Lightning protection system

Abstract

The invention relates to a lightning protection system for a wind turbine blade, the wind turbine blade having a root end and a tip end and a longitudinal axis, a pressure side and a suction side which are the outer surfaces of the wind turbine blade, and a structural element extending along the longitudinal axis, which is a girder or beam made of fiber reinforced polymer (FRP), the lightning protection system comprising: - a first down conductor extending from the tip end to a tip connection block arranged at a predetermined distance from the tip end, the first down conductor being electrically connected to the tip connection block; - a second down conductor extending from the tip connection block along the structural element and the pressure side between the structural element and the pressure side towards the root connection block arranged at the root end; - a third down conductor extending from the tip connection block along the structural element and the suction side between the structural element and the suction side towards the root connection block; The second down conductor comprises a first expanded foil or first mesh, the third down conductor comprises a second expanded foil or second mesh, the first expanded foil or first mesh and the second expanded foil or second mesh are made of a conductive material, and the first expanded foil or first mesh and the second expanded foil or second mesh comprise a plurality of conductive connection points, the conductive connection points being disposed near the tip connection block and the root connection block and electrically connected to the tip connection block and the root connection block, respectively.

Description

Technical Field

[0005] , ,

[0001] The present invention relates to a lightning protection system for a wind turbine blade, the wind turbine blade comprising a root end portion and a tip end portion and a longitudinal axis, a pressure side and a suction side which are outer surfaces of the wind turbine blade, and a structural element extending along the longitudinal axis which is a spar or beam made of a fiber reinforced polymer (FRP).

Background Art

[0002] The most well-known lightning protection system for wind turbine blades comprises one or more down conductors arranged inside and a plurality of lightning receptors arranged on the outer surface of the blade.

[0003] A well-known problem with such a system is that lightning strikes not only fall on the wind turbine blade at the intended location, i.e. the external strike point, the so-called lightning receptor, but can also directly attack the internal conductive part of the lightning protection system through the structure of the blade. Such an event can typically cause structural damage of the strength of the wind turbine blade due to the large amount of energy released in connection with a lightning strike.

[0004] [[ID=​​​​​​​​​​The object of the present invention is to overcome, in whole or in part, the above-mentioned disadvantages and drawbacks of the prior art. More specifically, the object is to provide an improved lightning protection system for wind turbine blades having structural elements that are girders or beams made of fiber-reinforced polymer (FRP). [Means for solving the problem]

[0006] The above objectives, along with many other objectives, advantages, and features that will become apparent from the following description, are achieved by the solution according to the present invention by a lightning protection system for wind turbine blades, wherein the wind turbine blade comprises a root end and a tip end as well as a longitudinal axis, pressure side and intake side which are the outer surfaces of the wind turbine blade, and structural elements extending along the longitudinal axis which are girders or beams made of fiber-reinforced polymer (FRP), and the lightning protection system is - A first down conductor extending from the tip to a tip connection block located at a predetermined distance from the tip, and electrically connected to the tip connection block, - A second down conductor extending from the tip connection block between the structural element and the pressure side, along the structural element and the pressure side, toward the root connection block located at the root end, - A third down conductor extending from the tip connection block towards the root connection block, along the structural element and the suction side, between the tip connection block and the structural element and the suction side, Equipped with, - The second down conductor comprises the first sheet, and the third down conductor comprises the second sheet, and the first and second sheets are made entirely or partially of a conductive material. The first and second sheets are provided with a plurality of conductive connection points, which are located near the tip connection block and the root connection block, and are electrically connected to the tip connector block and the root connector block, respectively.

[0007] Therefore, the tip connection block functions as an interface between the first down conductor extending from the tip of the wind turbine blade and the two sheets within each blade shell, which act as down conductors from the tip of the FRP girder cap. Furthermore, coupling or equipotentialization between the pressure-side down conductor and the suction-side down conductor is performed in a single unit. Simultaneously, the second and third down conductors can act as receptor bases against lightning strikes hitting the tips of the sheets. This component is carefully designed to withstand the full lightning current and avoid interruption failure through its insulating casting.

[0008] Furthermore, the structural elements may be girders or beams made of conductive carbon fiber reinforced polymer (CFRP).

[0009] The predetermined distance may be 5 to 25 meters from the tip of the wind turbine blade, depending on the total length of the wind turbine blade.

[0010] Furthermore, the first expanded foil or first mesh, and the second expanded foil or second mesh, may be arranged symmetrically on both sides of the structural element and may be substantially equal in size.

[0011] Furthermore, the conductive connection points may be made of metal, other conductive materials, or a combination thereof.

[0012] Furthermore, the metal may be tin, aluminum, copper, brass, silver, gold, or any alloy thereof.

[0013] Furthermore, the conductive connection point may comprise a first layer and a second layer.

[0014] The first layer may be made of the first material, and the second layer may be made of the second material. The first material is different from the second material.

[0015] Further, the conductive connection point may be connected directly or indirectly to the connection block.

[0016] In one embodiment, each conductive connection point can have a geometry that presents an outer closed curved portion with a minimum radius of curvature between 3 mm and 200 mm, preferably between 5 mm and 100 mm.

[0017] Furthermore, the conductive connection point can have a major axis and a minor axis.

[0018] The major axis and the minor axis may be equal to provide a circular outer perimeter.

[0019] Furthermore, the major axis and the minor axis may be different to provide an oval or elliptical outer perimeter.

[0020] Furthermore, the major axis may be oriented at a predetermined angle with respect to the longitudinal axis of the wind turbine blade.

[0021] The predetermined angle may be between 0 degrees and 90 degrees.

[0022] Also, the conductive connection point may be partially or completely circular or oval.

[0023] Furthermore, the connection point can have an asymmetric shape.

[0024] Furthermore, the outer perimeter of the conductive connection point may be defined by curves and straight lines.

[0025] Furthermore, the conductive connection point may not have sharp corners.

[0026] Furthermore, the conductive connection point may have a thickness greater than 0.5 mm, preferably greater than 1.0 mm.

[0027] Also, the thickness of the conductive connection point may extend in both directions with respect to the thickness of the sheet.

[0028] Furthermore, the conductive connection points may be mechanically connected to the sheet.

[0029] The conductive connection points may be bonded to the sheet with a conductive adhesive.

[0030] Furthermore, the receptor bolt may be screwed into the connection block, passing through the conductive connection point.

[0031] Furthermore, the screw threads may be provided within the conductive connection point.

[0032] Furthermore, the receptor bolt may be terminated within the conductive connection point.

[0033] Furthermore, the lateral receptor may be connected to a conductive connection point.

[0034] Multiple intermediate conductive connection points may be positioned on the opposite side of the structural element at a predetermined intermediate distance from the tip connection block.

