Patent Description:
As wind turbines and wind turbine blades increase in size, the risk of lighting striking the wind turbine increases. It is therefore of increasing interest to provide wind turbines and in particular wind turbine blades with lightning protection measures.

It is known to provide blades for wind turbines with lightning receptors that are, inside the blade, in electric connection with a metallic down conductor that is able to connect a lightning current to earth.

Wind turbine blades of fibre-reinforced polymer and in particular the aerodynamic shells of wind turbine blades are usually manufactured in moulds, where the pressure side and the suction side of the blade are manufactured separately by arranging glass fibre mats and/or other fibre-reinforcement material, such as carbon fibre, in each of the two mould parts. Afterwards, the two halves are positioned on top of each other, and the two halves are glued together. The blade parts may be positioned on top of each other by turning and repositioning the complete half mould.

As the demand for blades for wind turbines tends towards blades of increasing lengths, a need concurrently arises for manufacture of blades having increased rigidity and a comparatively lower weight. One way of achieving these properties is to combine various types of fibres in the laminate of the blades, for instance it is an option to combine glass fibres and carbon fibres, and likewise carbon fibres or glass fibres may advantageously be combined with steel fibres. Combinations with other types of fibres are thus also possible and it is also an option to exclusively employ carbon fibres or other suitable fibre types. Combination of e.g. glass fibres with carbon fibres in a so-called hybrid laminate may possess a problem in that some of the fibre types are electrically conductive, e.g. carbon fibres and steel fibres. A lightning strike directly into the laminate may cause damage to a blade comprising electrically conductive fibres, as they would conduct the current and thereby i. be greatly heated. This is particularly problematic in case of fibres having comparatively poor conductivity, such as carbon fibres, and in case of hybrid laminates with fibres in e.g. mat-shape, where the individual mat may e.g. have a small portion of electrically conductive fibres and a larger portion of e.g. glass fibres that are not electrically conductive.

Further as the demands for blades for wind turbines tend towards blades of increasing lengths, attention is increasing on concepts of manufacturing blades in sections for being assembled at the installation site. Elements provided for allowing a secure and reliable connection between individual sections of the wind turbine blade bring about another challenge to protect the wind turbine blade from damages caused by lightning strikes. Such wind turbine blade, comprising a plurality of sections, may be known as a split blade, or two-part blade, or segmented blade or similar. Document <CIT> is a prior art example of a segmented wind turbine blade comprising a lightning protection system.

It is an object of the present disclosure to provide ways for lightning protection of a wind turbine blade, such as a split/segmented blade, where the wind turbine blade is manufactured by manufacturing two (or more) blade sections and then joining them. In particular, it is an objective of the present disclosure to provide coupling for a wind turbine blade comprising a first and a second down conductor, adapted for lightning protection, e.g. for protecting the wind turbine blade against lightning strikes, e.g. in a more advantageous way.

The present disclosure provides ways of improving lightning protection of a wind turbine blade, in particular being a split/segmented blade. The disclosure advantageously provides ways of combining different lightning protection concepts, facilitating decreased risk of damaging lightning strikes, and reducing material costs and production costs.

Accordingly, a wind turbine blade is disclosed, according to claim <NUM> and extending along a longitudinal axis from a root end through a first airfoil region and a second airfoil region to a tip end. The wind turbine blade comprises a first blade section and a second blade section. The wind turbine blade may be a split blade, or two-part blade, or segmented blade. The first blade section extends along the longitudinal axis from to a first end. The second blade section extends along the longitudinal axis from a second end towards the tip end. The first blade section may extend from the root. The second blade section may extend to the tip end. The first blade section may comprise a root region, optionally including the root end. The first blade section comprises the first airfoil region. The first blade section may comprise a transition region between the root region and the first airfoil region. The second blade section comprises the second airfoil region. The second airfoil region may comprise the tip end. The first blade section and the second blade section comprise a pressure side and a suction side. The first blade section and the second blade section may comprise a chord line extending between a leading edge and a trailing edge.

The wind turbine blade comprises a spar beam configured for connecting, e.g. structurally connecting, the first blade section and the second blade section. The spar beam extends longitudinall along a spar beam axis from a first beam position, e.g. a first beam end, to a second beam position, e.g. a second beam end. The spar beam axis may be substantially parallel to the longitudinal axis of the wind turbine blade. The spar beam is configured to be positioned such that the first beam position is located in the first airfoil region and the second beam position is located in the second airfoil region. The spar beam may be configured to be positioned such that a third beam position, between the first beam position and the second beam position, is aligned with the second end of the second blade section and/or the first end of the first blade section.

