Rotor blade with lightning protection system, wind turbine and method of assembly

Abstract

The invention relates to a rotor blade (1) for a wind turbine (2), the rotor blade (1) comprising a first downlead conductor (6) extending from a tip section (3) to a root section (4), where the first downlead conductor (6) is electrically coupled to a root block (7) of the root section (4), where the root block (7) is electrically coupled to a second downlead conductor (8). The invention relates to a rotor blade (1) comprising a second down-lead connector (8) electrically coupled with a current distribution plate (9), where the current distribution plate (9) is attached to a fixing device (10) for fixing the rotor blade (1) to a first bearing ring (11a) of a bearing (11) of a hub (12). The invention also relates to a wind turbine (2) and to a method for assembling a rotor blade (1) to a hub (12) of a wind turbine (2) and establishing a conduction path between a first down-lead connector (6) of the rotor blade (1) and the hub (12).

Description

Technical Field

[0001] The invention relates to a rotor blade for a wind turbine. The invention also relates to a wind turbine having a universal turbine blade. Furthermore, the invention relates to a method for assembling a rotor blade to a hub of a wind turbine and establishing a conduction path between a first down connector of the rotor blade and the hub. Background Art

[0002] A major challenge in the development of modern wind turbines is to protect them from lightning. Wind turbines are usually the tallest structures in the area where they are located, especially in offshore wind farms. Therefore, the probability of being struck by lightning is very high. Mainly, lightning strikes the highest point, which is usually the tip section of the rotor blades of the wind turbine.

[0003] The development of wind turbines, in particular for offshore wind farms, is directed towards increasing the power generation. This leads to an increase in the size of the generator, the rotor blade tower and thus the overall size of the wind turbine. However, an unavoidable disadvantage is that the probability of attracting lightning strikes increases with the height of the wind turbine, since the attraction of lightning strikes increases with the height of an object. Therefore, the importance of a reliable lightning protection system increases with the height of the wind turbine.

[0004] In modern wind turbines, a lightning protection system with an extensive network of down conductor systems is used to protect the wind turbine from lightning strikes. This down conductor system extends from the outer tip section of the turbine blades (which will be the highest point of the wind turbine when the rotor blades are oriented vertically upwards) to the base of the wind turbine's tower.

[0005] Besides this huge and complex network of downconductors that allows easy flow of high amplitude lightning currents, the shape and design of these downconductors and brackets also play a vital role in the long term transmission of lightning currents.

[0006] A potential weak point of a wind turbine with a lightning protection system is the lightning transmission system from the rotor blades to the hub, since this usually has a direct impact on the installation procedure of the wind turbine when the rotor blades are assembled to the hub and an electrical connection has to be established between the down conductor system of the rotor blades and the down connector system of the hub.

[0007] The installation of rotor blades for wind turbines, in particular for large offshore wind turbines, is an operation that requires a lot of effort and careful planning. The assembly task requires the use of special cranes, wherein the operating costs of these cranes are very high. It is therefore very important to optimize the design of the wind turbine with respect to the assembly process in order to reduce the assembly time and by these means to reduce the operating time required for such cranes. By reducing the operating time of the cranes, the assembly costs of the wind turbine can also be reduced.

[0008] According to the prior art, the connection of the down-conductor system of the rotor blade to the down-conductor system of the hub is implemented separately from the mechanical connection of the rotor blade to the hub. According to the prevailing design, the rotor blade is connected to the bearing ring of the bearing of the hub, and the down-conductor of the rotor blade is connected to the hub via a separate connection plate.

[0009] For this process, several bolts are used. The duration of electrically connecting the down-conductor of each rotor blade can take between 10 and 15 minutes. For a standard wind turbine with three rotor blades, this amounts to 30 to up to 45 minutes. During this time, the crane needs to wait until the next rotor blade can be installed. The additional cost of this idle time is between 20,000 and 25,000 euros.

