Patent Description:
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.

A document representing the prior art is e.g. <CIT>.

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 <NUM> and <NUM>, in particular between <NUM> and <NUM>, 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.

The drawings, however, are only principal sketches designed solely for the purpose of illustration and do not limit the invention. The drawings show:.

In <FIG>, an embodiment of a wind turbine <NUM> is shown. The wind turbine <NUM> comprises a plurality of wind turbine rotor blades <NUM>, which are attached to a hub <NUM> of the wind turbine <NUM>. The hub <NUM> is mounted at a nacelle <NUM> of the wind turbine <NUM>, wherein the nacelle <NUM> is supported on a tower <NUM> of the wind turbine <NUM>.

Since the rotor blades <NUM> of a wind turbine <NUM> are prone to be hit by lightning strikes, each of the rotor blades <NUM> comprises a lightning down conductor arrangement <NUM> for grounding lightning strikes. Therefore, the lightning down conductor arrangement <NUM> of the rotor blade <NUM> is connected to a further lightning down conductor arrangement <NUM> arranged in the hub <NUM>, the nacelle <NUM> and the tower <NUM> for grounding lightning strikes hitting the rotor blade <NUM>. For connecting the lightning down conductor arrangement <NUM> to the further lightning down conductor arrangement <NUM>, the lightning down conductor arrangement <NUM> comprises at least one root-side end terminal <NUM> arranged at the root-side end <NUM> of the rotor blade <NUM>. The root-side end terminal <NUM> is used for creating an electrical connection to the further lightning down conductor arrangement <NUM>.

The lightning down conductor arrangement <NUM> of the rotor blade <NUM> is shown in <FIG> only in a schematical manner. The lightning down conductor arrangement <NUM> may 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 blade <NUM>, or between the root-side end <NUM> and a tip-side end <NUM> of the rotor blade <NUM>, respectively.

In <FIG>, a detailed view of the rotor blade <NUM> is shown. <FIG> depicts an inboard section <NUM> of the rotor blade, which spans between the root-side end <NUM> and a position <NUM>, in which the rotor blade <NUM> has the largest chord length, hence the largest width in cord-wise direction. In <FIG>, the cord-wise direction is denoted as y-axis, wherein the spanwise direction spans in x-direction towards the tip <NUM> of the rotor blade <NUM>. Hence, the spanwise direction lies along a longitudinal axis of the rotor blade, wherein the longitudinal axis spans from the root-side end <NUM> to the tip-side end <NUM> of the rotor blade <NUM> along a straight line or along a curve, depending on the shape of the rotor blade <NUM>.

The shell <NUM> is made from at least one fiber-laminate based structure. In <FIG>, the shell <NUM> is shown transparently, so that further components of the rotor blade <NUM> arranged within an interior <NUM> of the rotor blade <NUM> can be seen. The rotor blade <NUM> further comprises a web structure <NUM> which spans between two opposing sides of the shell <NUM> and therefore at least partly through the interior <NUM>. Also the web structure <NUM> is made from at least one fiber laminate-based structure. The lightning down conductor arrangement <NUM> comprises a web terminal <NUM>, which is at least partly embedded in the web structure <NUM>.

Both the shell <NUM> and the web structure can be created simultaneously in a casting process forming the rotor blade <NUM> from 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 terminal <NUM>, a lightning down conductor <NUM> of the lightning down conductor arrangement <NUM> and/or a plurality of electrically conductive shell components <NUM>.

The web terminal <NUM> arranged at the web structure <NUM> is at least partly embedded in the web structure <NUM>. The web terminal <NUM> is connected to the at least one lightning down conductor <NUM> of the lightning down conductor arrangement <NUM> as well as to the conductive shell sections <NUM>, as will be described later in further detail. The web terminal <NUM> and the root-end terminal <NUM> are arranged in a spanwise distance towards each other. The spanwise distance between the web terminal <NUM> and the root-end terminal <NUM> may for instance be between <NUM> and <NUM>, in particular between <NUM> and <NUM>.

