Patent Description:
Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. Said rotation generates a torque that is normally transmitted through a rotor shaft to a generator, either directly or through a gearbox. This way, the generator produces electricity which can be supplied to the electrical grid.

The wind turbine hub may be rotatably coupled to a front of the nacelle. The wind turbine hub may be connected to a rotor shaft, and the rotor shaft may then be rotatably mounted in the nacelle using one or more rotor shaft bearings arranged in a frame inside the nacelle. The nacelle is a housing arranged on top of a wind turbine tower that contains and protects e.g. the gearbox (if present) and the generator and, depending on the wind turbine, further components such as a power converter, and auxiliary systems.

Power cables carry electrical energy from the generator in the nacelle down the wind turbine tower and up to the electrical grid. A power cable usually includes a bunch of metallic wires, e.g. copper wires, surrounded by a protective and flexible cover, e.g. a rubber cover. Power cables in wind turbine are expected to withstand vibrations, bending, torsion, abrasion, a wide range of temperature and electromagnetic interferences. In offshore wind turbines, they should also be resistant to salt water and salt sea air.

Power cables should allow the nacelle to yaw while constantly and reliably carrying electrical energy. When a wind direction changes, the nacelle changes its orientation to align with the wind direction. A nacelle may make up to three or more complete turns before unwinding in the opposite direction. The power cable has to be able to withstand the corresponding torsion. The torsion also leads to shortening of the power cables. And the power cables need to have an additional extra length in order to be able to compensate. This additional length is usually provided through a cable saddle i.e. a portion of the cable is guided over a curved structure. The curved structure may be formed as a semi-cylinder. The power cables may be guided over the top surface of the semi-cylinder. The radius of the semi-cylinder may be determined depending on the cable used. The minimum bending radius of the cables needs to be respected.

The minimum bending radius of a cable may depend inter alia on the power rating and voltage rating of the cable. The amount of electrical insulation and the diameter of the wire bundles in the cable may depend particularly on the voltage rating. Similarly the torsion capability of the cables may depend on the cable configuration.

It is an objective of the present disclosure to provide cable arrangements and methods for guiding cables in large wind turbines with relatively high power ratings. It is a further objective of the present disclosure to provide methods and systems for guiding medium or high voltage power cables in wind turbines. A prior art example of guiding high voltage power cables in a wind turbine tower is disclosed in <CIT>.

In an aspect of the present disclosure, a tower for a wind turbine is provided. The tower comprises a top section supporting a nacelle of the wind turbine about a yaw axis, wherein the nacelle comprises an electric power component and a power cable for electrically connecting the electric power component to an electrical connection point in a lower section of the tower. The power cable extends downwards from the nacelle along a substantially central area of the tower, and at a first height, the power cable comprises a power cable loop. The power cable loop including an upwards curve, and a downwards curve. The power cable loop comprises a movable cable part, and a fixed cable part, and the fixed cable part comprises at least a portion of the downwards curve.

A loop as used throughout the present disclosure may be understood as a segment of a cable comprising subsequent portions extending longitudinally in opposite directions. In other words, a loop is formed by a cable extending in a first direction, comprising a portion that extends substantially in the opposite direction, and a portion that continues again in the first direction. In particular, in the present disclosure, a loop comprises a downwards portion (from the nacelle down the tower), a subsequent upwards portion and a further subsequent downwards portion (or if regarded in the opposite direction an upwards portion, a subsequent downwards portion followed by a further upwards portion). A cable loop may provide slack for absorbing movements of the nacelle. The subsequent cable portions along which the cable changes direction may be curved. The upwards portion may form an upward curve, and the downwards portion before and after the upwards portion together may form a downward curve.

These subsequent cable portions may form a curve completing <NUM>°. The cable portions may form a substantially circular segment, but do not need to form a complete circle, nor does the segment need to be circular.

In accordance with this aspect, a tower for a wind turbine is provided with a power cable arrangement which is able to accommodate cables of increased minimum bending radius. Because the cable loop is partly movable and partly fixed, and part of the cable loop is formed by the fixed cable part, the movable part which is configured to provide slack and is able to absorb movements does not need to make a complete loop from downwards, upwards and further downwards. The radius of the power cable loop can thus be increased. Cable arrangements with sufficient power and voltage rating (and related torsion capability) may thus be provided within sections of the tower with an acceptable diameter.

