Wind turbine blade assembly and method of manufacturing the same

Abstract

Wind turbine blade assembly (1a, 1b, 1c, 1d), comprising: - a wind turbine blade (2) having a blade root (7) for connection to the hub of a wind turbine, - an assembly tip (10), wherein the wind turbine blade assembly spans a length (11) from the blade root to the assembly tip, and - a lightning protection system comprising an internal down conductor (3) within the wind turbine blade and a plurality of lightning receptor devices (4, 6, 14) having receptors (15), the receptors (15) being conductively coupled to the down conductor, wherein the length of the wind turbine blade assembly is divided into a first portion (12) and a second portion (13), the first portion (12) having the internal down conductor and spanning from the blade root to at least one first lightning receptor device (4), the second portion (13) spanning from the first lightning receptor device to the assembly tip, wherein the lightning protection system further comprises: - a second lightning receptor device (6) in the second portion, and - an external conductive strip (5) extending between a pair of first and second lightning receptor devices (4, 6) in the second portion and being conductively coupled to their receptors.

Description

Technical Field

[0001] The present invention relates to a wind turbine blade assembly, comprising:

[0002] - a wind turbine blade having a blade root for connection to a hub of a wind turbine,

[0003] - a component tip formed by a blade tip of the wind turbine blade or an attachment tip of a wind turbine blade attachment attached to the blade tip of the wind turbine blade, wherein the wind turbine blade assembly spans a length from the blade root to the component tip, and

[0004] - a lightning protection system comprising an internal down conductor within the wind turbine blade and a plurality of air termination devices having at least one receiver, the receiver being conductively coupled to the down conductor.

[0005] The present invention also relates to a method for manufacturing such a wind turbine blade assembly with a wind turbine blade attachment. Background Art

[0006] Modern wind turbines typically include a tower, with a nacelle and a hub mounted on top of the tower. The wind turbine blades are mounted to the hub at their blade roots. Since wind turbines tend to become taller and / or wind turbine blades tend to become longer, the likelihood of lightning strikes in the area of the wind turbine blade tips increases. The likelihood of a lightning strike impact is highest at the blade tip end and generally decreases towards the blade root.

[0007] It has also been proposed in the art to retrofit wind turbine blades with so-called tip attachments (wind turbine blade attachments), such as extensions and / or fins. In the context of the present invention, a wind turbine blade assembly can be a wind turbine blade without a wind turbine blade attachment, or a wind turbine blade equipped with a wind turbine blade attachment (tip attachment). In a retrofitted wind turbine blade, the end of the wind turbine blade attachment can become the new tip end of the wind turbine blade assembly, such that hereinafter, the term "component tip" refers to the blade tip of a wind turbine blade without a tip attachment, or the attachment tip of a wind turbine blade with a tip attachment. The use of wind turbine blade attachments increases the effective blade length. Thus, in this case, the wind turbine blade attachment is the component with the highest risk of being affected by lightning strikes. The wind turbine blade attachment as well as the blade tip of the wind turbine blade can be made of a non-conductive material that is highly susceptible to lightning.

[0008] To protect the components of a wind turbine blade assembly from lightning strikes, a lightning protection system (LPS) is used. Such a lightning protection system typically includes a lightning receptor, which is also known as an air termination point and is usually part of a lightning arrester device that additionally includes a lightning arrester base. The LPS also includes a lightning downconductor and a ground in the soil of the wind turbine. While the lightning receptor is typically placed on the surface of the wind turbine blade assembly, for the downconductor, they can be installed on the inside or outside of the wind turbine blade. Typically, it has been chosen to install the downconductor on the inside of the wind turbine blade to maintain the aerodynamic characteristics of the blade surface. However, concepts and products for external downconductors for wind turbine blades have also been proposed.

[0009] For example, in an article “External Lightning Protection System for Wind Turbines Blades – Further Considerations” by A.S. Ayub et al. at the 2015 Asia-Pacific International Conference on Lightning (APL), Nagoya, Japan, a problem was addressed: whether a single external downconductor could be deployed at an optimal location with the least impact on aerodynamic performance. The results showed that the aerodynamic characteristics decreased the least at the trailing edge or leading edge of the blade, indicating that it might be feasible to install an external downconductor in this area.

[0010] In addition, Jomitek has also proposed a product called “FluoroGrip LS - 1000 Lightning tape” to support retrofit protection for installed blades. In this way, the potential of the internal part and the surface should be equal.

[0011] However, these solutions also have drawbacks. Having an internal downconductor increases the risk of lightning penetrating into the laminate because it can attach to the streamers emitted from them, resulting in structural damage and possible explosive expansion of water. The insulating material increases the weight of the wind turbine blade when in use. If a metal mesh is used as an external downconductor, its service life is limited and it requires frequent maintenance. Such meshes are typically based on copper and aluminum, making them also likely to experience corrosion. Galvanic corrosion when combined with carbon-based materials is another problem.

