Lightning protection system

Abstract

The invention relates to a lightning protection system for a wind turbine blade, the wind turbine blade comprising a root end and a tip end and a longitudinal axis, a pressure side and a suction side, the pressure side and the suction side being an outer surface of the wind turbine blade, and a structural element extending along the longitudinal axis, the structural element is a rod or beam made of fiber reinforced polymer (FRP), the lightning protection system comprising: a first downlead conductor, a second downlead conductor and a third downlead conductor, the second downlead conductor comprising a first expansion foil or a first mesh, and the third downlead conductor comprising a second expansion foil or a second mesh, the first expansion foil or the first net and the second expansion foil or the second net are made of conductive materials and comprise a plurality of conductive connecting points, and the conductive connecting points are arranged near the top connecting block and the root connecting block and are electrically connected with the top connecting block and the root connecting block respectively. Thus, the wind turbine blade can be protected from structural damage caused by lightning impacts over the entire length.

Description

[0001] This application is a divisional application of Chinese invention patent application "Lightning Protection System" filed on December 23, 2021, with a priority date of December 23, 2020 and application number 202180087173.X. Technical Field

[0002] This invention relates to a lightning protection system for wind turbine blades. The wind turbine blade includes a root end and a tip end, a longitudinal axis, a pressure side and a suction side, and structural elements extending along the longitudinal axis. The pressure side and suction side are the outer surfaces of the wind turbine blade, and the structural elements are rods or beams made of fiber reinforced polymer (FRP). Background Technology

[0003] Most known lightning protection systems for wind turbine blades consist of one or more down conductors located inside the blade and multiple lightning receivers located on the outer surface of the blade.

[0004] A well-known problem with this system is that lightning strikes can not only adhere to the wind turbine blade at the intended location (i.e., at the external attachment point (the so-called lightning receiver)), but can also strike the internal conductive parts of the lightning protection system directly through the blade's structure. Due to the typically large amount of energy released by a lightning strike, such events can cause severe structural damage to the wind turbine blade.

[0005] As the size of wind turbines increases, so too does the size of their blades. Therefore, the structural design of wind turbine blades becomes increasingly important, as there is always a desire to design blades as lightweight as possible without compromising their strength. Consequently, protecting wind turbine blades along their entire length from structural damage caused by lightning strikes is even more crucial. Summary of the Invention

[0006] The object of this invention is to completely or partially overcome the aforementioned disadvantages and defects of the prior art. More specifically, the object is to provide an improved lightning protection system for wind turbine blades having structural elements made of fiber-reinforced polymer (FRP) rods or beams.

[0007] The foregoing objectives, as will become apparent from the following description, and many other objectives, advantages, and features are achieved by the solution according to the invention through a lightning protection system for a wind turbine blade, the wind turbine blade comprising a root end and a tip end, a longitudinal axis, a pressure side and a suction side, and structural elements extending along the longitudinal axis, the pressure side and suction side being the outer surfaces of the wind turbine blade, the structural elements being rods or beams made of fiber-reinforced polymer (FRP), the lightning protection system comprising: - A first down conductor extends from the top end to the top connecting block, which is positioned at a predetermined distance from the top end. The first down conductor is electrically connected to the top connecting block. - The second down conductor extends from the top connecting block between the structural element and the pressure side, and along the structural element and the pressure side toward the root connecting block arranged at the root end. - The third down conductor extends from the top connecting block between the structural element and the suction side, and along the structural element and the suction side toward the root connecting block. - The second down conductor includes the first sheet, and the third down conductor includes the second sheet, wherein the first and second sheets are wholly or partially made of conductive material. The first sheet and the second sheet include multiple conductive connection points, which are arranged near the top connection block and the root connection block and are electrically connected to the top connection block and the root connection block, respectively.

[0008] Therefore, the top connecting block serves as an interface between the first down conductor extending from the top of the wind turbine blade and two sheets in each blade shell, which function as down conductors from the tips of the FRP rod caps. Additionally, bonding or equipotentialization between the pressure-side and suction-side down conductors is performed within a single unit. Simultaneously, the second and third down conductors can serve as receiver bases for lightning strikes attached to the sheet tips. This section is carefully designed to handle the entire lightning current and avoid interception failures due to its insulating casting.

[0009] In addition, structural elements can be rods or beams made of conductive carbon fiber reinforced polymer (CFRP).

[0010] Depending on the total length of the wind turbine blades, the predetermined distance can be 5 to 25 meters from the tip of the wind turbine blades.

[0011] Furthermore, the first expansion foil or the first mesh and the second expansion foil or the second mesh can be arranged symmetrically on opposite sides with respect to the structural elements, and their dimensions are substantially equal.

[0012] In addition, conductive connection points can be made of metal or other conductive materials or combinations thereof.

[0013] In addition, the metal can be tin, aluminum, copper, brass, silver, gold, or any alloy thereof.

[0014] In addition, the conductive connection point may include a first layer and a second layer.

[0015] The first layer can be made of a first material, and the second layer can be made of a second material. The first material is different from the second material.

[0016] In addition, conductive connection points can be directly or indirectly connected to the connection block.

[0017] In an embodiment, each conductive connection point may have a geometry that presents an external closed curve, the minimum radius of curvature of which is between 3 mm and 200 mm, preferably between 5 mm and 100 mm.

[0018] In addition, conductive connection points can have a semi-major axis and a semi-minor axis.

[0019] The semi-major axis and semi-minor axis can be equal, thus providing a circular outer perimeter.

[0020] Furthermore, the semi-major axis and semi-minor axis can be different, thus providing an oval or elliptical outer periphery.

[0021] In addition, the semi-major axis can be oriented at a predetermined angle about the longitudinal axis of the wind turbine blade.

[0022] The preset angle can be between 0 degrees and 90 degrees.

[0023] Furthermore, the conductive connection points can be partially or completely circular or elliptical.

[0024] In addition, the connection points can have asymmetrical shapes.

[0025] In addition, the outer perimeter of the conductive connection point can be defined by curves and straight lines.

[0026] Furthermore, conductive connection points can be made without any sharp corners.

[0027] In addition, the conductive connection point may have a thickness greater than 0.5 mm, preferably greater than 1.0 mm.

[0028] Furthermore, the thickness of the conductive connection point can extend in two directions relative to the thickness of the sheet.

[0029] In addition, the conductive connection points can be mechanically connected to the sheet.

[0030] Conductive connection points can be adhered to the sheet using conductive adhesive.

[0031] In addition, the receiver bolts can be screwed into the connecting block through the conductive connection points.

[0032] In addition, threads can be incorporated into conductive connection points.

[0033] In addition, the receiver bolt can terminate at the conductive connection point.

[0034] Additionally, the side receiver can be connected to a conductive connection point.

