WIND TURBINE ROTOR BLADE AND WIND TURBINE

Wind turbine rotor blade comprising a shell (13), a web structure (14), and a lightning down conductor arrangement (6), wherein the rotor blade (2) extends in a spanwise direction between a tip-side end (10) and a root-side end (9), wherein the web structure (15) is made from at least one fiber-laminate-based structure, wherein the lightning down conductor arrangement (6) comprises at least one web terminal (16) at least partly embedded in the web structure (15) and at least one root-side end terminal (8) arranged in a root-side end portion of the shell (13) in a spanwise distance to the web terminal (16), wherein the root-side end terminal (8) is connected to the web terminal (16) by an end conductor (19) arranged at the inner surface (20) of the shell (13).

The invention relates to a wind turbine rotor blade comprising a shell, a web structure, and a lightning down conductor arrangement, wherein the rotor blade extends in a spanwise direction between a tip-side end and a root-side end, wherein the web structure is made from at least one fiber-laminate-based structure, wherein the lightning down conductor arrangement comprises at least one web terminal at least partly embedded in the web structure and at least one root-side end terminal arranged in a root-side end portion of the shell in a spanwise distance to the web terminal. Furthermore, the invention relates to a wind turbine rotor blade.

A wind turbine rotor blade may require one or more lightning down conductors to ground lightning strikes which may hit the rotor blade when it is mounted at the hub of a wind turbine, in particular due to the exposed position of the rotor blade. In order to provide such lightning down conductors, it is known to integrate conductive elements in the rotor blade during manufacturing and/or to arrange conductors in the rotor blade after manufacturing. These conductive elements may be arranged for instance in or at the shell of the rotor blade and/or in or at a web structure of the rotor blade.

The lightning down conductors of a rotor blade may for instance be connected to receptors, which may be arranged at the tip, the outer surface or other portions of the shell of the rotor blade. On the root-side end of the rotor blade, a connection occurs to the hub of the rotor blade so that a lightning strike which has hit the rotor blade can be grounded through connected down conductors in the hub and the remainder of the wind turbine.

Therefore, a connection terminal at the root-side end section of the rotor blade has to be integrated into the lightning down conductor system, or connected to the lightning down conductors in the rotor blade, respectively. This may in particular include a connection between a conductor or a corresponding terminal that is arranged on the inboard end of the web structure of the rotor blade and a further terminal at the root-side end of the rotor blade used for connecting the lightning down conductor system in the rotor blade rotor blade to the lighting down conductor system in the hub.

Rotor blades for wind turbines are commonly manufactured using fiber-based material, so that in particular the shell and also the web structure arranged in the shell of the rotor blade may comprise or consist of fiber-laminate-based structures. Electrical conductors used for instance as lightning down conductors may be embedded in the fiber structure during the casting of the rotor blade.

However, depending on the manufacturing method of the rotor blade, the integration of such lightning conductors may be difficult. In particular, within an inboard section of the rotor blade, in particular between the root-wise end of the web structure and the root-side end of the rotor blade, the integration of lightning conductors in the fiber structure of the rotor blade may be tedious and complicated, in particular due to the increased thickness of the fiber structures used for creating the required mechanical stability of the inboard section of the rotor blade.

This may apply in particular for wind turbine rotor blades, which are manufactured in a blade mold from dry sandwiched laminates and/or from preassembled preform elements, which comprise one or more dry fiber layers and/or one or more rigid core components such as balsa wood and/or foam materials already attached to each other prior to their arrangement in the blade mold. Since the conductors have to be integrated between the fiber layers and/or the further components in the blade mold, the arrangement of the conductors may be tedious and difficult, in particular since the dry fiber layers and/or the core components of the preform elements may be untransparent so that the localization and/or arrangement of a conductor to be embedded may be difficult. Furthermore, the integration of the conductor may require one or more cuts through the dry fiber layers in order to rout the conductor properly through the fiber layers prior to the casting process. However, since the conductor may not be recognizable through the untransparent fiber layers, it may be difficult to provide the cuts with the desired precision, in particular when a zig-zag cut pattern with less influence on the mechanical strength of the shell shall be created.

It is therefore the object of the invention to provide an improved rotor blade, in particular with an improved electrical connection in an inboard section of the rotor blade.

According to the invention, this object is solved by a wind turbine rotor blade as initially described, wherein the root-side end terminal is connected to the web terminal by an end conductor arranged at the inner surface of the shell.