[0012] External lightning protection systems may also have aerodynamic and noise constraints. To minimize these, the external down conductors are manufactured to have a very thin thickness. External down conductors such as tapes may have a limited service life. For example, the lightning protection tapes of Jomitek cited above can typically only withstand a single lightning strike of 200 kA. Thus, the tapes act as vulnerable parts and require expensive on-site maintenance. However, a key constraint is mechanical strain, especially flap-wise and edge-wise bending. This is particularly applicable when the tape is used along the entire length of a wind turbine blade as it has to pass through high-strain locations. Additionally, the installation of adhesive-based external down conductors is challenged by the peeling forces originating from the wind.

[0013] Regarding wind turbine blade add-ons, in particular extensions and / or winglets, methods for lightning protection have also been proposed in the prior art. For example, in the unpublished European patent application EP 18 196 894.2, an internal down conductor can be connected to or connected to the corresponding internal conductor of the rotor blade, especially via a corresponding interface. Such a lightning protection system can also be electrically insulated. Additionally, in the "Design Guide for Glass Fiber Reinforced Plastic (GFRP) Wind Turbine Blades" of Shine Wire Products Inc., available from "https: / / wxguardwind.com / ", the use of continuous or segmented metal shunt strips is proposed, which extends the interception range of the tip receivers on existing wind turbine blades.

[0014] The first-mentioned method requires the design of an interface between the lightning protection system in the wind turbine blade add-on and the existing wind turbine blade. This interface is difficult to implement and is typically a weak point in the system, especially as it also coincides with the location of the structural interface. Manufacturing and integration can be cumbersome. Another problem is that such a lightning protection system is typically "tip-heavy". Additionally, having an internal down conductor also increases the risk of lightning penetrating into the structure of the wind turbine blade and / or add-on. On the other hand, the shunt strips can be regarded as vulnerable parts that need to be replaced regularly. Additionally, the segmented shunt strips are limited in their interception range. Another common drawback is that the interface between the corresponding lightning protection system in the wind turbine blade add-on and the existing wind turbine blade requires on-site installation, i.e., installation on the installed blade under variable environmental conditions, which is very complex and expensive.

[0015] WO 2013 / 097855 A2 discloses a wind turbine blade and a method for manufacturing a wind turbine blade. The lightning protection system of the wind turbine blade includes an internal lightning conductor positioned along a longitudinal portion of the wind turbine blade, wherein a lightning receiver module is arranged on an outer surface of the wind turbine blade and electrically coupled to the lightning conductor. An elongated receiver strip is mounted above the lightning receiver module on the outer surface of the wind turbine blade, and the receiver strip is arranged to receive a lightning strike and transmit current from the lightning strike through the lightning receiver module to the lightning conductor. The elongated receiver strip includes a crease in a longitudinal cross-sectional profile of the elongated receiver strip.

[0016] WO 01 / 77527 A1 discloses a lightning protection system for a wind turbine and a wind turbine blade having such a lightning protection system. The system includes one or more internal conduction means and also has one or more external lightning conduction means mounted on or adjacent to the surface of the turbine and connection means by which the internal and external lightning conduction means are connected.

[0017] Both of these solutions use conduction strips on the outer surface of the wind turbine blade. However, this method relies on a strip placed above an existing internal down conductor, i.e., parallel to the existing internal down conductor, thereby providing the possibility of a lightning strike entering the laminate, which can lead to structural damage. Summary of the Invention

[0018] Accordingly, an object of the present invention is to provide a lightning protection system having a reduced risk of structural damage to blade components and, in particular, in the case of wind turbine blade add-ons, which is easy to install and cost-effective.

[0019] This object is achieved by providing a wind turbine blade assembly according to the independent claims and a method for manufacturing a wind turbine blade assembly. Advantageous embodiments are described in the dependent claims.

[0020] According to the present invention, in a wind turbine blade assembly as initially described, the length of the wind turbine blade assembly is divided into a first part and a second part, the first part spanning from the blade root to at least one first lightning arrester device, wherein an internal down conductor extends in the first part, the second part spanning from the first lightning arrester device to the assembly tip, wherein the lightning protection system further includes:

[0021] - at least one second lightning arrester device in the second part, and

[0022] - At least one external conductive strip that extends at least between a pair of first and second lightning receptor devices in the second part and is conductively coupled to their receivers.

[0023] "Conductively coupled" means that there is a direct conductive connection or, in the case of lightning, that is, once a certain potential threshold is exceeded, at least one spark gap provides conductivity. "External" means extending on the outer surface of the wind turbine blade assembly.

[0024] Thus, the present invention proposes to divide the length of the wind turbine blade assembly into two parts, where, in one part, an internal lightning downconductor extends within the wind turbine blade and, in the second part, an external downconductor is implemented by a conductive strip that conductively couples the lightning receivers of two lightning receptor devices. That is, the at least one second lightning receptor device, or its corresponding lightning receiver, is not directly connected to the internal downconductor but instead indirectly uses the conductive strip and the receiver of the at least one first lightning receptor device. The main idea of the present invention is that the component tip is the most exposed area of the wind turbine blade assembly and must be adequately protected against lightning damage. Therefore, a combined receiver-downconductor device is employed in the outermost area of the wind turbine blade outside the surface of the wind turbine blade assembly, and the internal downconductor is used for the remaining length of the wind turbine blade assembly. In the absence of an internal downconductor in the second part, there is little or no reason for lightning to enter the laminate, such that structural damage can be prevented. This has particular advantages for wind turbine blade add-ons as they can be made of pure structural components.