[0035] Multiple intermediate conductive connection points can be arranged relative to the structural elements at a predetermined intermediate distance from the top connection block.

[0036] In addition, the intermediate conductive connection point can be connected to structural components.

[0037] Furthermore, the predetermined intermediate distance can be less than 1500 mm, preferably between 1500 mm and 500 mm, more preferably between 500 mm and 100 mm, and most preferably between 100 mm and 10 mm.

[0038] In addition, conductive connection points can be made by molten material, which connects the liquid molten material to the sheet, thereby providing a mechanical and conductive connection between the conductive connection points and the sheet when the material hardens.

[0039] The melting of materials can be performed by induction heating or resistance heating.

[0040] Alternatively, conductive connections can be made by spraying molten metal onto a sheet and then welding it.

[0041] The conductive connection point may include at least two disks arranged on opposite sides of the sheet, and each disk is subsequently mechanically fastened to the other.

[0042] In addition, the conductive connection point may include at least two disks arranged on opposite sides of the sheet and subsequently pressed together around the sheet by plastic deformation.

[0043] In addition, the conductive connection point may include at least two disks arranged on opposite sides of the sheet and subsequently spot-welded together.

[0044] The conductive connection point may include at least two disks arranged on opposite sides of the sheet and subsequently pulse-melted together.

[0045] In addition, the conductive connection point includes at least two disks arranged on opposite sides of the sheet and subsequently glued together by a conductive adhesive.

[0046] In addition, the conductive connection point has an edge or outer perimeter, and the current density at the edge or outer perimeter may not exceed 1500 A / mm.

[0047] Advantageously, the first and second sheets are expanded foil or mesh.

[0048] The conductive material of the first expansion foil or the first mesh and the second expansion foil or the second mesh can be a metal, such as aluminum, copper, steel or an associated alloy.

[0049] In addition, the conductive material of the sheet or mesh can be non-metallic, such as composite materials or fibers.

[0050] The first expansion foil or the first mesh may be arranged such that it at least completely covers the first side of the structural element facing the pressure side, and the second expansion foil or the second mesh may be arranged such that it at least completely covers the second side of the structural element facing the suction side.

[0051] In addition, the lengths of the first expansion foil or the first mesh and the second expansion foil or the second mesh can be equal to or longer than the length of the structural element.

[0052] Furthermore, the first expanding foil or the first mesh may have a first area, and the second expanding foil or the second mesh may have a second area, the first area and the second area being substantially equal.

[0053] Expanded foil can be made into a single piece.

[0054] In addition, the mesh can be provided by braiding conductive wires.

[0055] The mesh can also be provided by non-braided conductive wire.

[0056] In addition, the top connecting block can electrically connect the first lead conductor to the first expansion foil or the first mesh and the second expansion foil or the second mesh via conductive connection points.

[0057] In addition, the top connection block may include at least one first receiver base and at least one second receiver base, the first receiver base being configured to connect the conductive connection point of the first expanded foil to the top connection block, and the second receiver base being configured to connect the conductive connection point of the second expanded foil to the top connection block.

[0058] Alternatively, the receiver bolt can be screwed into the receiver base through the conductive connection point.

[0059] In addition, the top connection block may include at least a first pair of receiver bases and at least a second pair of receiver bases, the first pair of receiver bases being configured to connect the conductive connection points of the first expansion foil to the top connection block, and the second pair of receiver bases being configured to connect the conductive connection points of the second expansion foil to the top connection block.

[0060] In addition, an equal number of receiver bases can be arranged for connecting the first expansion foil or the first mesh and the second expansion foil or the second mesh to the top connecting block.

[0061] In addition, the top connection block can be configured to prevent interception faults by ensuring sufficient insulation class.

[0062] Furthermore, the root connector block can be configured to electrically connect the first expansion foil and the second expansion foil to a single root down conductor.

[0063] The root connector can be Y-shaped.

[0064] In addition, a first intermediate connecting block can be arranged between the first expansion foil and the root connecting block, the first intermediate connecting block electrically connecting the first expansion foil and the root connecting block, and a second intermediate connecting block is arranged between the second expansion foil and the root connecting block, the second intermediate connecting block electrically connecting the second expansion foil and the root connecting block.

[0065] Each intermediate connecting block may include at least one first receiver base and at least one second receiver base, the first receiver base being configured to connect a connection point of a first expansion foil to the intermediate connecting block, and the second receiver base being configured to connect a connection point of a second expansion foil to the intermediate connecting block.

[0066] In addition, each intermediate connection block may include at least one pair of receiver bases configured to connect the conductive connection points of the expanded foil to the intermediate connection block.

[0067] In addition, the receiver bolt can be screwed through the conductive connection point into the receiver base of the intermediate connecting block.

[0068] Furthermore, the first cable can be arranged between the first intermediate connecting block and the root connecting block, and the second cable can be arranged between the second intermediate connecting block and the root connecting block. The first cable and the second cable serve as down conductors.

[0069] Furthermore, the structural elements can be conductive and manufactured from pultruded components. Pultruded components can be made using pre-impregnated glass fiber sheets in a dry fabric lamination and vacuum-assisted resin infusion process.

[0070] Alternatively, structural components can be manufactured, for example, through the following steps: - Assemble and stack several conductive pultruded profiles, pour in and heat them into complete structural components; - Dry the fabric layers, then perform a vacuum-assisted resin infusion process and heating; or - Stack pre-impregnated fiber sheets, then vacuum and heat them.

[0071] The present invention also relates to a wind turbine blade comprising a root end and a tip end, a longitudinal axis, a pressure side and a suction side, structural elements extending along the longitudinal axis, and a lightning protection system as described above, wherein the pressure side and the suction side are the outer surfaces of the wind turbine blade, and the structural elements are rods or beams made of conductive carbon fiber reinforced polymer (CFRP).

[0072] The present invention also relates to a wind turbine having one or more wind turbine blades having a lightning protection system as described above.

[0073] The present invention further relates to a method for setting conductive connection points of a lightning protection system onto a sheet (such as an expanded foil or mesh), comprising: - Melt conductive materials, - Apply a liquid, molten conductive material to surround an expanded foil or mesh. - Allows the molten material to harden in order to provide a mechanical and electrical connection between the connection point and the expanded foil or mesh.

[0074] The process of melting materials can be performed by induction heating or resistance heating.

[0075] The step of applying molten bonding material is performed by casting.

[0076] The present invention also relates to a method for setting conductive connection points of a lightning protection system onto a sheet (such as an expansion foil or mesh), the method comprising: - Provides molded conductive materials. - Apply the molded conductive material to the expanded foil or mesh. - Welding molded conductive material to provide mechanical and conductive connection between the connection point and the expanded foil or mesh.