[0035] Furthermore, the intermediate conductive connection point may be connected to a structural element.

[0036] Furthermore, the predetermined intermediate distance may 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.

[0037] Furthermore, conductive connection points may be created by melting the material such that the molten material in a liquid state is connected to the sheet, thereby providing a mechanical and conductive connection between the conductive connection point and the sheet when the material hardens.

[0038] The material may be melted by electric induction heating or electric resistance heating.

[0039] Furthermore, conductive connection points may be created by spraying molten metal onto the sheet that will subsequently be soldered.

[0040] The conductive connection point comprises at least two disks positioned on both sides of the sheet, and the disks can then be mechanically fixed to each other.

[0041] Furthermore, the conductive connection point may comprise at least two disks, which, after being positioned on both sides of the sheet, are compressed against each other around the sheet by plastic deformation.

[0042] Furthermore, the conductive connection point may comprise at least two disks, which are spot-welded to each other after being positioned on both sides of the sheet.

[0043] The conductive connection point may comprise at least two disks, which are pulse-melted together after being placed on both sides of the sheet.

[0044] Furthermore, the conductive connection point comprises at least two disks, which are then bonded together by a conductive adhesive after being placed on both sides of the sheet.

[0045] Furthermore, the conductive connection point has an edge or outer periphery, and the current density at the edge or outer periphery may be 1500 A / mm or less.

[0046] Advantageously, the first and second sheets are expanded foil or mesh.

[0047] The conductive material of the first expanded foil or first mesh and the second expanded foil or second mesh may be a metal such as aluminum, copper, steel, or related alloys.

[0048] Furthermore, the conductive material of the sheet or mesh may be a non-metallic material such as a composite or fiber.

[0049] The first expanded foil or first mesh may be positioned to at least completely cover the first side of the structural element facing the pressure side, and the second expanded foil or second mesh may be positioned to at least completely cover the second side of the structural element facing the suction side.

[0050] Furthermore, the length of the first expanded foil or first mesh and the second expanded foil or second mesh may be greater than or equal to the length of the structural element.

[0051] Furthermore, the first expanded foil or first mesh may have a first area, and the second expanded foil or second mesh may have a second area, and the first area and the second area are substantially equal.

[0052] Expanded foil may be manufactured as a monolithic, unified entity.

[0053] The mesh may also be provided by weaving conductive threads.

[0054] The mesh may also be provided by nonwoven conductive yarn.

[0055] Furthermore, the tip connection block can electrically connect the first down conductor to the first expanded foil or first mesh and the second expanded foil or second mesh, respectively, via conductive connection points.

[0056] Furthermore, the tip connector block may comprise at least one first receptor base and at least one second receptor base, wherein the first receptor base is configured to connect the conductive connection point of the first expanded foil to the tip connector block, and the second receptor base is configured to connect the conductive connection point of the second expanded foil to the tip connector block.

[0057] Furthermore, the receptor bolt may be screwed into the receptor base, passing through the conductive connection point.

[0058] Furthermore, the tip connector block may comprise a first pair of at least one receptor base and a second pair of at least one receptor base, wherein the first pair is configured to connect the conductive connection points of a first expanded foil to the tip connector block, and the second pair is configured to connect the conductive connection points of a second expanded foil to the tip connector block.

[0059] Furthermore, an equal number of receptor bases may be arranged to connect the first expanded foil or first mesh and the second expanded foil or second mesh to the tip connection block.

[0060] Furthermore, the tip connection block may be configured to avoid interruption failure by ensuring that the insulation level is sufficient.

[0061] Furthermore, the root connector block may be configured to electrically connect the first and second expanded foils to a single root pull-down conductor.

[0062] The base connector block may be formed in a Y shape.

[0063] Furthermore, a first intermediate connection block may be placed between the first expanded foil and the root connection block, and the first intermediate connection block electrically connects the first expanded foil to the root connection block. Additionally, a second intermediate connection block may be placed between the second expanded foil and the root connection block, and the second intermediate connection block electrically connects the second expanded foil to the root connection block.

[0064] Each intermediate connection block may comprise at least one first receptor base and at least one second receptor base, the first receptor base configured to connect the connection point of the first expanded foil to the intermediate connection block, and the second receptor base configured to connect the connection point of the second expanded foil to the intermediate connector block.

[0065] Furthermore, each intermediate connection block may include at least one pair of receptor bases, the pair of receptor bases configured to connect the conductive connection points of the expanded foil to the intermediate connection block.

[0066] Furthermore, the receptor bolt may be screwed through the conductive connection point into the receptor base of the intermediate connection block.

[0067] Furthermore, the first cable may be positioned between the first intermediate connection block and the root connection block, and the second cable may be positioned between the second intermediate connection block and the root connection block. The first and second cables function as down conductors.

[0068] Furthermore, the structural elements may be conductive and may be manufactured by pultruded parts. The pultruded parts may be made using pre-impregnated fiberglass sheets in a dry fabric lamination and vacuum-assisted resin injection process.

[0069] Furthermore, structural elements include, for example, - Assembling and stacking several conductive extruded profiles, then injecting and heating them into a complete structural element. - Dry fabric lamination, followed by a vacuum-assisted resin injection process and heating, or - Lamination of pre-impregnated fiber plies, followed by reduced pressure and heating. It may be manufactured by [unspecified method].

[0070] 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 which are the outer surfaces of the wind turbine blade, a structural element extending along the longitudinal axis which is a girder or beam made of conductive carbon fiber reinforced polymer (CFRP), and the lightning protection system described above.

[0071] The present invention also relates to a wind turbine having one or more wind turbine blades including the lightning protection system described above.

[0072] The present invention provides a method for providing conductive connection points for a lightning protection system on a sheet such as expanded foil or mesh, - A step of melting the conductive material, - A step of applying molten conductive material in a liquid state to surround an expanded foil or mesh, - A step of curing the molten material to enable the provision of a mechanical and conductive connection between the connection point and the expanded foil or mesh, Further details regarding methods including those mentioned above.

[0073] The step of melting the material may be carried out by electric induction heating or electric resistance heating.

[0074] The step of applying the molten conductive material is carried out by casting.

[0075] The present invention also provides a method for providing conductive connection points for a lightning protection system on a sheet such as expanded foil or mesh, - A step of preparing a moldable conductive material, - The step of applying the moldable conductive material onto an expanded foil or mesh, - A step of soldering a molded conductive material to provide a mechanical and conductive connection between the connection point and the expanded foil or mesh, Regarding methods including

[0076] The present invention provides a method for providing conductive connection points for a lightning protection system on a sheet such as expanded foil or mesh, - A step of preparing at least two disks made of conductive material, - The steps of placing two discs on either side of the expanded foil or mesh, - A step of fixing the disks together with an expanded foil or mesh between them to provide a conductive connection between the disks, Further details regarding methods including those mentioned above.