[0010] Another connection between the down-conductor of a rotor blade and the down-conductor of a hub is known from document EP2783110 Bl. The rotor blade down-conductor is positioned in a central rotor blade chamber. In the root section, a radially extending first conductor element is provided for electrically connecting the down-conductor of the rotor blade with the root bushing of the rotor blade. A radially extending second conductor element is provided for electrically connecting the root bushing with the down-conductor of the hub. This system has the disadvantage that an additional assembly step of connecting the down-conductor of the hub with the second conductor element is necessary. In addition to this, this solution requires additional structural modifications in the root section of the rotor blade, such as an axially extending hole, resulting in potential weaknesses in the structure of the rotor blade. Summary of the invention

[0011] Therefore, the object of the present invention is to eliminate or at least partially eliminate the above described disadvantages in the case of a wind turbine. In particular, the object of the present invention is to create a rotor blade for a wind turbine, a wind turbine and a method for assembling a rotor blade to a hub of a wind turbine, which method provides improved assembly in a simple and inexpensive manner.

[0012] The above objects are achieved by the claims. Accordingly, the problem is solved by a rotor blade for a wind turbine having the features of the independent claim 1, a wind turbine having the features of the subordinate claim 8 and a method for assembling a rotor blade to a hub of a wind turbine and establishing a conduction path between a first down connector of the rotor blade and the hub having the features of the subordinate claim 10. Further features and details of the invention emerge from the dependent claims, the description and the drawings. Features and details described in connection with the rotor blade according to the invention naturally also apply in connection with the wind turbine according to the invention and the method according to the invention and vice versa, so that, with respect to the disclosure of the various aspects of the invention, reference is made to each other or can always be made to each other.

[0013] According to a first aspect of the present invention, the object is achieved by a rotor blade for a wind turbine, the rotor blade comprising a tip section, a root section and an intermediate section between the tip section and the root section. The rotor blade further comprises a first down conductor extending from the tip section to the root section, wherein the first down conductor is electrically coupled to a root block of the root section. The root block is electrically coupled to a second down conductor.

[0014] According to the invention, the second down connector is electrically coupled to a current distribution plate, wherein the current distribution plate is attached to a fixing device for fixing the rotor blade to a first bearing ring of a bearing of a hub.

[0015] The rotor blade is preferably designed as a composite laminate with reinforcing fibers (e.g. glass fibers, carbon fibers, etc.) and a matrix material (e.g. resin, etc.). The rotor blade comprises a plurality of sections, such as a tip section, a middle section and a root section. In the installed state, the tip section points in a direction away from a hub of the wind turbine. Preferably, the lightning receiving end of the first down conductor or the lightning receiving device electrically connected to the first down connector protrudes from the tip section in a direction away from the root section. Thus, during operation of the wind turbine, a lightning strike can be directly transmitted to the first down connector.

[0016] The first down connector is preferably integrated into the wall of the rotor blade, preferably by a lamination process for manufacturing the rotor blade. The first down connector preferably ends in a root section of the rotor blade, preferably spaced apart from a fixing device for fixing the rotor blade to the hub. Thus, the structure of the rotor blade in the region of the fixing device is not further weakened by the first down connector.

[0017] In the root section, the first down connector is electrically coupled to a root block. The root block is configured to provide an electrical connection between the first down connector and an inner chamber of the rotor blade. The root block is preferably integrated into a wall of the rotor blade, preferably by a lamination process for manufacturing the rotor blade.

[0018] The second down-conductor connector is electrically coupled to the root block, preferably by screws, bolts, welding or the like. Alternatively, the second down-conductor connector may be integrally formed with the root block. Preferably, the second down-conductor connector is spaced apart from a wall of the rotor blade. The second down-conductor connector is electrically coupled to the current distribution plate.

[0019] The root segment is configured to be mounted to a first bearing ring of a hub of a wind turbine by means of a plurality of fixing means. Preferably, the fixing means are distributed over the circumference of the root segment, in particular evenly distributed. The fixing means preferably comprise a cylindrical nut, which is arranged in a radially extending hole of the rotor blade. The plurality of holes are distributed around the circumference of the rotor blade, in particular evenly distributed, preferably distributed in two adjacent rows. Each cylindrical nut comprises a threaded portion for fixing a threaded column. Preferably, the threaded column protrudes from the root segment of the rotor blade in a direction parallel to the longitudinal axis of the rotor blade. The threaded column is configured to be inserted into a through hole of a first bearing ring, in particular an inner bearing ring, of the hub and to be fixed to the first bearing ring by means of a nut.

[0020] The current distribution plate is attached to a fixing device for fixing the rotor blade to the hub. Furthermore, the current distribution plate is mechanically coupled to the fixing device. When the fixing device comprises a barrel nut, it is preferred that the current distribution plate is mechanically fixed to the barrel nut, preferably by screws, bolts or the like. By these means, an electrical connection between the first down connector and the barrel nut is established.