[0077] The present invention also relates to a method for setting conductive connection points of a lightning protection system onto a sheet (such as an expansion foil or mesh), the method comprising: - Provide at least two disks made of conductive material. - Arrange the two discs on opposite sides of the expansion foil or mesh. - Secure the discs together so that the expanded foil or mesh is positioned between the discs to provide a conductive connection between the expanded foil or mesh and the discs.

[0078] Alternatively, the discs can be fastened together using mechanical connections.

[0079] In addition, the two discs can be fastened together by plastic deformation by pressing them together around an expansion foil or mesh.

[0080] In addition, the discs can be fastened together by spot welding.

[0081] In addition, the discs can be fastened together by pulse melting.

[0082] Alternatively, the discs can be fastened together by applying a conductive adhesive between them and holding the discs in place until the adhesive cures. Attached Figure Description

[0083] The invention and its many advantages will now be described in more detail with reference to the accompanying illustrative drawings, which, for illustrative purposes, show some non-limiting embodiments, and in which: Figure 1 A wind turbine with three wind turbine blades is shown. Figure 2 A cross-sectional view through the wind turbine blades is shown. Figures 3 to 6 The diagram schematically illustrates the areas struck by lightning and wind turbine blades. Figure 7 The lightning protection system according to the present invention is illustrated schematically. Figure 8 Another lightning protection system according to the present invention is shown. Figures 9 to 12 Different shapes of conductive connection points are shown. Figures 13 to 14 The top connecting block arranged between the sheets is shown. Figures 15 to 16 An embodiment of the top connecting block is shown. Figures 17 to 18 Different embodiments of the intermediate connecting block are shown. Figure 19 An intermediate connecting block is shown, which connects to the sheet and the connecting patch. Figures 20 to 21 Different embodiments of the root connector block are shown. Figures 22 to 25 An embodiment of the top unit is shown. Figures 26 to 29 Different embodiments of the side receiver are shown. Figure 30 Another embodiment of the top unit is shown. Figures 31 to 33 The connection between the patch and the conductive connection point is shown, and Figure 34 Another embodiment of the connecting patch is shown. Detailed Implementation

[0084] All accompanying drawings are highly schematic and not necessarily drawn to scale, and they only show those parts necessary to illustrate the invention; other parts are omitted or are only suggested.

[0085] Figure 1 A wind turbine 100 is shown, which has a tower 107, a nacelle 108, and three wind turbine blades 101. Each wind turbine blade 101 has a tip 103 and a root end 102 connected to a hub 109. The wind turbine blade 101 has a longitudinal axis 106 extending from the root end 102 to the tip 103.

[0086] Figure 2 A cross-sectional view of a wind turbine blade 101 is shown. The wind turbine blade 101 has a pressure side 111 and a suction side 110, which are the outer surfaces of the wind turbine blade 101. The wind turbine blade 101 also has a leading edge 104 and a trailing edge 105. The wind turbine blade 101 has a structural element 112 extending along a longitudinal axis, which is a rod or beam made of conductive carbon fiber reinforced polymer (CFRP). The CFRP rod or beam enhances the strength of the wind turbine blade 101. This embodiment shows the structural element 112 arranged within the shell of the wind turbine blade 101. The CFRP element can be connected via a mesh, for example, a sandwich structure made of GFRP and a core material (PVC foam or balsa wood).

[0087] The present invention relates in particular to enhancing lightning protection for wind turbine blades 101 having structural elements made of CFRP and thus conductive.

[0088] Over the years, field inspections have consistently demonstrated how the blade tip is the most exposed part of a wind turbine; see [link to relevant documentation]. Figure 3 This validated the numerical model describing the lightning attachment process. The results have led to the development of a zoning concept for wind turbine blades, which describes which parts of the blade are most exposed and to what magnitude of lightning current.

[0089] Numerical simulations were performed on conventional blades ranging from 40 m to 80 m in length to investigate the distribution of lightning strikes attached to the turbine under different current amplitudes. The results clearly show that for downward-initiated lightning strikes, most of all lightning strikes attach to the blade tip, and for lower amplitude lightning strikes, the attachment point can move inward on the blade and attach to other parts of the wind turbine and less exposed parts (hub, nacelle, tower, etc.).

[0090] The concept of zoning can be used to describe the possible lightning strike amplitudes for different areas on a blade. In some interpretations of the LPL1 requirement in the IEC 61400-24 standard, all lightning strikes with amplitudes between, for example, 3kA and 200kA must be safely intercepted and directed towards the ground, while damage from lightning strikes outside these extreme values ​​is permissible. In practice, this means that since lightning strikes may occur on the inner sections of the blade (although the probability is very low), the blade must be able to withstand these strikes to avoid unexpected operational stoppages. In practice, the amplitude distribution follows a normal distribution, meaning that "small" currents can seep inwards, and lightning protection systems are designed to handle this.

[0091] Furthermore, if we consider the probability of the blade being struck by such a small-amplitude lightning strike by taking into account the probability density function described in the lightning protection standard, we can conclude that protection against such low-amplitude lightning strikes is unnecessary because these strikes occur very infrequently.

[0092] Lightning protection system design should focus more on protecting the more exposed parts of the blades by ensuring the intended air termination at the top region.

[0093] like Figure 3 , Figure 5 and Figure 6 As shown, over 75% of the damage occurs within the first few meters of the tip, making protection of these areas of the blades crucial. Even though lightning strikes occurring 10 meters from the tip are relatively rare, CFRP rods or beams are typically arranged along the longitudinal axis from that point. Therefore, ensuring adequate lightning protection for CFRP rods or beams remains extremely important.

[0094] Figure 7 The lightning protection system 1 according to the present invention is schematically shown. The lightning protection system 1 includes a first down conductor 2 extending from a top end 103 to a top connecting block 3 disposed at a predetermined distance from the top end, and the first down conductor 2 is electrically connected to the top connecting block 3.

[0095] Furthermore, the second lead conductor 4 extends from the top connecting block 3 between the structural element 112 and the pressure side and along the structural element and the pressure side toward the root connecting block 5 arranged at the root end 102.

[0096] In addition, the third lead conductor ( Figure 7 (Not shown) The top connecting block extends between the structural element and the suction side and along the structural element and the suction side toward the root connecting block.

[0097] The second down conductor includes a first sheet, and the third down conductor includes a second sheet, the first sheet and the second sheet being made of conductive material for use as down conductors.

[0098] The first sheet and the second sheet include a plurality of conductive connection points 6, which are arranged near the top connecting block 3 and the root connecting block 5, and are electrically connected to the top connecting block and the root connecting block, respectively.