[0025] Furthermore, the conductive strip can be simply added to the surface of the wind turbine blade assembly so as to span a part of the add-on and a part of the wind turbine blade without having to provide a special electrical interface at the structural interface between two components of the wind turbine blade assembly. The strip can be made of an environmentally stable material and can have a thickness of approximately a few millimeters to many millimeters, for example, 2 to 50 mm.

[0026] The proposed lightning protection system and method have the following advantages: simple and fast integration, inexpensive, easy to inspect and maintain, but most importantly, provide enhanced protection for the structure of the wind turbine blade tip / wind turbine blade attachment through preventive control. In particular, in a lightning protection system located outside the component tip region of the blade, in the absence of an internal downconductor in this region (the second part of the length), it is expected that lightning will not penetrate the structure of the blade tip and / or the wind turbine blade attachment. Therefore, the so-called puncture damage mode in this second part will be close to abandonment. This in turn allows for the reduction of certain quality requirements, such as the size and distribution of trapped air during production, or the degree of increased on-site moisture that causes so-called "split tips". As a result, the costs and time for manufacturing and repair are also reduced.

[0027] Note that since the strip is only provided in the second part of the length, it is not subject to the strain of the wind turbine blade because the component tip is a low-strain region. Additionally, a common receiver-conductor system is used in the component tip region, which can act as a giant receiver with a larger interception range and is suitable for handling lightning erosion throughout the blade life. In other words, the lightning receiver of the lightning arrester device, which is a vulnerable part, is under less pressure because a wider area is available for lightning reception due to the at least one strip.

[0028] Using a strip that conductively connects a pair of first and second lightning arrester devices provides an externally visible structure that is easy to monitor for manufacturing and lifecycle defects. This is even possible on a moving blade. If desired, stronger integration into the blade structure / blade geometry can also be achieved by placing the lightning arrester base of the lightning arrester device in a foam core airfoil block.

[0029] The simplicity of the concept according to the present invention allows for easy adaptation to any wind turbine blade / wind turbine blade attachment type with minimal lead time and cost. Additionally, the weight of possible insulation materials will be saved. When applied to a wind turbine blade assembly with a wind turbine blade attachment, the strip preferably acts as a bridge between the original wind turbine blade and the tip attachment. For example, the wind turbine blade attachment can be an extension and / or a winglet.

[0030] Generally, the conductive strip can be made of metal, metal matrix composite, carbon, and / or similar materials, including their composite materials that may contain metal particles of different shapes and sizes. The conductive strip may also include a hybrid structure, such as a multi-layer structure involving metal, carbon, ETC, and / or their composite materials. The conductive strip can be solid, hollow, slotted, notched, internally porous, reticulated, woven, or in other such forms. Preferably, the conductive strip can be in a reticulated or notched form to reduce weight. It can be provided with recesses or grid markings to facilitate adhesion. The edges of the conductive strip do not necessarily need to be straight edges, and the thickness distribution does not necessarily need to be flat, as will be discussed further below. The conductive strip can generally be straight, but can also be curved or bent.

[0031] The strip can be made of a continuous material or can be segmented. For example, the conductive strip can be in the form of a continuous metal strip or a segmented shunt strip. In certain cases where different conductivities should be enforced, using segmented strips may be advantageous. For example, different segment distances can be provided in different strips and / or different sections of the strip, especially to favor a certain receiver to receive a lightning strike. In this way, lightning can be guided to certain lightning receivers, especially increasing the likelihood of a certain receiver being targeted.

[0032] In a preferred embodiment, the strip can be conductively coupled to the receivers of the respective first and second lightning protection devices through a spark gap. In this way, the strip can be installed without having to approach or manipulate the lightning protection devices. The strip can simply terminate at a predetermined distance from the receivers of the lightning protection devices, such that a spark gap is formed, which becomes conductive once there is a certain potential drop, resulting in the ionization of the air between the lightning receiver and the strip, at least in the case of a lightning strike.

[0033] However, since the ends of the strip may be subject to erosion and / or other wear effects when using a spark gap, different advantageous measures can be taken according to the present invention to ensure a high lifespan and a high number of cycles of the conductive strip. Of course, these measures / embodiments can be combined.

[0034] Preferably, the strip can be at least partially in a ring shape around at least one of the receivers at a predetermined distance. For example, the conductive strip can terminate as a flat ring around the flash point, thus providing a larger edge for the spark gap.

[0035] Additionally or alternatively, it may be advantageous to increase the width and / or thickness of the conductive material of the strip in the coupling region around the respective receiver relative to the non-coupled region that is further away from the receiver. In this way, more conductive material can be added at the ends of the conductive strip where more erosion is expected. This addition of material is preferably in the thickness direction, while an increase in area in terms of dimensions is also possible. For example, in the direction towards the receiver, the conductive strip may have a continuously increasing thickness distribution. Generally, the ends of the strip can take various shapes, such as rectangular or circular. Note that similarly, the conductive strip segments at the ends of the segmented strip can also be thickened and / or enlarged. In these embodiments, melting and / or erosion due to the spark gap can be compensated for.

