Lightning protection system for modular blades and method for forming stacked components

Abstract

A lightning protection system for a modular blade joint. The joint comprises multiple coated metal elements (15) connected to multiple stacks (9) arranged on the sides of the upper blade cap (4) and the lower blade cap (5) and a lightning strike section (17) at equipotential bonding. The preform of the joint comprises two stacks (9) at the leading edge (7) and two more stacks (9) at the trailing edge (8). The stacks (9) are formed of layers of carbon fiber (21) and glass fiber (22) and the glass fiber layers are replaced by copper mesh (24) starting from the equipotential line (23). The stacks (9) include metal strips (12) on their sides, which are connected to metal strips (13) connecting the tip blade cap (2) and the root blade cap (3) and are covered with layers of glass fiber. Multiple metal strips (14) are bolted to all Xpacers (15) and are connected to the metal strips (13) and corresponding plates that hold the webs (18) together. A method of forming a stack includes the steps of: folding a copper mesh (24) comprising the metal strips (12), covering it with glass fibers (27, 28), and infusing the entire assembly.

Description

Technical Field

[0001] A lightning protection system for a connector for modular blades, the modular blade connector comprising two modular parts connected together: a root region or inner side and a tip region or outer side, and a method for forming a stack of metal elements accommodating the blade connector. Background Technology

[0002] For lightning protection systems in wind turbine blades to be effective, all non-current-carrying conductive elements must be electrically connected to the lightning transmission cable via equipotential bonding. Carbon fiber, as the conductive material, must be equipotentially bonded to the lightning rod system. A challenge in isolating the conductive elements is the large potential difference generated between them due to induction caused by lightning strikes as they pass through the protection system.

[0003] The stacked metal components housing the connector are very thick. Because it is very difficult to construct such a large thickness, a combination of glass fiber layers or fabric sandwiched between carbon fiber layers or fabric is used. This laminate allows for resin distribution during the infusion process and permits the use of a larger thickness. The addition of glass fiber results in an insulating effect. This potential difference can lead to arcing that must be avoided.

[0004] Therefore, different solutions exist in the prior art, applicable to both integral and modular blades. The first group includes the following:

[0005] Patent application EP1826402A1 uses a plate integrated into carbon fiber as a bypass for the main lightning protection cable. The plate is placed during lamination and curing. A conductive resin-based nanocomposite material is also described, which is laminated during the construction of a blade beam.

[0006] Patent application EP1692752A1 connects carbon fiber to lightning protection cables by using a potential equalization component as an electrical conductor. The electrical conductor is a flexible metal strip or flexible mesh added to the carbon fiber to improve its conductivity (because the conductivity in the longitudinal direction of the fiber is not very good).

[0007] Patent application EP1664528A1 discloses a protection method in which a fiber-reinforced main layer is connected to a receiver and a lightning protection cable. The fibers can be carbon fiber, steel fiber, etc. In one embodiment, a stack of glass fiber and carbon fiber (7:1 ratio) is described, wherein to compensate for the lack of conductive glass fiber, a glued receiver (with conductive silver paste) is added to the steel fiber layer, the steel fiber layer being added to achieve equipotentiality of the components.

[0008] For modular blades, lightning strikes the receiver located at the blade tip and travels through internal cables to the blade root, eventually reaching the ground. When the blade has structural discontinuities, all components constituting the discontinuities must be equipotentially bonded and connected to the lightning transfer cable.

[0009] Patent application EP1561947A1 describes a metal plate placed between two parts of a modular blade and conductive wires inside the blade. In the event of a lightning strike, current can be guided to the outside of the blade through the metal plate and conductive wires. The connection is achieved using nuts, bolts, and their corresponding plates.

[0010] Patent application EP1950414A1 discloses a modular blade made of fiber-reinforced plastic (FRP). In this manner, non-conductive parts are connected by means of fasteners arranged on the inside of the blade, and a lightning discharge conductive cable is added to all these components. The fasteners are arranged in their corresponding holes and covered with non-conductive caps, but some protruding fasteners pass through these non-conductive caps. Extensions of the lightning conductor cable are connected to each fastener.

