Patent Description:
Wind turbines are broadly used to convert the wind power into electricity. The generated electricity can be supplied to an electrical grid and directed to consumers. Wind turbines generally comprise a tower on top of which a nacelle is mounted. A rotor comprising a rotor hub, or hub, and a plurality of blades are generally rotatably mounted with respect to the nacelle. The plurality of blades use the aerodynamic forces generated by the wind to produce a net positive torque on a rotating shaft, resulting in the production of mechanical power, which is then transformed to electricity in a generator.

The blades may be directly connected to the rotor hub or may be connected through a pitch bearing. A pitch system can rotate a blade along its longitudinal axis, allowing modification of the angle of attack of the wind turbine blade with respect to the incoming air flow. The aerodynamic forces acting on the blade can thereby be controlled.

Wind turbines have evolved rapidly over the last decades and wind turbine components have been modified to withstand higher loads and adverse weather conditions. Due to the height and exposure of wind turbines, it is important to provide them with effective lightning protection systems to evacuate lightning discharges from the lightning impact location to ground without affecting electrical or structural components of the wind turbine.

In general, lightning protection systems include a lightning receptor provided on a wind turbine blade to conduct the lightning discharge to a ground connection via a lightning down conductor provided within the blade. One of the main issues with known lightning protection systems is how to conduct the lightning discharge from the down conductor in the blade to a ground connection provided at the wind turbine rotor hub, nacelle or tower.

Spark gaps and/or electrical brushes are generally used with this objective, providing an electrical path between wind turbine moving components such as the wind turbine blade root and the rotor hub and/or the rotor hub and the nacelle. However, these approaches present some drawbacks. Providing spark gaps in a blade is not a trivial solution. These systems comprise at least two conductive strips arranged close to each other in order to provide a conductive connection between them to bypass a connection between wind turbine components, for example the blade root to rotor hub connection. In such spark gap systems, the lightning down conductor may need to pass through the wall of the blade body or through the blade root flange to contact the first conductor strip and therefore in some cases, a through hole on the blade root should be provided. Said through hole may have a negative impact on the structural stability of the blade, requiring further blade strengthening. Further, the through hole should be sealed once the down conductor has been inserted to avoid any leakage to the interior of the blade. In addition to the aforementioned drawbacks, periodical maintenance of the spark gap system should be carried out to assure cleanness and precise clearance gap.

Further, a potential malfunction of the lightning protection system due to the misalignment of its components, due to accumulation of debris from atmospheric deposition and/or wear of the components can promote the lightning discharge not to follow the established electric path to ground but a least resistive path through other wind turbine components. This implies that electrical and/or structural components, such as blade pitch bearings, may act as lightning discharge conductors, shortening severely their lifespan and incurring in high replacement costs. Documents <CIT> and <CIT> are prior art examples of wind turbines comprising a lightning discharge system.

The present disclosure provides methods and systems to at least partially overcome some of the aforementioned drawbacks.

In an aspect of the present disclosure, a lightning bypass system for a wind turbine according to claim <NUM> is provided. The lightning bypass system comprises a connector assembly including a blade connector comprising an electrically insulating material. Further, the blade connector comprises a first end configured to be electrically connected to a down conductor cable of the blade and a second end configured to conduct a lightning discharge to a rotor hub of the wind turbine. The blade connector further comprises a core of electrically conductive material configured to be electrically connected to the first end and the second end. The blade connector is configured to be located substantially in a rotational axis of a blade root of a wind turbine blade.

According to this aspect, the fact that the blade connector is located substantially in a rotational axis of the blade root allows a compact and robust lightning bypass system layout, wherein the rotation of the blade to modify the blade pitch angle does not generate a relative movement between components of the lightning bypass system. This allows adjusting the length of the conductive elements associated with the lightning system and to establish a conductive path that does not change its internal location within the blade with the blade pitch angle. Both of these aspects lead to a more secure connection and allow using the internal blade and rotor space more efficiently.

Further, in this way, the system bypasses any structural and electrical blade component not intended to receive the lightning discharge, and in particular the pitch bearing. The components of the pitch bearing system are thus protected from strong temperature gradients and their lifespan may be enhanced.