[0021] The material of the first down conductor and / or the second down conductor and / or the root block and / or the current distribution plate is preferably selected for improved conductivity in order to conduct the high current of a lightning strike without overheating due to inertial resistance. Preferred materials for this purpose are copper, stainless steel, aluminum, etc.

[0022] The rotor blade according to the invention has the advantage over conventional rotor blades that the assembly to the hub of a wind turbine is improved in a simple and inexpensive manner. Since the current distribution plate is already attached to the fixture during the production of the rotor blade, only the rotor blade needs to be assembled to the hub via the fixture at the construction site, and advantageously, during this process, the electrical connection of the rotor blade lightning protection device to the hub, i.e. the bearing of the hub, is automatically established without the need for further assembly steps. As a result, the time for the installation procedure at the construction site can be significantly reduced, and the costs for a special crane can thereby also be reduced.

[0023] According to a preferred further development of the invention, the rotor blade can be provided with a current distribution plate being attached to three fixing means for fixing the rotor blade to the first bearing ring of the hub. When the fixing means comprise a barrel nut, preferably, the current distribution plate is mechanically fixed to the three barrel nuts, each preferably by means of a screw, a bolt or the like. In these ways, an electrical connection between the first downconductor and the three barrel nuts is established. This has the advantage that the current from the current distribution plate is divided into three fixing means in a simple and inexpensive manner, and the electrical stress of each fixing means is reduced. Thus, the risk of damage to the rotor blade due to a lightning strike is further reduced.

[0024] Preferably, the current distribution plate is attached to three barrel nuts of the fixture, wherein the barrel nuts are arranged in two different barrel nut rings of the rotor blade. Each barrel nut ring comprises a plurality of barrel nuts, which are distributed over the circumference of the rotor blade, in particular evenly distributed. Thus, the current distribution plate is attached to two adjacent barrel nuts of a first barrel nut ring and to one adjacent barrel nut of a second barrel nut ring. Preferably, the barrel nuts of the two barrel nut rings are provided with an offset between the two barrel nut rings. The offset is preferably such that the barrel nut of the second barrel nut ring is arranged in the middle of two adjacent barrel nuts of the first barrel nut ring relative to the circumferential direction of the rotor blade. Furthermore, the barrel nut rings are spaced apart from each other relative to the axial direction of the rotor blade. In other words, preferably, the imaginary connecting lines between the center points of the barrel nuts involved form an isosceles triangle. This has the advantage that the current from the current distribution plate is divided into three barrel nuts and three threaded columns in a simple and inexpensive manner, wherein the electrical stress of each barrel nut and threaded column is reduced. Thus, the risk of damage to the rotor blades due to lightning strikes is further reduced.

[0025] More preferably, the current distribution plate comprises a stress compensation section between the barrel nut rings. A stress compensation section may be understood as a section which is configured to compensate for relative tolerances between two barrel nut rings. Such tolerances may occur due to manufacturing problems, mechanical stresses, thermal expansion, etc. Preferably, the stress compensation section comprises a bending and / or kinking area to better allow relative movement of the barrel nuts of different barrel nut rings. Additionally or alternatively, the stress compensation section may comprise a reduced thickness and / or width of the current distribution plate. This has the advantage that the preassembly of the rotor blades may be improved in a simple and inexpensive manner and the risk of damage to the walls, barrel nuts and current distribution plates of the rotor blades due to stresses (e.g. due to different thermal expansions of the walls and plates, in particular due to lightning strikes) may be reduced.

[0026] In a particularly preferred embodiment of the invention, a spacer is provided between the wall of the rotor blade and the second down-conductor in the root section between the root block and the current distribution plate. Preferably, the spacer is made of a non-conductive material. Preferably, the spacer is laminated to the wall, in particular during the process of laminating the wall of the rotor blade. The spacer has the technical effect of ensuring a safe distance between the second down-conductor and the wall, so as to avoid uncontrolled lightning jumps between the second down-conductor and the wall. This has the advantage that the risk of damage to the rotor blade due to a lightning strike is further reduced in a simple and inexpensive manner.