[0036] In an alternative and less preferred embodiment, the conductive strip can be mechanically fastened to the lightning receptor device by the receiver, in particular being clamped between the receiver and the lightning receptor base of the lightning receptor device. In this way, the conductive strip is in physical and conductive contact with the lightning receiver, i.e., the flash point. Preferably, the conductive strip can be pressed between the receiver of the lightning receptor device and the lightning receptor base. In an embodiment, the connection between the strip and the lightning receptor device can ideally be achieved using a standard bolted lightning receptor, in particular a threaded receiver. However, the design can be modified to retain the screw function while reducing the lightning receptor function to a non-profile or lower profile. For example, a shear bolt without a receiver head, a bolt with a countersunk receiver head, or a bolt with a round receiver head can be used as the bolt. These geometries can be used to relocate a part of the receiving function to the strip. However, other methods, such as riveting, welding, etc., can also be used to fasten the strip to the lightning receptor device. Note that mechanically fastening the strip, especially by a threaded receiver, is also advantageous because this may be the main method for fastening, so that fixing by adhesives etc. can be omitted or at least reduced. Thus, EHS and weather constraints will be minimized.

[0037] As explained, the receiver can be, in particular, a threaded bolt that has a head protruding from the strip or flush with the strip surface.

[0038] Generally, it is preferred to fasten the strip to the surface of the wind turbine blade assembly by an adhesive and / or mechanically, in particular by screw or bolt connection. That is, even if the conductive strip is electrically coupled to the receiver through a spark gap, mechanical fastening can be achieved, thereby reducing the need for adhesives and minimizing EHS and weather constraints due to the main mechanical fastening of the strip. This also provides ease of implementation and service on the ground and from a platform.

[0039] In a preferred embodiment, the strip may be placed in a recess in the surface of the wind turbine blade assembly and / or may include a lateral seal layer, particularly if placed on a flat portion of the surface, the lateral seal layer tapering. While the strip may be placed directly on the surface of the wind turbine blade assembly, it may be preferred to place it in a channel / groove in the surface. The edges of the strip may be sealed due to the ingress of dust / water and / or for aerodynamic reasons. Such a seal may slightly overlap the conductive strip.

[0040] Note that since the conductive strip is limited to the component tip region, i.e., the second part of the length, and can be mounted in a recessed manner, such as in a slot / groove, it does not relevantly affect the aerodynamic and / or noise characteristics.

[0041] As already explained, the second part of the length, i.e., in particular the at least one conductive strip, only spans the component tip region. In particular, the second part may span at least 1 to 3 meters of the distal part of the wind turbine blade. However, preferably, the second part comprises less than 50% of the length of the wind turbine blade assembly, particularly less than 25% of the length of the wind turbine blade assembly.

[0042] Preferably, the at least one strip may extend on both the windward side and the leeward side of the wind turbine blade assembly. Note that the windward side may also be referred to as the pressure side and the leeward side may also be referred to as the suction side. In a typical scenario, two particularly metallic strips are employed on each of the windward side and the leeward side of the wind turbine blade assembly, where they are conductively coupled between two lightning arrester devices, particularly between a first lightning arrester device and a second lightning arrester device. In this way, a receiving area / structure for lightning is provided on both sides.

[0043] However, in an alternative embodiment, it may also be provided that the at least one strip is only provided on the windward side or the leeward side of the wind turbine blade assembly, where the second lightning arrester devices are provided on both sides and their receivers are conductively coupled. That is, the conductive strip may be used only on one side of the wind turbine blade assembly. In this case, a local lightning arrester is provided only on the opposite side, i.e., at least one second lightning arrester device having a lightning receiver. In this scenario, the opposite receivers are conductively coupled, for example, by using a conductive lightning arrester base. However, other dedicated conductive structures and / or spark gaps may also be used.

[0044] However, equally typically, the second lightning receptor devices on the windward side and the leeward side may include a common lightning receptor base, which may be separable, but conductively coupled (either via a solid metal connection or via a spark gap), or may be separable and conductively disconnected. If the at least one strip is provided only on one side of the wind turbine blade assembly, the latter embodiment should not be used. As is known from the prior art, the conductive, in particular metallic, lightning receptor base may also be insulated if required.

[0045] In an embodiment, at at least one of the windward side and the leeward side of the wind turbine blade assembly, a plurality of strips may be arranged in a parallel and / or series configuration. In this way, certain advantageous field distributions with respect to lightning can be achieved, in particular with respect to the formation of streamers and leaders.