[0011] Patent application EP2282057A1 discloses a mesh for equipotential bonding and reinforcing fiber blades, wherein the cables of the mesh are grouped at tapered ends to achieve connection points. Different cable reconfigurations result in different practical performances: in the case of modular blades, cross cables are intertwined to form tapered ends (the tapered ends connect to their free ends). Longitudinal wires form joints and have multiple tapered ends. In another embodiment of modular blades, L-shaped contact strips are used to establish physical connections.

[0012] Patent application WO2020094633A1 describes an internal carbon fiber beam to which conductive elements are added for equipotential bonding of the assembly. The conductive elements extend along the outer side of the main beam structure or along the corners of the outer side of the main beam structure. The beam can consist of two beams or a single beam. Modularization of the blade is also considered through the assembly of the aforementioned beams.

[0013] The solutions analyzed in these analyses constitute prior art, but a different form of integration is employed between the fiber stack and the metal components in this proposal. The most significant difference in this invention is the fan-shaped equipotential bonding of the layers adjacent to the metal connecting elements and the connection between the metal components themselves and the lightning protection cable. This technical solution, presented in the main claim, does not appear in any prior art. Summary of the Invention

[0014] The present invention aims to:

[0015] - Equipotential bonding composite layer: a combination of carbon and glass, which houses the metal components of the joint, and

[0016] - Metal components of the joint for modular blades with equipotential bonding.

[0017] The purpose of this invention is that the carbon fiber and glass fiber layers forming part of the joint area of ​​the modular blade, as well as the metal elements constituting the joint, are equipotentially bonded when connected to the lightning down-drop section, and therefore, lightning strikes will not damage them.

[0018] Another object of the present invention is to replace the non-conductive layers corresponding to glass fibers with copper or aluminum mesh, both of which are conductive materials. The carbon fiber layer, acting as a conductor and mixed with the glass fiber layer, is mixed with only a few copper meshes starting from a certain point, thereby achieving equipotential bonding throughout the assembly.

[0019] The stacked component of the present invention comprises a plurality of folds in carbon fibers dispersed with a plurality of copper meshes and covered by glass fibers, the glass fibers covering the entire assembly. The stacked component also includes internal metal strips for:

[0020] - Connected to metal connecting elements, and

[0021] - Connected to the lightning down-drop section.

[0022] The lightning protection system is located on the blade cap or wing and covers the same width as the preform forming the joint. Equipotential bonding is injected simultaneously with the cap formation. This equipotential bonding is not filler added to the sides of the cap after its fabrication.

[0023] The following advantages arise from the above description. The thickness of the resulting stack facilitates handling the copper mesh during its manufacturing process, folding the copper mesh, and quickly and easily inserting metal strips into the copper mesh. Covering the entire exterior of the stack with glass fiber facilitates the subsequent potting process, thereby providing adequate protection for the assembly. Attached Figure Description

[0024] A series of accompanying drawings, which will help to better understand the invention, will now be briefly described. These drawings explicitly relate to embodiments of the invention presented as non-limiting examples.

[0025] Figure 1 The outline of the modular blade is shown, in which two connecting preforms overlap inside.

[0026] Figure 2a Show Figure 1A portion of the lower beam cap of the preform, which has an arrangement of equipotential bonding of stacked components.

[0027] Figure 2b A second embodiment is shown, wherein the stacked components are arranged behind the block used by the centering pin.

[0028] Figure 3 Details of the modular blade joint are shown.

[0029] Figure 4 It shows Figure 2b Details of the lightning protection system and all electrical connections.

[0030] Figure 5a This is a cross-sectional view of the blade, showing the upper and lower beam caps.

[0031] Figure 5b The connection between the metal joint and the web plate starting from the trailing edge is shown.

[0032] Figure 5c The connection between the metal joint and the web plate passing through the leading edge is shown.

[0033] Figure 6 Details of the perforated beam cap are shown, in which connecting elements and centering pins are inserted.