In an additional aspect, a method for providing a lightning bypass assembly system according to claim <NUM> is provided. The method comprises providing a blade connector made of an electrically insulating material substantially located in a rotational axis of a blade root of the wind turbine. The blade connector comprises a first end, a second end and a core of electrically conductive material electrically connected to the first end and the second end. The method further comprises connecting the first end of the blade connector to a down conductor cable of a lightning receptor of a blade, providing a rotatable connection between the first end and the second end of the blade connector, and conductively coupling the blade connector to a lightning grounding system of a wind turbine.

In a further aspect of the present disclosure, a wind turbine hub assembly is provided. The assembly includes a wind turbine rotor hub, at least one wind turbine blade, and a lightning bypass system. The wind turbine blade comprises a blade root, and the lightning bypass system comprises a blade connector comprising an electrically insulating material secured to the wind turbine blade and located substantially in a rotational axis of the blade root of the wind turbine, and a hub connector made of an electrically insulating material secured to the rotor hub of the wind turbine. Further, the blade connector comprises a first end configured to be electrically connected to a down conductor cable of the blade, a second end configured to conduct a lightning discharge to the hub connector and a core of electrically conductive material configured to electrically connect the first end and the second end, wherein the second end is rotatable with respect to the first end.

Additional objects, advantages and features of examples of the present disclosure will become apparent to those skilled in the art upon examination of the description, or may be learned by practice of the disclosure.

Throughout the present disclosure, and with respect to the various examples disclosed herein, it should be noted that that the blade root portion might be directly coupled to a rotor hub, to rotor hub extenders, to pitch bearings or to any other element of the rotor hub known in the art for this purpose.

Electrically insulating materials as used throughout the present disclosure may be understood to refer to materials in which electric current does not flow freely. Electrical insulators have a high electrical resistivity. Rubbers, glass and plastics are examples of electrical insulators. Electrically conducting materials as used throughout the present disclosure may be understood as materials that allow the flow of electrical current. Electrically conducting materials have a low electrical resistivity. Copper and aluminum wires or cables are examples of electrical conductors.

Reference now will be made in detail to embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not as a limitation thereof. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope of the present disclosure as defined in the appended claims. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims.

In examples, the rotor blades <NUM> may have a length ranging from about <NUM> meters (m) to about <NUM> or more. Rotor blades <NUM> may have any suitable length that enables the wind turbine <NUM> to function as described herein. For example, non-limiting examples of blade lengths include <NUM> or less, <NUM>, <NUM>, <NUM>, <NUM> or a length that is greater than <NUM>. As wind strikes the rotor blades <NUM> from a wind direction <NUM>, the rotor <NUM> is rotated about a rotor axis <NUM>. As the rotor blades <NUM> are rotated and subjected to centrifugal forces, the rotor blades <NUM> are also subjected to various forces and moments. As such, the rotor blades <NUM> may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position.

In the example, the wind turbine controller <NUM> is shown as being centralized within the nacelle <NUM>, however, the wind turbine controller <NUM> may be a distributed system throughout the wind turbine <NUM>, on the support system <NUM>, within a wind farm, and/or at a remote-control center. The wind turbine controller <NUM> includes a processor <NUM> configured to perform the methods and/or steps described herein. Further, many of the other components described herein include a processor.

As used herein, the term "processor" is not limited to integrated circuits referred to in the art as a computer, but broadly refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific, integrated circuit, and other programmable circuits, and these terms are used interchangeably herein. It should be understood that a processor and/or a control system can also include memory, input channels, and/or output channels.