[0099] Thus, the top connecting block 3 serves as an interface between the first down conductor 2 from the top of the wind turbine blade 101 and the first and second sheets in each blade housing, which serve as down conductors from the tip portion of the CFRP rod or beam. Additionally, bonding or equipotentialization between the pressure-side down conductor (i.e., the first sheet) and the suction-side down conductor (i.e., the second sheet) is performed within a single unit. Simultaneously, the second and third down conductors act as receiver bases for lightning strikes attached to the top of the sheets. This section is carefully designed to handle the full lightning current and avoid interception failures due to its insulating casting.

[0100] Figure 8 An embodiment of a lightning protection system 1 according to the present invention is shown. The lightning protection system 1 includes a first down conductor 2 extending from a top end 103 to a top connecting block 3, the top connecting block being arranged at a predetermined distance from the top end, and the first down conductor 2 being electrically connected to the top connecting block 3.

[0101] The second lead conductor 4 is connected from the top connecting block 3 in the structural element ( Figure 8 (Not shown) The third lead conductor 7 extends from the top connecting block 3 between the structural element and the suction side and along the structural element and the suction side toward the root connecting block 102.

[0102] The second down conductor 4 includes a first sheet 4, and the third down conductor 7 includes a second sheet 7, wherein the first sheet 4 and the second sheet 7 are made of conductive material to serve as down conductors.

[0103] like Figure 8 As shown, the first sheet 4 and the second sheet 7 include a plurality of conductive connection points 6, which are arranged near the top connecting block 3 and the root connecting block 5 and are electrically connected to the top connecting block 3 and the root connecting block 5, respectively.

[0104] In this embodiment, two conductive connection points 6 are arranged to electrically connect the first sheet 4 to the top connecting block 3, and two conductive connection points 6 are arranged to electrically connect the second sheet 7 to the top connecting block 3. In other embodiments, only one conductive connection point connects the first sheet to the top connecting block, and one conductive connection point connects the second sheet to the top connecting block. Alternatively, multiple connection points can connect the first sheet to the top connecting block, and multiple connection points can connect the second sheet to the top connecting block. Advantageously, the number of conductive connection points connecting the first sheet to the top connecting block is the same as the number of connection points connecting the second sheet to the top connecting block. This also applies to the root connecting block.

[0105] like Figure 8 As shown, the first sheet 4 and the second sheet 7 are arranged symmetrically on opposite sides about the structural element, and their dimensions are substantially equal. Therefore, due to the Faraday cage geometry, the CFRP structural element is protected, and the risks of high current density in the CFRP structural element, as well as high voltage differences between the parts of the CFRP structural element and the risk of internal flashover, are avoided.

[0106] The conductive connection point is preferably made of metal or other conductive materials or combinations thereof. The metal may be tin, aluminum, copper, brass, silver, gold or any alloy thereof.

[0107] Furthermore, the conductive connection point may include a first layer and a second layer. The first layer may be made of a first material, and the second layer may be made of a second material. The first material may be different from the second material.

[0108] Figure 9 An embodiment of the conductive connection point 6 is shown. Each connection point 6 may have a geometry that presents an outer closed curve 8, the minimum radius of curvature of which is between 3 mm and 200 mm, preferably between 5 mm and 100 mm.

[0109] Additionally, connection point 6 has a semi-major axis 9 and a semi-minor axis 10, such as Figure 9 As shown. When the lengths of the semi-major axis 9 and the semi-minor axis 10 are equal, a circular outer periphery is provided for the conductive connection point, such as... Figure 9 As shown.

[0110] When the semi-major axis 9 and the semi-minor axis 10 are different, an oval or elliptical outer periphery is provided for the conductive connection point 6, such as Figure 10 As shown. Additionally, the semi-major axis 9 can be oriented at a predetermined angle α about the longitudinal axis 106 of the wind turbine blade. The predetermined angle α can be between 0 degrees and 90 degrees.

[0111] Therefore, connection point 6 can be partially or completely circular or elliptical.

[0112] In addition, the connection points can have asymmetrical shapes.

[0113] Furthermore, the outer perimeter 11 of connection point 6 can be defined by curves and straight lines, such as... Figure 11 As shown.

[0114] Currently, it is preferred that connection point 6 has no sharp corners.

[0115] like Figure 12 As can be seen, the connection point 6 can have a thickness t, which is greater than 0.5 mm, preferably greater than 1.0 mm. The thickness t of the connection point 6 can extend in two directions relative to the thickness of the sheet.

[0116] The first sheet 4 and the second sheet 7 are made of a conductive material. The conductive material can be a metal, such as aluminum, copper, steel, or an associated alloy.

[0117] In other embodiments, the conductive material is non-metallic, such as a composite material or fiber.

[0118] To minimize the weight of the first and second sheets, the first and second sheets can be configured as expanded foil or mesh.

[0119] The first expansion foil or the first mesh may be arranged such that it at least completely covers the first side of the structural element facing the pressure side, and the second expansion foil or the second mesh may be arranged such that it at least completely covers the second side of the structural element facing the suction side.

[0120] In addition, the lengths of the first expansion foil or the first mesh and the second expansion foil or the second mesh can be equal to or longer than the length of the structural element.

[0121] Furthermore, the first expanding foil or the first mesh may have a first area, and the second expanding foil or the second mesh may have a second area, the first area and the second area being substantially equal.

[0122] In addition, expanded foil can be made into a single piece.

[0123] The mesh can be provided by braiding conductive wires.

[0124] In another embodiment, the mesh can be provided by non-braided conductive wire.

[0125] The conductive connection point 6 can be set onto the sheet, such as an expanded foil or a mesh, in the following ways.

[0126] - Melt conductive materials, - Apply a liquid, molten conductive material to surround an expanded foil or mesh. - Allows the molten material to harden in order to provide a mechanical and conductive connection between the conductive connection point and the expanded foil or mesh.

[0127] The melting of materials can be performed by induction heating or resistance heating.

[0128] Molten bonding material can be applied by pouring it into a mold arranged in connection with an expanded foil or mesh. This mold defines the outer perimeter of the conductive connection point. The conductive material can be a metal, such as tin.

[0129] The conductive connection point 6 can also be attached to a sheet, such as an expanded foil or a mesh, in the following ways: - Provides molded conductive materials. - Apply the molded conductive material to the expanded foil or mesh. - Welding molded conductive material to provide mechanical and conductive connection between the connection point and the expanded foil or mesh.

[0130] Additionally, conductive connection point 6 can be attached to the sheet, such as expanded foil or mesh, in the following ways: - Provide at least two disks made of conductive material. - Arrange the two discs on opposite sides of the expansion foil or mesh; - Secure the discs together so that the expanded foil or mesh is positioned between the discs to provide a conductive connection between the expanded foil or mesh and the discs.

[0131] The discs can be fastened together by mechanical connection.

[0132] In another embodiment, the two discs can be secured to each other by pressing them together around an expanded foil or mesh through plastic deformation.