[0034] Figure 7a , Figure 7b , Figure 7c , Figure 7d and Figure 7e A method for stacking equipotentially bonded composite materials is shown step by step. Detailed Implementation

[0035] Wind turbine blades have a tip and a root. Furthermore, if the blades are modular, such as... Figure 1 As shown, the blade consists of two parts: a connecting region (1), a tip beam cap (2) from the joint to the blade tip, and a root beam cap (3) from the joint to the blade root. The blade has an internal structure consisting of two beam caps and two webs consisting of composite materials forming the inner beams, with an upper and lower shell arranged on the inner beams. Metal elements conforming to the joint of this modular blade are arranged in the upper beam cap (4) and the lower beam cap (5). The upper beam cap (4) and the lower beam cap (5), along with their corresponding webs and the connecting region (1), constitute two preforms, one in the upper part and one in the lower part, which overlap on the original beam structure of the blade. Thus, as they move away from the connecting region (1), the beam caps narrow and their thickness decreases, making the overlap with the rest of the blade interior more effective. The materials used in the beam caps are glass fiber and carbon fiber, in a ratio of 20% to 80%.

[0036] Figure 2a The connection area (1) between the lower beam cap (5) and its tip beam cap (2) and root beam cap (3) is shown. The metal joint rests on the lower shell of the blade, and due to its aerodynamic configuration, the preform of the joint is closer to the leading edge (7) and further away from the trailing edge (8). Stacks (9) are arranged on both sides of the lower beam cap (5) to equipotentially bond the composite material housing the metal elements of the joint. Figure 2a and Figure 2b The lightning protection system of the lower beam cap (5) shown has two stacked pieces (9) on the front edge (7) and two more stacked pieces (9) on the rear edge (8).

[0037] exist Figure 2b In the second embodiment shown, the side of the lower beam cap (5) accommodates some centering pins (10), which facilitate in-situ assembly of the modular blades, and then the centering pins are removed. With these centering pins (10) in the connection area (1), the stack (9) moves into the interior of the tip beam cap (2) and the root beam cap (3), respectively, but in both cases the dimensions of the stack remain unchanged.

[0038] The stacked part (9) is approximately 150 mm or 250 mm long and approximately 50 mm or 80 mm wide. Measurements are taken starting from the connection area (1) and more specifically from the last metal element that makes up the joint.

[0039] Figure 3 A section of the modular blade object of the present invention is shown. It includes a tip spar cap (2), a root spar cap (3), a leading edge (7), a trailing edge (8), and a connection area (1) covered by metal elements constituting the joint itself, which are a set of Xpacer® elements that cover and prestress the connecting bolts, which are then screwed into their corresponding inserts, which are glued to a laminate of carbon fiber and glass fiber that must be equipotentially bonded. The Xpacer is the metal element visible when the joint is completed. The shell covering the blade has holes (11) in the connection area (1) to allow access during assembly. These holes (11) will then be covered by the outer shell.

[0040] like Figure 4As shown in the actual embodiment, the stack (9) that mates with the trailing edge (8) includes a metal strip (12) protruding from its interior. The metal strip (12) has holes for connection with other components. The stack (9) of the blade tip cap (2) corresponding to the lower beam cap (5) and the stack (9) of the blade root cap (3) are connected together by another metal strip (12), which is screwed through the corresponding connection holes of the aforementioned metal strip (12). This connection is supplemented by a metal strip (14) covering all Xpacers (15). The metal strip (14) is screwed to each and every Xpacer (15) included in the connection area (1). Finally, the joint (16) connecting the metal strip (12) of the stacked parts (9) corresponding to the blade tip cap (2) and the blade root cap (3) to the metal strip (14) of the Xpacer (15) also serves as a connection to the lightning drop section (17), where the entire assembly is equipotentially bonded. This joint (16), along with the rest of the connector, is preferably a threaded connection.

[0041] like Figure 5a , Figure 5b and Figure 5c As shown, the beam cap is responsible for accommodating the components of the metal joint. The Xpacer (15) has an upper surface and a lower surface. On these surfaces, the corresponding metal strips (14) are tightened at their upper and lower parts.

[0042] The upper beam cap (4) is fitted with a metal plate that is connected to the web (18) of the trailing edge (8) by a strip that is screwed to the metal strip (14) of the Xpacer (15). The lower beam cap (5) is fitted with a metal sheet that is connected to the web (18) of the leading edge (7) by a connection to another strip that is screwed to its corresponding metal strip (14) of the Xpacer (15). The arrangement of the metal strips (14) on the top and / or bottom of the Xpacer (15) and their connection to the plate that connects the web (18) of the leading edge (7) or trailing edge (8) is a design based on the blade length and the number of Xpacers (15) constituting the joint.