The usage of the end conductor arranged at the inner surface of the shell facilitates providing an electrical connection between the web terminal and the root-side end terminal, in particular since the end conductor may be arranged after casting of the rotor blade, or after casting of the shell and the web structure, respectively. By using the end conductor arranged at the inner surface of the shell, providing an electrical connection within the inboard section of the rotor blade is facilitated, since the electrical connection may be established without the need for integrating the conductor in the rotor blade mold prior to the casting of the rotor blade, or prior to a resin infusion into the fiber layers arranged in a blade mold, respectively.

The end conductor connects in particular a web terminal arranged at or close to the root-wise end of the web structure to the root-end terminal at the root-side end of the rotor blade. The web terminal may be for example the element or one of the elements of the lightning down conductor arrangement which is arranged closest to the root-side end of the blade,

The end conductor is used to provide an electrical connection in particular within the inboard section of the rotor blade. In this respect, the term inboard section refers in particular to the section of the rotor blade between a maximum cord-wise width of the rotor blade and the root-side end of the rotor blade, or to the rotor blade root, respectively.

The inboard section is hence the section of the rotor blade, in which the rotor blade cross-section transforms from an airflow shape at the maximum chord position to a circular cross-section at the root side end of the rotor blade. The circular cross-section at the root-side end of the rotor blade may be required in particular for connecting the rotor blade to a circular hub interface and/or to a circular pitch bearing of a wind turbine hub. The section of the rotor blade between the blade tip and the maximum chord position may be denominated as outboard section of the rotor blade, respectively.

The web terminal and the root-side end terminal are arranged in a spanwise distance, which may for instance be between 5 m and 30 m, in particular between 12 m and 20 m, depending on the total spanwise length of the rotor blade. The spanwise distance is bridged by the end conductor in order to provide an electrical connection between the web terminal of the lightning down conductor arrangement of the rotor blade and the root-side end terminal. By this connection, the root-side end terminal is connected to the lightning down conductor arrangement so that by using the root-side end terminal, a connection of the lightning down conductor arrangement to further lightning conductor structures in the wind turbine is possible.

The usage of the end conductor arranged at the inner surface of the shell has the further advantage, that an integration of the conductor into the laminated structure of the shell and/or the web is not required, In particular, at the inboard section of the rotor blade, the laminate thickness may be much larger than in the outboard section of the rotor blade in order to provide the required mechanical strength of the rotor blade. An electrical conductor integrated in the thick laminate structure may be covered by several layers of fiber structures and/or by thicker laminate layers in a dry state so that it cannot be seen or inspected visually. The material may become transparent only after casting, when a rearrangement of the conductor is nor possible anymore. This applies both for wind turbine rotor blades manufactured using preforms and to rotor blades fabricated from dry sandwiched laminates.

Advantageously, the usage of the conductor arranged at the inner surface of the shell avoids additional cutting in the fiber laminates at the inboard-portion of the rotor blade which is beneficial with regard of the mechanical strength of the rotor blade. Also, there is no need to visually inspect the conductor during the mold packaging process, since the arrangement of the end conductor may occur in particular after casting of the rotor blade.

The over-lamination of a conductor during the manufacturing of the rotor blade is a complicated process that may include manual placement of many small mats of a fiber-based material, for instance glass-fiber mats. Due to the numerous process steps, also the risk of casting errors during the manufacturing of the rotor blade is increased, in particular, since the additional covering mats introduced for over-laminating the cable are extra material which is put into a mold used for manufacturing of the rotor blade, This can in some situations lead to the movement of structured mats and/or to the formation of wrinkles in the fiber used for over-laminating the cable and/or for manufacturing the shell and/or the web structure.

Since the end conductor can be retrofitted after the casting of the rotor blade, the complexity of the blade mold packaging process is reduced. Furthermore, the risk of a failure of the connection between the web terminal and the root-end terminal is reduced, since there no need for handling the respective conductor during production of the rotor blade.

Since the end conductor is arranged at the inner surface of the shell, the service of the rotor blade, in particular of lightning down conductor system of the rotor blade, is facilitated due to the improved visibility and the improved accessibility of the end conductor.

In addition, since a connection between the root-end terminal and an embedded conductor may be avoided, the root-terminal may be smaller and/or of a simpler shape, so that it may be provided at less costs. Furthermore, a smaller root-end terminal, or a root-end terminal protruding less from the inner surface of the shell, respectively, may reduce the wear on mandrels used to occupy the interior of the rotor blade during manufacturing. Since the mandrels are removed after casting of the blade, for instance by sliding them out of the root-end of the blade, a flatter or less protruding root-end terminal reduces the wear of the outer surface of the mandrels.

Preferably, the end conductor is a cable, or the end conductor is a solid conductor rail. The end conductor may be a flat cable, a braided cable or a round cable and it may be insulated or non-insulated. The end conductor may also be a solid conductor rail, in particular an uninsulated conductor rail. The end conductor may for instance consist at least partly of copper or another conductive metal.