[0046] In an embodiment, at least two second lightning receptor devices are provided at at least one of the windward side and the leeward side, wherein at least one of the at least one strip is conductively coupled to the receivers of more than one second lightning receptor device. That is, on at least one side of the wind turbine blade assembly which includes, where applicable, a tip attachment, the strip may be connected between more than two lightning receptor devices. For example, if a wind turbine blade attachment is used, the wind turbine blade itself may have a pair of second lightning receptor devices, while the attachment may include two additional second lightning receptor devices. The strip may now extend from the nearest first lightning receptor device across a second intermediate lightning receptor device in the blade tip region (or alternatively, already on the wind turbine blade attachment) to an external second lightning receptor device on the wind turbine blade attachment, thereby conductively coupling all their receivers. However, particularly in the case where a spark gap is used to conductively couple the strip to the receiver, two strips may also be provided, with the first strip connecting the first lightning receptor device and the intermediate second lightning receptor device on the wind turbine blade or attachment, and the second strip conductively coupling the intermediate second lightning receptor device and the external second lightning receptor device on the wind turbine blade attachment. In an embodiment, if one strip is used, the one strip may also extend in a loop around the intermediate second lightning receptor device to provide a spark gap.

[0047] At least one of the at least one strip may also extend in a tipward direction beyond the second lightning receptor device to which the strip is conductively coupled to the receiver. In this way, the free end of the strip may be without any connection, or formed or connected to conductively couple to, for example, the receiver of a second lightning receptor device on the opposite side of the wind turbine blade assembly.

[0048] For example, in a specific embodiment, the strip may extend on the tip to the other side of the wind turbine blade assembly, in particular conductively connected to another strip and / or another receiver of the second lightning arrester device, and / or the strip may be conductively connected to at least one additional strip that at least partially surrounds the wind turbine blade assembly. For example, a conical or annular structure may be formed for the two purposes of enhancing structural constraints and / or lightning interception.

[0049] In a further preferred embodiment, the surface of the at least one strip includes at least one aerodynamic structure, in particular a vortex generator. Such an aerodynamic structure may also be referred to as an aerodynamically active structure or an air guiding element, and may preferably include a vortex generator. In other words, the continuous or segmented conductive strip may actually take the form of a vortex generator, such as a flat strip with protruding fins, to perform both lightning protection and aerodynamic functions simultaneously. The conductive material of the strip itself may be configured to provide such an aerodynamic function. However, the strip may also be covered with separate elements, such as or forming a vortex generator. These separate elements may be conductive or non-conductive.

[0050] The present invention also relates to a method for manufacturing a wind turbine blade assembly according to the present invention, wherein the wind turbine blade assembly includes a wind turbine blade attachment having at least one second lightning arrester device. The method includes the following steps:

[0051] - adding the wind turbine blade attachment to the wind turbine blade, and

[0052] - attaching the at least one strip on the surface so as to conductively couple the receiver of the at least one second lightning arrester device of the wind turbine blade attachment to the receiver of at least one of the at least one first lightning arrester devices of the wind turbine blade.

[0053] All features and comments regarding the wind turbine blade assembly also apply to the method according to the present invention, such that the same advantages can be achieved. In particular, there is no need for a complex interface structure for conductively coupling the internal downlead of the wind turbine blade attachment to the internal downlead of the wind turbine blade, but simply and cost-effectively adding the at least one strip is the only measure required to include the wind turbine blade attachment into the lightning protection system of the wind turbine blade. Description of the Drawings

[0054] Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. However, the drawings are only schematic diagrams designed for illustrative purposes and do not limit the present invention. The drawings show:

[0055] Figure 1: Schematic diagram of a first embodiment of a wind turbine blade assembly according to the present invention,

[0056] Figure 2 : First schematic diagram of the component tip region of the first embodiment,

[0057] Figure 3 : Second schematic diagram of the component tip region of the first embodiment,

[0058] Figure 4 : Schematic diagram of a second embodiment of a wind turbine blade assembly according to the present invention,

[0059] Figure 5 : First schematic diagram of the component tip region of the second embodiment,

[0060] Figure 6 : Second schematic diagram of the component tip region of the second embodiment,

[0061] Figure 7 : Schematic diagram of the component tip region of a third embodiment of a wind turbine blade assembly according to the present invention,

[0062] Figure 8 : First schematic diagram of the component tip region of a fourth embodiment of a wind turbine blade assembly according to the present invention,

[0063] Figure 9 : Second schematic diagram of the component tip region of the fourth embodiment,

[0064] Figure 10 : Side view of a strip that can be used in the fourth embodiment,

[0065] Figure 11 : Top view of a second variant of a strip that can be used in the fourth embodiment,

[0066] Figure 12 : Top view of a third variant of a strip that can be used in the fourth embodiment,

[0067] Figure 13 : Segmented strip,

[0068] Figure 14 : Variant of the present invention using two tandemly positioned strips,

[0069] Figure 15 : Schematic diagram of two parallel strips,

[0070] Figure 16 : View of a variant in the component tip region of the first embodiment,

[0071] Figure 17 : View of a variant in the component tip region of the second embodiment,

[0072] Figure 18 : View of the variant in the component tip region of the third embodiment,

[0073] Figure 19 : Schematic view of the strip contacting two receivers of the second lightning receptor device,