<FIG> is an enlarged sectional view of a portion of the wind turbine <NUM>. In the example, the wind turbine <NUM> includes the nacelle <NUM> and the rotor <NUM> that is rotatably coupled to the nacelle <NUM>. More specifically, the hub <NUM> of the rotor <NUM> is rotatably coupled to an electric generator <NUM> positioned within the nacelle <NUM> by the main shaft <NUM>, a gearbox <NUM>, a high-speed shaft <NUM>, and a coupling <NUM>. In the example, the main shaft <NUM> is disposed at least partially coaxial to a longitudinal axis (not shown) of the nacelle <NUM>. A rotation of the main shaft <NUM> drives the gearbox <NUM> that subsequently drives the high-speed shaft <NUM> by translating the relatively slow rotational movement of the rotor <NUM> and of the main shaft <NUM> into a relatively fast rotational movement of the high-speed shaft <NUM>. The latter is connected to the generator <NUM> for generating electrical energy with the help of a coupling <NUM>. Furthermore, a transformer <NUM> and/or suitable electronics, switches, and/or inverters may be arranged in the nacelle <NUM> in order to transform electrical energy generated by the generator <NUM> having a voltage between 400V to <NUM> V into electrical energy having medium voltage (<NUM> - <NUM> KV). Said electrical energy is conducted via power cables from the nacelle <NUM> into the tower <NUM>.

The gearbox <NUM>, generator <NUM> and transformer <NUM> may be supported by a main support structure frame of the nacelle <NUM>, optionally embodied as a main frame <NUM>. The gearbox <NUM> may include a gearbox housing that is connected to the main frame <NUM> by one or more torque arms <NUM>. In the example, the nacelle <NUM> also includes a main forward support bearing <NUM> and a main aft support bearing <NUM>. Furthermore, the generator <NUM> can be mounted to the main frame <NUM> by decoupling support means <NUM>, in particular in order to prevent vibrations of the generator <NUM> to be introduced into the main frame <NUM> and thereby causing a noise emission source.

In some examples, the wind turbine may be a direct drive wind turbine without gearbox <NUM>. Generator <NUM> operate at the same rotational speed as the rotor <NUM> in direct drive wind turbines. They therefore generally have a much larger diameter than generators used in wind turbines having a gearbox <NUM> for providing a similar amount of power than a wind turbine with a gearbox.

For positioning the nacelle <NUM> appropriately with respect to the wind direction <NUM>, the nacelle <NUM> may also include at least one meteorological measurement system <NUM> which may include a wind vane and anemometer. The meteorological measurement system <NUM> can provide information to the wind turbine controller <NUM> that may include wind direction <NUM> and/or wind speed. In the example, the pitch system <NUM> is at least partially arranged as a pitch assembly <NUM> in the hub <NUM>. The pitch assembly <NUM> includes one or more pitch drive systems <NUM> and at least one sensor <NUM>. Each pitch drive system <NUM> is coupled to a respective rotor blade <NUM> (shown in <FIG>) for modulating the pitch angle of a rotor blade <NUM> along the pitch axis <NUM>. Only one of three pitch drive systems <NUM> is shown in <FIG>.

In the example, the pitch assembly <NUM> includes at least one pitch bearing <NUM> coupled to hub <NUM> and to a respective rotor blade <NUM> (shown in <FIG>) for rotating the respective rotor blade <NUM> about the pitch axis <NUM>. The pitch drive system <NUM> includes a pitch drive motor <NUM>, a pitch drive gearbox <NUM>, and a pitch drive pinion <NUM>. The pitch drive motor <NUM> is coupled to the pitch drive gearbox <NUM> such that the pitch drive motor <NUM> imparts mechanical force to the pitch drive gearbox <NUM>. The pitch drive gearbox <NUM> is coupled to the pitch drive pinion <NUM> such that the pitch drive pinion <NUM> is rotated by the pitch drive gearbox <NUM>. The pitch bearing <NUM> is coupled to pitch drive pinion <NUM> such that the rotation of the pitch drive pinion <NUM> causes a rotation of the pitch bearing <NUM>.

Pitch drive system <NUM> is coupled to the wind turbine controller <NUM> for adjusting the pitch angle of a rotor blade <NUM> upon receipt of one or more signals from the wind turbine controller <NUM>. In the example, the pitch drive motor <NUM> is any suitable motor driven by electrical power and/or a hydraulic system that enables pitch assembly <NUM> to function as described herein. Alternatively, the pitch assembly <NUM> may include any suitable structure, configuration, arrangement, and/or components such as, but not limited to, hydraulic cylinders, springs, and/or servomechanisms. In certain embodiments, the pitch drive motor <NUM> is driven by energy extracted from a rotational inertia of hub <NUM> and/or a stored energy source (not shown) that supplies energy to components of the wind turbine <NUM>.