In a preferred embodiment, the end conductor is attached to the inner surface of the shell by one or more fixation means adhered to the inner surface of the shell. By fixating the end conductor to the inner surface of the shell, an unintended movement of the conductor during operation on the wind turbine rotor blade can be prevented. The usage of fixation means adhered to the inner wall has the advantage that their fixation may occur after casting of the blade and without any influence on the structure and/or the stability of the rotor blade shell. Hence, no additional laminate layers and no conductor has to be added during the manufacturing of the rotor blade.

Preferably, the fixation means is a fastening strip or a lamination layer. The fastening strip may for instance be used for attaching an insulated cable to the inner surface of the shell, since no additional insulation is required in this case.

In addition or alternatively to the fastening strips, one or more lamination layers may be used for adhering the end conductor to the inner surface of the shell, in particular when an uninsulated conductor is used as end conductor, since by the lamination layer, an insulation of the conductor can be obtained. The attachment of the end conductor using the lamination layers may occur in particular after the shell has been casted, so that the lamination layers are laminated to the inner surface of the shell after the shell has been casted.

Preferably, the web terminal is connected to a lightning down conductor of the lightning down conductor arrangement, wherein the lightning down conductor is at least sectionally arranged at and/or embedded in the web structure. Hence, the web terminal may be an end point of a lightning down conductor embedded in and/or arranged at the web structure. The web terminal may in particular be close to the inboard end of the web structure. Preferably, the lightning down conductor may be an in-casted electrical cable or wire, for instance a non-insulated flat conductive cable, a round and/or an insulated conductive cable or any combination thereof.

In a preferred embodiment, the lightning down conductor is electrically connected to at least one connection terminal at least partly embedded in the web structure, wherein the connection terminal is electrically connected to at least one electrically conductive shell section. The at least one connection terminal is used to allow for an electrical connection between the lightning down conductor at the web structure to one or more electrically conductive shell sections.

The connection terminal and the web terminal may be provided by a mutual terminal element. Alternatively, the connection terminal may be a separate terminal arranged in a spanwise distance to the web terminal.

The electrically conductive shell section may be part of the shell and connected to the lightning down conductor arrangement in order to allow for grounding lightning strikes which hit the electrically conductive shell section and/or for providing a potential equalization between the conductive shell sections and the lightning down conductor at the web structure.

Preferably, the connection terminal comprises at least two terminal elements, wherein a section of the lightning down conductor is enclosed between the terminal elements, wherein at least one of the terminal elements is connected to the conductive shell section. Hence, the section of the lightning down conductor is sandwiched between the terminal elements. The section of the lightning down conductor arranged between the terminal elements may be an intermediate section of the lightning down conductor or an end section of the lightning down conductor.

One of the terminal elements or each of terminal elements may be connected to one or more conductive shell sections. The connection terminal may be embedded in such manner in the web structure, that one connection terminal or both connection terminals are accessible from the outside.

In particular, the connection terminal may be integrated in the web structure in such manner that a first terminal element is for instance accessible from a leading edge side of the web structure and the second terminal element is accessible from a trailing edge side of the web structure. This allows for providing electrical connections to both sides of the web structure and therefore to provide electrical connections to conductive shell sections on both sides of the web structure in a so-called T-connection. Advantageously, by providing the connection terminal in such manner that it is accessible from both sides of the web structure, the cutting of holes through the web section after casting can be avoided. Alternatively, the connection terminal may be embedded in such manner that only one of the terminal elements is accessible from outside, wherein in particular also electrical connections to conductive shell sections occur only on one side of the web structure.

In an alternative embodiment, the connection terminal comprises an electrically conductive connector element with a first contact portion connected to the conductive shell section and two second contact portions, wherein one of the second contact portions is connected to the lightning down conductor and the other second contact portion is connected to a further lightning down conductor. In this embodiment of the connection terminal, the first contact portion, which is in particular accessible from outside the web structure, is connected to the conductive shell section. The connection may for instance occur by a cable, which is attached to the first contact portion with one end, wherein the other end is connected to the conductive shell section, either directly or via a shell terminal electrically connected to the electrically conductive shell section.

The second contact portions of the contact element are each connected to one lightning down conductor, wherein in particular an electrical connection between the down conductor and the further lighting down conductor is created via the connector element. One of the down conductors connected to the second section may connect the connection terminal to the web terminal.