[0133] In addition, the discs can be fastened together by spot welding or brazing.

[0134] In addition, the discs can be fastened together by pulse melting.

[0135] Alternatively, the discs can be secured to each other by applying a conductive adhesive between them and holding the discs in place until the adhesive cures.

[0136] Figure 13 and Figure 14An embodiment is shown where a top connecting block 3 is connected to the first sheet 4 and the second sheet 7. Conductive connection points 6 are respectively arranged at predetermined positions on the first sheet 4 and the second sheet, and the top connecting block 3 is arranged such that the conductive connection points 6 can be electrically connected to the top connecting block 3. In this embodiment, a connecting bolt 16 has been screwed into the top connecting block 3 through the conductive connection points 6. This provides an electrical connection between the first down conductor 2 and the first sheet 4 (i.e., the second down conductor) and the second sheet 7 (i.e., the third down conductor), such that lightning current from a lightning strike can be guided from the first down conductor 2 through the top connecting block 3 and via the conductive connection points 6 into the first sheet 4 and the second sheet 7, and thus downward toward the root of the wind turbine blade.

[0137] The top connecting block 3 includes at least one first receiver base 49 and at least one second receiver base 50. The first receiver base 49 is configured to connect the conductive connection point 6 of the first sheet 4 to the top connecting block 3, and the second receiver base 50 is configured to connect the connection point 6 of the second sheet 7 to the top connecting block 3. Figure 13 and 14 In the embodiment shown, the top connecting block 3 has two first receiver bases 49 and two second receiver bases 50.

[0138] As mentioned above, the connecting bolt 16 or the receiver bolt passes through the connection point 6 and is screwed into the base 49, 50 of the block receiver. Therefore, in this embodiment, the connection point is directly connected to the connecting block.

[0139] The top connecting block may include at least a first pair of block receiver bases and at least a second pair of block receiver bases, the first pair of block receiver bases being configured to connect the connection point of the first expansion foil to the top connecting block, and the second pair of block receiver bases being configured to connect the connection point of the second expansion foil to the top connecting block.

[0140] An equal number of block receiver bases can be arranged for connecting the first sheet and the second sheet to the top connecting block.

[0141] Figure 15 and Figure 16 Another embodiment of the top connecting block 3 is shown. In this embodiment, the top connecting block 3 is designed with a first portion 17 and a second portion 18 connected via a middle portion 51. The first portion 17 is larger than the second portion 18, allowing the top connecting block to be arranged within the wind turbine blade, with the first portion 17 positioned closer to the leading edge than the second portion 18. Both the first portion 17 and the second portion 18 include a first receiver base 49 on one side and a second receiver base 50 on the opposite side.

[0142] Figure 16It shows Figure 15 A cross-sectional view of the top connecting block 3. The top connecting block 3 has a conductive core 19 that extends from the first portion 17 via the intermediate portion 51 to the second portion 18, such that all portions are electrically connected. The entire core 19 is covered by an insulating layer 20. In this embodiment, the first down conductor 2 is connected to the core of the second portion 18. Importantly, a connecting bolt is screwed into the conductive core of the top connecting block 3 through the conductive connection point to provide electrical connection. The conductive material of the core 19 can be a metal, such as aluminum or brass.

[0143] The design and shape of the top connector 3 can vary depending on the different wind turbine blade designs and its intended location within the blade. However, the top connector is constructed to prevent interception faults by ensuring sufficient insulation class. Furthermore, the top connector is constructed to adequately withstand lightning current.

[0144] Before screwing the connecting bolts or receiver bolts through the conductive connection point, create threads in the conductive connection point.

[0145] Furthermore, if a side receiver opposite to the first and second sheets is required for the lightning protection system, the receiver bolt terminates at the connection point, and the side receiver can be connected to the connection point.

[0146] Back Figure 8 The lightning protection system 1 also includes a top unit 25 and a plurality of side receivers 30 disposed between the top end 103 and the top connecting block 3. The top unit 25 and the side receivers 30 are connected via a first down conductor 2. The following will combine... Figures 22 to 23 An embodiment of the top unit is described further.

[0147] Compared to the space at the root tip, the space between the blade shell sections at the tip is quite limited. Therefore, the root connector is typically arranged at a greater distance from the first sheet 4 and the second sheet 7. In the lightning protection system 1, two intermediate connectors 13 are arranged to electrically connect the conductive connection points of the first sheet 4 and the second sheet 7, respectively. Each intermediate connector 13 has cables 14, 15 that electrically connect the intermediate connector to the root connector 5. The root connector 5 is electrically connected to a single root down conductor 24, which is electrically connected to the ground via the wind turbine nacelle and tower (not shown).

[0148] Additionally, the first sheet 4 and the second sheet 7 may have intermediate conductive connection points 12 arranged opposite to the structural elements. The intermediate conductive connection point closest to the top may be arranged at a predetermined distance from the top connecting block 3. The predetermined distance is less than 1500 mm, preferably between 1500 mm and 500 mm, more preferably between 500 mm and 100 mm, and most preferably between 100 mm and 10 mm.

[0149] Because the structural elements of the blades are made of CFRP, direct coupling or induced lightning current from lightning strikes will be guided through the structural elements. By arranging the first sheet 4 and the second sheet 7 outside and opposite the extension of the CFRP rod or beam, most of the lightning current will be guided through the first and second sheets, minimizing the magnitude of the lightning current in the CFRP beam or rod. Residual current that will still flow in the CFRP beam or rod must be controlled to equalize the potential difference in the material and prevent accidental electrical flashover between CFRP beams or rods.

[0150] Therefore, the intermediate connection point 12 is electrically connected to the structural element when necessary, so that a certain current is guided from the first and second sheets in the CFRP structural element, thereby equalizing the potential difference in the materials and preventing damaging current and energy from being applied to the CFRP structural element. Thus, the lightning protection system 1 according to the invention will maintain the function of the CFRP structural element.

[0151] At the root ends of the first sheet 4 and the second sheet 7, an intermediate conductive connection point 12 is arranged to be electrically connected to the structural element when needed, so as to ensure that the current flowing in the structural element is led out through the first sheet 4 and the second sheet 7 via the intermediate conductive connection point 12 and reaches the root connection block 5 from there.

[0152] Figure 17 An embodiment of the intermediate connecting block is shown. The intermediate connecting block 13 functions in the same manner as the top connecting block as described above.

[0153] However, as mentioned above, the first intermediate connecting block is arranged between the first sheet 4 and the root connecting block, and the first intermediate connecting block electrically connects the first sheet and the root connecting block, and the second intermediate connecting block is arranged between the second sheet and the root connecting block, and the second intermediate connecting block electrically connects the second expanded metal foil to the root connecting block.