[0027] Preferably, the second down connector is clamped or screwed to the current distribution plate. In a preferred embodiment, the second down connector comprises a wire eye, wherein the wire eye is screwed or bolted to the current distribution plate. In another preferred embodiment, the second down connector is clamped between a fixing plate and the current distribution plate, wherein the fixing plate is preferably screwed or bolted to the current distribution plate. This has the advantage that tolerance compensation for attaching the current distribution plate to the fixing device can be provided in a simple and inexpensive manner. Thus, pre-assembly of the rotor blade is improved.

[0028] According to a preferred embodiment of the invention, the second down-conductor connector is attached to the root block via a connection plate. Preferably, the second down-conductor connector is clamped between the connection plate and the root block. The connection plate is preferably fixed to the root block with screws. This has the advantage that tolerance compensation for attaching the current distribution plate to the fixture can be provided in a simple and inexpensive manner. Thus, the pre-assembly of the rotor blade is improved.

[0029] According to a second aspect of the invention, the object is achieved by a wind turbine comprising a foundation, a tower, a nacelle and a hub, wherein the hub is rotatably mounted to the nacelle and is coupled to a generator for converting mechanical energy into electrical energy. According to the invention, a rotor blade according to the first aspect of the invention is attached to a first bearing ring of the hub by a plurality of fixing means.

[0030] Preferably, the wind turbine comprises three rotor blades according to the first aspect of the invention, each rotor blade being attached to the first bearing ring of the hub by a plurality of fixing means. Preferably, the fixing means comprises a barrel nut, a fixing stud and a fixing nut.

[0031] Since the rotor blade is fixed to the first bearing ring (preferably the inner bearing ring), the lightning protection system of the rotor blade is coupled with the bearing of the hub. Preferably, the second bearing ring of the hub is electrically coupled with the base downconductor of the base. Thus, the current from the lightning strike can easily flow from the tip section of the rotor blade to the base of the wind turbine, reducing the risk of damage to components of the wind turbine.

[0032] The wind turbine according to the invention has all the advantages that have been described for the rotor blade according to the first aspect of the invention. Accordingly, the wind turbine according to the invention has the advantage compared to conventional wind turbines that the assembly of the rotor blades to the hub of the wind turbine is improved in a simple and inexpensive manner. Since the current distribution plate is already attached to the fixture during the production of the rotor blades, at the construction site, only the rotor blades need to be assembled to the hub via the fixture, and advantageously, during this process, the electrical connection of the rotor blade lightning protection device to the hub, i.e. the bearing of the hub, is automatically established without the need for further assembly steps. As a result, the time for the installation procedure at the construction site can be significantly reduced, and the costs for a special crane can thereby also be reduced.

[0033] According to the present invention, it is preferred that the first bearing ring is electrically connected to a current bypass device for providing a further conduction path from the first bearing ring to the second bearing ring of the bearing, thereby electrically bypassing the roller arrangement of the bearing. Preferably, the current bypass device comprises a bypass brush. It is also preferred that the bypass brush contacts the first bearing ring in a manner that allows the first bearing ring to rotate relative to the bypass brush. The bypass brush is preferably fixedly attached to the second bearing ring. In the event of a lightning strike, a first part of the current from the first bearing ring will be transmitted to the second bearing ring via the current bypass device, and a second part of the current will be transmitted to the second bearing ring via the roller arrangement of the bearing. This has the advantage that in the event of a lightning strike, the stress of the roller arrangement of the bearing is reduced and thereby the risk of damage is reduced in a simple and inexpensive manner. Thus, the durability of the wind turbine is further improved.

[0034] According to a third aspect of the present invention, the object is achieved by a method for assembling a rotor blade to a hub of a wind turbine and establishing a conductive path between a first down connector of the rotor blade and the hub. The method comprises:

[0035] - providing a hub having a bearing, said bearing comprising a first bearing ring and a second bearing ring, said hub being mounted on a tower,

[0036] - providing a rotor blade according to the first aspect of the invention, wherein a fixing device is provided at a root section of the rotor blade,

[0037] - inserting an end section of the fixing device through a hole in the first bearing ring, and

[0038] - Fixing the rotor blade to the first bearing ring by attaching a fixing nut to the end section of the fixing device.

[0039] Preferably, the fixing device comprises a cylindrical nut and a threaded column, wherein the cylindrical nut is positioned within the wall of the rotor blade in the root section of the rotor blade; each threaded column is screwed into a cylindrical nut, and the opposite ends of each threaded column are guided through a hole in the first bearing ring and fixed to the first bearing ring by the nut.