To allow for connecting the lightning down conductor arrangement <NUM> to a further lightning down conductor arrangement <NUM> at the hub <NUM> of the wind turbine <NUM>, the web terminal <NUM> is connected to the root-end terminal <NUM> by an end conductor <NUM> for bridging the spanwise distance between the web terminal <NUM> and the end terminal <NUM>. The end conductor <NUM> is arranged at the inner surface <NUM> of the shell <NUM>. In particular, the end conductor <NUM> may be arranged in the interior <NUM> after casting the shell <NUM>, or the entire rotor blade <NUM>, respectively.

By providing an end conductor <NUM> arranged at the inner surface <NUM> of the shell <NUM>, the usage of an embedded conductor, which is embedded in the shell <NUM> and/or in the web structure <NUM>, can be avoided. This facilitates to establish the electrical connection between the web terminal <NUM> and the end terminal <NUM>, in particular since the fiber laminate-based structure of the shell <NUM> and/or the web <NUM> can have a significant thickness at the inboard section <NUM> to provide sufficient mechanical strength of the rotor blade <NUM>.

The end conductor <NUM> is for instance a cable, which is attached with one end to the web terminal <NUM> and with the other end to the root-end terminal <NUM>. The cable may be provided as a round, flat or braided insulating cable, wherein the end conductor <NUM> is attached to the inner surface <NUM> for instance by using a plurality of fastening means <NUM>. In <FIG>, only one fastening means <NUM> is shown exemplarily. The end conductor <NUM> may be attached to the inner surface <NUM> using a plurality of fastening means <NUM>, in particular for attaching at least one section or the entire end conductor <NUM> to the inner surface <NUM>.

Alternatively, the end conductor <NUM> may 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 surface <NUM> of the shell <NUM> by one or more fixation means <NUM>, which are each provided as a lamination layer <NUM>. In <FIG>, two lamination layers <NUM> are shown exemplarily in dashed lines. The lamination layers <NUM> may be laminated to the inner surface <NUM> of the shell <NUM> in particular after casting of the shell <NUM>, or the entire rotor blade <NUM>, respectively. By the lamination layers <NUM>, at least one section or the entire end conductor <NUM> may be adhered to the inner surface <NUM>. Advantageously, the usage of the lamination layers <NUM> allows for creating an insulation when an uninsulated cable and/or an uninsulated conductor rail is used as end conductor <NUM>.

At the web structure <NUM>, a connection terminal <NUM> is arranged, wherein the connection terminal <NUM> is neighbouring to the web terminal <NUM> along the lightning down conductor <NUM>. It is alternatively possible that the connection terminal <NUM> and the web terminal <NUM> are provided by a mutual terminal element.

The connection terminal <NUM> is used to connect the lightning down conductor <NUM> to at least one electrically conductive shell section <NUM>. The connection terminal <NUM> is at least at one side of the web structure <NUM> accessible from the interior <NUM> of the rotor blade <NUM> to allow for establishing the electrical connections to the conductive shell sections <NUM>. Since the lightning down conductor <NUM> may be at least partly integrated in the web structure <NUM>, so that it is surrounded by the fiber laminate-based structure forming the web structure <NUM>, it may not accessible for the application of further electrical connections. Therefore, the lightning down conductor <NUM> is connected to at least one connection terminal <NUM>, which is accessible at least at one side of the web structure <NUM> for establishing electrical connections. Different embodiments for the connection terminal <NUM> will be described later in further detail.

The connection terminal <NUM> is connected to two shell terminals <NUM>, for instance by one or more cables <NUM>. Also, the cables <NUM> are arranged in the interior <NUM> after casting of the web structure <NUM> and/or the shell <NUM>, so that they are also not embedded in a fiber laminate-based structure. The cables <NUM> may 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 conductor <NUM>.

The shell terminals <NUM> are each connected to a shell conductor <NUM>, which is embedded at least partly in the shell <NUM>, or in the fiber laminate-based structure forming the shell <NUM>, respectively. The shell conductors <NUM> are connected to the electrically conductive shell sections <NUM> by a plurality of carbon fiber-based structures <NUM> which surround the shell conductor <NUM> at least partly and which are electrically connected and/or integrated into the electrically conductive sections <NUM>.