It is possible that in the inboard section and optionally also in the outboard section of the rotor blade, more than one connection terminal is arranged, in particular to enable electrical connections to one or more electrically conductive shell section at a plurality of positions over the spanwise length of the blade. The connection terminals may all be manufactured according to one of the aforementioned embodiments. Alternatively, also a combination of these embodiments may be used for a plurality of the connection terminals of a rotor blade.

Preferably, the conductive shell section is connected to at least one shell terminal by at least one shell conductor embedded in the shell, wherein the shell terminal is connected to the connection terminal, in particular by at least one cable.

The electrically conductive shell section may be connected to the shell conductor for instance by one or more carbon-fiber based structures embedded in the shell, so that an electrical connection between the shell conductor and the conductive shell section is obtained. The shell conductor is connected to at least one shell terminal, wherein the shell terminal is connected to the connection terminal for integrating the electrically conductive shell sections in the lightning down conductor system of the rotor blade.

The connection between the shell terminal and the connection terminal at the web may occur in particular by a cable, which is not embedded in the shell and/or in the web structure.

Hence, the cable can be arranged after casting of the rotor blade connecting the shell terminal to the connection terminal at the web. The cable can be in particular an insulated flat, braided or round cable, for example a copper cable. In particular, the same type of cable may be used as for providing the end conductor.

In a preferred embodiment, the shell terminal comprises at least two terminal elements, wherein the section of the shell conductor is enclosed between the terminal elements, wherein at least one of the terminal elements is connected to the connection terminal, or the shell terminal comprises an electrically conductive connector element with a first contact portion connected to the connection terminal and a second contact portion connected to the shell conductor, wherein at least the second contact portion is embedded in the shell.

By providing the shell terminal by at least two terminal elements, advantageously the same terminal elements as for providing the connection terminal at the web may be used. This reduces the number of different terminals required for the manufacturing of the rotor blade, which may be beneficial for simplicity and for cost-saving purposes.

Alternatively, the shell terminal may be provided as an electrically conductive connector element, which comprises a first contact portion and a second contact portion. The first contact portion is connected to the connection terminal, in particular by at least one cable, wherein the second contact portion is connected to the shell conductor embedded in the shell. In this case, in particular the first contact portion is accessible from outside, wherein the second contact portion as well as the section of the shell conductor attached to the second contact portion are embedded in the shell.

In a preferred embodiment, the electrically conductive shell section is a carbon beam, a carbon spar cap, a carbon fiber-based shell section and/or a lightning receptor. Also a combination of different types of electrically conductive shell section may be arranged in the shell and connected to the lightning down conductor arrangement as previously described. The lightning receptor may be part of a lightning receptor system at the outer surface of the shell, wherein the lightning receptor may be, at least partly, exposed to the exterior blade environment for capturing lightning strikes.

Preferably, the web terminal comprises at least two electrically conductive terminal elements, wherein an end section of the lightning down conductor is enclosed between the terminal elements of the web terminal, or the web terminal comprises an electrically conductive connector element with a first contact portion connected to the end conductor and a second contact portion connected to the lightning down conductor, wherein at least the second contact portion is embedded in the web structure.

By providing also the web terminal with two terminal elements, the same terminal elements as used for the connection terminal at the web structure and/or for the shell terminals may be used further reducing the number of different parts used for manufacturing the rotor blade. Alternatively, also the web terminal may be provided as an electrically conductive connector element with a first contact portion and a second contact portion, so that the web terminal may be provided in the same manner as the shell terminals, allowing for usage of the same type of connector elements both for providing the shell terminals and the web terminals. This also beneficially affects the manufacturing process.

In a preferred embodiment, the root-side end terminal comprises at least one end terminal connector element with a contact surface connected to the end conductor, wherein the end terminal connector element is arranged on the inner surface of the shell or partly embedded in the shell. The end terminal connector element may be arranged on the inner surface, so that it may be mounted after casting of the rotor blade, in particular together with the end conductor. Alternatively, the end terminal connector element may be partly embedded in the shell and therefore arranged in the fiber-based laminate structure of the shell prior to the casting.

In particular, the contact surface of the root-end terminal is not embedded in the shell so that it is accessible from the outside allowing for providing the electrical connection to the end conductor, in particular after casting the shell. The end conductor may be connected to the contact surface for instance by at least one electrically conductive fixation means like a screw, by welding or by other fixation methods, It is also possible that the end terminal connector element is integrated in the end conductor, or that the end conductor and the end terminal connector element are provided as a one-piece element.

A wind turbine according to the invention comprises at least one wind turbine rotor blade according to the invention.