The first blade section comprises a first down conductor. The second blade section comprises a second down conductor. The wind turbine blade comprises a conductive connector element for electrically connecting the first down conductor and the second down conductor. The second down conductor may be connected to a lightning receptor, such as a lighning receptor positioned at or near the tip end. For example, the second down conductor may extend from the lightning receptor.

It is an advantage of the present disclosure, that lightning protection for a segmented wind turbine blade, in particular a segmented wind turbine blade utilizing a spar beam for connecting sections of the wind turbine blade, may be provided and enhanced.

It is an advantage of the present disclosure that assembly of a segmented wind turbine blade may be improved by having a first and a second down conductor. It is a further advantage of the present disclosure that the assembly of a segmented wind turbine blade is made easier, more convenient and more flexible. Such advantage may particularly be achieved by the first blade section comprising a first down conductor and the second blade section comprising a second down conductor, which may be manufactured separately. Blade sections and down conductors may be assembled and connected at the same time providing for a faster assembly of the wind turbine blade.

Also disclosed is a method for assembling a wind turbine blade, according to claim <NUM>, extending along a longitudinal axis from a root end through a first airfoil region and a second airfoil region to a tip end. The wind turbine blade comprises a first blade section extending along the longitudinal axis to a first end and a second blade section extending along the longitudinal axis from a second end towards the tip end. The first blade section may extend from the root. The second blade section may extend to the tip end. The first blade section may comprise a root region, optionally including the root end. The first blade section comprises the first airfoil region. The first blade section may comprise a transition region between the root region and the first airfoil region. The second blade section comprises the second airfoil region. The second airfoil region may comprise the tip end. The first blade section and the second blade section comprise a pressure side and a suction side. The first blade section and the second blade section may comprise a chord line extending between a leading edge and a trailing edge. The wind turbine blade comprises a spar beam configured for connecting, such as structurally connecting, the first blade section and the second blade section. The spar beam longitudinally extends along a spar beam axis from a first beam position, e.g. a first beam end, to a second beam position, e.g. a second beam end. The spar beam axis may be substantially parallel to the longitudinal axis of the wind turbine blade. The first blade section comprises a first down conductor and the second blade section comprises a second down conductor.

The method comprises positioning the spar beam such that the first beam position is located in the first airfoil region and the second beam position is located in the second airfoil region. Positioning the spar beam may comprise that a third beam position, between the first beam position and the second beam position, is aligned with the second end of the second blade section and/or the first end of the first blade section.

The method further comprises electrically connecting the first down conductor and the second down conductor with a conductive connector element.

The conductive connector element may be formed by a plurality of conductive connector elements. For example, the conductive connector element may comprise a first conductive connector element. The first conductive connector element may be in electrical connection with the first down conductor. The conductive connector element may comprise a second conductive connector element. The second conductive connector element may be in electrical connection with the second down conductor. The first conductive connector element and the second conductive connector element may be configured to couple, e.g. to electrically connect the first down conductor and the second down conductor.

Electrically connecting the first down conductor and the second down conductor may comprise coupling the first conductive connector element and the second conductive connector element.

The first conductive connector element may form part of the first down conductor. The second conductive connector element may form part of the second down conductor.

The conductive connector element and/or the first conductive connector element and/or the second conductive connector element may be located in the first blade section. Alternatively or additionally, the conductive connector element and/or the first conductive connector element and/or the second conductive connector element may be located in the second blade section.

The first conductive connector element and the second conductive connector element may form a plug and a socket. For example, the first conductive connector element may be a plug. The second conductive connector element may be a socket. The first conductive connector element may be configured to engage with the second conductive connector element.

Coupling the first conductive connector element and the second conductive connector element may comprise clamping, soldering, bolting or mating the first conductive connector element and the second conductive connector element.

The first down conductor may be located at a first primary distance from the pressure side, e.g. of the first blade section, and a first secondary distance from the suction side, e.g. of the first blade section.

The first primary distance and the first secondary distance along a first primary part may be substantially the same. For example, the first primary distance and the first secondary distance may be substantially the same throughout the majority of the first blade section.

In some portions of the wind turbine blade, the first primary distance and the first secondary distance may be different, e.g. to allow space for other components of the wind turbine blade and/or to allow for an easier connection of elements, such as connection the first down conductor and the second down conductor. For example, the first primary distance may be smaller than the first secondary distance along a first secondary part. Alternatively, the first primary distance may be larger than the first secondary distance along the first secondary part.

