensioning member 8.

[0067] In some examples, conductive material can be attached to the outer surface 6a of the blade connecting member 6 or the pretensioning member 8. This allows conductive material to be added to the connecting member 6 or pretensioning member 8 after it has been manufactured or modified to an existing connecting member 6 or pretensioning member 8. The conductive material can be secured to the connecting member 6 or pretensioning member 8 at one or more points, or connected substantially along the entire length of the connecting member 6 or pretensioning member 8. The connecting material 85 can cover the conductive material (e.g., cable 82), such as... Figure 11As shown in the example, the connecting material may be wrapped around the entire connecting member 6 or pre-tensioning member 8, or otherwise disposed between the conductive material and the connecting member 6 or pre-tensioning member 8. The connecting material 85 provides a means of attaching the conductive material to the connecting member 6. Furthermore, by covering the conductive material, the connecting material 85 can protect the conductive material from damage (e.g., impact and abrasion damage) and provide UV protection. The connecting material 85 may be adhesively attached to the connecting member 6. The connecting material 85 may be co-cured to the connecting member 6. The connecting material 85 may be a cable tie or include hook and loop fasteners. The connecting material 85 may be formed from a polymer material or other suitable material.

[0068] Figure 12 An example is shown in which a conductive material (e.g., cable 82) is separated from or spaced apart from the connecting member 6 by a support 84, such that lightning currents that may flow through the cable 82 are isolated from the connecting member 6 or the pretensioning member 8. In an alternative example, an insulating layer or the like may be positioned between the conductive material and the connecting member 6 or the pretensioning member 8.

[0069] Conductive material can be helically wound around the connecting member 6 or the pretensioning member 8. For example, cable 82 can be helically wound along the connecting member 6 or the pretensioning member 8. The conductive material (e.g., cable 82) can be adhesively attached to the connecting member 6 or the pretensioning member 8. This can increase the effective axial elongation of the conductive material due to the helical angle of the conductive material relative to the load path through the connecting member 6 or the pretensioning member 8. This can be beneficial when the connecting member 6 or the pretensioning member 8 and the conductive material are different materials, as their material properties (e.g., coefficients of thermal expansion and tensile properties) will be different. Figure 13 An example is shown where conductive material, formed as multiple cables 82, is spirally wound around a connecting member 6 or a pre-tensioned member 8.

[0070] The pitch of the spirally wound conductive material can affect the behavior of the conductive material, because a cable 82 with a relatively large pitch will have a shorter total length and therefore a shorter conductive path, but will accommodate a smaller axial expansion of the connecting member 6 or the pretensioning member 8 before the cable 82 is axially stretched by the axial extension of the connecting member 6 or the pretensioning member 8.

[0071] In some examples, the conductive material can have regions with different pitches. Figure 14An example is shown in which the conductive material formed as cable 82 includes a first region 82a having a first pitch, positioned between two adjacent regions 82b having a relatively small pitch. The adjacent regions 82b can act as springs to account for any excessive axial strain in the connecting member 6 or the pre-tensioning member 8, while the first region 82a helps to shorten the overall length of cable 82. It should be understood that, in alternative examples, the conductive material may only be helically wound in some regions 82b of the connecting member 6, such that the conductive material in the other regions 83c of the connecting member 6 extends substantially coaxially with the longitudinal axis of the connecting member 6. Examples of this arrangement are shown in... Figure 15 As shown in the image.

[0072] It should be understood that the discussion of cable 82 can refer to solid cable or stranded cable.

[0073] In some examples, the conductive material may be provided in the form of a braided sleeve 83 surrounding the connecting member 6 or the pretensioning member 8, such that the conductive material is a braided hollow shield. The braided pattern can help prevent the conductive material from unraveling from the connecting member 6 or the pretensioning member 8 due to the interlocking pattern of the strands forming the braided sleeve 83. The braided sleeve 83 can also protect the connecting member 6, for example, by providing UV protection. Figure 16 An example of braided sleeve 83 is shown in the figure.

[0074] Figures 9 to 16 The examples shown are relative to connecting member 6, but it should be understood that these examples apply in the same way to pretensioning member 8.