[0074] Figure 20 : Variant of the invention using an annular strip,

[0075] Figure 21 : Variant of the invention using a tip covering strip,

[0076] Figure 22 –24: Variants of the second lightning receptor device,

[0077] Figure 25 –28: Variants of the lightning receivers in the lightning receptor device,

[0078] Figure 29 : Schematic view showing the strip guided in the groove,

[0079] Figure 30 : Strip on a flat surface with a tapered sealing layer, and

[0080] Figure 31 : Aerodynamically active structure on the strip. Detailed Description

[0081] Figure 1 Schematically illustrates a first embodiment of a wind turbine blade assembly 1a according to the present invention. In this embodiment, the wind turbine blade assembly 1a includes only the wind turbine blade 2 without any tip attachments (wind turbine blade attachments). The lightning protection system of the wind turbine blade assembly 1a includes an internal downconductor 3 which is conductively coupled to at least one first lightning receptor device 4. The receiver of the first lightning receptor device is in turn conductively coupled to an external conductive strip 5 which, in this case, terminates at the lightning receiver of a second lightning receptor device 6, the strip 5 being conductively coupled to the lightning receiver. At the blade root 7, a root terminal 8 is provided. In the region of the blade tip 9 which, in this case, also forms the component tip 10, the second lightning receptor device 6 is not directly conductively coupled to the internal downconductor 3 which terminates at the first lightning receptor device 4.

[0082] In other words, the total length 11 of the wind turbine blade assembly 1a from the blade root 7 to the assembly tip 10 is divided into a first part 12 and a second part 13. The downconductor 3 extends along the first part 12 to the first lightning receptor device 4. The second part 13 still has at least one second lightning receptor device 6 but no internal downconductor 3. Instead, an external conductive strip 5 is used to connect the pairs of first lightning receptor devices 4 and second lightning receptor devices 6, as shown.

[0083] Note that, as is known in the prior art, additional lightning receptor devices 14 may be used in the first part 12 of the length 11, but this will not be further discussed here.

[0084] In this embodiment, the strip 5 is in direct electrical contact with the receivers of the lightning receptor devices 4, 6. However, a spark gap may also be used to conductively couple the strip 5 to the receivers of the first and second lightning receptor devices 4, 6, as will be further discussed later.

[0085] The conductive strip 5 can be made of metal, metal matrix composite, carbon, or similar materials, including composite materials that may contain metal particles of different shapes and sizes. The conductive strip may also include a hybrid structure, such as a multi-layer structure involving metal, carbon, ETC, and / or their composites. In addition, the strip 5 can be solid, hollow, slotted, notched, internally porous, reticulated, woven, or in other such forms. In particular, the strip 5 can also be a band. Although in the illustrated embodiment, the strip 5 is mostly shown as straight, it can also be curved or bent.

[0086] Figure 2 and Figure 3 A more detailed schematic view of the assembly tip region of the first embodiment is shown. As can be seen, each lightning receptor device 4, 6 includes a receiver 15 and a lightning receptor base 16. As can be seen from Figure 3 As can be seen, the first and second lightning receptor devices 4, 6 are provided on the windward side 17 and the leeward side 18. In the illustrated embodiment, both lightning receptor devices 4, 6 use a common lightning receptor base 16. The strip 5 is provided on both sides 17, 18.

[0087] Figures 4 to 6Figure 2 schematically shows a second embodiment of a wind turbine blade assembly 1b according to the present invention. In this case, the wind turbine blade assembly 1b includes a blade 2 and an additional wind turbine blade add-on 19 (tip add-on), which is a tip extension 20 in this case. That is to say, the assembly tip 10 is no longer formed by the blade tip 9, but by the add-on tip 21. In this exemplary case, a first part 12 of the length 11 spans most of the wind turbine blade 2, while the second part 13 consists mainly of the wind turbine blade add-on 19. However, other embodiments can be envisaged, in which the wind turbine blade 2 is constructed as in accordance with Figures 1 to 3 the first embodiment, and has its own first lightning arrester device 4 and second lightning arrester device 6.

[0088] As Figure 5 and Figure 6 shown in more detailed schematic views of, the wind turbine blade assembly 1b also includes a pair of first and second lightning arrester devices 4, 6 on both the windward side 17 and the leeward side 18, and the receivers 15 of each pair are conductively coupled by a strip 5.

[0089] Figure 7 In a view corresponding to the view of Figure 3 and Figure 6 a view of the assembly tip region of a third embodiment of a wind turbine blade assembly 1c is shown. As can be seen, in this case, the blade tip 9 of the blade 2 is extended by a winglet 22 which is a wind turbine blade add-on 19. Otherwise, its construction is as shown in Figure 6 the

[0090] Figure 8 and Figure 9 show a view of the assembly tip region of a fourth embodiment of a wind turbine blade assembly 1d according to the present invention, which fourth embodiment is a modification of the second embodiment and has a tip extension 20 as a wind turbine blade extension 19. In contrast to the second embodiment, in this case, the strip 5 does not conductively contact the lightning receivers 15 of the lightning arrester devices 4, 6 directly, but is conductively coupled to them via a spark gap. In this way, when expanding the lightning protection system after installing the wind turbine blade add-on 19, there is no need to work on the lightning arrester devices 4, 6. Instead, all that is required to include the wind turbine blade add-on 19 into the lightning protection system is to attach the strip 5 to the surface of the wind turbine blade assembly 1d between the first lightning arrester device 4 and the second lightning arrester device 6. Preferably, the strip 5 is mechanically fastened, for example by bolts, however, adhesives can alternatively and / or additionally be used to fix the strip 5.