[0077] Furthermore, the disks may be secured to each other by mechanical connections.

[0078] Alternatively, the discs may be fixed to each other by compressing them around an expanded foil or mesh due to plastic deformation.

[0079] Furthermore, the discs may be fixed to each other by spot welding.

[0080] Furthermore, the disks may be fixed together by pulsed melting.

[0081] Furthermore, the discs may be fixed together by applying a conductive adhesive between them and holding them in place until the adhesive hardens.

[0082] The present invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings, which illustrate several non-limiting embodiments for illustrative purposes. [Brief explanation of the drawing]

[0083] [Figure 1] This is a diagram showing a wind turbine with three wind turbine blades. [Figure 2] This is a cross-sectional view of a wind turbine blade. [Figure 3]This diagram schematically shows the zones on a wind turbine blade that are affected by lightning strikes and impacts. [Figure 4] This diagram schematically shows the zones on a wind turbine blade that are affected by lightning strikes and impacts. [Figure 5] This diagram schematically shows the zones on a wind turbine blade that are affected by lightning strikes and impacts. [Figure 6] This diagram schematically shows the zones on a wind turbine blade that are affected by lightning strikes and impacts. [Figure 7] This is a schematic diagram illustrating the lightning protection system according to the present invention. [Figure 8] This figure shows another lightning protection system according to the present invention. [Figure 9] This figure shows different shapes of conductive connection points. [Figure 10] This figure shows different shapes of conductive connection points. [Figure 11] This figure shows different shapes of conductive connection points. [Figure 12] This figure shows different shapes of conductive connection points. [Figure 13] This figure shows the end connection blocks placed between the sheets. [Figure 14] This figure shows the end connection blocks placed between the sheets. [Figure 15] This figure shows one embodiment of a tip connection block. [Figure 16] This figure shows one embodiment of a tip connection block. [Figure 17] This figure shows different embodiments of the intermediate connection block. [Figure 18] This figure shows different embodiments of the intermediate connection block. [Figure 19] This diagram shows the intermediate connection blocks connected to the sheet and connection patch. [Figure 20] This figure shows different embodiments of the root connection block. [Figure 21] This figure shows different embodiments of the root connection block. [Figure 22] This figure shows one embodiment of the tip unit. [Figure 23] This figure shows one embodiment of the tip unit. [Figure 24] This figure shows one embodiment of the tip unit. [Figure 25] This figure shows one embodiment of the tip unit. [Figure 26] This figure shows different embodiments of a lateral receptor. [Figure 27] This figure shows different embodiments of a lateral receptor. [Figure 28] This figure shows different embodiments of a lateral receptor. [Figure 29] This figure shows different embodiments of a lateral receptor. [Figure 30] This figure shows another embodiment of the tip unit. [Figure 31] This diagram shows the connection of connection patches to conductive connection points. [Figure 32] This diagram shows the connection of connection patches to conductive connection points. [Figure 33] This diagram shows the connection of connection patches to conductive connection points. [Figure 34] This figure shows another embodiment of the connection patch. [Modes for carrying out the invention]

[0084] All figures are highly schematic and not necessarily to scale, and all figures show only the essential components necessary to clarify the invention; other components are omitted or merely suggested.

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

[0086] Figure 2 shows a cross-sectional view of a wind turbine blade 101. 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 structural elements 112 extending along its longitudinal axis, which are girders or beams made of conductive carbon fiber reinforced polymer (CFRP). The CFRP girders or beams increase the strength of the wind turbine blade 101. This embodiment shows that the structural elements 112 are located within the shell of the wind turbine blade 101. The CFRP elements can be connected via webs made, for example, as a sandwich structure of CFRP and a core material (PVC foam or balsa wood).

[0087] The present invention particularly aims to enhance lightning protection for wind turbine blades 101 having conductive structural elements made of CFRP.

[0088] Over many years, field inspections have consistently shown that the blade tips are the most exposed parts of the wind turbine (see Figure 3), supporting numerical models that explain the lightning strike process. These results have led to the development of zoning concepts for wind turbine blades, which explain which parts of the blade are most exposed and subjected to the amplitude of lightning currents.

[0089] Numerical simulations were conducted to examine the distribution of lightning strikes on turbines at various current amplitudes for typical blades ranging from 40m to 80m in length. The results clearly showed that, in the case of downward-starting lightning strikes, the majority of all lightning strikes fall on the blade tips, and that, in the case of lower-amplitude lightning strikes, the lightning can travel inward along the blade and strike other less exposed parts of the wind turbine (hub, nacelle, tower, etc.).

[0090] The zoning concept can be used to describe the possible strike amplitudes for different regions on a blade. Some interpretations of the LPL1 requirement in the IEC 61400-24 standard state that all strikes with amplitudes between, for example, 3 kA and 200 kA must be safely interrupted and directed to the ground, while damage is acceptable for strikes outside these limits. In practice, this means that since strikes can (albeit with a very low probability) occur on the inner sections of the blade, the blade must be able to withstand such strikes so as to avoid unplanned operational shutdowns. In practice, the amplitude distribution follows a normal distribution, meaning that "small" currents can penetrate inward, and the lightning protection system is designed to address this.

[0091] Furthermore, by considering the probability density function described in the lightning protection standards, it can be concluded that protection for such low-amplitude lightning strikes is unnecessary, as the probability of such small-amplitude lightning striking the blades is extremely rare.

[0092] The design of lightning protection systems should instead focus on protecting the more exposed parts of the blades by ensuring that lightning strikes the intended lightning-receiving areas in the tip region.

[0093] As can be seen in Figures 3, 5, and 6, over 75% of the damage occurs within the first 2 meters from the tip, making these zones of the blades crucial for protection. Although the occurrence of lightning strikes is significantly reduced 10 meters from the tip, CFRP girders or beams are often positioned along the longitudinal axis from this point. Therefore, ensuring adequate lightning protection for CFRP girders or beams remains extremely important.

[0094] A lightning protection system 1 according to the present invention is schematically shown in Figure 7. The lightning protection system 1 includes a first down conductor 2 that extends from the tip portion 103 to a tip connection block 3 located at a predetermined distance from the tip portion, and the first down conductor 2 is electrically connected to the tip connection block 3.

[0095] Furthermore, the second down conductor 4 extends from the tip connection block 3 along the structural element 112 and the pressure side between the structural element 112 and the pressure side toward the root connection block 5 located at the root end 102.

[0096] Furthermore, a third down conductor (not shown in Figure 7) extends from the tip connection block along the structural element and the suction side, between the structural element and the suction side, toward the base connection block.

[0097] The second down conductor comprises the first sheet, and the third down conductor comprises the second sheet, and the first and second sheets are made of a conductive material to function as down conductors.