[0075] Although the invention has been described above with reference to one or more preferred embodiments, it should be understood that various changes or modifications may be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. A pitch-controlled wind turbine, comprising a tower, a nacelle mounted on the tower, a hub rotatably mounted on the nacelle, and at least three wind turbine blades, wherein, Each wind turbine blade extends between a root end and a tip end, the root end being connected to the hub via a pitch mechanism; The wind turbine also includes at least three blade connection members, each blade connection member extending from a connection point on a wind turbine blade toward a connection point on an adjacent wind turbine blade, wherein the connection point on a given wind turbine blade is arranged at a certain distance from the root end of the wind turbine blade and at a certain distance from the tip end of the wind turbine blade. Each wind turbine blade includes an outer portion and an inner portion, the outer portion extending from the tip of the wind turbine blade to the connection point, and the inner portion extending from the root end of the wind turbine blade to the connection point. The wind turbine also includes a lightning protection system, and each blade connection member has a conductive material configured to conduct lightning current from the outer portion of the connection member of the wind turbine blade and along a path extending toward the tower together with the blade connection member.

2. The pitch-controlled wind turbine according to claim 1, wherein, The wind turbine also includes at least three pretensioning members, each pretensioning member being connected to one of the blade connection members and the hub, each pretensioning member thereby providing pretension in the blade connection member to which it is connected, and wherein each pretensioning member has a conductive material that forms part of the lightning protection system and is configured to conduct lightning current from the blade connection member to which the pretensioning member is connected and along a path extending toward the tower together with the pretensioning member.

3. The pitch-controlled wind turbine according to claim 1 or claim 2, wherein, The conductive material of the blade connecting member and / or the pretensioning member is embedded in the corresponding blade connecting member or pretensioning member.

4. The pitch-controlled wind turbine according to claim 1 or claim 2, wherein, The conductive material of the blade connecting member and / or the pretensioning member is attached to the outer surface of the corresponding blade connecting member or pretensioning member.

5. The pitch-controlled wind turbine according to claim 4, wherein, The conductive material is connected to the corresponding blade connecting member or pretensioning member inside or outside the contour of the corresponding blade connecting member or pretensioning member.

6. The pitch-controlled wind turbine according to claim 5, wherein, The conductive material is connected to the outer contour of the corresponding blade connecting member or pre-tensioning member via a support.

7. The pitch-controlled wind turbine according to any one of the preceding claims, wherein, The conductive material is formed as one or more of multiple strands, cables, or braided sleeves.

8. The pitch-controlled wind turbine according to any one of the preceding claims, wherein, The conductive material is spirally wound along the corresponding blade connecting member or pre-tensioning member.

9. The pitch-controlled wind turbine according to claim 8, wherein, In the first region of the corresponding blade connecting member or pretensioning member, the conductive material is spirally wound, and in the second region of the corresponding blade connecting member or pretensioning member, the conductive material extends substantially coaxially with the longitudinal axis of the corresponding blade connecting member or pretensioning member.

10. The pitch-controlled wind turbine according to claim 8, wherein, The conductive material is spirally wound at a first pitch in a first region of the corresponding blade connecting member or pretensioning member, and the conductive material is spirally wound at a second pitch, different from the first pitch, in a second region of the corresponding blade connecting member or pretensioning member.

11. The pitch-controlled wind turbine according to any one of the preceding claims, wherein, The blade connecting member and / or the pretensioning member comprises a metallic material, and the metallic material is a conductive material of the blade connecting member and / or the pretensioning member.

12. The pitch-controlled wind turbine according to any one of claims 1 to 10, wherein, The blade connecting member and / or the pretensioning member comprise polymer materials.

13. The pitch-controlled wind turbine according to any one of the preceding claims, wherein, The outer and inner portions of each wind turbine blade are connected to each other at a split position, wherein the connection points on the wind turbine blade are arranged at the split position.

14. The pitch-controlled wind turbine according to any one of the preceding claims, wherein, Compared to the lightning current conduction capacity of the outer portion of the wind turbine blade, the inner portion of each wind turbine blade has a reduced lightning current conduction capacity.

15. A pitch-controlled wind turbine according to any one of the preceding claims, wherein, The inner portion of each wind turbine blade is not configured to conduct lightning current from the outer portion of the wind turbine blade toward the tower.

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