The pitch assembly <NUM> may also include one or more pitch control systems <NUM> for controlling the pitch drive system <NUM> according to control signals from the wind turbine controller <NUM>, in case of specific prioritized situations and/or during rotor <NUM> overspeed. In the example, the pitch assembly <NUM> includes at least one pitch control system <NUM> communicatively coupled to a respective pitch drive system <NUM> for controlling pitch drive system <NUM> independently from the wind turbine controller <NUM>. In the example, the pitch control system <NUM> is coupled to the pitch drive system <NUM> and to a sensor <NUM>. During normal operation of the wind turbine <NUM>, the wind turbine controller <NUM> may control the pitch drive system <NUM> to adjust a pitch angle of rotor blades <NUM>.

According to an embodiment, a power generator <NUM>, for example comprising a battery and electric capacitors, is arranged at or within the hub <NUM> and is coupled to the sensor <NUM>, the pitch control system <NUM>, and to the pitch drive system <NUM> to provide a source of power to these components. In the example, the power generator <NUM> provides a continuing source of power to the pitch assembly <NUM> during operation of the wind turbine <NUM>. In an alternative embodiment, power generator <NUM> provides power to the pitch assembly <NUM> only during an electrical power loss event of the wind turbine <NUM>. The electrical power loss event may include power grid loss or dip, malfunctioning of an electrical system of the wind turbine <NUM>, and/or failure of the wind turbine controller <NUM>. During the electrical power loss event, the power generator <NUM> operates to provide electrical power to the pitch assembly <NUM> such that pitch assembly <NUM> can operate during the electrical power loss event.

In the example, the pitch drive system <NUM>, the sensor <NUM>, the pitch control system <NUM>, cables, and the power generator <NUM> are each positioned in a cavity <NUM> defined by an inner surface <NUM> of hub <NUM>. In an alternative embodiment, said components are positioned with respect to an outer surface of hub <NUM> and may be coupled, directly or indirectly, to the outer surface.

<FIG> is a schematical cross-sectional view of a wind turbine rotor hub comprising an example of a lightning bypass system. Note that the thickness of the internal walls has been included schematically and that the intersection of solid bodies with the cutting plane has not been indicated with hatching with the sole objective to reduce clutter.

<FIG> shows a lightning bypass system for a blade <NUM> of a wind turbine, the lightning bypass system comprising a blade connector <NUM> comprising an electrically insulating material <NUM> and configured to be located substantially in a rotational axis R of a blade root <NUM> of a wind turbine blade. The blade connector <NUM> comprises a first end <NUM> configured to be electrically connected to a down conductor cable <NUM> of the blade <NUM>, a second end <NUM> configured to conduct a lightning discharge to a hub <NUM> of the wind turbine and a core <NUM> of electrically conductive material configured to be electrically connected to the first end <NUM> and the second end <NUM>.

The blade connector comprises an electrically insulating fastener <NUM> for connecting the blade connector <NUM> to the blade root, in particular a blade flange, a plate arranged in the blade root or similar. The electrically insulating fastener <NUM> may be a bushing.

Additionally, <FIG> shows that the second end <NUM> of the blade connector <NUM> may be rotatable with respect to the first end. In the illustrated example, the second end <NUM> of the blade connector <NUM> includes a rotatable eye bolt connector <NUM>. However, other types of connectors can also be used.

In examples, the lightning bypass system may further comprise an electrical connection between the second end of the blade connector and a wind turbine nacelle. The rotatable electrical connection may comprise a conductive surface, a brush to provide electrical contact with the conductive surface, and the second end of the blade connector being electrically connected to one of the conductive surface and the brush. The electrical connection to the conductive surface or brush may be direct (e.g. a direct cable) or indirect (through further connectors, interfaces and elements).