[0098] The first and second sheets are provided with a plurality of conductive connection points 6, which are located near the tip connection block 3 and the root connection block 5, and are electrically connected to the tip connector block and the root connector block, respectively.

[0099] As a result, the tip connection block 3 functions as an interface between the first down conductor 2 from the tip of the wind turbine blade 101 and the first and second sheets within each blade shell, which act as down conductors from the tip portion of the CFRP girder or beam. Furthermore, coupling 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 in a single unit. Simultaneously, the second and third down conductors act as receptor bases against lightning strikes hitting the tips of the sheets. This component is carefully designed to withstand the full lightning current and avoid interruption failure through its insulating casting.

[0100] Figure 8 shows one embodiment of the lightning protection system 1 according to the present invention. The lightning protection system 1 includes a first down conductor 2 that extends from the tip portion 103 to a tip connection block 3 located at a predetermined distance from the tip portion, and the first down conductor 2 is electrically connected to the tip connection block 3.

[0101] The second down conductor 4 extends from the tip connection block 3 along the structural element and the pressure side between the structural element (not shown in Figure 8) and the pressure side, toward the root connection block 5 located at the root end 102. The third down conductor 7 extends from the tip connection block 3 along the structural element and the suction side between the structural element and the suction side, toward the root connection block 5.

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

[0103] As can be seen in Figure 8, the first sheet 4 and the second sheet 7 are provided with a plurality of conductive connection points 6, which are located near the tip connection block 3 and the base connection block 5, and are electrically connected to the tip connector block 3 and the base connector block 5, respectively.

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

[0105] As shown in Figure 8, the first sheet 4 and the second sheet 7 are arranged symmetrically on both sides of the structural element and are substantially equal in size. As a result, the CFRP structural element is protected due to the Faraday cage-like geometry, and the risk of high-density current in the CFRP structural element, as well as the risk of high voltage differences between components of the CFRP structural element and internal flashover are avoided.

[0106] The conductive connection points are preferably made of metal, other conductive materials, or a combination thereof. The metal may be tin, aluminum, copper, brass, silver, gold, or any alloy thereof.

[0107] Furthermore, the conductive connection point may comprise 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 shows one embodiment of a conductive connection point 6. Each connection point 6 may have a geometry that shows an outer closed curved portion 8 with a minimum radius of curvature between 3 mm and 200 mm, preferably between 5 mm and 100 mm.

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

[0110] If the semi-major axis 9 and semi-minor axis 10 are different, an oval or elliptical outer circumference of the conductive connection point 6 is provided, as shown in Figure 10. Furthermore, the semi-major axis 9 may be oriented at a predetermined angle α with respect to the longitudinal axis 106 of the wind turbine blade. The predetermined angle α may be between 0 and 90 degrees.

[0111] Therefore, connection point 6 may be partially or completely circular or oval.

[0112] Furthermore, the connection point can have an asymmetrical shape.

[0113] Furthermore, the outer circumference 11 of the connection point 6 may be defined by curves and straight lines, as shown in Figure 11.

[0114] It is currently preferable that connection point 6 does not have a pointed corner.

[0115] As can be seen in Figure 12, the connection point 6 may 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 may extend in both 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 may be a metal such as aluminum, copper, steel, or related alloys.

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

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

[0119] The first expanded foil or first mesh may be positioned to at least completely cover the first side of the structural element facing the pressure side, and the second expanded foil or second mesh may be positioned to at least completely cover the second side of the structural element facing the suction side.

[0120] Furthermore, the length of the first expanded foil or first mesh and the second expanded foil or second mesh may be greater than or equal to the length of the structural element.

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

[0122] Furthermore, the expanded foil may be manufactured as a monolithic, unified entity.

[0123] The mesh may be provided by weaving conductive threads.

[0124] In another embodiment, the mesh may be provided by nonwoven conductive yarn.

[0125] The conductive connection point 6 is - Melt the conductive material, - Apply the molten conductive material in a liquid state to surround the expanded foil or mesh, - To allow the molten material to harden, thereby providing a mechanical and conductive connection between the conductive connection point and the expanded foil or mesh. Therefore, it may be provided on a sheet such as expanded foil or mesh.

[0126] The material may be melted by electric induction heating or electric resistance heating.

[0127] The molten conductive material may be applied by pouring it into a mold positioned in conjunction with an expanded foil or mesh. The mold defines the outer periphery of the conductive connection point. The conductive material may be a metal such as tin.

[0128] The conductive connection point 6 also, - Prepare a moldable conductive material, - Apply the molded conductive material onto an expanded foil or mesh, - Solder molded conductive material to provide a mechanical and conductive connection between the connection point and the expanded foil or mesh. Therefore, it may be provided on a sheet such as expanded foil or mesh.

[0129] Furthermore, the conductive connection point 6 is - Prepare at least two disks made of conductive material, - Place the two discs on either side of the expanded foil or mesh. - To secure the disks together with an expanded foil or mesh between them, thereby providing a conductive connection between the disks. Therefore, it may be provided on a sheet such as expanded foil or mesh.

[0130] The disks may be secured to each other by mechanical connections.

[0131] In another embodiment, the disks may be fixed to each other by plastic deformation, which compresses the two disks together around the expanded foil or mesh.

[0132] Furthermore, the discs may be fixed to each other by spot welding or soldering.

[0133] Furthermore, the disks may be fixed together by pulsed melting.

[0134] Furthermore, the discs may be fixed together by applying a conductive adhesive between them and holding them in place until the adhesive hardens.

[0135] Figures 13 and 14 show one embodiment of a tip connection block 3 connected to a first sheet 4 and a second sheet 7. Conductive connection points 6 are positioned at predetermined locations on each of the first sheet 4 and the second sheet, and the tip connection block 3 is positioned so that the conductive connection points 6 can be electrically connected to the tip connection block 3. In this embodiment, a connecting bolt 16 is screwed into the tip connection block 3 through the conductive connection points 6. As a result, the first down conductor 2 is electrically connected to the first sheet 4, i.e., the second down conductor, and the second sheet 7, i.e., the third down conductor, so that lightning current from a lightning strike can be guided from the first down conductor 2 through the tip connection block 3, through the conductive connection points 6, to the first sheet 4 and the second sheet 7, and thereby descend toward the root end of the wind turbine blade.

[0136] The tip connector block 3 comprises at least one first block receptor base 49 and at least one second block receptor base 50, wherein the first block receptor base 49 is configured to connect the conductive connection point 6 of the first sheet 4 to the tip connector block 3, and the second block receptor base 50 is configured to connect the connection point 6 of the second sheet 7 to the tip connector block 3. In the embodiments shown in Figures 13 and 14, the tip connector block 3 has two first block receptor bases 49 and two second block receptor bases 50.