The second down conductor may be located at a second primary distance from the pressure side and a second secondary distance from the suction side. The second primary distance and second secondary distance along a second primary part may be substantially the same. For example, the second primary distance and the second secondary distance may be substantially the same throughout the majority of the second blade section.

In some portions of the wind turbine blade, e.g. near the second end or the tip end of the second blade section, the second primary distance and the first secondary distance may be different, e.g. to allow space for other components of the wind turbine blade and/or to allow for an easier connection of elements, such as connection the first down conductor and the second down conductor. For example, the second primary distance may be smaller than the second secondary distance along a second secondary part. Alternatively, the second primary distance may be larger than the second secondary distance along a second secondary part.

The wind turbine blade may comprise one or more hatches, such as a first hatch and/or a second hatch, e.g. to allow coupling of down conductors inside the wind turbine blade. A hatch of the wind turbine blade may be on the surface of the wind turbine blade, e.g. a hatch may be provided in the suction side of the wind turbine blade.

The first blade section may comprise the first hatch, e.g. near the first end of the first blade section. The first hatch may allow access to the interior of the first blade section between a first primary hatch position and a first secondary hatch position along the longitudinal axis.

The method of assembling the wind turbine blade may comprise opening a first hatch near the first end of the first blade section, such as the first hatch as described above, to allow access to the interior of the first blade section between a first primary hatch position and a first secondary hatch position along the longitudinal axis.

The conductive connector element and/or the first conductive connector element may be located underneath the first hatch. The conductive connector element and/or the first conductive connector element may be located at a first connector position between the first primary hatch position and the first secondary hatch position.

The second blade section may comprise the second hatch, e.g. near the second end of the second blade section. The second hatch may allow access to the interior of the second blade section between a second primary hatch position and a second secondary hatch position along the longitudinal axis.

The method of assembling the wind turbine blade may comprise opening a second hatch near the second end of the second blade section, such as the second hatch as described above, to allow access to the interior of the second blade section between a second primary hatch position and a second secondary hatch position along the longitudinal axis.

The first and/or second hatch may allow access to the interior of the blade, e.g. providing a way of connecting a first and a second down conductor, e.g. providing for a faster assembly of the wind turbine blade. The conductive connector element may provide a convenient way of coupling a first and a second down conductor.

The conductive connector element and/or the second conductive connector element may be located underneath the second hatch. The conductive connector element and/or the second conductive connector element may be located at a second connector position between the second primary hatch position and the second secondary hatch position.

The first down conductor may comprise a first down conductor portion, e.g. near the first end of the first blade section. The first down conductor portion may be configured to be movable. For example, the first down conductor may be configured to allow movement of the first down conductor portion, such as to allow a constructor to manipulate the first down conductor portion to a suitable position, e.g. during assembly of the first blade section and the second blade section.

The first down conductor, such as the first down conductor portion, is configured to extend to a first down conductor position located in the second blade section. The first down conductor portion may be configured to be attached to the spar beam in the second blade section, such as between the second beam position and the third beam position. For example, the first down conductor portion may be repositioned to the second blade section and subsequently be attached to the spar beam in the second blade section.

The method of assembling the wind turbine blade may comprise attaching a first down conductor portion of the first down conductor, such as the first down conductor portion as described above, to the spar beam, e.g. in the second blade section, e.g. between the second beam position and the third beam position.

The second down conductor may comprise a second down conductor portion e.g. near the second end of the second blade section. The second down conductor portion may be configured to be movable. For example, the second down conductor may be configured to allow movement of the second down conductor portion, such as to allow a constructor to manipulate the second down conductor portion to a suitable position, e.g. during assembly of the first blade section and the second blade section.

The second down conductor, such as the second down conductor portion, is configured to extend to a second down conductor position located in the first blade section. The second down conductor portion of the second down conductor may be configured to be attached to a shear web or side of a spar in the first blade section. For example, the second down conductor portion may be repositioned to the first blade section and subsequently be attached to the shear web or side of a spar in the first blade section.

The method of assembling the wind turbine blade may comprise attaching a second down conductor portion of the second down conductor, such as the second down conductor portion as described above, to a shear web in the first blade section.