The electrically conductive shell section <NUM> may be for instance a pultruded carbon profile, forming in particular a carbon beam or a carbon fiber-based spar cap of the rotor blade <NUM>. The carbon-fiber based structures <NUM> may be for instance unidirectional carbon fiber mats, which may lay loosely on the electrically conductive shell section <NUM> and which may be wrapped for instance around the shell conductor <NUM>.

The carbon fiber-based structures <NUM> are shown to be arranged at an angle of <NUM>° to the spanwise direction of the shell conductor <NUM>, or to the spanwise direction of the electrically conductive shell section <NUM>. However, also other orientations or angles, for example an angle of <NUM>°, are possible.

The electrically conductive shell sections <NUM> may for instance be, lightning receptors, carbon-fiber-based shell portions, carbon fiber-based beams and/or carbon spar caps of the wind turbine rotor blade <NUM>, which are electrically conductive and which are connected to the lightning down conductor <NUM> for 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 conductors <NUM> are arranged, wherein these conductors <NUM> are also connected to the electrically conductive shell sections <NUM> by the carbon fiber-based structures <NUM>. For connecting these shell conductors <NUM> to the lightning conductors <NUM>, further connection terminals <NUM>, further shell terminals <NUM> as well as further cables <NUM> may be used, as it is schematically shown in <FIG> for the most inboard connection, or the connection closest to the root-end <NUM> of the rotor blade <NUM>, respectively.

In <FIG>, a cross-sectional view of the rotor blade <NUM> is shown. The cables <NUM>, which connect the shell terminals <NUM> to the connection terminal <NUM> are attached to the inner surface <NUM> of the shell <NUM> and/or to the surface of the web structure <NUM> by fastening means <NUM>, which are provided as fastening strips <NUM> as previously described for the end conductor <NUM>.

The upper shell terminal <NUM> is connected to an electrically conductive shell section <NUM> at a pressure side of the blade <NUM>, wherein the other shell terminal <NUM> is connected to an electrically conductive portion <NUM> at the suction side of the blade <NUM>. As can be seen from <FIG>, the electrically conductive sections <NUM> may be electrically conductive spar caps attached to the suction side and pressure side ends of the web structure <NUM>. Additionally or alternatively, the electrically conductive sections <NUM> may be lightning receptors used for catching lightning strikes at an outer surface of the shell <NUM>.

The web structure <NUM> divides the interior <NUM> of the rotor blade <NUM> into a leading-edge side <NUM> and a trailing edge side <NUM>. In the embodiment shown in <FIG>, the connections to the connection terminal <NUM> occur at the trailing edge side <NUM>. It is however possible, that alternatively or additionally, one or more connections are also arranged in the leading-edge side <NUM> of the web structure <NUM>. Therefore, the shell conductors <NUM>, or further shell conductors <NUM>, respectively, as well as the carbon fiber structures <NUM>, or further carbon fiber structures <NUM>, respectively may be arranged at the leading-edge side <NUM> of the web <NUM>.

In <FIG>, the connection terminal <NUM> at the web structure <NUM> is shown in detail. From the web structure <NUM>, which is a fiber laminate-based structure, only a core panel <NUM> is shown, wherein one or more fiber-based players covering the core panel <NUM> on the depicted surface, and/or on the opposing surface, respectively, are omitted.

The connection terminal <NUM> is shown in an exploded view. The connection terminal <NUM> comprises two terminal elements <NUM>, <NUM>, wherein a section of the lightning down conductor <NUM> is enclosed between the terminal elements <NUM>, <NUM>. Hence, an intermediate or end section of the lightning conductor <NUM> is sandwiched between the two terminal elements <NUM>, <NUM>. The terminal elements <NUM> and <NUM> of the connection terminal <NUM> are electrically conductive and may be for instance made of metal, for example copper or the like. By the connection terminal <NUM>, an electrical connection between the cables <NUM>, or the conductive shell sections <NUM>, respectively, and the lightning down conductor <NUM> is established.