Furthermore, <FIG> shows that the connector assembly may further comprise a hub connector <NUM> made of an electrically insulating material <NUM> and secured to the hub <NUM> of the wind turbine. The hub connector <NUM> may also comprise a core <NUM> of electrically conductive material, electrically connected to the second end <NUM> of the blade connector <NUM> through a conductive element <NUM>.

The conductive element may define a path of connection <NUM>. Note that the path of connection <NUM> has been illustrated conceptually with broken lines. In the illustrated example of <FIG>, the hub connector <NUM> is electrically coupled to a grounding system <NUM>; however, other arrangements are also possible. For instance, in situations wherein the hub connector <NUM> is not present the grounding system <NUM> can be alternatively coupled to the second end <NUM> of the hub connector <NUM>.

The hub connector <NUM> may include a fastener made of an electrically insulating material for connecting to a portion of the hub. The fastener <NUM> may be a bushing.

<FIG> also shows a partial view of a wind turbine blade comprising the lightning bypass system previously disclosed. More particularly, <FIG> illustrates the blade root portion <NUM> of a wind turbine blade and the arrangement of the lightning bypass system within the same. In addition, in this example the wind turbine blade further comprises at least one crossbar <NUM> located across the blade root <NUM> to secure the blade connector <NUM> substantially in the rotational axis R of the blade root <NUM>. Alternatively, an extension of a blade flange <NUM> or other alternatives may also be used to secure the blade connector <NUM> in place. As an example, the wind turbine blade may also or alternatively comprise a blade root stiffener or blade flange <NUM> substantially covering the complete blade root. In the example shown, the wind turbine blade comprises both a stiffener or flange <NUM> and a crossbar <NUM> connecting diametrically opposed sides of the same and securing the blade connector <NUM> in place.

<FIG> shows a detailed view of another example of a lightning bypass assembly wherein several components, such as the grounding system, have not been illustrated to reduce clutter. This figure shows an example of the path of connection between the blade connector <NUM> and the previously disclosed hub connector <NUM>. In this example, the conductive element <NUM> is a metal sling which may include an electrically insulating material cover to protect other components from the current that may flow through it during lightning discharge. Other types of conductive elements such as a metal rods or cables can also be used. Further, <FIG> shows that the hub connector <NUM> may also comprise an eye bolt connector <NUM> to provide additional rotational freedom and reduce torsion stresses on connecting elements.

The eye bolt connector <NUM> (in both examples of <FIG> and <FIG>) may be rotatably mounted in electrically insulating bushing <NUM>. Similarly, the eye bolt connector <NUM> may be rotatably mounted in electrically insulating bushing <NUM>.

In examples, the conductive element <NUM> may define a path of connection that serves as a guide for additional cable bundles <NUM>. In the present example, the cable bundle <NUM> may be a bundle of cables (e.g. fibre optic cables) connected to sensors in the blade. The sensors and cables may form part of wind turbine subsystems (i.e. blade monitoring system, lightning monitoring system, de-icing system, blade aviation lightning system) that extends from the blade root <NUM> to the rotor hub <NUM> following said path of connection. The cable bundle <NUM> may be coupled to the conductive element <NUM> by means of fasteners <NUM> and/or may be guided by the blade and hub connectors <NUM>, <NUM>.

<FIG> is a schematical cross-sectional view of a wind turbine rotor hub and nacelle comprising yet another example of a lightning bypass system. The connection between down conductor from the blade towards the hub may generally be the same or similar to the example illustrated in <FIG>.

In the example shown in <FIG>, the lightning bypass system further comprises a rotatable electrical connection between the second end <NUM> of the blade connector <NUM> and a wind turbine nacelle <NUM>. The rotatable electrical connection comprises a conductive surface <NUM>, and a brush <NUM> to provide electrical contact with the conductive surface <NUM>. The lightning bypass system further comprises a conductive connection to the second end <NUM> of the blade connector <NUM> and to one of the conductive surface <NUM> and the brush <NUM>. In the example shown, a conductive cable <NUM> is physically connected to a hub connector <NUM>, which in the way described before with reference to <FIG>, is connected to blade connector <NUM> and the lightning protection system in the blade. However, the hub connector <NUM> could be omitted and the conductive cable <NUM> coupled directly to the blade connector <NUM>.