Any of the mentioned beam positions may alternatively be denoted beam axis positions. Any of the mentioned beam positions, such as the third beam position, the fourth beam position, the fifth beam position, the sixth beam position, the seventh beam position, the eighth beam position, the ninth beam position, the tenth beam position, the eleventh beam position, the twelfth beam position, the thirteenth beam position, the fourteenth beam position and/or the fifteenth beam position, may be between the first beam end and the second beam end, such as between the first beam position and the second beam position.

Embodiments of the disclosure will be described in more detail in the following with regard to the accompanying figures. The figures show one way of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

<FIG> illustrates a conventional modern upwind wind turbine <NUM> according to the so-called "Danish concept" with a tower <NUM>, a nacelle <NUM> and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub <NUM>, and three blades <NUM> extending radially from the hub <NUM>, each having a blade root <NUM> nearest the hub and a blade tip <NUM> furthest from the hub <NUM>.

The wind turbine blade <NUM> comprises a blade shell may comprise two blade shell parts, a first blade shell part <NUM> and a second blade shell part <NUM>, typically made of fibre-reinforced polymer. The first blade shell part <NUM> is typically a pressure side or upwind blade shell part. The second blade shell part <NUM> is typically a suction side or downwind blade shell part. The first blade shell part <NUM> and the second blade shell part are typically glued together along bond lines or glue joints <NUM> extending along the trailing edge <NUM> and the leading edge <NUM> of the blade <NUM>. Typically, the root ends of the blade shell parts <NUM>, <NUM> has a semi-circular or semi-oval outer cross-sectional shape.

The wind turbine blade <NUM> extends along a longitudinal axis L. The root end <NUM> extends in a root end plane, substantially perpendicular to the longitudinal axis L.

<FIG> is a schematic diagram illustrating a cross sectional view of an exemplary wind turbine blade <NUM>, e.g. a cross sectional view of the airfoil region of the wind turbine blade <NUM>. The wind turbine blade <NUM> comprises a leading edge <NUM>, a trailing edge <NUM>, a pressure side <NUM> and a suction side <NUM>.

The wind turbine blade <NUM> comprises a chord line <NUM> between the leading edge <NUM> and the trailing edge <NUM>.

The wind turbine blade <NUM> comprises shear webs <NUM>, such as a leading edge shear web 40b and a trailing edge shear web 40a. The shear webs <NUM> could alternatively be a spar box with spar sides, such as a trailing edge spar side and a leading edge spar side.

<FIG> is a schematic diagram illustrating an exemplary wind turbine blade <NUM> seen from the suction side, such as the wind turbine blade <NUM> of the previous figures. The wind turbine blade <NUM> comprises a leading edge <NUM>, a trailing edge <NUM>, a tip end <NUM> and a root end <NUM>. The wind turbine blade <NUM> comprises shear webs <NUM>, such as a leading edge shear web 40b and a trailing edge shear web 40a.

The wind turbine blade <NUM> is a so-called split blade, or two-part blade, or segmented blade. The wind turbine blade <NUM> comprises a first blade section <NUM> and a second blade section <NUM>. The first blade section <NUM> extends along the longitudinal axis L from a root, such as the root end <NUM>, to a first end <NUM>. The second blade section <NUM> extends along the longitudinal axis L from a second end <NUM> to a tip, such as the tip end <NUM>. The first blade section comprises <NUM> a root region <NUM>, a first airfoil region 34a and a transition region <NUM> between the root region <NUM> and the first airfoil region 34a. The second blade section <NUM> comprises a second airfoil region 34b with the tip, such as the tip end <NUM>. The first blade section <NUM> and the second blade section <NUM> may be connected with a spar beam <NUM>. The spar beam <NUM> may comprise carbon fibre, e.g. the spar beam <NUM> may comprise pultruded carbon fibre reinforced polymer.

The spar beam <NUM> extends along a spar beam axis B. The spar beam axis B may be coinciding and/or parallel with the longitudinal axis of the wind turbine blade <NUM>. The spar beam <NUM> extends from a first beam position pb1 in the first airfoil region 34a to a second beam position pb2 in the second airfoil region 34b.

A third beam position pb3 is between the first beam position pb1 and second beam position pb2. The third beam position pb3 is aligned with the second end <NUM> of the second blade section <NUM>.