The connection terminal elements <NUM>, <NUM> may be attached towards each other by a plurality of fastening means <NUM>, which may for instance be provided as screws. The lightning down conductor <NUM> may for instance be a flat or braided cable or a conductor rail, which may comprise corresponding holes for the insertion of the fixation means <NUM> so that a stable attachment of the lightning down conductor <NUM> between the terminal elements <NUM>, <NUM> can be obtained.

The connection terminal <NUM> is arranged in a corresponding recess <NUM>, which is provided in the core element <NUM> of the web structure <NUM>. Also for the lightning down conductor <NUM>, a corresponding recess <NUM> may be provided, so that the lightning down conductor <NUM> can be embedded in the web structure <NUM> underneath one or more fiber laminate layers covering the lightning down conductor <NUM> and the core panel <NUM>. These covering laminates may comprise an opening, so that the terminal element <NUM> remains accessible. It is possible, that the recess <NUM> is provided as a through hole, so that also the opposite terminal element <NUM> may be accessed from the opposing side of the web structure <NUM> for also providing electrical connections to shell terminals <NUM> at the other side of the web structure <NUM> as previously described.

In <FIG>, the connection terminal <NUM> is shown in the mounted state, wherein also two fiber laminates layers <NUM>, <NUM> are shown, which cover the core element <NUM>. The attachment of the cables <NUM> to the connection terminal <NUM>, or the respective terminal element <NUM>, respectively, occurs by a plurality of fastening means <NUM>, as will be described later in more detail.

The fiber laminate layer <NUM> covering the side of the core element <NUM>, on which the cables <NUM> are arranged, may comprise an opening which gives access to the entire terminal element <NUM>. Alternatively, also small holes may be provided in the fiber laminate layer <NUM>, so that only the fastening means <NUM> may penetrate the fiber laminate layer <NUM> for creating an electrical connection between the cables <NUM> and the connection arrangement <NUM>.

In <FIG>, an alternative embodiment of the connection terminal <NUM> is shown. In this embodiment, the connection terminal <NUM> is provided as an electrically conductive connector element <NUM>. The connector element <NUM> comprises a first contact portion <NUM> connected to the conductive shell section <NUM>. Furthermore, the connector element <NUM> comprises two second connection portions <NUM>, which are each connected to a lightning down conductor <NUM> of the lightning down conductor arrangement <NUM>. In this embodiment, the connection terminal <NUM> is used to connect a lightning down conductor <NUM> to a further lightning down conductor <NUM>. As previously described, also the connector element <NUM> may be arranged in a corresponding recess <NUM> of the core panel <NUM> of the web structure <NUM>, wherein in particular the second connection portions <NUM>, the lightning down conductors <NUM> can be embedded under at least one fiber layer (not shown) and/or in a corresponding recess (not shown).

The connection between the first connection portion <NUM> and the cables <NUM> occurs by using the fastening means <NUM>, which are provided as screws. The fastening means <NUM> are connected to cable shoes <NUM> of the cables <NUM>, wherein the connection to the first connection portion <NUM> occurs via the usage of at least one distance element <NUM> as well as the usage of one or more washers <NUM>, <NUM>. The lightning down conductors <NUM> are connected to the second connection portions <NUM> of the connector element <NUM> by a fastening means <NUM> and a rectangular washer <NUM>.

In <FIG>, the second embodiment of the connection terminal <NUM> is shown in its mounted state. The connection terminal <NUM> is embedded in the web structure <NUM>, wherein the first contact portion <NUM> and the second contact portion <NUM> are embedded underneath a fiber layer <NUM> as previously described.

It is possible, that the recess <NUM> is provided as a through hole, so that the connector element <NUM> is accessible also from the opposing side of the web structure <NUM>. In this case, the thickness of the connector element <NUM> between the first connection portion <NUM> and an opposing backside <NUM> of the connector element <NUM> may be equal or approximately equal to the thickness of the core element <NUM> of the web structure <NUM>, as shown schematically in dashed lines.