In the example in <FIG>, the conductive surface <NUM> is secured to the wind turbine hub <NUM> and the brush <NUM> is fixed to the wind turbine nacelle <NUM> and provides an electrical path between the rotatable wind turbine hub <NUM> and the wind turbine nacelle <NUM>.

The conductive surface <NUM> in the present example is fixed to the rotor hub <NUM> by means of non-conductive supports <NUM> to prevent the lightning discharge to be transferred to the rotor hub <NUM>, and therefore avoiding that the lightning discharge passes through the rotor bearings <NUM>'. The brush <NUM> may be fixed to the nacelle <NUM> following a similar approach, although the corresponding supports have not been depicted in this figure to reduced clutter. Alternatively, the conductive surface <NUM> may be secured to the wind turbine nacelle <NUM> and the brush <NUM> may be fixed to a wind turbine hub <NUM> to provide an electrical path between the wind turbine hub <NUM> and the wind turbine nacelle <NUM>.

In the illustrated example, the conductive surface <NUM> is an annular metal disk, although the geometry of this element can be adapted to specific requirements of the lightning system.

In another aspect, <FIG> also shows a wind turbine hub assembly including a wind turbine rotor hub <NUM>, at least one wind turbine blade <NUM>, and a lightning bypass system. The wind turbine blade <NUM> comprises a blade root <NUM>, and the lightning bypass system comprises a blade connector <NUM> made of an electrically insulating material <NUM> secured to the wind turbine blade and located substantially in a rotational axis R of the blade root <NUM> of the wind turbine, and a hub connector <NUM> made of an electrically insulating material <NUM> secured to the rotor hub <NUM> of the wind turbine. The blade connector <NUM> comprises a first end <NUM> configured to be electrically connected to a down conductor cable <NUM> of the blade, a second end <NUM> configured to conduct a lightning discharge to the hub connector <NUM> and a core <NUM> of electrically conductive material configured to electrically connect the first end <NUM> with the second end <NUM>, wherein the second end <NUM> is rotatable with respect to the first end.

The blade connector comprises a bushing made of an electrically insulating material.

Further, the wind turbine hub assembly may include a hub connector <NUM> comprises a core <NUM> of electrically conductive material, electrically connected to the second end <NUM> of the blade connector <NUM> through a conductive element <NUM>, the conductive element defining a path of connection <NUM>.

The wind turbine hub assembly may further comprise a conductive surface <NUM> secured to the wind turbine rotor hub <NUM>. In examples, the assembly may further comprise a brush <NUM> for providing electrical contact with the conductive surface <NUM>, and a conductive cable <NUM> electrically connected to the hub connector <NUM> and to the conductive surface <NUM>. The brush <NUM> is fixed to a wind turbine nacelle <NUM> and provides an electrical path between the wind turbine rotor hub <NUM> and the wind turbine nacelle <NUM>.

Further, <FIG> illustrates that the rotor hub <NUM> may be mounted on a frame <NUM> through hub bearings <NUM>', forming a rotatable connection between the hub and frame. The frame <NUM> supporting the rotor hub <NUM> may be connected to a further frame or other structural support in the nacelle <NUM>.

In examples, the rotor hub may be connected to a rotor shaft through a flexible coupling. The flexible coupling may be configured to transmit torsion loads but to avoid transmission bending loads (or at least reduce the transmission hereof). The rotor shaft may drive a generator directly, or may form the slow speed shaft which forms the input shaft of a gearbox.

In the example of <FIG>, a direct drive wind turbine is schematically illustrated. In this example, the rotor hub <NUM> may be jointed to an outer structure <NUM>, which may include or be connected to a generator rotor. Thus, the outer structure <NUM> may rotate around a nacelle inner structure <NUM>, which may include or form the generator stator.