A lightning conductor extends from the root end <NUM> towards the tip end <NUM>. The lightning conductor comprises a first down conductor <NUM> in the first blade section <NUM> and a second down conductor <NUM> in the second blade section <NUM>. The first down conductor <NUM> is attached to the trailing edge shear web 40a. Alternatively or additionally, the first down conductor <NUM> may be attached to the leading edge shear web 40b. The second down conductor <NUM> is attached to the spar beam <NUM> in the second blade section <NUM>. The first down conductor <NUM> and the second down conductor <NUM> may be attached to the shear web or the spar beam with e.g. to a bracket, by soldering and/or other suitable means. The second down conductor <NUM> is connected to a lightning receptor <NUM>. Although not illustrated, the wind turbine blade <NUM> may comprise a plurality of lightning receptors being connected to the first down conductor <NUM> and/or the second down conductor <NUM>.

The lightning conductor comprises a conductive connector element <NUM>. The conductive connector element <NUM> is located in the first blade section <NUM>. The conductive connector element <NUM> may alternatively be located in the second blade section <NUM> (see e.g. <FIG> or <FIG>). The conductive connector element <NUM> may be one element, which for example, may be in electrical and/or mechanical connection with the first down conductor <NUM> before assembly of the first blade section <NUM> and the second blade section <NUM> of the wind turbine blade <NUM>. Alternatively, the conductive connector element <NUM> may be in electrical and/or mechanical connection with the second down conductor <NUM> before assembly of the first blade section <NUM> and the second blade section <NUM> of the wind turbine blade <NUM>. The conductive connector element <NUM> may, for example, be a cable shoe, which can be clamped around a part of the first down conductor <NUM> and/or a part of the second down conductor <NUM>. After assembly of the first blade section <NUM> and the second blade section <NUM> of the wind turbine blade <NUM>, the conductive connector element <NUM> is electrically and/or mechanically coupled to the first down conductor <NUM> and the second down conductor <NUM>.

Alternatively, the conductive connector element may comprise a first conductive connector element <NUM> in electrical connection with the first down conductor <NUM> and a second conductive connector element <NUM> in electrical connection with the second down conductor <NUM>, which are to be connected to form the conductive connector element. For example, the first conductive connector element <NUM> may be a plug and the second conductive connector element <NUM> may be a socket. Alternatively, the first conductive connector element <NUM> may be a socket and the second conductive connector element <NUM> may be a plug.

<FIG> is a schematic diagram illustrating part of an exemplary wind turbine blade <NUM> seen from the trailing edge, such as the wind turbine blade <NUM> of the previous figures. The wind turbine blade <NUM> comprises a pressure side <NUM>, a suction side <NUM>, a tip end <NUM>, a first blade section <NUM>, a second blade section <NUM>, a shear web <NUM> and a spar beam <NUM>. For illustrative purposes the shear web <NUM> and the spar beam <NUM> are drawn separately from the shell parts <NUM> and <NUM>. The wind turbine blade <NUM> comprises a first down conductor <NUM> located in the first blade section <NUM>, a second down conductor <NUM> located in the second blade section <NUM>, and a conductive connector element <NUM> coupling the first down conductor <NUM> and the second down conductor <NUM>. The second down conductor <NUM> is connected to a lightning receptor <NUM>.

The first down conductor <NUM> is located at a first primary distance d11 from the pressure side <NUM> and a first secondary distance d12 from the suction side <NUM>. The first primary distance d11 and the first secondary distance d12 along a first primary part 87a is substantially the same, e.g. to reduce the risk of lightning striking the first down conductor <NUM>.

The second down conductor <NUM> is located at a second primary distance d21 from the pressure side <NUM> and a second secondary distance d22 from the suction side <NUM>. The second primary distance d21 and second secondary distance d22 along a second primary part 88a is substantially the same, e.g. to reduce the risk of lightning striking the second down conductor <NUM>.

The first primary distance d11 and the first secondary distance d12 along a first secondary part 87b is different, e.g. the first primary distance d11 is smaller than the first secondary distance d12 along the first secondary part 87b. The second primary distance d21 and the second secondary distance d22 along a second secondary part 88b is different, e.g. the second primary distance d21 is smaller than the second secondary distance d12 along the second secondary part 88b. Thus, the first down conductor <NUM>, the conductive connector element <NUM> and the second down conductor <NUM> may be configured to run under an assembly point <NUM> in a plane parallel to the shear web <NUM>. Alternatively, the first primary distance d11 may be larger than the first secondary distance d12 along the first secondary part 87b and/or the second primary distance d21 may be larger than the second secondary distance d12 along the second secondary part 88b. Thus, the first down conductor <NUM>, the conductive connector element <NUM> and the second down conductor <NUM> may be configured to run over the assembly point <NUM> in a plane parallel to the shear web <NUM>. The assembly point <NUM> may be a hole through the shear web <NUM> and the spar beam <NUM>, e.g. configured to receive a pin, such as to lock the spar beam <NUM> in position with respect to the first blade section <NUM>.