[0137] As described above, the connecting bolt 16 or receptor bolt is screwed through the connection point 6 into the block receptor bases 49, 50. Therefore, in this embodiment, the connection point is directly connected to the connecting block.

[0138] The tip connector block may comprise a first pair of at least one block receptor base and a second pair of at least one block receptor base, wherein the first pair is configured to connect the connection point of a first expanded foil to the tip connector block, and the second pair is configured to connect the connection point of a second expanded foil to the tip connector block.

[0139] Equal numbers of block receptor bases may be arranged to connect the first and second sheets to the tip connection block.

[0140] Figures 15 and 16 show another embodiment of the tip connection block 3. In this embodiment, the tip connection block 3 is designed to include a first portion 17 and a second portion 18 connected via an intermediate portion 51. The first portion 17 is larger than the second portion so that the first portion 17 can be positioned closer to the leading edge than the second portion 18, allowing the first portion 17 to be positioned within the wind turbine blade. Both the first portion 17 and the second portion 18 are provided with a first block receptor base 49 on one side and a second block receptor base 50 on the opposite side.

[0141] Figure 16 shows a cross-sectional view of the tip connection block 3 of Figure 15. The tip connection block 3 has a core 19 of conductive material extending from a first portion 17 through an intermediate portion 51 to a second portion 18, so that all parts are electrically connected. The entire core 19 is covered with an insulating layer 20. In this embodiment, the first down conductor 2 is connected to the core of the second portion 18. Furthermore, it is important that connecting bolts are screwed through the conductive connection points into the conductive core of the tip connection block 3 to provide an electrical connection. The conductive material of the core 19 may be a metal such as aluminum or brass.

[0142] The design and shape of the tip connection block 3 may vary due to the various wind turbine blade designs and the position where the tip connection block 3 is located within the blade. However, the tip connection block is configured to avoid interruption failure by ensuring sufficient insulation levels. Furthermore, the tip connection block is configured to adequately transmit lightning current.

[0143] Before a connecting bolt or receptacle bolt is passed through and screwed into the conductive connection point, threads are provided on the conductive connection point.

[0144] Furthermore, if the receptor bolts are terminated within the connection point, and if it is necessary to provide lateral receptors on the opposite side of the first and second sheets in the lightning protection system, the lateral receptors may be connected to the connection point.

[0145] Referring back to Figure 8, the lightning protection system 1 also comprises a tip unit 25 and a plurality of lateral receptors 30 positioned between the tip 103 and the tip connection block 3. The tip unit 25 and the lateral receptors 30 are connected via a first down conductor 2. An embodiment of the tip unit will be further described below in relation to Figures 22 to 23.

[0146] The space between the blade shell components at the tip is considerably more limited compared to the space at the root end. Therefore, the root connection block is often positioned further away from the first sheet 4 and the second sheet 7. In the lightning protection system 1, two intermediate connection blocks 13 are provided to electrically connect the conductive connection points of the first sheet 4 and the second sheet 7, respectively. Each intermediate connection block 13 has cables 14, 15 that electrically connect the intermediate connection block to the root connection block 5. The root connection block 5 is electrically connected to a single root down conductor 24 that is electrically connected to the ground through the wind turbine nacelle and tower (not shown).

[0147] Furthermore, the first sheet 4 and the second sheet 7 may have intermediate conductive connection points 12 located on the opposite side of the structural element. The intermediate conductive connection point closest to the tip may be located at a predetermined distance from the tip connection 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.

[0148] Since the vane's structural elements are made of CFRP, lightning currents directly coupled or induced from lightning strikes will be guided through these structural elements. The magnitude of the lightning current in the CFRP beam or girder is minimized by positioning the first sheet 4 and the second sheet 7 outside and on the opposite side of the CFRP girder or beam so that the majority of the lightning current is conducted through the first and second sheets. Any remaining current that may still flow through the CFRP beam or girder must be controlled to equalize the potential difference in the material and avoid unintentional electrical flashover between the CFRP beam or girder.

[0149] Therefore, the intermediate connection point 12 is electrically connected to the structural element when necessary, and as a result, a specific current is guided from the first and second sheets to the CFRP structural element, thereby equalizing the potential difference in the material, and no harmful current and energy are applied to the CFRP structural element. Thus, the function of the CFRP structural element is maintained by the lightning protection system 1 according to the present invention.

[0150] If necessary, intermediate conductive connection points 12 are positioned at the root ends of the first sheet 4 and the second sheet 7, electrically connected to the structural elements, to ensure that current flowing through the structural elements is guided out of the first sheet 4 and the second sheet 7 via intermediate conductive connection points 12 and then down to the root connection block 5.

[0151] Figure 17 shows one embodiment of an intermediate connection block. The intermediate connection block 13 functions in the same way as the end-connection block described earlier.

[0152] However, as mentioned above, the first intermediate connection block is positioned between the first sheet 4 and the root connection block, electrically connecting the first sheet to the root connection block, and the second intermediate connection block is positioned between the second sheet and the root connection block, electrically connecting the second expanded metal foil to the root connection block.

[0153] Each intermediate connection block 13 comprises at least one receptor base 49 configured to connect the conductive connection points of the sheet to the intermediate connection block. In the embodiment shown in Figure 17, the intermediate connection block 13 has two receptor bases 49. Similar to the end connection block, a connecting bolt or receptor bolt is screwed through the conductive connection point into the receptor base 49 of the intermediate connection block 13. A first cable 14 is positioned between the first intermediate connection block 13 and the root connection block, and a second cable is positioned between the second intermediate connection block and the root connection block.

[0154] Figure 18 shows another embodiment of the intermediate connection block. This intermediate connection block is very similar to the intermediate connection block shown in Figure 17, but intermediate connection block 13 includes an intermediate cable 21 electrically connected to the CFRP structural element, as shown in Figure 19.

[0155] As shown in Figure 19, the connection patch 22 is electrically connected to the CFRP structural element 112. The connection patch 22 also has a cable connector 23 which is connected to the intermediate cable 21, and the intermediate cable 21 is connected to the intermediate connection block 13. As a result, the current flowing through the CFRP structural element 112 can be conveniently guided to the intermediate connection block 13. The intermediate connection block 13 can be connected to the second sheet 7 via the conductive connection point 6 in the same manner as described earlier.

[0156] Figure 20 shows one embodiment of the root connection block 5. The root connection block functions in the same manner as described above, and lightning currents from the first cable 14 and the second cable 15 are interfaced in the root connection block 5 and led into a single root down conductor 24.

[0157] Figure 21 shows another embodiment of the root connection block 5. In this embodiment, the root connection block 5 is formed in a Y shape, but functions in the same manner as described in relation to Figure 20. By having a Y-shaped root connection block 5, the weight of the connection block is considerably minimized.