<FIG> shows another example of the lightning system according to the present disclosure in a wind turbine configuration comprising a main rotor shaft <NUM> on which the rotor hub <NUM> is mounted. The main shaft <NUM> is configured to drive and may be operatively coupled to a shaft of a generator rotor, either directly or indirectly. In this example, the rotor shaft <NUM> is rotatably supported in the nacelle <NUM> by means of main bearings <NUM>.

The lightning system according to the present disclosure is therefore suitable for a broad range of wind turbine configurations, i.e. direct drive wind turbines or wind turbines comprising a gearbox system among others.

In another aspect of the disclosure, a method <NUM> is provided. Method <NUM> is suitable for providing a lightning bypass system. Method <NUM> is schematically illustrated in <FIG>.

The method comprises, at block <NUM>, providing a blade connector <NUM> comprising an electrically insulating material <NUM> substantially located in a rotational axis R of a blade root <NUM> of (a wind turbine blade of) the wind turbine, wherein the blade connector <NUM> comprises a first end <NUM>, a second end <NUM> and a core <NUM> of electrically conductive material electrically connected to the first end <NUM> and the second end <NUM>. The blade connector <NUM> may be or comprise an electrically insulated bushing.

The method <NUM> also comprises, at block <NUM>, connecting the first end <NUM> of the blade connector <NUM> to a down conductor cable <NUM> connected to a lightning receptor of a blade. Further, the method <NUM> comprises, at block <NUM> providing a rotatable connection between the first end <NUM> and the second end <NUM> of the blade connector <NUM>. The rotatable connection can be provided, for example, by means of an eye bolt connector <NUM> located at the second end <NUM> of the blade connector <NUM>.

Besides, the method <NUM>, at block <NUM>, comprises conductively coupling the second end of the blade connector to a lightning grounding system <NUM> of a wind turbine.

In examples, the method <NUM> for providing a lightning bypass system may comprise providing a conductive surface <NUM> secured to one of a wind turbine rotor hub <NUM> and a wind turbine nacelle <NUM> and electrically isolated from the same. Besides, it may comprise providing a brush <NUM> for electrical contact with the conductive surface <NUM>, the brush <NUM> being fixed to the other of the wind turbine rotor hub <NUM> and the turbine nacelle <NUM> where the conductive surface <NUM> is secured, providing an electrical path between the wind turbine hub <NUM> and a wind turbine nacelle <NUM>; and conductively coupling a cable <NUM> from the second end <NUM> of the blade connector <NUM> to the conductive surface <NUM>.

In additional examples, the method <NUM> may comprise providing a hub connector <NUM> made of an electrically insulating material <NUM> secured to the hub <NUM> of the wind turbine; wherein the hub connector <NUM> comprises a core <NUM> of electrically conductive material; conductively coupling the second end <NUM> of the blade connector <NUM> to the hub connector <NUM> through a conductive element <NUM>, the conductive element <NUM> defining a path of connection <NUM>; and guiding a cable bundle <NUM> along the path of connection <NUM> defined by the conductive element <NUM>. The cable bundle <NUM> may be part of a blade subsystem such as a blade monitoring system, a lightning monitoring system, a de-icing system or a blade aviation lightning system among others.

Claim 1:
A lightning bypass system for a blade (<NUM>) of a wind turbine (<NUM>), the lightning bypass system comprising:
a blade connector (<NUM>) comprising an electrically insulating material (<NUM>) and configured to be located substantially in a rotational axis (R) of a blade root (<NUM>) of a wind turbine blade (<NUM>); wherein
the blade connector (<NUM>) comprises a first end (<NUM>) configured to be electrically connected to a down conductor cable (<NUM>) of the blade (<NUM>), a second end (<NUM>) configured to conduct a lightning discharge to a rotor hub (<NUM>) of the wind turbine (<NUM>) and a core (<NUM>) of electrically conductive material configured to be electrically connected to the first end (<NUM>) and the second end (<NUM>), characterised in that the blade connector (<NUM>) comprises an electrically insulating fastener (<NUM>) for connecting the blade connector (<NUM>) to the blade root (<NUM>); and wherein
the first end (<NUM>) and the second end (<NUM>) of the blade connector (<NUM>) form a rotatable connection.