[0043] Figure 6The construction of the beam cap is shown, and its different layers are illustrated. Line (19) marks the position of the layers changing from the front (19') to the rear (19''). The front (19'') is a layer of constant thickness and consists of carbon fiber and glass fiber in a ratio of approximately 80:20. This is where the cavity is drilled, and the insert is then inserted and glued into the cavity. The joint is completed by screwing bolts into the insert and facing the mating beam cap. The bolts are inserted into the mating beam cap by unscrewing the bolts from the first beam cap. Finally, the bolts are covered by Xpacer and prestressed. The rear (19'') is a narrower and thinner layer to facilitate the overlap of the preform with the rest of the blade beam cap.

[0044] exist Figure 2a and Figure 2b Two practical embodiments, one with a centering pin (10) and the other without a centering pin (10), have already been described. Figure 6 In the diagram, holes (20) for centering pins are shown on both sides of the beam cap. This forces the equipotential stack (9) to be set laterally and the metal strip (12) to extend from the stack (9) to the apex of the connecting area (1). Without the centering pin (10), the metal strip (12) can be shorter.

[0045] Figure 7a , Figure 7b , Figure 7c , Figure 7d and Figure 7e A method for forming an equipotential bonding layer of a stack (9) is described. For illustrative purposes, the hole closest to the stack (9) is shown; in this practical embodiment, this hole is the cavity of the insert, which is longer than the cavity of the centering pin. The existing layer of the hole is a stack of carbon fiber (21) and glass fiber (22), and this combination is repeated until an equipotential bonding line (23) is obtained. Starting from this line, the glass fiber (22) is replaced by a copper mesh (24) that extends beyond the ends of the stack (9), causing it to protrude from the ends. The lower copper mesh (25) is longer than the remaining portion of the copper mesh (24).

[0046] like Figure 7b As shown, the copper mesh (24) folds towards the top of the stack (9), starting from the top and continuing at the bottom. The protruding ends of the copper mesh (24) overlap less than those of the stack formed by a set of carbon fibers (21) and their corresponding glass fibers (22). The second copper mesh covers at most half of the first copper mesh.

[0047] A wall is formed on the side of the stack (9) by overlapping copper mesh (24). A metal strip (12) ending at a hole (26) is arranged on the surface so that it can be screwed onto a metal strip (13) connecting... Figure 4The stacked components (9) of the leaf tip beam cap (2) and the stacked components (9) of the leaf root beam cap (3) shown are in the Figure 4 The equipotential bonding line (23) is also shown. Once the metal strip (12) is arranged, the lower copper mesh (25) is folded, and due to its longer length, the lower copper mesh overlaps with the metal strip (12) and ends at the top of the stack (9), as can be seen from... Figure 7c and Figure 7d As seen in the text.

[0048] In all Figure 7a , Figure 7b , Figure 7c , Figure 7d and Figure 7e The stack (9) depicted has a long lower glass fiber layer (27) that protrudes from the sidewall of the stack (9). Once the lower glass fiber (27) is folded, its ends are covered by a final upper glass fiber layer (28), which covers the folds of the copper mesh (24) and carbon fibers (21) of the stack (9). This completes the final overlap of the two glass fiber layers (27 and 28), which facilitates overall infusion. This covering can also be made of a single layer.

[0049] Once the stack (9) has been filled and the modular blades have been joined, we proceed with the equipotential bonding by tightening the metal strips (12, 13 and 14) together and to the wire of the lightning drop section (17).