[0158] As mentioned above, the structural elements are conductive and may be manufactured by pultruded parts. The pultruded parts are made using pre-impregnated glass fiber sheets in a dry fabric lamination and vacuum-assisted resin injection process.

[0159] For example, structural elements are, - Assembling and stacking several conductive extruded profiles, then injecting and heating them into a complete structural element. - Dry fabric lamination, followed by a vacuum-assisted resin injection process and heating, or - Lamination of pre-impregnated fiber plies, followed by reduced pressure and heating. It may be manufactured by [unspecified method].

[0160] Figure 22 shows a tip unit 25 positioned at the tip of the wind turbine blade 101. The tip unit 25 is preferably attached to the wind turbine blade 101 with a suitable adhesive such as a two-component epoxy adhesive, a fast-curing polyurethane adhesive, a two-component polyurethane adhesive, a two-component curing acrylic acid adhesive, or another polymer adhesive.

[0161] The tip unit 25 is positioned with its longitudinal axis at least substantially parallel to the longitudinal axis of the wind turbine blade 101 such that the outer portion 27 of the tip 26 forms the tip of the wind turbine blade 101, and the insulating cable 28 forms the outermost portion of a first down conductor that extends along the longitudinal axis of the wind turbine blade 101 toward the tip connection block.

[0162] The tip unit 25 comprises four conductive elements, namely the outer portion 27 and inner portion 32 of the tip 26, the inner portion 32 being electrically and mechanically connected to the lateral receptor base 31 through the inner tip unit conductor. The inner tip unit conductor is connected to the lateral receptor base 31 by an integrated connecting element. The insulated electrical cable 28, which forms the outermost portion of the first down conductor of the lightning protection system, is connected to the lateral receptor base 31 by the same connecting element. Thus, all conductive portions 32, 31, and 28 of the tip unit 5 are electrically and mechanically connected to one another.

[0163] Figure 23 shows the insulating material 29 arranged around the components of the tip unit 25. Thus, all conductive parts of the tip unit 25 are completely covered by an electrical insulating material 29, such as a polymer nanocomposite, thermoplastic material, thermosetting material, insulating foam, or any combination thereof, except for the portion of the insulated electrical cable 28 that forms a down conductor extending inward from the tip unit 25 toward the tip connection block and the end of the internal portion 32 of the tip 26. The thickness, geometry, and material properties of this insulating material 29 are sized to withstand environmental conditions (vibration, temperature, temperature cycles, humidity, etc.) as well as the electric field during lightning exposure and normal operation of the wind turbine blades.

[0164] Therefore, there are only two ways in which a lightning strike can reach the internal portion of the tip unit 25, and thus the portion of the single down conductor that extends through this portion of the wind turbine blade 101. One is through the tip receptor of the lightning protection system formed by the external portion 27 of the tip 26, the external portion 27 being mechanically and electrically connected through its end to the internal portion 32 of the tip 26, the internal portion 32 not covered by the electrical insulating material 29. The other method is through the lateral receptor 30, which is positioned on the outer surface of the shell or positioned to be coplanar with the shell surface of the wind turbine blade 101, and is not part of the tip unit 25 itself. The lateral receptor 30 is mechanically and electrically connected to the lateral receptor base 31 through the electrical insulating material 29 covering the outer surface of the wind turbine blade 101 and the lateral receptor base 31. The fact that lightning strikes can only reach the internal lightning protection system through the tip receptor and the lateral receptors 30 located on the outer surface of the wind turbine blade 101 means that lightning strikes do not pass through the structural components of this part of the wind turbine blade 101. Therefore, the risk of damage or even destruction of the structural components at the tip of the wind turbine blade 101 is eliminated or at least greatly reduced.

[0165] The insulating material 29 forms recesses on its surface at the ends of the cylindrical parts of the tip unit 25 around the lateral receptor base 31 for the installation of adhesive material.

[0166] Figures 24 and 25 are a side view and a cross-sectional view of the tip unit 25 shown in Figure 23, respectively.

[0167] Figure 26 schematically shows a lateral receptor 30. The lateral receptor 30 is preferably aligned with the outer surface of the wind turbine blade and mounted within the outer surface, and is mechanically and electrically connected to a lateral receptor base located within the wind turbine blade and covered with an insulator. In other embodiments not shown, the lateral receptor 30 may be formed as a bolt, and the connection to the lateral receptor base consists simply of a screw connection.

[0168] Figures 26 and 27a are perspective and cross-sectional views, respectively, of a receptor assembly in the form of a lateral receptor 30 mounted inside the outer surface of a wind turbine blade. The receptor cylinder 33 constitutes the conductive portion of the lateral receptor 30. The upper circular end of the receptor cylinder 33 forms the external portion of the lateral receptor 30 that is substantially aligned with the surface of the wind turbine blade when the lateral receptor 30 is mounted inside. This is the portion that will be struck by lightning strikes.

[0169] The opposite end of the receptor cylinder 33 forms a contact surface 34, and lightning current enters the lateral receptor base 31 to which the lateral receptor 30 is connected, through the contact surface 34 from the lateral receptor 30. The receptor cylinder 33 is mechanically connected to the lateral receptor base 31 by mounting bolts 35, the heads of which are hidden inside the receptor cylinder 33, and the threaded portion of which protrudes through a central hole in the contact surface 34 of the receptor cylinder 33.

[0170] In the embodiments shown in these figures, the contact surface 34 is planar and perpendicular to the longitudinal axis of the receptor cylinder 33. In other embodiments, the contact surface 34 or at least a portion thereof may be oblique.

[0171] Figure 27a shows how the insulator 29 covers the lateral receptor base 31 and the lateral receptor 30 connected thereto. This is crucial to ensure that lightning strikes actually pass through the lateral receptor 30 rather than bypassing it by penetrating the shell of the adjacent wind turbine blade on the path to the lateral receptor base 31 and down conductor inside the wind turbine blade.

[0172] A washer may be placed between the head of the mounting bolt 35 and the inner surface of the receptor cylinder 33 in order to tighten the mounting bolt 35.

[0173] In the shown embodiment, the lateral receptor 30 includes an optional blade surface protector 36 in the form of a circular sheet of heat-resistant material positioned around the receptor cylinder 33 to prevent damage to the outer surface of the wind turbine blade due to excessive thermal energy after a lightning strike impacts the lateral receptor 30. Advantageously, this blade surface protector 36 adheres to the surface of the wind turbine blade during installation of the lateral receptor 30 into the wind turbine blade.

[0174] The sealant 37 ensures a tight connection between the lateral receptor 30 and the outer surface surrounding the wind turbine blade.