<FIG> and <FIG> are schematic diagrams illustrating part of an exemplary wind turbine blade <NUM>, such as the wind turbine blade <NUM> of the previous figures. The wind turbine blade <NUM> comprises a pressure side (not visible), a suction side <NUM>, a tip end <NUM>, a first blade section <NUM>, a second blade section <NUM>, a shear web <NUM> and a spar beam <NUM>. The wind turbine blade <NUM> comprises a first down conductor <NUM> located in the first blade section <NUM> and a second down conductor <NUM> located in the second blade section <NUM>. The wind turbine blade <NUM> comprises a first conductive connector element <NUM> in electrical connection with the first down conductor <NUM> and a second conductive connector element <NUM> in electrical connection with the second down conductor <NUM>. The first conductive connector element <NUM> and the second conductive connector element <NUM> electrically and/or mechanically couple the first down conductor <NUM> and the second down conductor <NUM>. The second down conductor <NUM> is connected, such as electrically connected, to a lightning receptor <NUM>. The first conductive connector element <NUM> and the second conductive connector element <NUM> may be positioned and/or coupled in the first blade section <NUM> (<FIG>) or in the second blade section <NUM> (<FIG>).

<FIG> illustrates, the wind turbine blade <NUM> comprising a first hatch <NUM> near the first end <NUM> of the first blade section <NUM>. The first hatch <NUM> is provided in the suction side <NUM> of the wind turbine blade <NUM>. The first hatch <NUM> allows access to the interior of the first blade section <NUM> between a first primary hatch position ph11 and a first secondary hatch position ph12 along the longitudinal axis L. The first conductive connector element <NUM>, e.g. a first end, a second end or a centre position of the first conductive connector element <NUM>, is located at a first connector position pc1 between the first primary hatch position ph11 and the first secondary hatch position ph12. By opening the first hatch <NUM> the first conductive connector element <NUM> and the second conductive connector element <NUM> may be accessed and coupled.

<FIG> illustrates the wind turbine blade <NUM> comprising a second hatch <NUM> near the second end <NUM> of the second blade section <NUM>. The second hatch <NUM> is provided in the suction side <NUM> of the wind turbine blade <NUM>. The second hatch <NUM> allows access to the interior of the second blade section <NUM> between a second primary hatch position ph21 and a second secondary hatch position ph22 along the longitudinal axis L. The second conductive connector element <NUM>, e.g. a first end, a second end or a centre position of the second conductive connector element <NUM>, is located at a second connector position pc2 between the second primary hatch position ph21 and the second secondary hatch position ph22. By opening the second hatch <NUM> the first conductive connector element <NUM> and the second conductive connector element <NUM> may be accessed and coupled.

The wind turbine blade <NUM> may comprise both a first hatch <NUM> as illustrated in <FIG>, and a second hatch <NUM> as illustrated in <FIG>.

<FIG> and <FIG> are schematic diagrams illustrating part of an exemplary wind turbine blade <NUM>, such as the wind turbine blade <NUM> of the previous figures. The wind turbine blade <NUM> comprises a first blade section <NUM>, a second blade section <NUM>, a shear web <NUM> and a spar beam <NUM>. For illustrative purposes the shear web <NUM> and the spar beam <NUM> are drawn separate from the shell parts <NUM>, <NUM>. The wind turbine blade <NUM> comprises a first down conductor <NUM> located in the first blade section <NUM>, a second down conductor <NUM> located in the second blade section <NUM>, and a conductive connector element <NUM> coupling the first down conductor <NUM> and the second down conductor <NUM>.

The conductive connector element <NUM> may be a single element coupling the first down conductor <NUM> and the second down conductor <NUM>.

<FIG> illustrates, the first down conductor <NUM> comprising a first down conductor portion <NUM> near the first end <NUM> of the first blade section <NUM>. The first down conductor portion <NUM> is configured to be movable, such as to allow manipulation of the first down conductor portion <NUM> into the second blade section <NUM> and/or to allow coupling of the first down conductor <NUM> and the second down conductor <NUM>. The first down conductor <NUM> is configured to extend to a first down conductor position pdc1, e.g. located in the second blade section <NUM>, such as in a second airfoil region of the second blade section <NUM>, as illustrated. The second connector position pc2 of <FIG> may be the same as the first down conductor position pdc1. The first down conductor portion <NUM> is configured to be attached to the spar beam <NUM> of the second blade section <NUM>, e.g. to reduce mechanical stress caused by movement of the first down conductor portion <NUM>, when the wind turbine blade <NUM> is in operation. The first down conductor <NUM>, the conductive connector element <NUM> and the second down conductor <NUM> is configured to run under an assembly point <NUM> in a plane parallel to the shear web <NUM>. Alternatively, the first down conductor <NUM>, the conductive connector element <NUM> and the second down conductor <NUM> is configured to run over an assembly point <NUM> in a plane parallel to the shear web <NUM>.