[0040] The method according to the invention has all the advantages already described for the rotor blade according to the first aspect of the invention and for the wind turbine according to the second aspect of the invention. Accordingly, the method according to the invention has the advantage over conventional methods that the assembly of the rotor blade to the hub of a wind turbine is improved in a simple and inexpensive manner. Since the current distribution plate is already attached to the fixture during the production of the rotor blade, at the construction site, only the rotor blade needs to be assembled to the hub via the fixture, and advantageously, during this process, the electrical connection of the rotor blade lightning protection device to the hub, i.e. the bearing of the hub, is automatically established without the need for further assembly steps. As a result, the time for the installation procedure at the construction site can be significantly reduced and the costs for a special crane can thereby also be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Further advantages, features and details of the invention emerge from the following description, in which a working example of the invention is described in detail with reference to the accompanying drawings. Thus, the features from the claims and the features mentioned in the description may be essential to the invention alone or in any combination. In the drawings:

[0042] FIG. 1 shows a schematic detailed view of a root section of a rotor blade after assembly to a hub according to the prior art,

[0043] Figure 2 shows a schematic side view of a preferred embodiment of a rotor blade according to the invention,

[0044] Figure 3 shows a schematic detailed view of a root section of a rotor blade after assembly to a hub according to a preferred first embodiment of the invention,

[0045] Figure 4 shows a schematic detailed view of a root section of a rotor blade after assembly to a hub according to a preferred second embodiment of the invention,

[0046] Figure 5 shows a schematic detailed view of a root section of a rotor blade after assembly to a hub according to a preferred third embodiment of the invention,

[0047] Figure 6 shows a schematic detailed view of a root section of a rotor blade after assembly to a hub according to a preferred fourth embodiment of the invention,

[0048] Figure 7 A schematic front view showing a preferred embodiment of a wind turbine according to the invention, and

[0049] Figure 8A schematic flow chart of a preferred embodiment of the method according to the present invention is shown.

[0050] In FIGS. 1-8 , elements having the same function and effect are denoted by the same reference numerals, respectively. DETAILED DESCRIPTION

[0051] In FIG1 , a root section 4 of a rotor blade 1 according to the prior art is shown in a schematic detailed view after being assembled to a hub 12. A second down conductor 8 of a lightning protection system of the rotor blade 1 is mounted with a first end to a root block 7 and with a second end to the hub 12 by means of a plurality of fixing means 10, such as screws. The root block 7 is integrated into the wall 15 of the rotor blade 1. Furthermore, the rotor blade 1 is secured to the rotor blade 1 by means of a barrel nut 10a with a threaded stud 10c (not shown) (see FIG. Figure 3 ) and a fixing nut 10b (not shown) (see Figure 3 ) is fitted and fixed to the impeller hub 12. The cylindrical nut 10a is arranged in two cylindrical nut rings 13.

[0052] exist Figure 2 , a preferred embodiment of a rotor blade 1 according to the invention is shown in a schematic side view. The rotor blade 1 comprises a tip section 3, a root section 4 and an intermediate section 5 located between the tip section and the root section 4. In the tip section 3, a lightning receptor 23 protrudes through the wall 15 of the rotor blade 1. The lightning receptor 23 is connected to a first down conductor 6 (see FIG. 1 ) of the rotor blade 1 (not shown). Figure 3 ) are electrically connected. In the root section 4, two barrel nut rings 13 with barrel nuts 10a are provided. Each barrel nut 10a is mechanically coupled to a threaded stud 10c. The threaded stud 10c protrudes from the root section 4, facing away from the middle section 5. In this state, the rotor blade 1 is configured for being assembled to a wind turbine 2 (see Figure 7 ) of the blade hub 12 (see Figure 3 ).

[0053] exist Figure 3 , a root section 4 of a rotor blade 1 after being assembled to a hub 12 according to a preferred first embodiment of the invention is illustrated in a schematic detailed view. The rotor blade 1 is assembled to the hub 12 by means of a plurality of fixing devices 10. The fixing devices 10 comprise threaded studs 10c cooperating with cylindrical nuts 10a, which are positioned in the wall 15 of the rotor blade 1. The threaded studs 10c are inserted into the holes 21 of the first bearing ring 11a of the bearing 11 of the hub 12 and are fixed to the first bearing ring 11a by means of fixing nuts 10b. The first bearing ring 11a is configured as an inner bearing ring of the bearing 11.