Preferably, the rotor blade is attached to a hub of the wind turbine, wherein the root-side end terminal of the rotor blade is connected to a further lightning down conductor arrangement arranged at least partly in the hub, By this connection, the lightning down conductor arrangement of the rotor blade is connected to the further lightning down conductor arrangement in the hub so that lightning strikes hitting the rotor blade of the wind turbine may be grounded through the lightning down conductor arrangement in the rotor blade and the further lightning down conductor arrangement arranged at least partly in the hub. The further lightning down conductor arrangement is in particular connected to ground to allow for grounding of the lightning strikes.

All details and advantages described in relation to the wind turbine rotor blade according to the invention apply correspondingly to the wind turbine according to the invention and vice versa.

InFIG.1, an embodiment of a wind turbine1is shown, The wind turbine1comprises a plurality of wind turbine rotor blades2, which are attached to a hub3of the wind turbine1. The hub3is mounted at a nacelle4of the wind turbine1, wherein the nacelle4is supported on a tower5of the wind turbine1.

Since the rotor blades2of a wind turbine1are prone to be hit by lightning strikes, each of the rotor blades2comprises a lightning down conductor arrangement6for grounding lightning strikes, Therefore, the lightning down conductor arrangement6of the rotor blade2is connected to a further lightning down conductor arrangement7arranged in the hub3, the nacelle4and the tower5for grounding lightning strikes hitting the rotor blade2. For connecting the lightning down conductor arrangement6to the further lightning down conductor arrangement7, the lightning down conductor arrangement6comprises at least one root-side end terminal8arranged at the root-side end9of the rotor blade2. The root-side end terminal8is used for creating an electrical connection to the further lightning down conductor arrangement7.

The lightning down conductor arrangement6of the rotor blade2is shown inFIG.1only in a schematical manner. The lightning down conductor arrangement6may comprise a plurality of lightning down conductors, lightning receptors and the like, which are electrically connected to each other and distributed over the spanwise length of the rotor blade2, or between the root-side end9and a tip-side end10of the rotor blade2, respectively.

InFIG.2, a detailed view of the rotor blade2is shown.FIG.2depicts an inboard section11of the rotor blade, which spans between the root-side end9and a position12, in which the rotor blade2has the largest chord length, hence the largest width in cord-wise direction. InFIG.2, the cord-wise direction is denoted as y-axis, wherein the spanwise direction spans in x-direction towards the tip10of the rotor blade6. Hence, the spanwise direction lies along a longitudinal axis of the rotor blade, wherein the longitudinal axis spans from the root-side end9to the tip-side end10of the rotor blade2along a straight line or along a curve, depending on the shape of the rotor blade2.

The shell13is made from at least one fiber-laminate based structure, InFIG.2, the shell13is shown transparently, so that further components of the rotor blade2arranged within an interior14of the rotor blade2can be seen. The rotor blade2further comprises a web structure15which spans between two opposing sides of the shell13and therefore at least partly through the interior14. Also the web structure15is made from at least one fiber laminate-based structure, The lightning down conductor arrangement6comprises a web terminal16, which is at least partly embedded in the web structure15.

Both the shell13and the web structure can be created simultaneously in a casting process forming the rotor blade2from a plurality of components, including fiber-based structures and further materials like core structures or the like. In addition, also electrically conductive components may be included, for instance the web terminal16, a lightning down conductor17of the lightning down conductor arrangement6and/or a plurality of electrically conductive shell components18.

The web terminal16arranged at the web structure15is at least partly embedded in the web structure15, The web terminal16is connected to the at least one lightning down conductor17of the lightning down conductor arrangement6as well as to the conductive shell sections18, as will be described later in further detail. The web terminal16and the root-end terminal8are arranged in a spanwise distance towards each other. The spanwise distance between the web terminal16and the root-end terminal18may for instance be between 5 m and 30 m, in particular between 12 m and 20 m.

To allow for connecting the lightning down conductor arrangement6to a further lightning down conductor arrangement7at the hub3of the wind turbine1, the web terminal16is connected to the root-end terminal8by an end conductor19for bridging the spanwise distance between the web terminal16and the end terminal8. The end conductor19is arranged at the inner surface20of the shell13. In particular, the end conductor19may be arranged in the interior14after casting the shell13, or the entire rotor blade2, respectively.

By providing an end conductor19arranged at the inner surface20of the shell13, the usage of an embedded conductor, which is embedded in the shell13and/or in the web structure15, can be avoided. This facilitates to establish the electrical connection between the web terminal16and the end terminal8, in particular since the fiber laminate-based structure of the shell13and/or the web15can have a significant thickness at the inboard section11to provide sufficient mechanical strength of the rotor blade2.