<FIG> illustrates, the second down conductor <NUM> comprising a second down conductor portion <NUM> near the second end <NUM> of the second blade section <NUM>. The second down conductor portion <NUM> is configured to be movable, such as to allow manipulation of the second down conductor portion <NUM> into the first blade section <NUM> and/or to allow coupling of the first down conductor <NUM> and the second down conductor <NUM>. The second down conductor <NUM> is configured to extend to a second down conductor position pdc2, e.g. located in the first blade section <NUM>, such as in a first airfoil region of the first blade section <NUM>, as illustrated. The first connector position pc1 of <FIG> may be the same as the second down conductor position pdc2. The second down conductor portion <NUM> is configured to be attached to the shear web <NUM> of the first blade section <NUM>, e.g. to reduce mechanical stress caused by movement of the second down conductor portion <NUM>, when the wind turbine blade <NUM> is in operation. The second down conductor <NUM>, the conductive connector element <NUM> and the second down conductor <NUM> is configured to run under an assembly point <NUM> in a plane parallel to the shear web <NUM>. Alternatively, the first down conductor <NUM>, the conductive connector element <NUM> and the second down conductor <NUM> is configured to run over an assembly point <NUM> in a plane parallel to the shear web <NUM>.

<FIG> is a schematic diagram illustrating part of an exemplary wind turbine blade <NUM>, such as the wind turbine blade <NUM> of the previous figures. The wind turbine blade <NUM> comprises a first blade section <NUM>, a second blade section <NUM>, a shear web <NUM> and a spar beam <NUM>. For illustrative purposes the shear web <NUM> and the spar beam <NUM> are drawn separately from the shell parts <NUM>, <NUM>. The wind turbine blade <NUM> comprises a first down conductor <NUM> located in the first blade section <NUM> and a second down conductor <NUM> located in the second blade section <NUM>. The first down conductor <NUM> comprises a first primary part 87a and a first secondary part 87b. The second down conductor <NUM> comprises a second primary part 88a and a second secondary part 88b. The wind turbine blade <NUM> comprises a first connection part <NUM> in the first blade section <NUM> connecting the first primary part 87a and the first secondary part 87b of the first down conductor <NUM>. The first connection part <NUM> is configured to provide for electrically connecting a lightning receptor, such as a receptor cable from the lightning receptor, to the first down conductor <NUM>. The wind turbine blade <NUM> comprises a second connection part <NUM> in the second blade section <NUM> connecting the second primary part 88a and the second secondary part 88b of the second down conductor <NUM>. The second connection part <NUM> is configured to provide for electrically connecting a lightning receptor, such as a receptor cable from the lightning receptor, to the second down conductor <NUM>. The connection part(s) <NUM>, <NUM> may be formed by exothermal welding together the respective cable parts.

The wind turbine blade <NUM> comprises a first conductive connector element <NUM> in electrical connection with the first down conductor <NUM> and a second conductive connector element <NUM> in electrical connection with the second down conductor <NUM>. The first conductive connector element <NUM> and the second conductive connector element <NUM> electrically and/or mechanically couple the first down conductor <NUM> and the second down conductor <NUM>.

The second down conductor <NUM> comprises a second secondary part 88b near the second end <NUM> of the second blade section <NUM>. The second secondary part 88b is configured to be movable, such as to allow manipulation of the second secondary part 88b into the first blade section <NUM> and/or to allow coupling of the first down conductor <NUM> and the second down conductor <NUM>. The second down conductor <NUM> is configured to extend to a second down conductor position pdc2, e.g. located in the first blade section <NUM>, such as in a first airfoil region of the first blade section <NUM>, as illustrated. The second secondary part 88b may be configured to be attached to the shear web <NUM> of the first blade section <NUM>. The first down conductor <NUM>, the conductive connector element <NUM> and the second down conductor <NUM> is configured to run under an assembly point <NUM> in a plane parallel to the shear web <NUM>. Alternatively, the first down conductor <NUM>, the conductive connector element <NUM> and the second down conductor <NUM> may be configured to run over an assembly point <NUM> in a plane parallel to the shear web <NUM>.