[0054] For transmitting the lightning from the lightning receiver 23 (see Figure 2) is embedded in the wall 15 of the rotor blade 1 and is electrically connected to the root block 7. The root block 7 is partially embedded in the wall 15 and protrudes into the inner chamber 24 of the rotor blade 1. A second down conductor 8 is positioned within the inner chamber. The second down conductor 8 is electrically connected to the root block 7 and to the current distribution plate 9. The current distribution plate 9 is electrically connected to several barrel nuts 10a, for example by bolts or screws not shown. Thus, by mounting the rotor blade 1 to the hub 12, an electrical path from the lightning receptor 23 through the first down conductor, the root block 7, the second down conductor 8, the current distribution plate 9, the barrel nuts 10a, the threaded column 10c, the inner bearing ring 11a, the roller arrangement 11c of the bearing 11 and the second bearing ring 11b of the bearing 11 to the body 25 of the hub is automatically established without the need for further assembly steps. The second bearing ring 11b is configured as an outer bearing ring of the bearing 11.

[0055] Figure 4 In a schematic detailed view, a root section 4 of a rotor blade 1 after being assembled to a hub 12 according to a preferred second embodiment of the invention is shown. The second embodiment corresponds to the first embodiment and further comprises a current bypass device 20 at the bearing 11 of the hub 12. The current bypass device 20 is fixedly attached to the second bearing ring 11b and comprises a conductive brush 22 in contact with the first bearing ring 11a. By these means, the stress of the roller device 11c in the event of a lightning strike is reduced, because part of the current from the first bearing ring 11a is transferred to the second bearing ring 11b via the current bypass device 20.

[0056] exist Figure 5 , the root section 4 of the rotor blade 1 after being assembled to the hub 12 according to a preferred third embodiment of the present invention is illustrated in a schematic detailed view. The second down conductor 8 is attached to the root block 7 by means of a connecting plate 16 (for example, by screws not shown). The current distribution plate 9 is assigned to one tubular nut 10a of the upper tubular nut ring 13 (in this view) and two tubular nuts 10a of the lower tubular nut ring 13 (in this view). Alternatively, the current distribution plate 9 may be assigned to one or more tubular nuts 10a of the upper tubular nut ring 13 and one or more tubular nuts 10a of the lower tubular nut ring 13.

[0057] Figure 6In a schematic detailed view, a root section 4 of a rotor blade 1 after being assembled to a hub 12 according to a preferred fourth embodiment of the invention is shown. The fourth embodiment corresponds to the third embodiment and differs in the formation of a current distribution plate 9. The current distribution plate 9 is assigned to two tubular nuts 10a of an upper tubular nut ring 13 (in this view) and one tubular nut 10a of a lower tubular nut ring 13 (in this view). In addition, the current distribution plate 9 includes a stress compensation section 9a between the two tubular nut rings 13 for compensating tension caused by temperature differences, for example, caused by a lightning strike. Alternatively, the current distribution plate 9 can be assigned to one or more tubular nuts 10a of the upper tubular nut ring 13 and one or more tubular nuts 10a of the lower tubular nut ring 13. In addition, a spacer 14 is arranged between the second down conductor 8 and the wall 15 for keeping the second down conductor 8 reliably spaced apart from the wall 15.

[0058] exist Figure 7 , a preferred embodiment of a wind turbine 2 according to the invention is shown in a schematic front view. The wind turbine 2 is configured for offshore deployment and comprises a foundation 17, a tower 18 and a nacelle 19 mounted to the tower 18. At the nacelle 19, a hub 12 is arranged, which has three mounted rotor blades 1 according to the invention.

[0059] Figure 8 A preferred embodiment of the method according to the invention is shown in a schematic flow chart. In a first action 100, a hub 12 is provided which is mounted on a tower 18. The hub 12 comprises a plurality of (preferably three) bearings 11, each bearing 11 having a first bearing ring 11a, a second bearing ring 11b and a plurality of roller devices 11c. In a second action 200, a rotor blade 1 according to the invention is provided. The rotor blade 1 comprises in a root section 4 a plurality of fixing devices 10, preferably cylindrical nuts 10a cooperating with threaded columns 10c, for fixing the rotor blade 1 to the first bearing ring 11a. Preferably, all threaded columns 10c protrude from the rotor blade 1 in the same assembly direction, facing away from the middle section 5 of the rotor blade 1.