[0175] The open end of the receptor cylinder 33 is closed by a receptor plug 38, which may be made from a solid conductive or insulating material, or composed of a heat-resistant paste. The receptor plug 38 covers the head of the mounting bolt 35 to prevent damage from impacting lightning strikes. If the receptor plug 38 is composed of a paste, a screw cap 39 protects the threads of the mounting bolt 35 from, for example, the ingress of such paste.

[0176] Furthermore, this embodiment of the lateral receptor 30 includes a bolt insulator 40 positioned around the head of the mounting bolt 35 to ensure electrical insulation between the mounting bolt 35 and the receptor cylinder 33, so that lightning currents pass through the contact surface 34 rather than through the threads of the mounting bolt 35 on their path from the lateral receptor 30 to the lateral receptor base 31.

[0177] Figure 27b shows another embodiment of the lateral receptor 30. The design of this lateral receptor 30 is substantially the same as that shown and described above in Figure 27a. In the embodiment shown in Figure 27b, the receptor cylinder 33 is surrounded by an insulating member 60. The insulating member 60 is made of an insulating material to ensure electrical insulation in addition to the seal 40.

[0178] Figure 28 is an enlarged cross-sectional view of the lateral receptor 30 in the previous two figures, and Figure 29 is a cross-sectional view of a receptor assembly in the form of a lateral receptor 30 according to another embodiment.

[0179] One difference from the embodiment shown in Figure 28 is that in the embodiment shown in Figure 29, the receptor cylinder 33 is provided with a receptor ruff extending outward from the upper circular end of the receptor cylinder 33. Such a receptor ruff is useful in ensuring a tight and weather-resistant connection between the lateral receptor 30 and the outer surface around the wind turbine blade, and also provides additional material for arc root erosion and thus natural wear of the lateral receptor 30.

[0180] Furthermore, the edges of the receptor cylinder 33 are chamfered so that at least a portion of the contact surface 34 is beveled. This increases the area of ​​the contact surface 34 and thus improves the electrical connection to the lateral receptor base 31. In addition, it ensures better mechanical stability of the connection between the lateral receptor 30 and the lateral receptor base 31.

[0181] Figure 30 is a cross-sectional view of a receptor assembly in the form of a tip receptor assembly.

[0182] In this embodiment of the present invention, the tip receptor 27 is attached to the tip receptor base 41 by two threaded rods 42. These threaded rods 42 are screwed into threaded holes in the tip receptor base 41, and conductive bushings 61 are positioned around each of the threaded rods 42. The free ends of the threaded rods 42 are inserted into holes on the surface of the tip receptor 27 facing the tip receptor base 41, and nuts are fitted and tightened around those ends of the threaded rods 42 inside the tip receptor 27 through openings on the sides of the tip receptor 27. In another embodiment not shown, the tip receptor may be attached by a single threaded rod or bolt. Alignment members may be present to align the tip receptor with the tip receptor base.

[0183] This means that the tip receptor 27 is in mechanical and electrical contact with one end of the conductive bushing 61, and the tip receptor base 41 is in mechanical and electrical contact with the other end of the conductive bushing 61. The figure shows how the tip receptor base 41 is covered by a layer of electrical insulating material 29, and two openings penetrating the layer of electrical insulating material 29 provide means for the threaded rod 42 and the surrounding bushing 61 to make electrical and mechanical contact with the tip receptor base 41.

[0184] The fact that lightning currents tend to travel along the surface of a conductor rather than through the more central part of the conductor means that when a receptor assembly is subjected to a lightning strike, the majority of the lightning current passes through the conductive bushing 61, with only a small portion passing through the threaded rod 42, and therefore the threaded rod 42 remains undamaged. Thus, the threaded rod 42 and nut remain intact and can usually be reused when the need arises to replace the tip receptor assembly or its components.

[0185] The opening through which the nut is attached may be closed using a receptor plug (not shown) made of a heat-resistant paste such as silicone, or made of a solid material such as metal, plastic, rubber, or glass fiber.

[0186] Figure 31 shows a connection patch 22. The connection 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 is connected to a conductive connection point 6 located on the first sheet 4. As a result, a flexible connection is obtained.

[0187] Figures 32 and 33 show how the connection point connector 44 is connected to the conductive connection point 6. The first connector disk 45 is positioned on one side of the conductive connection point 6, and the second connector disk 46 is positioned on the opposite side of the conductive connection point, thus enclosing the conductive connection point 6. The conductive connection point is electrically connected to the first sheet as previously described. In this embodiment, the first and second connector disks are connected by a connector bolt 47, as seen in Figure 33.

[0188] Figure 34 shows the cable connector 23 of the connection patch 22. The cable 43 is connected to the cable connector via a bolt head 48. This embodiment helps ensure that any manufacturing tolerances can be overcome by the cable 43.

[0189] 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 which are the outer surfaces of the wind turbine blade, a structural element extending along the longitudinal axis which is a girder or beam made of conductive carbon fiber reinforced polymer (CFRP), and the lightning protection system described above.

[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 which are the outer surfaces of the wind turbine blade, a component extending along the longitudinal axis which is a girder or beam made of glass fiber reinforced polymer (GFRP), and the lightning protection system described above.

[0191] While the present invention has been described above in relation to preferred embodiments of the present invention, it will be apparent to those skilled in the art that several modifications can be envisioned without departing from the present invention, as defined by the following claims. [Explanation of symbols]

[0192] 1. Lightning protection system 2. First down conductor 3. Tip connection block 4. Second down conductor, first sheet 5. Root connection block 6. Conductive connection points 7. Third down conductor, second sheet 8. Curved section 9 semi-major axis 10 semi-short axis 11 Outer perimeter 12 Intermediate conductive connection points 13 Intermediate connection block 14 Cable, 1st Cable 15 Cable, 2nd Cable 16 connecting bolts 17 Part 1 18. Part 2 19 cores 20 Insulating layer 21 Intermediate Cable 22 Connection Patch 23 Cable Connectors 24 Root-down conductor 25 Tip Unit 26 Tip 27 External parts, tip receptor 28. Insulated cables, insulated electrical cables 29. Insulating materials, insulators 30 Lateral receptors 31 Lateral receptor base 32 Internal part 33 Receptor Cylinder 34 Contact surfaces 35 Mounting bolts 36. Surface protection for the blades 37 Sealant 38 Receptor Plugs 39 Screw cap 40-volt insulator, sealing 41. Advanced Receptor Base 42 threaded rods 43 Cables 44 Connection Point Connectors 45. First connector disk 46. ​​Second connector disk 47 Connector bolts 48 Bolt head 49. First block receptor base 50 Second block receptor base 51 Middle part 60 Insulating material 61 Conductive Bushing 100 Wind Turbines 101 Wind turbine blades 102 Root end 103 Tip 104 Leading edge 105 Trailing edge 106 Long axis 107 Tower 108 Nasser 109 Hub 110 Suction side 111 Pressure side 112 Structural elements