Providing an accessible backside <NUM> of the connector element <NUM> by arranging the connector element <NUM> in a through hole facilitates the localization of the connector element <NUM> and therefore of the connection terminal <NUM> also from the opposing side of the web structure <NUM> after casting. Further cables <NUM> arranged at the opposing side of the web structure <NUM> may be connected to electrically conductive shell sections <NUM> arranged in the shell <NUM> at least partly on the opposing side of the web structure <NUM>, as previously described. The further cables <NUM> may be connected to the backside <NUM> of the conductor element <NUM> for instance by using the same fixation methods as for fixating the cables <NUM> to the first connection portion <NUM>.

The further cables <NUM> may be arranged in parallel to the cables <NUM>, and therefore corresponding to the course of the cables <NUM> as shown in <FIG>. Alternatively, the cables <NUM> and the further cables <NUM> may be arranged in other orientations, in particular without significant parallel segments of the cables <NUM>, <NUM> to avoid repelling of the cables <NUM> due to the electric field created in case of a lightning strike, since the repelling could cause damage to the cables <NUM>, <NUM> and/or to their connections to the connector element <NUM>.

In <FIG>, the connection of the cable <NUM> to a first embodiment of a shell terminal <NUM> is shown. The shell terminal <NUM> is provided using two terminal elements <NUM>, <NUM>, which are embedding an end portion of the shell conductor <NUM>. The shell conductor <NUM> as well as the shell terminal <NUM> are embedded in a recess <NUM> provided in a core element <NUM> of the fiber-based laminate structure of the shell <NUM>. Also, the core element <NUM> of the shell <NUM> is arranged between two fiber layers <NUM>, <NUM>.

The terminal elements <NUM>, <NUM> are in particular fabricated in the same way as the terminal elements <NUM>, <NUM> used for creating the connection terminal <NUM> at the web structure <NUM>, so that equally fabricated elements can be used. Also, the connection between the cable <NUM> and the shell terminal <NUM> occurs in the same manner as described in relation to the connection terminal <NUM>.

In <FIG>, a second embodiment of a shell terminal <NUM> is shown in an exploded view. The shell terminal <NUM> comprises an electrically conductive connector element <NUM> with a first contact portion <NUM> and a second contact portion <NUM>. The first contact portion <NUM> is connected to the connection terminal <NUM> at the web <NUM>, in particular by means of an electrical cable <NUM> as previously described.

The second connection portion <NUM> is connected to an end section <NUM> of the shell conductor <NUM>, in particular by using a fastening means <NUM> and a rectangular washer <NUM> as previously described in relation to <FIG>. The connector element <NUM> is electrically conductive and may be manufactured using an electrically conductive metal, for instance copper or the like.

Also, connector element <NUM> may be arranged in a corresponding recess <NUM> in the core panel <NUM> of the shell <NUM>. The covering fabric layers <NUM>, <NUM>, which may at least partially embed the shell terminal <NUM> and the shell conductors <NUM>, are not shown in <FIG>. The embedding of the connector element <NUM> occurs in particular correspondingly to the connection terminal <NUM> in the web structure <NUM> and hence correspondingly to <FIG>.

In <FIG>, an alternative connection between a cable <NUM> and the shell terminal <NUM> is shown. The same type of connection may also be used to connect the cable <NUM> to one of the embodiments of the connection terminal <NUM> at the web structure <NUM>.

In this embodiment, the connection of the cable <NUM> occurs by using a threaded intermediate section <NUM>, which comprises a male threaded portion <NUM> and a female threaded portion <NUM>. The cable shoe <NUM> is connected to the threaded intermediate portion <NUM> using a fastening means <NUM>, which is provided as a screw. The washers <NUM> and <NUM> may be used in between the fastening means <NUM> and the cable show <NUM>, or in between the threaded intermediate section <NUM> and the top surface of the shell connection terminal <NUM>, respectively.