[0060] In a third action 300 , an end section of the fixing device 10 , preferably of the threaded stud 10 c , is passed through the hole 21 of the first bearing ring 11 a , preferably in such a way that the end section protrudes from the hole 21 .

[0061] In a fourth action 400 , the rotor blade 1 is fixed to the first bearing ring 11 a by attaching the fixing nut 10 b to an end section of the fixing device 10 , preferably to a protruding end section of the threaded stud 10 c .

[0062] Preferably, the second to fourth actions 200 to 400 are repeated in order to assemble other rotor blades 1. In this way, the rotor blade 1 is assembled to the hub 12 and the electrical connection of the lightning receptor 23 to the hub 12 is established without requiring further assembly actions.

Claims

1. A rotor blade (1) for a wind turbine (2), the rotor blade (1) comprising a tip section (3), a root section (4) and an intermediate section (5) between the tip section (3) and the root section (4), wherein: The rotor blade (1) further comprises a first down conductor (6), the first down conductor (6) extending from the tip section (3) to the root section (4), wherein the first down conductor (6) is electrically coupled to a root block (7) of the root section (4), wherein the root block (7) is electrically coupled to a second down conductor (8), It is characterized in that The second down-conductor (8) is electrically coupled to a current distribution plate (9), wherein the current distribution plate (9) is attached to a fixing device (10) for fixing the rotor blade (1) to a first bearing ring (11a) of a bearing (11) of a hub (12).

2. The rotor blade (1) according to claim 1, It is characterized in that The current distribution plate (9) is attached to three fixing devices (10) for fixing the rotor blade (1) to the first bearing ring (11a).

3. The rotor blade (1) according to claim 1 or 2, It is characterized in that The current distribution plate (9) is attached to three barrel nuts (10a) of the fixing device (10), wherein the barrel nuts (10a) are arranged in two different barrel nut rings (13) of the rotor blade (1).

4. The rotor blade (1) according to claim 3, It is characterized in that The current distribution plate (9) comprises a stress compensation section (9a) between the barrel nut rings (13).

5. A rotor blade (1) according to any one of the preceding claims, It is characterized in that A spacer (14) is provided between a wall (15) of the rotor blade (1) and the second down connector (8) in the root section (4) between the root block (7) and the current distribution plate (9).

6. A rotor blade (1) according to any one of the preceding claims, It is characterized in that The second downconductor connector (8) is clamped or screwed to the current distribution plate (9).

7. A rotor blade (1) according to any one of the preceding claims, It is characterized in that The second downconductor (8) is attached to the root block (7) by means of a connection plate (16).

8. A wind turbine (2) comprising a base (17), a tower (18), a nacelle (19) and a hub (12), wherein: The hub (12) is rotatably mounted to the nacelle (19) and is coupled to a generator for converting mechanical energy into electrical energy. It is characterized in that A rotor blade (1) according to any of the preceding claims is attached to a first bearing ring (11a) of the hub (12) by means of a plurality of fixing means (10).

9. A wind turbine (2) according to claim 8, It is characterized in that The first bearing ring (11a) is electrically connected to a current bypass arrangement (20) for providing an alternative conduction path from the first bearing ring (11a) to a second bearing ring (11b) of the bearing (11), thereby electrically bypassing a roller arrangement (11c) of the bearing (11).

10. A method for assembling a rotor blade (1) to a hub (12) of a wind turbine (2) and establishing a conductive path between a first down connector (6) of the rotor blade (1) and the hub (12), the method comprising: - providing a hub (12) having a bearing (11), the bearing (11) comprising a first bearing ring (11a) and a second bearing ring (11b), the hub (12) being mounted on a tower (18), - providing a rotor blade (1) according to any one of claims 1 to 7, wherein a fixing device (10) is provided at a root section (4) of the rotor blade (1), - inserting an end section of the fixing device (10) through a hole (21) in the first bearing ring (11a), and - fixing the rotor blade (1) to the first bearing ring (11a) by attaching a fixing nut (10b) to the end section of the fixing device (10).

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