[0091] Note that for the case without the add-on 19 (first embodiment) or the add-on 19 in the form of a winglet (third embodiment), the spark gap configuration is of course also applicable.

[0092] Since a spark gap is used in the fourth embodiment, the ends of the strip 5 may be subject to melting and / or erosion. Therefore, the strip 5 is preferably configured to withstand erosion and / or melting at its ends, and in Figures 10 to 12 a variant of such a strip 5 that can also be used cumulatively is shown.

[0093] Figure 10 A variant of the strip 5 is shown, in which the thickness of the conductive material 23 increases towards the end 24 of the strip 5.

[0094] In Figure 11 a variant, the area of the conductive material 23 of the strip 5, in particular the width, increases at the end 24.

[0095] In Figure 4 a variant is shown, in which the end 24 of the strip 5 surrounds the lightning receiver 15 at a spark gap distance like a ring.

[0096] Although in Figures 1 to 12 the strip 5 is shown as having a continuous conductive material 23, segmented strips can also be used, as shown in Figure 13 wherein, in this variant, the strip 5 is a segmented shunt strip of sections 25 with dot-like conductive material 23, and these sections 25 can be arranged on a substrate 26. The distance between the sections 25 can be different along a single strip 5 or for different strips 5 to promote certain paths or distributions of the lightning current in the case of a lightning strike.

[0097] Figure 14 And Figure 15 show an embodiment in which a plurality of strips 5 can be used on the side 17 of the wind turbine blade assembly, and this embodiment is a variant of the second embodiment 1b in this case. In Figure 14 a tandem configuration of the strips 5 is used, where the first strip 5 extends between the first lightning arrester device 4 and the intermediate second lightning arrester device 6, and the second strip 6 extends between the intermediate second lightning arrester device 6 and another second lightning arrester device 6 outside.

[0098] In Figure 15 a variant, two parallelly positioned strips 5 are used to conductively couple the lightning receivers 15 of the shown first lightning arrester device 4 to the lightning receivers 15 of the shown second lightning arrester device 6 respectively.

[0099] Figures 16 to 18Variants of the first to third embodiments 1a, 1b, and 1c are shown. In each of these cases, the strip 5 is only used at one of the sides 17, 18, and the receivers 15 of the first and second lightning protection devices 4, 6 on the other side 18, 17 are not conductively coupled via the strip 5. In this case, the second lightning protection devices 6 each include a conductive common lightning protection base 16 such that the receivers 15 can also receive lightning current, which can be transmitted to the down conductor 3 via the opposite side.

[0100] Figures 19 to 21 Additional variants of the second embodiment of the wind turbine assembly 1b are shown. In Figure 19 , the receivers 15 of the plurality of second lightning protection devices 6 are conductively coupled via one and the same strip 5. In Figure 20 a possible extension of the strip 5 as a loop 27 around the add-on tip 21 is shown. In Figure 21 an arrow-shaped extension 28 is used.

[0101] In Figures 22 to 24 various configurations of the opposing second lightning protection devices 6 are shown. In Figure 22 each of the second lightning protection devices 6 shares a common lightning protection base 16, which can be conductive to create a conductive connection between the receivers 15. In Figure 23 the case of Figure 24 a conductive connector 29 is used to electrically and mechanically connect the lightning protection bases 16. Figure 24 The case of a separated and disconnected lightning protection base 16 is shown.

[0102] Figures 25 to 28 Various variants of the threaded receivers 15 for mechanically fixing the strip 5 at the lightning protection devices 4, 6 are shown. In Figure 25 the case of Figure 26 a shear-off bolt 31 is used. In Figure 27 the case of Figure 28 a countersunk bolt 32 is employed, and in Figure 25 the case of

[0103] Finally, Figures 29 to 31 variants of fixing the strip 5 on the surface 34 of the wind turbine blade assembly are shown. In Figure 29 the case of

[0104] In Figure 30In the case where the strip 5 is deployed on the flat surface 34, the sealing layer 36 is tapered to provide improved aerodynamic properties, in particular to reduce the aerodynamic impact of the strip 5 on the wind turbine blade assembly.

[0105] Note that, as an additional element or integrally formed in the conductive material 23, the strip 5 may also include an aerodynamic structure, in particular a vortex generator. For example, as Figure 31 shown, protruding fins 37 on an otherwise flat strip 5 may be used.

[0106] Although the invention has been described in detail with reference to preferred embodiments, the invention is not limited by the disclosed examples, and those skilled in the art can obtain other variations from the disclosed examples without departing from the scope of the invention.