[0154] Each intermediate connecting block 13 includes at least one receiver base 49 configured to connect a conductive connection point of the sheet to the intermediate connecting block. Figure 17 In the illustrated embodiment, the intermediate connecting block 13 has two receiver bases 49. Connecting bolts or receiver bolts are screwed into the receiver bases 49 of the intermediate connecting block 13 through conductive connection points, similar to those of the top connecting block. A first cable 14 is arranged between the first intermediate connecting block 13 and the root connecting block, and a second cable is arranged between the second intermediate connecting block and the root connecting block.

[0155] Figure 18 Another embodiment of the intermediate connecting block is shown in the figure. This intermediate connecting block is related to... Figure 17The intermediate connection blocks shown are very similar; however, intermediate connection block 13 includes an intermediate cable 21 electrically connected to the CFRP structural element, such as... Figure 19 As shown.

[0156] like Figure 19 As can be seen, the connecting patch 22 is electrically connected to the CFRP structural element 112. The connecting patch 22 has a cable connector 23, which is again connected to the intermediate cable 21, which in turn connects to the intermediate connecting block 13. Therefore, the current flowing in the CFRP structural element 112 can be advantageously diverted to the intermediate connecting block 13. The intermediate connecting block 13 can be connected to the second sheet 7 via the conductive connection point 6 in the same manner as described above.

[0157] Figure 20 An embodiment of the root connector 5 is shown. The root connector operates in the same manner as described above, and the lightning current from the first cable 14 and the second cable 15 is connected in the root connector 5 and led into a single root down conductor 24.

[0158] Figure 21 Another embodiment of the root connecting block 5 is shown. In this embodiment, the root connecting block 5 is Y-shaped, however, it is connected with... Figure 20 The same method described works. By using the Y-shaped root connector 5, the weight of the connector is significantly minimized.

[0159] As mentioned earlier, the structural elements are conductive and can be manufactured from pultruded components. Pultruded components are made using pre-impregnated glass fiber sheets in a dry fabric lamination and vacuum-assisted resin infusion process.

[0160] For example, structural components can be manufactured in the following ways: - Assemble and stack several conductive pultruded profiles, pour in and heat them into complete structural components; - Dry the fabric layers, then perform a vacuum-assisted resin infusion process and heating; or - Stack pre-impregnated fiber sheets, then vacuum and heat them.

[0161] Figure 22 A top unit 25 is shown disposed at the tip of a wind turbine blade 101. Preferably, the top unit 25 is attached to the wind turbine blade 101 by means of a suitable adhesive, such as a two-component epoxy adhesive, a fast-curing polyurethane adhesive, a two-component polyurethane adhesive, a two-component curing acrylate adhesive, or other polymer adhesive.

[0162] The top unit 25 is arranged such that its longitudinal axis is at least substantially parallel to the longitudinal axis of the wind turbine blade 101, such that the outer portion 27 of the top 26 forms the top tip of the wind turbine blade 101, and the insulated cable 28 forms the outermost portion of the first down conductor extending along the longitudinal axis of the wind turbine blade 101 in the direction of the top connecting block.

[0163] The top unit 25 includes four conductive elements: an outer portion 27 and an inner portion 32 of the top 26, which are electrically and mechanically connected to the side receiver base 31 via an inner top unit conductor. The inner top unit conductor is connected to the side receiver base 31 by means of a connecting element integrated therein. The insulated cable 28, forming the outermost portion of the first down conductor of the lightning protection system, is connected to the side receiver base 31 by means of the same connecting element. Therefore, all conductive portions 32, 31, and 28 of the top unit 25 are electrically and mechanically connected to each other.

[0164] Figure 23 The arrangement of the insulating material 29 around the top unit 25 is shown. Therefore, except for the portion of the insulated cable 28 forming inwards from the top unit 25 toward the down conductor of the top connecting block and the end portion of the inner portion 32 of the top 26, all conductive portions of the top unit 25 are completely covered by the electrical insulating material 29 (such as polymer nanocomposite materials, thermoplastic materials, thermosetting insulating foam, or any combination thereof). The thickness, geometry, and material properties of this insulating material 29 are designed to withstand environmental conditions (vibration, temperature, temperature cycling, humidity, etc.) and electric fields during lightning exposure and normal operation of the wind turbine blades.

[0165] Therefore, there are only two ways in which a lightning strike can reach the internal portion of the top unit 25 and thus the portion through which the single downconductor extends into the wind turbine blade 101. One way is through a top receiver of the lightning protection system formed by the outer portion 27 of the top 26, which is mechanically and electrically connected to the internal portion 32 of the top 26 via its end portion not covered by the electrical insulation material 29. The other way is through a side receiver 30, which is arranged on the outer surface of the shell or flush with the shell surface of the wind turbine blade 101 and is not part of the top unit 25 itself. The side receiver 30 is mechanically and electrically connected to the side receiver base 31 by penetrating the outer surface of the wind turbine blade 101 and covering the side receiver base 31 with the electrical insulation material 29. The fact that a lightning strike can only reach the internal lightning protection system through the top receiver and the side receiver 30 arranged on the outer surface of the wind turbine blade 101 means that no lightning strike penetrates the structural components of that portion of the wind turbine blade 101. As a result, the risk of damage or even destruction of the structural components at the top of the wind turbine blade 101 is eliminated or at least significantly reduced.

[0166] At the end of the cylindrical portion of the top unit 25 surrounding the base 31 of the side receiver, the insulating material 29 forms a recess in its surface for placing the adhesive material.

[0167] Figure 24 and Figure 25 They are Figure 23 The side view and cross-sectional view of the top unit 25 are shown.

[0168] Figure 26 A side receiver 30 is schematically shown. The side receiver 30 is mounted within, preferably aligned with, the outer surface of the wind turbine blade, and is mechanically and electrically connected to a side receiver base disposed within the wind turbine blade and covered by an insulator. In an embodiment not shown, the side receiver 30 may be formed as a bolt, and the connection to the side receiver base simply includes a threaded connection.

[0169] Figure 26 and Figure 27a These are perspective and cross-sectional views of a receiver assembly in the form of a side receiver 30 installed within the outer surface of a wind turbine blade. The receiver cylinder 33 constitutes the conductive portion of the side receiver 30. The upper circular end of the receiver cylinder forms the outer portion of the side receiver 30, which is substantially aligned with the surface of the wind turbine blade when the side receiver 30 is installed in the wind turbine blade. This is the portion struck by lightning.

[0170] The opposite ends of the receiver cylinder 33 form a contact surface 34 through which the lightning current enters from the side receiver 30 and connects to the side receiver base 31. The receiver cylinder 33 is mechanically connected to the side receiver base 31 by means of a mounting bolt 35, the head of which is hidden inside the receiver cylinder 33, and the threaded portion of the mounting bolt 35 protrudes through a central hole in the contact surface 34 of the receiver cylinder 33.