Claims

1. A lightning protection system for modular blades, wherein, The metal elements of the joint are arranged at the upper beam cap (4) and the lower beam cap (5) and together with the web of the beam and the metal plate connecting the web, form a preform integrated with the blade beam. The connecting metal elements include multiple metal element portions (15) visible when the joint is completed. The metal element portions have upper and lower surfaces. The metal element portions apply prestress to multiple bolts, which are screwed into drilled inserts. The combination of carbon fiber layer (21) and glass fiber layer (22) is bonded into the composite material. The lightning protection system is characterized by comprising: - A stack of (9) on the front edge (7) of the upper beam cap (4) and a stack of (9) on the rear edge (8) of the upper beam cap (4), and two other stacks of (9) on the side of the lower beam cap (5). - Metal strip (12), which protrudes from each stack (9) and is connected to the plate (18) connecting the web, the metal strip connecting the metal element portion (15), the lightning protection drop section (17), and the metal strip connecting the blade tip spar cap (2) and the blade root spar cap (3). Each stack (9) consists of a carbon fiber layer (21) and a glass fiber layer (22), with the glass fiber layer replaced by a copper mesh (24) starting from the equipotential bonding line (23). The copper mesh protrudes from the sidewall of the stack (9), folds over itself, and forms the surface to which the metal strip (12) is attached. - Each stack (9) is completed by a lower glass fiber layer (27) and an upper glass fiber layer (28) that completely cover the stack.

2. The lightning protection system for modular blades according to claim 1, wherein, The joint layer is formed of glass fiber and carbon fiber in a ratio of 20:80, and is formed of copper mesh (24) and carbon fiber layer (21) in the same ratio starting from the equipotential bonding line (23).

3. The lightning protection system for modular blades according to claim 1, wherein, The joint is constructed including a centering pin (10), and the arrangement of the stack (9) fixed to the side of the beam cap (4, 5) at a distance equal to the size of the centering pin (10) is delayed and away from the connection area (1), and the metal strip (12) is extended until it covers the distance.

4. A lightning protection system for modular blades according to any one of the preceding claims, wherein, Without using centering pins (10), the stack (9) has a length of 200 mm to 250 mm and a width of 50 mm to 80 mm, measured from the connecting area (1).

5. The lightning protection system for modular blades according to any one of claims 1 to 3, wherein, The metal element portion (15) of the joint forming the blade tip cap (2) and the blade root cap (3) is connected to a metal strip, which is arranged on the upper and / or lower part of the metal element portion (15) and is also connected to the connecting plate of the web (18).

6. A method for forming a stacked component (9), characterized in that: - The existing layer is a stack of carbon fiber layer (21) and glass fiber layer (22), and starting from the equipotential bonding line (23), the glass fiber layer (22) is replaced by a copper mesh (24) that extends beyond the end of the stack (9) and has protruding ends. The lower copper mesh (25) is longer than the rest of the copper mesh (24). - Fold the protruding end of the copper mesh (24) toward the top of the stack (9), thereby forming a sidewall on the side of the stack (9). - A metal strip (12) is arranged on the side wall. - Once the metal strip (12) is laid out, the lower copper mesh (25) is folded, the lower copper mesh overlapping the metal strip (12) and terminating at the top of the stack (9). -The lower glass fiber layer (27) and the upper glass fiber layer (28) cover the folds of the copper mesh (24) and the carbon fiber layer (21) of the stack (9), and finally, - Infusion components.

7. The method for forming a stacked component (9) according to claim 6, characterized in that, During the folding of the copper mesh (24), the folding begins with the upper copper mesh and is immediately followed by the lower copper mesh, such that the second copper mesh covers at most half of the first copper mesh.

8. The method for forming a stacked component (9) according to claim 6, wherein, The lower glass fiber layer (27) is longer and protrudes from the sidewall of the stack (9), while the final upper glass fiber layer (28) is a glass fiber layer that overlaps with the lower glass fiber layer, thereby covering the folds of the carbon fiber layer (21) and the copper mesh (24) of the stack (9), so that the entire assembly is covered with glass fiber, which is beneficial for the subsequent infusion of the assembly.

9. The method for forming a stacked component (9) according to claim 6, characterized in that, Once the filling and connection are completed, metal strips (12) ending with holes (26) are arranged on the sidewalls formed by overlapping the copper mesh (24). The metal strips are tightened to the metal strips connecting the tip beam cap (2) of the stack (9) and the root beam cap (3) of the stack (9) and to the metal strips of the metal element portion and the lightning drop portion (17), which has an upper surface and a lower surface.

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