Claims

1. A lightning protection system (1) for a wind turbine blade (101), wherein the wind turbine blade (101) comprises a root end (102) and a tip end (103) and a longitudinal axis (106), a pressure side (110) and a suction side (111) which are the outer surfaces of the wind turbine blade, and a structural element (112) extending along the longitudinal axis, which is a girder or beam made of fiber-reinforced polymer (FRP). The aforementioned lightning protection system A first down conductor (2) extends from the tip portion (103) to a tip connection block (3) located at a predetermined distance from the tip portion, and is electrically connected to the tip connection block. A second down conductor (4) extends from the tip connection block (3) between the structural element (112) and the pressure side (110) and toward the root connection block (5) located at the root end (102), along the structural element (112) and the pressure side (110), A third down conductor (7) extends from the tip connection block (3) towards the base connection block (5) along the structural element (112) and the suction side (111) between the structural element (112) and the suction side (111), Equipped with, The second down conductor (4) comprises a first expanded foil or a first mesh, and the third down conductor (7) comprises a second expanded foil or a second mesh, and the first expanded foil or first mesh and the second expanded foil or second mesh are made of a conductive material. Lightning protection system (1), wherein the first expanded foil or first mesh and the second expanded foil or second mesh are provided with a plurality of conductive connection points (6), the conductive connection points (6) are located near the tip connection block (3) and the root connection block (5), and are electrically connected to the tip 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 girder 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 tip portion (103).

4. A lightning protection system (1) according to any one of claims 1 to 3, wherein the first expanded foil or first mesh and the second expanded foil or second mesh are arranged symmetrically on both sides of the structural element (112) and are substantially equal in size.

5. The lightning protection system (1) according to any one of claims 1 to 4, wherein the conductive connection point (6) is made of a metal or another conductive material, or a combination thereof.

6. The lightning protection system (1) according to any one of claims 1 to 5, wherein the conductive connection point (6) is directly or indirectly connected to the tip connection block (3) and the root connection block (5).

7. A lightning protection system (1) according to any one of claims 1 to 6, wherein each conductive connection point (6) has a geometric shape that provides an outer closed curved portion (8) having a minimum radius of curvature between 3 mm and 200 mm.

8. The lightning protection system (1) according to any one of claims 1 to 7, wherein the conductive connection point (6) has a semi-long axis (9) and a semi-short axis (10).

9. The lightning protection system (1) according to claim 8, wherein the semi-major axis (9) and the semi-minor axis (10) are different, and an oval or elliptical outer circumference (11) is provided.

10. The lightning protection system (1) according to claim 8 or 9, wherein the semi-long axis (9) is directed at a predetermined angle with respect to the longitudinal axis (106) of the wind turbine blade.

11. The lightning protection system (1) according to claim 10, wherein the predetermined angle is between 0 degrees and 90 degrees.

12. The lightning protection system (1) according to any one of claims 1 to 11, wherein the conductive connection point (6) has an edge or outer circumference, and the current density at the edge or outer circumference is 1500 A / mm or less.

13. The lightning protection system (1) according to any one of claims 1 to 12, wherein the conductive connection point (6) has a thickness greater than 0.5 mm.

14. The lightning protection system (1) according to claim 13, wherein the thickness of the conductive connection point (6) extends in both directions relative to the thickness of the sheet.

15. The lightning protection system (1) according to any one of claims 1 to 14, wherein a receptor bolt is screwed into the connection block through the conductive connection point (6).

16. A lightning protection system (1) according to any one of claims 1 to 15, wherein a plurality of intermediate conductive connection points (12) are arranged on the opposite side of the structural element (112) at a predetermined intermediate distance from the tip connection block (3).

17. The lightning protection system (1) according to claim 16, wherein the intermediate conductive connection point (12) is connected to the structural element (112).

18. The lightning protection system (1) according to claim 16 or 17, wherein the predetermined intermediate distance is less than 1500 mm.

19. Lightning protection system (1) according to any one of claims 1 to 18, wherein the conductive material of the first expanded foil or first mesh and the second expanded foil or second mesh is a metal such as aluminum, copper, steel, or a related alloy.

20. The lightning protection system (1) according to any one of claims 1 to 19, wherein the first expanded foil or first mesh is arranged to at least completely cover the first side of the structural element (112) facing the pressure side (110), and the second expanded foil or second mesh is arranged to at least completely cover the second side of the structural element (112) facing the suction side (111).

21. The lightning protection system (1) according to claim 20, wherein the length of the first expanded foil or first mesh and the second expanded foil or second mesh are greater than or equal to the length of the structural element (112).

22. The lightning protection system (1) according to any one of claims 1 to 21, wherein the tip connection block (3) electrically connects the first down conductor (2) to the first expanded foil or first mesh and the second expanded foil or second mesh, respectively, via the conductive connection point (6).

23. The lightning protection system (1) according to any one of claims 1 to 22, wherein the tip connection block (3) comprises at least one first receptor base and at least one second receptor base, the first receptor base is configured to connect the conductive connection point (6) of the first expanded foil or first mesh to the tip connection block (3), and the second receptor base is configured to connect the conductive connection point (6) of the second expanded foil or second mesh to the tip connection block (3).

24. The lightning protection system (1) according to any one of claims 1 to 23, wherein the root connection block (5) is configured to electrically connect the first expanded foil or first mesh and the second expanded foil or second mesh to a single root down conductor (24).

25. A wind turbine blade (101) comprising a root end (102) and a tip end (103), a longitudinal axis (106), a pressure side (110) and an intake side (111) which are the outer surfaces of the wind turbine blade, a structural element (112) extending along the longitudinal axis (106) which is a girder or beam made of conductive carbon fiber reinforced polymer (CFRP), and a lightning protection system (1) according to any one of claims 1 to 24.

26. A wind turbine (100) having one or more wind turbine blades (101), comprising a lightning protection system (1) according to any one of claims 1 to 24.

27. A method for providing a conductive connection point (6) of a lightning protection system (1) according to any one of claims 1 to 24 on an expanded foil or mesh, A step of melting the conductive material, The steps include applying the molten conductive material in a liquid state to surround the expanded foil or mesh, The steps include curing the molten material to enable the provision of a mechanical and conductive connection between the conductive connection point and the expanded foil or mesh, Methods that include...

28. A method for providing a conductive connection point (6) of a lightning protection system (1) according to any one of claims 1 to 24 on an expanded foil or mesh, The steps include preparing at least two disks made of conductive material, The steps include placing the two disks on both sides of the expanded foil or mesh, The steps include fixing the disks together with the expanded foil or mesh between them to provide a conductive connection between the disks, Methods that include...

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