[0171] In the embodiments shown in these figures, the contact surface 34 is planar and perpendicular to the longitudinal axis of the receiver cylinder 33. In other embodiments, the contact surface 34, or at least a portion thereof, may be inclined.

[0172] Figure 27a The diagram shows how insulator 29 covers the side receiver base 31 and the side receiver 30 connected to the side receiver base. This is crucial to ensure that a lightning strike actually passes through the side receiver 30 and does not bypass the side receiver by penetrating the shell of the wind turbine blade near the side receiver 30 through its path leading to the side receiver base 31 and the interior of the wind turbine blade.

[0173] A washer can be placed between the head of the mounting bolt 35 and the inner surface of the receiver tube 33 to secure the mounting bolt 35.

[0174] In the illustrated embodiment, the side receiver 30 includes an optional blade surface protector 36, which is in the form of a circular sheet of heat-resistant material arranged around the receiver cylinder 33 to protect the outer surface of the wind turbine blade from damage caused by excessive heat energy after a lightning strike to the side receiver 30. Advantageously, the blade surface protector 36 is adhered to the surface of the wind turbine blade during the installation of the side receiver 30 in the wind turbine blade.

[0175] The sealant 37 ensures a tight bond between the side receiver 30 and the outer surface surrounding the wind turbine blade.

[0176] The open end of the receiver tube 33 is sealed by a receiver plug 38, which may be made of a solid conductive or insulating material, or of a heat-resistant paste. The receiver plug 38 covers and protects the head of the mounting bolt 35 from damage caused by lightning strikes. A nut 39 protects the slot of the mounting bolt 35, for example, preventing the entry of slurry if the receiver plug 38 is made of slurry.

[0177] Furthermore, this embodiment of the side receiver 30 includes a bolt insulator 40 arranged around the head of the mounting bolt 35 to ensure electrical insulation between the mounting bolt 35 and the receiver cylinder 33, such that lightning current is forced through the contact surface 34 rather than through the threads of the mounting bolt 35 on its path from the side receiver 30 to the side receiver base 31.

[0178] Figure 27b Another embodiment of the side receiver 30 is shown. The design of this side receiver 30 is basically as follows: Figure 27a As shown and as described above. Figure 27b In the illustrated embodiment, the receiver tube 33 is surrounded by an isolation member 60. The isolation member 60 is made of an insulating material and also ensures electrical isolation in addition to the seal 40.

[0179] Figure 28 This is an enlarged cross-sectional view of the side receiver 30 in the previous two attached figures, while Figure 29 This is a cross-sectional view of a receiver assembly in the form of a side receiver 30 according to another embodiment.

[0180] and Figure 28 One difference in the illustrated embodiment is that, Figure 29 In the illustrated embodiment, the receiver tube 33 is provided with a receiver flange extending outward from the upper circular end of the receiver tube 33. This receiver flange can be used to ensure a tight and weather-resistant connection between the side receiver 30 and the surrounding outer surface of the wind turbine blade, and to provide additional material for the arc root erosion of the side receiver 30 and the resulting natural wear.

[0181] Furthermore, the edge of the receiver tube 33 is beveled, such that at least a portion of the contact surface 34 is beveled. This increases the area of ​​the contact surface 34 and thereby improves the electrical connection with the side receiver base 31. In addition, it ensures better mechanical connection stability between the side receiver 30 and the side receiver base 31.

[0182] Figure 30 This is a cross-sectional view of the receiver component in the form of a top receiver component.

[0183] In this embodiment of the invention, the top receiver 27 is mounted to the top receiver base 41 by means of two threaded rods 42. These threaded rods 42 are screwed into threaded holes within the top receiver base 41, and conductive bushings 61 are arranged around each of the threaded rods 42. The free ends of the threaded rods 42 are inserted into holes in the surface of the top receiver 27 facing the top receiver base 41, and nuts are mounted and tightened around these ends of the threaded rods 42 within the top receiver 27 through openings in the side of the top receiver 27. In another embodiment, not shown, the top receiver may be mounted by means of a single threaded rod or bolt. Alignment members may be present for aligning the top receiver with the top receiver base.

[0184] This means that the top receiver 27 is in mechanical and electrical contact with one end of the conductive bushing 61, and the top receiver base 41 is in mechanical and electrical contact with the other end of the conductive bushing 61. The figure shows how the top receiver base 41 is covered by an electrically insulating layer 29, through which two openings provide passage for the threaded rod 42 and the surrounding bushing 61 to make electrical and mechanical contact with the top receiver base 41.

[0185] The fact that lightning current tends to travel along the surface of the conductor rather than through the more central part of the conductor means that when the receiver assembly is struck by lightning, the vast majority of the lightning current passes through the conductive bushing 61, and only a negligible portion passes through the threaded rod 42, so the threaded rod will not be damaged. Therefore, the threaded rod 42 and the nut remain intact and can be used normally if the top receiver assembly or its components need to be replaced.

[0186] The opening through its mounting nut can be closed with a receiver plug (not shown), which is made of, for example, heat-resistant paste (such as silicone) or solid material (such as metal, plastic, rubber or glass fiber).

[0187] Figure 31 The diagram shows a connecting patch 22. The connecting patch 22 has a cable connector 23 that is electrically connected to a cable 43. The cable 43 electrically connects the cable connector 23 to a connection point connector 44. The connection point connector 44 connects to a conductive connection point 6 arranged in the first sheet 4. This results in a flexible connection.

[0188] Figure 32 and Figure 33The diagram illustrates how the connector 44 connects to the conductive contact point 6. A first connector pad 45 is arranged on one side of the conductive contact point 6, and a second connector pad 46 is arranged on the opposite side, thereby encapsulating the conductive contact point 6. As described above, the conductive contact point is electrically connected to the first sheet. In this embodiment, the first and second connector pads are connected by connector bolts 47, as shown below. Figure 33 As can be seen in the text.

[0189] Figure 34 The image shows a cable connector 23 connecting patch 22. Cable 43 is connected to the cable connector via bolt head 48. This embodiment helps ensure that cable 43 can overcome any manufacturing tolerances.

[0190] The present invention also relates to a wind turbine blade comprising a root end and a tip end, a longitudinal axis, a pressure side and a suction side, structural elements extending along the longitudinal axis, and a lightning protection system as described above, wherein the pressure side and the suction side are the outer surfaces of the wind turbine blade, and the structural elements are rods or beams made of conductive carbon fiber reinforced polymer (CFRP).

[0191] The present invention also relates to a wind turbine blade comprising a root end and a tip end, a longitudinal axis, a pressure side and a suction side, structural elements extending along the longitudinal axis, and a lightning protection system as described above, wherein the pressure side and the suction side are the outer surfaces of the wind turbine blade, and the structural elements are rods or beams made of glass fiber reinforced polymer (GFRP).