Claims

1. A wind turbine blade assembly (1a, 1b, 1c, 1d), comprising: - A wind turbine blade (2) having a blade root (7) for connection to a hub of a wind turbine, - An assembly tip (10) formed by a blade tip (9) of the wind turbine blade (2) or an attachment tip (21) of a wind turbine blade attachment (19) attached to the blade tip (9) of the wind turbine blade (2), wherein the wind turbine blade assembly (1a, 1b, 1c, 1d) spans a length (11) from the blade root (7) to the assembly tip (10), and - A lightning protection system comprising an internal down conductor (3) within the wind turbine blade (2) and a plurality of lightning receptor devices (4, 6, 14) having at least one receptor (15), the receptor (15) being conductively coupled to the down conductor (3), characterized in that the length (11) of the wind turbine blade assembly (1a, 1b, 1c, 1d) is divided into a first part (12) and a second part (13), the first part (12) spanning from the blade root (7) to at least one first lightning receptor device (4), the internal down conductor (3) extending in the first part (12), the second part (13) spanning from the first lightning receptor device (4) to the assembly tip (10), with no internal down conductor (3) in the second part (13), wherein the lightning protection system further comprises: - At least one second lightning receptor device (6) in the second part (13), and - At least one external conductive strip (5) extending at least between a pair of first and second lightning receptor devices (4, 6) in the second part (13) and being conductively coupled to their receptors (15), wherein at least one of the at least one strip (5) extends in a tip - ward direction beyond the second lightning receptor device (6), the strip (5) being conductively coupled to the receptor (15) of the second lightning receptor device (6).

2. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 1, characterized in that, The strip (5) is made of a continuous material or is segmented.

3. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 1 or 2, characterized in that, The strip (5) is conductively coupled to the receptors (15) of the respective first and second lightning receptor devices (4, 6) through a spark gap.

4. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 3, characterized in that, The strip (5) at least partially surrounds at least one of the receptors (15) at a predetermined distance.

5. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 3, characterized in that, The width and / or thickness of the conductive material (23) of the strip (5) increases in a coupling region around the respective receptor (15) relative to a non - coupled region further away from the receptor (15).

6. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 1 or 2, characterized in that, The strip (5) is mechanically fastened to the lightning receptor devices (4, 6) through the receptors (15).

7. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 6, characterized in that, The receptors (15) are bolts (31, 32) having heads protruding from or flush with the surface of the strip (5).

8. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 1 or 2, characterized in that, The strip (5) is fastened to the surface (34) of the wind turbine blade assembly (1a, 1b, 1c, 1d) by an adhesive and / or mechanically.

9. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 1 or 2, characterized in that, The strip (5) is placed in a recess (35) in the surface (34) of the wind turbine blade assembly (1a, 1b, 1c, 1d) and / or includes a lateral sealing layer (36).

10. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 1 or 2, characterized in that, At least one strip (5) extends on both the windward and leeward sides (17, 18) of the wind turbine blade assembly (1a, 1b, 1c, 1d).

11. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 1 or 2, characterized in that, At least one strip (5) is provided only on the windward side (17) or the leeward side (18) of the wind turbine blade assembly (1a, 1b, 1c, 1d), wherein second lightning protection devices (6) are provided on both sides (17, 18) and their receivers (15) are conductively coupled.

12. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 1 or 2, characterized in that, The strip (5) extends on the component tip (10) to the other side of the wind turbine blade assembly (1a, 1b, 1c, 1d).

13. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 1 or 2, characterized in that, The surface of at least one strip (5) includes at least one aerodynamic structure.

14. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 4, characterized in that, The strip (5) surrounds at least one of the receivers (15) in a ring shape.

15. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 6, characterized in that, The strip (5) is clamped between the receiver (15) of the lightning protection device (4, 6) and the lightning protection base (16).

16. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 7, characterized in that, The bolts (31, 32) are threaded.

17. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 8, characterized in that, The strip (5) is fastened to the surface (34) of the wind turbine blade assembly (1a, 1b, 1c, 1d) by screw or bolt connection.

18. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 9, characterized in that, If the strip (5) is placed on a flat part of the surface (34), the sealing layer (36) is tapered.

19. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 12, characterized in that, The strip (5) is conductively connected to another strip (5) and / or another receiver (15) of the second lightning protection device, and / or is conductively connected to at least one additional strip (27, 28) that at least partially surrounds the wind turbine blade assembly (1a, 1b, 1c, 1d).

20. The wind turbine blade assembly (1a, 1b, 1c, 1d) according to claim 13, characterized in that, The at least one aerodynamic structure is a vortex generator.

21. A method for manufacturing a wind turbine blade assembly (1a, 1b, 1c, 1d) according to any one of claims 1 to 20, the wind turbine blade assembly (1a, 1b, 1c, 1d) including a wind turbine blade attachment (19) having at least one second lightning protection device (6), the method comprising the steps of: - adding the wind turbine blade attachment (19) to a wind turbine blade (2), - attaching at least one strip (5) to the surface (34) so as to conductively couple the receiver (15) of the at least one second lightning protection device (6) to the receiver (15) of at least one of at least one first lightning protection device (4).

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