The web terminal <NUM> may be provided in the same manner as the shell terminals <NUM>, hence either from two terminal elements <NUM>, <NUM> and/or from a connector element <NUM>. In case of the web terminal <NUM> provided as a connector element <NUM>, an end section <NUM> of the lightning down conductor <NUM> is connected to the second connection portion <NUM>, wherein the first connection portion <NUM> is connected to the root-side end terminal <NUM> using the side end conductor <NUM>. The same applies, when the web terminal <NUM> is provided as two terminal elements <NUM>, <NUM>, wherein an end section <NUM> of the lightning down conductor <NUM> is embedded between the terminal elements <NUM>, <NUM>, and wherein one or both of the terminal elements <NUM>, <NUM> are connected to the root-side end terminal <NUM> using one or more side end conductors <NUM>.

In <FIG>, an embodiment of a root-side end terminal <NUM> is shown. Additionally, also a portion of the end conductor <NUM> is shown. The end conductor <NUM> is provided as an insulated round cable, which is attached to the inner surface <NUM> of the shell <NUM> by a fastening means <NUM>. The fastening means <NUM> is a fastening strip <NUM>, which is for instance adhered to the inner surface <NUM> of the shell <NUM>.

The web terminal <NUM> is provided as an electrically conductive end terminal connector element <NUM>, which is partly embedded in the shell <NUM>, or partly arranged underneath a top laminate layer <NUM> of the shell <NUM>, respectively. In an alternative embodiment, the root-side end terminal <NUM> comprises a further end terminal connector element <NUM>, which is arranged under the end terminal connector element <NUM> and which is shown in <FIG> in dashed lines.

By providing the further end terminal connector element <NUM>, an opening <NUM> may be provided, in which a flat conductor embedded in the shell <NUM> may also be connected to the root-side end terminal <NUM>, if necessary. If such a connection is not required, the further end terminal connector element <NUM> is preferably omitted, so that the root-side end terminal <NUM> protrudes less into the interior <NUM> of the rotor blade <NUM>. This may facilitate the manufacturing of the rotor blade, for instance the pulling out of mandrels arranged in the interior <NUM> of the rotor blade <NUM> prior to a resin infusion in a plurality of fabric layers arranged around the mandrels for manufacturing of the shell <NUM> and/or the web structure <NUM>.

The connection of the end conductor <NUM> to the root-side end terminal <NUM> may occur by using at least one fixation element <NUM>, for instance a screw, a plurality of washers and/or the like, for attaching a cable shoe <NUM> of the end conductor <NUM> to the electrically conductive root-side end terminal <NUM>. Alternatively, also other fixation methods like welding may be used. Furthermore, the root-side end terminal <NUM> may be used for attaching one or more conductors used for connecting the lightning down conductor arrangement <NUM> in the rotor blade <NUM> to the further lightning down conductor arrangement <NUM> at the hub <NUM> as previously described.

It is alternatively possible that the end terminal connector element <NUM> is integrated in the end conductor <NUM>, or that the end conductor <NUM> and the end terminal connector element <NUM> are provided as a one-piece element, respectively. In this case, both the end conductor <NUM> and the end terminal connector element <NUM> may be retrofitted after casting of the rotor blade shell <NUM>.

Claim 1:
Wind turbine rotor blade comprising a shell (<NUM>), a web structure (<NUM>), and a lightning down conductor arrangement (<NUM>), wherein the rotor blade (<NUM>) extends in a spanwise direction between a tip-side end (<NUM>) and a root-side end (<NUM>),
characterized in that
the web structure (<NUM>) is made from at least one fiber-laminate-based structure, wherein the lightning down conductor arrangement (<NUM>) comprises at least one web terminal (<NUM>) at least partly embedded in the web structure (<NUM>) and at least one root-side end terminal (<NUM>) arranged in a root-side end portion of the shell (<NUM>) in a spanwise distance to the web terminal (<NUM>), wherein the root-side end terminal (<NUM>) is connected to the web terminal (<NUM>) by an end conductor (<NUM>) arranged at the inner surface (<NUM>) of the shell (<NUM>).