The end conductor19is for instance a cable, which is attached with one end to the web terminal16and with the other end to the root-end terminal8. The cable may be provided as a round, flat or braided insulating cable, wherein the end conductor19is attached to the inner surface20for instance by using a plurality of fastening means21. InFIG.2, only one fastening means21is shown exemplarily. The end conductor19may be attached to the inner surface20using a plurality of fastening means21, in particular for attaching at least one section or the entire end conductor19to the inner surface20.

Alternatively, the end conductor19may be a non-insulated cable or a solid conductor rail consisting at least partly of an electrically conductive metal like copper that is attached to the inner surface20of the shell13by one or more fixation means21, which are each provided as a lamination layer23. InFIG.2, two lamination layers23are shown exemplarily in dashed lines. The lamination layers23may be laminated to the inner surface20of the shell13in particular after casting of the shell13, or the entire rotor blade2, respectively. By the lamination layers23, at least one section or the entire end conductor19may be adhered to the inner surface20. Advantageously, the usage of the lamination layers23allows for creating an insulation when an uninsulated cable and/or an uninsulated conductor rail is used as end conductor19.

At the web structure15, a connection terminal24is arranged, wherein the connection terminal24is neighbouring to the web terminal16along the lightning down conductor17. It is alternatively possible that the connection terminal24and the web terminal16are provided by a mutual terminal element.

The connection terminal24is used to connect the lightning down conductor17to at least one electrically conductive shell section18. The connection terminal24is at least at one side of the web structure15accessible from the interior14of the rotor blade2to allow for establishing the electrical connections to the conductive shell sections18. Since the lightning down conductor17may be at least partly integrated in the web structure15, so that it is surrounded by the fiber laminate-based structure forming the web structure15, it may not accessible for the application of further electrical connections. Therefore, the lightning down conductor17is connected to at least one connection terminal24, which is accessible at least at one side of the web structure15for establishing electrical connections. Different embodiments for the connection terminal25will be described later in further detail.

The connection terminal24is connected to two shell terminals25, for instance by one or more cables26. Also, the cables26are arranged in the interior14after casting of the web structure15and/or the shell13, so that they are also not embedded in a fiber laminate-based structure. The cables26may each be an insulated flat, braided or round cable, for example a copper cable. In particular, the same type of cable may be used as for providing the end conductor19.

The shell terminals25are each connected to a shell conductor27, which is embedded at least partly in the shell3, or in the fiber laminate-based structure forming the shell13, respectively. The shell conductors27are connected to the electrically conductive shell sections18by a plurality of carbon fiber-based structures28which surround the shell conductor27at least partly and which are electrically connected and/or integrated into the electrically conductive sections18.

The electrically conductive shell section18may be for instance a pultruded carbon profile, forming in particular a carbon beam or a carbon fiber-based spar cap of the rotor blade2. The carbon-fiber based structures28may be for instance unidirectional carbon fiber mats, which may lay loosely on the electrically conductive shell section18and which may be wrapped for instance around the shell conductor27.

The carbon fiber-based structures28are shown to be arranged at an angle of 45° to the spanwise direction of the shell conductor27, or to the spanwise direction of the electrically conductive shell section18. However, also other orientations or angles, for example an angle of 90°, are possible.

The electrically conductive shell sections18may for instance be, lightning receptors, carbon-fiber-based shell portions, carbon fiber-based beams and/or carbon spar caps of the wind turbine rotor blade2, which are electrically conductive and which are connected to the lightning down conductor17for the grounding of lightning strikes and/or for providing a potential equalization.

It is in particular possible, that along the spanwise length of the blade, further shell conductors27are arranged, wherein these conductors27are also connected to the electrically conductive shell sections18by the carbon fiber-based structures28. For connecting these shell conductors27to the lightning conductors17, further connection terminals24, further shell terminals25as well as further cables26may be used, as it is schematically shown inFIG.2for the most inboard connection, or the connection closest to the root-end9of the rotor blade2, respectively.

InFIG.3, a cross-sectional view of the rotor blade2is shown. The cables26, which connect the shell terminals25to the connection terminal24are attached to the inner surface20of the shell13and/or to the surface of the web structure15by fastening means21, which are provided as fastening strips22as previously described for the end conductor19.

The upper shell terminal25is connected to an electrically conductive shell section18at a pressure side of the blade2, wherein the other shell terminal25is connected to an electrically conductive portion18at the suction side of the blade2. As can be seen fromFIG.3, the electrically conductive sections18may be electrically conductive spar caps attached to the suction side and pressure side ends of the web structure15, Additionally or alternatively, the electrically conductive sections18may be lightning receptors used for catching lightning strikes at an outer surface of the shell13.

InFIG.4, the connection terminal24at the web structure15is shown in detail. From the web structure15, which is a fiber laminate-based structure, only a core panel30is shown, wherein one or more fiber-based players covering the core panel13on the depicted surface, and/or on the opposing surface, respectively, are omitted.