<FIG> is a flow diagram illustrating an exemplary method <NUM> for assembling a wind turbine blade, such as a wind turbine blade as described in relation to previous figures, such as a wind turbine blade comprising a first blade section extending along a longitudinal axis from a root end to a first end and a second blade section extending along the longitudinal axis from a second end to a tip end. The first blade section comprises a root region and a first airfoil region. The second blade section comprises a second airfoil region with the tip end. The first blade section and the second blade section comprise a pressure side and a suction side. The wind turbine blade comprises a spar beam configured for connecting the first blade section and the second blade section. The spar beam longitudinally extends along a spar beam axis from a first beam position to a second beam position. The first blade section comprises a first down conductor and the second blade section comprises a second down conductor. The method <NUM> comprises positioning <NUM> the spar beam such that the first beam position is located in the first airfoil region and the second beam position is located in the second airfoil region.

The method <NUM> comprises electrically connecting <NUM> the first down conductor and the second down conductor with a conductive connector element, e.g. comprising a first conductive connector element and a second conductive connector element. The first conductive connector element may be in electrical connection with the first down conductor and the second conductive connector element may be in electrical connection with the second down conductor. Electrically connecting <NUM> the first down conductor and the second down conductor may comprise clamping or soldering the conductive connector element and the first down conductor and the second down conductor.

Electrically connecting <NUM> the first down conductor and the second down conductor may comprise coupling the first conductive connector element and the second conductive connector element. Coupling the first conductive connector element and the second conductive connector element may comprise clamping, soldering, bolting or mating the first conductive connector element and the second conductive connector element.

The method <NUM> may comprise opening <NUM> a first hatch, e.g. near the first end of the first blade section. Opening <NUM> the first hatch may allow access to the interior of the first blade section between a first primary hatch position and a first secondary hatch position along the longitudinal axis of the wind turbine blade.

The method <NUM> may comprise opening <NUM> a second hatch, e.g. near the second end of the second blade section. Opening <NUM> the second hatch may allow access to the interior of the second blade section between a second primary hatch position and a second secondary hatch position along the longitudinal axis of the wind turbine blade.

Opening <NUM> the first hatch and/or opening <NUM> the second hatch may be performed prior to electrically connecting <NUM> the first down conductor and the second down conductor.

The method <NUM> may comprise attaching <NUM> a first down conductor portion of the first down conductor to the spar beam, e.g. between the second beam position and a third beam position in the second blade section. The third beam position may be a position of the spar beam aligned with the first end of the first blade section and/or the second end of the second blade section.

The method <NUM> may comprise attaching <NUM> a second down conductor portion of the second down conductor to a shear web in the first blade section.

The term "receptor" is to be understood as an electrically conductive object being configured with a view to capturing and conducting a lightning current.

Throughout the disclosure, the term "conductive", if not specified otherwise, is to be understood as electrically conductive.

Claim 1:
A wind turbine blade extending along a longitudinal axis from a root end (<NUM>) through a first airfoil region (<NUM>) and a second airfoil region (34b) to a tip end, the wind turbine blade comprising a first blade section (<NUM>) extending along the longitudinal axis to a first end (<NUM>) and a second blade section (<NUM>) extending along the longitudinal axis from a second end towards the tip end (<NUM>), the first blade section comprising the first airfoil region, the second blade section comprising the second airfoil region, the first blade section and the second blade section comprise a pressure side and a suction side,
wherein the first end of the first blade section is closer to the root end than the second end of the second blade section, and wherein the second end of the second blade section is closer to the tip than the first end of the first blade section,
the wind turbine blade comprising a spar beam (<NUM>) configured for structurally connecting the first blade section and the second blade section, the spar beam longitudinally extending along a spar beam axis from a first beam position (PB1) to a second beam position (PB2) and being configured to be positioned such that the first beam position is located in the first airfoil region and the second beam position is located in the second airfoil region, the first blade section comprises a first down conductor (<NUM>) and the second blade section comprises a second down conductor (<NUM>),
wherein the wind turbine blade comprises a conductive connector element (<NUM>) for electrically connecting the first down conductor and the second down conductor, and characterized in that the first down conductor is configured to extend to a first down conductor position located in the second blade section or the second down conductor is configured to extend to a second down conductor position located in the first blade section.