[0192] Although the invention has been described above in conjunction with preferred embodiments, it will be apparent to those skilled in the art that several modifications may be conceived without departing from the invention as defined by the appended claims.

Claims

1. A lightning protection system (1) for a wind turbine blade (101), the wind turbine blade (101) comprising: The root end (102) and the apex (103) and the longitudinal axis (106); Pressure side (110) and suction side (111), the pressure side and the suction side are the outer surfaces of the wind turbine blades; as well as Structural element (112) extending along the longitudinal axis, the structural element being a rod or beam made of fiber-reinforced polymer (FRP), The lightning protection system includes: - A first down conductor (2) extends from the top end (103) to a top connecting block (3), the top connecting block being arranged at a predetermined distance from the top end, the first down conductor (2) being electrically connected to the top connecting block. - Second down conductor (4), the second down conductor extends from the top connecting block (3) between the structural element (112) and the pressure side (110) along the structural element and the pressure side toward the root connecting block (5) arranged at the root end (102), - A third down conductor (7), which extends from the top connecting block (3) between the structural element (112) and the suction side (111) along the structural element and the suction side toward the root connecting block (5). - The second down conductor (4) includes a first expanded foil or a first mesh, and the third down conductor (7) includes a second expanded foil or a second mesh, wherein the first expanded foil or the first mesh and the second expanded foil or the second mesh are made of conductive material. The first expansion foil or first mesh and the second expansion foil or second mesh include a plurality of conductive connection points (6), which are arranged near the top connection block (3) and the root connection block (5) and are electrically connected to the top connection block (3) and the root connection block (5) respectively.

2. The lightning protection system (1) according to claim 1, wherein, The structural element (112) is a rod or beam made of conductive carbon fiber reinforced polymer (CFRP).

3. The lightning protection system (1) according to claim 1 or 2, wherein, The predetermined distance is approximately 5 to 25 meters from the top (103).

4. The lightning protection system (1) according to any one of the preceding claims, wherein, The first expansion foil or first mesh and the second expansion foil or second mesh are arranged symmetrically on opposite sides about the structural element (112) and are substantially equal in size.

5. The lightning protection system (1) according to any one of the preceding claims, wherein: The conductive connection point (6) is made of metal or other conductive materials or a combination thereof; and / or The conductive connection point (6) is directly or indirectly connected to the connecting block (3, 5); and / or Each conductive connection point (6) has a geometry exhibiting an external closed curve (8), the minimum radius of curvature of which is between 3 mm and 200 mm, preferably between 5 mm and 100 mm; and / or The conductive connection point (6) has a semi-major axis (9) and a semi-minor axis (10), wherein the semi-major axis (9) and the semi-minor axis (10) are preferably different, thereby providing an oval or elliptical outer periphery (11); and / or The conductive connection point (6) has a semi-major axis (9) and a semi-minor axis (10), wherein the semi-major axis (9) is oriented at a predetermined angle about the longitudinal axis (106) of the wind turbine blade, wherein the predetermined angle is preferably between 0 degrees and 90 degrees; and / or The conductive connection point (6) has an edge or outer periphery, and the current density at the edge or outer periphery is not greater than 1500 A / mm; and / or The conductive connection point (6) has a thickness greater than 0.5 mm, preferably greater than 1.0 mm, wherein the thickness of the conductive connection point (6) preferably extends in two directions relative to the thickness of the sheet.

6. The lightning protection system (1) according to any one of the preceding claims, wherein, The receiver bolt passes through the conductive connection point (6) and is screwed into the connecting block.

7. The lightning protection system (1) according to any one of the preceding claims, wherein, Multiple intermediate conductive connection points (12) are arranged relative to the structural element (112) at a predetermined intermediate distance from the top connecting block (3), wherein the intermediate conductive connection points (12) are preferably connected to the structural element (112).

8. The lightning protection system (1) according to claim 7, wherein, The predetermined intermediate distance is less than 1500 mm, preferably between 1500 mm and 500 mm, more preferably between 500 mm and 100 mm, and most preferably between 100 mm and 10 mm.

9. The lightning protection system (1) according to any one of the preceding claims, wherein, The conductive materials of the first expanded foil or first mesh and the second expanded foil or second mesh are metals, such as aluminum, copper, steel or associated alloys.

10. The lightning protection system (1) according to any one of the preceding claims, wherein, The first expansion foil or first mesh is arranged such that it at least completely covers the first side of the structural element (112) facing the pressure side (110), and the second expansion foil or second mesh is arranged such that it at least completely covers the second side of the structural element (112) facing the suction side (111). The lengths of the first expansion foil or the first mesh and the second expansion foil or the second mesh are preferably equal to or longer than the length of the structural element (112).

11. The lightning protection system (1) according to any one of the preceding claims, wherein, The top connecting block (3): The first lead conductor (2) is electrically connected to the first expansion foil or the first mesh and the second expansion foil or the second mesh via the conductive connection point (6), and / or It includes at least one first receiver base and at least one second receiver base, the first receiver base being configured to connect the conductive connection point (6) of the first expanded foil or the first mesh to the top connecting block (3), and the second receiver base being configured to connect the conductive connection point (6) of the second expanded foil or the second mesh to the top connecting block (3).

12. The lightning protection system (1) according to any one of the preceding claims, wherein, The root connector (5) is configured to electrically connect the first expansion foil or first mesh and the second expansion foil or second mesh to a single root lead-down conductor (24).

13. A wind turbine blade (101), comprising: The root end (102) and the apex (103) and the longitudinal axis (106). The pressure side (110) and the suction side (111) are the outer surfaces of the wind turbine blades, and Structural element (112) extending along the longitudinal axis (106), said structural element (112) being a rod or beam made of conductive carbon fiber reinforced polymer (CFRP), and Lightning protection system (1) according to any one of the preceding claims.

14. A wind turbine (100) having one or more wind turbine blades (101) having a lightning protection system (1) according to any one of claims 1 to 12.

15. A method for disposing the conductive connection point (6) of the lightning protection system (1) according to any one of claims 1 to 12 on an expansion foil or mesh, comprising the method according to step A) or step B): in, The method according to step A) includes: - Melt conductive materials, - Apply a liquid, molten conductive material around the expanded foil or mesh. - Solidify the molten material to provide a mechanical and conductive connection between the conductive connection point and the expanded foil or mesh; The method according to step B) includes: - Provide at least two disks made of conductive material. - Arrange the two discs on opposite sides of the expanded foil or mesh. - Secure the discs together so that the expanded foil or mesh is sandwiched between the discs to form a conductive connection between the expanded foil or mesh and the discs.

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