The connection terminal25is shown in an exploded view. The connection terminal25comprises two terminal elements31,32, wherein a section of the lightning down conductor17is enclosed between the terminal elements31,32. Hence, an intermediate or end section of the lightning conductor17is sandwiched between the two terminal elements31,32. The terminal elements31and32of the connection terminal25are electrically conductive and may be for instance made of metal, for example copper or the like. By the connection terminal25, an electrical connection between the cables26, or the conductive shell sections18, respectively, and the lightning down conductor17is established.

The connection terminal elements31,32may be attached towards each other by a plurality of fastening means33, which may for instance be provided as screws. The lightning down conductor17may for instance be a flat or braided cable or a conductor rail, which may comprise corresponding holes for the insertion of the fixation means33so that a stable attachment of the lightning down conductor17between the terminal elements31,32can be obtained.

The connection terminal25is arranged in a corresponding recess34, which is provided in the core element30of the web structure15. Also for the lightning down conductor17, a corresponding recess35may be provided, so that the lightning down conductor17can be embedded in the web structure15underneath one or more fiber laminate layers covering the lightning down conductor17and the core panel13. These covering laminates may comprise an opening, so that the terminal element32remains accessible. It is possible, that the recess34is provided as a through hole, so that also the opposite terminal element31may be accessed from the opposing side of the web structure15for also providing electrical connections to shell terminals25at the other side of the web structure15as previously described.

InFIG.5, the connection terminal24is shown in the mounted state, wherein also two fiber laminates layers36,37are shown, which cover the core element30. The attachment of the cables26to the connection terminal24, or the respective terminal element32, respectively, occurs by a plurality of fastening means61, as will be described later in more detail.

The fiber laminate layer36covering the side of the core element30, on which the cables26are arranged, may comprise an opening which gives access to the entire terminal element32. Alternatively, also small holes may be provided in the fiber laminate layer36, so that only the fastening means61may penetrate the fiber laminate layer36for creating an electrical connection between the cables26and the connection arrangement24.

InFIG.6, an alternative embodiment of the connection terminal24is shown. In this embodiment, the connection terminal24is provided as an electrically conductive connector element38. The connector element38comprises a first contact portion39connected to the conductive shell section18. Furthermore, the connector element38comprises two second connection portions40, which are each connected to a lightning down conductor17of the lightning down conductor arrangement6. In this embodiment, the connection terminal24is used to connect a lightning down conductor17to a further lightning down conductor17, As previously described, also the connector element38may be arranged in a corresponding recess34of the core panel30of the web structure15, wherein in particular the second connection portions14, the lightning down conductors17can be embedded under at least one fiber layer (not shown) and/or in a corresponding recess (not shown).

The connection between the first connection portion39and the cables26occurs by using the fastening means61, which are provided as screws. The fastening means61are connected to cable shoes41of the cables26, wherein the connection to the first connection portion39occurs via the usage of at least one distance element42as well as the usage of one or more washers43,44. The lightning down conductors17are connected to the second connection portions40of the connector element30by a fastening means45and a rectangular washer46.

InFIG.7, the second embodiment of the connection terminal24is shown in its mounted state. The connection terminal24is embedded in the web structure15, wherein the first contact portion39and the second contact portion40are embedded underneath a fiber layer36as previously described.

It is possible, that the recess34is provided as a through hole, so that the connector element38is accessible also from the opposing side of the web structure15. In this case, the thickness of the connector element38between the first connection portion39and an opposing backside63of the connector element38may be equal or approximately equal to the thickness of the core element30of the web structure15, as shown schematically in dashed lines.

Providing an accessible backside63of the connector element38by arranging the connector element38in a through hole facilitates the localization of the connector element38and therefore of the connection terminal24also from the opposing side of the web structure15after casting, Further cables64arranged at the opposing side of the web structure15may be connected to electrically conductive shell sections18arranged in the shell13at least partly on the opposing side of the web structure15, as previously described. The further cables64may be connected to the backside63of the conductor element34for instance by using the same fixation methods as for fixating the cables26to the first connection portion39.

The further cables64may be arranged in parallel to the cables26, and therefore corresponding to the course of the cables26as shown inFIG.2. Alternatively, the cables26and the further cables64may be arranged in other orientations, in particular without significant parallel segments of the cables26,64to avoid repelling of the cables26due to the electric field created in case of a lightning strike, since the repelling could cause damage to the cables26,64and/or to their connections to the connector element38.

InFIG.8, the connection of the cable26to a first embodiment of a shell terminal25is shown. The shell terminal25is provided using two terminal elements47,48, which are embedding an end portion of the shell conductor27. The shell conductor27as well as the shell terminal25are embedded in a recess34provided in a core element30of the fiber-based laminate structure of the shell13. Also, the core element30of the shell13is arranged between two fiber layers36,37.

The terminal elements47,48are in particular fabricated in the same way as the terminal elements31,32used for creating the connection terminal24at the web structure15, so that equally fabricated elements can be used. Also, the connection between the cable26and the shell terminal25occurs in the same manner as described in relation to the connection terminal24.

InFIG.9, a second embodiment of a shell terminal25is shown in an exploded view. The shell terminal25comprises an electrically conductive connector element49with a first contact portion50and a second contact portion51. The first contact portion50is connected to the connection terminal24at the web15, in particular by means of an electrical cable26as previously described.

The second connection portion51is connected to an end section52of the shell conductor27, in particular by using a fastening means45and a rectangular washer46as previously described in relation toFIG.6. The connector element49is electrically conductive and may be manufactured using an electrically conductive metal, for instance copper or the like.

Also, connector element49may be arranged in a corresponding recess34in the core panel30of the shell13. The covering fabric layers36,37, which may at least partially embed the shell terminal25and the shell conductors27, are not shown inFIG.9. The embedding of the connector element49occurs in particular correspondingly to the connection terminal25in the web structure15and hence correspondingly toFIG.7.

InFIG.10, an alternative connection between a cable26and the shell terminal25is shown. The same type of connection may also be used to connect the cable26to one of the embodiments of the connection terminal24at the web structure15.

In this embodiment, the connection of the cable26occurs by using a threaded intermediate section53, which comprises a male threaded portion54and a female threaded portion55. The cable shoe41is connected to the threaded intermediate portion46using a fastening means56, which is provided as a screw. The washers43and44may be used in between the fastening means56and the cable show41, or in between the threaded intermediate section36and the top surface of the shell connection terminal25, respectively.

The web terminal16may be provided in the same manner as the shell terminals25, hence either from two terminal elements47,48and/or from a connector element49. In case of the web terminal8provided as a connector element49, an end section52of the lightning down conductor17is connected to the second connection portion51, wherein the first connection portion50is connected to the root-side end terminal8using the side end conductor19. The same applies, when the web terminal16is provided as two terminal elements47,48, wherein an end section52of the lightning down conductor17is embedded between the terminal elements47,48, and wherein one or both of the terminal elements47,48are connected to the root-side end terminal8using one or more side end conductors19.

InFIG.11, an embodiment of a root-side end terminal8is shown. Additionally, also a portion of the end conductor19is shown. The end conductor19is provided as an insulated round cable, which is attached to the inner surface20of the shell13by a fastening means21. The fastening means21is a fastening strip22, which is for instance adhered to the inner surface20of the shell13.

The web terminal8is provided as an electrically conductive end terminal connector element57, which is partly embedded in the shell13, or partly arranged underneath a top laminate layer36of the shell13, respectively. In an alternative embodiment, the root-side end terminal8comprises a further end terminal connector element58, which is arranged under the end terminal connector element57and which is shown inFIG.11in dashed lines.

By providing the further end terminal connector element58, an opening62may be provided, in which a flat conductor embedded in the shell13may also be connected to the root-side end terminal8, if necessary. If such a connection is not required, the further end terminal connector element58is preferably omitted, so that the root-side end terminal8protrudes less into the interior14of the rotor blade2. This may facilitate the manufacturing of the rotor blade, for instance the pulling out of mandrels arranged in the interior14of the rotor blade2prior to a resin infusion in a plurality of fabric layers arranged around the mandrels for manufacturing of the shell13and/or the web structure15.

The connection of the end conductor19to the root-side end terminal8may occur by using at least one fixation element60, for instance a screw, a plurality of washers and/or the like, for attaching a cable shoe41of the end conductor19to the electrically conductive root-side end terminal8. Alternatively, also other fixation methods like welding may be used. Furthermore, the root-side end terminal8may be used for attaching one or more conductors used for connecting the lightning down conductor arrangement6in the rotor blade2to the further lightning down conductor arrangement7at the hub3as previously described.

It is alternatively possible that the end terminal connector element58is integrated in the end conductor19, or that the end conductor19and the end terminal connector element58are provided as a one-piece element, respectively. In this case, both the end conductor19and the end terminal connector element58may be retrofitted after casting of the rotor blade shell13.

Although the present invention has been described in detail with reference to the preferred embodiment, the present invention is not limited by the disclosed examples from which the skilled person is able to derive other variations without departing from the scope of the invention.