In a further aspect, a method for guiding a power cable in a wind turbine is provided. The method comprises connecting the power cable to an electrical power component in a nacelle of the wind turbine and arranging the power cable through a central area of a bottom of the nacelle such that the power cable extends substantially vertically downwards from the nacelle to a first height along a central area of a tower. The method further comprises directing the power cable from the central area of the tower to an inside wall of the tower near the first height and attaching the power cable to the inside wall of the tower to form a substantially vertical loop.

In a further aspect, a wind turbine comprises a wind turbine rotor including a plurality of rotor blades, a generator operatively coupled to the wind turbine rotor for generating electrical power, a power electronic converter for converting the electrical power generated by the generator to a converted AC power of predetermined frequency and voltage and a main wind turbine transformer having a low voltage side and a high voltage side for transforming the converted AC power to a higher voltage. The wind turbine further comprises a nacelle comprising the generator, the power electronic converter and the main transformer and a tower for rotatably supporting the nacelle. The wind turbine further comprises a power cable for electrically connecting the high voltage side of the main wind turbine transformer to an electrical connection point in a lower portion of the tower. The power cable is arranged from the nacelle downwards along a central area of the tower, and wherein the power cable comprises a vertical power cable loop arranged at least partially along an inner surface of the tower.

Each example is provided by way of explanation of the invention, not as a limitation of the invention.

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) or higher voltage, e.g. 66kV. Said electrical energy is conducted via power cables <NUM> from the nacelle <NUM> into the tower <NUM>.

The gearbox <NUM>, generator <NUM> in 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.

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 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 angel 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 supply <NUM>, for example comprising a battery, electric capacitors hence letter or an electrical generator driven by the rotation of the hub <NUM>, 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 supply <NUM> provides a continuing source of power to the pitch assembly <NUM> during operation of the wind turbine <NUM>. In an alternative embodiment, power supply <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 supply <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 supply <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 outer surface.

<FIG> schematically illustrate an example of an arrangement of a power cable in a wind turbine tower. In one aspect of the present disclosure, a tower <NUM> for a wind turbine comprises a top section <NUM> supporting a nacelle <NUM> of the wind turbine about a yaw axis <NUM>, wherein the nacelle <NUM> comprises an electric power component and a power cable <NUM> for electrically connecting the electric power component to an electrical connection point in a lower portion of the tower. The power cable extends <NUM> downwards from the nacelle, at least to a first height H1 along a substantially central area of the tower <NUM>. Substantially at the first height H1, the power cable <NUM> comprises a power cable loop, wherein the power cable loop comprises an upwards curve and a downwards curve. The power cable loop comprises a movable cable part <NUM>, and a fixed cable loop <NUM>. The fixed cable part <NUM> comprises at least a part <NUM> of the downwards loop.

In this example, the movable cable part <NUM> comprises a movable downwards portion <NUM>, and a (subsequent) movable upwards portion <NUM>. The fixed cable part <NUM> is attached to an end of the movable upwards portion <NUM>.

In this example, the fixed cable part <NUM> comprises at least an upwards portion <NUM> and a downwards portion <NUM>. The upwards portion <NUM> of the power cable loop <NUM> is herein arranged along an inner surface of the tower <NUM>.

In this example, the movable upwards portion <NUM> and fixed upwards portion <NUM> together form an upward curve. The power cable loop is completed by the movable downwards portion <NUM>, and fixed downwards portion <NUM> together forming a downward curve.

A movable cable part as used throughout the present disclosure may be regarded as a part of a cable loop that is not fixed in place, but instead is movably arranged to as to be able to absorb movements of the power cable, and in particular shortening of the power cable and/or torsion of the power cable caused by yawing of the nacelle. A fixed cable loop as used throughout the present disclosure may be regarded as a part of a cable loop that is fixed in place, and therefore is not specifically configured to absorb torsion and/or shortening of the cable by changing its position or orientation.

Herein, the electric power component arranged in the nacelle <NUM> may be a generator or a power electronic converter of the wind turbine. A top end <NUM> of power cable <NUM> may be connected to the generator or power electronic converter. The electrical connection point in a lower portion of the tower (i.e. below the power cable loop) may be at or near a bottom section of the tower and may be a power electronic converter or a main wind turbine transformer.

Alternatively, the electric power component arranged in the nacelle <NUM> may be a main wind turbine transformer, and top end <NUM> of power cable <NUM> may be connected to the main wind turbine transformer, in particular to the high voltage side of the main wind turbine transformer. The electrical connection point in a lower portion of the tower, e.g. at or near a bottom of a section of the tower, may be an electrical connection to a wind park grid. The electrical connection may be e.g. through a switchgear.

In the example of <FIG>, the downwards portion <NUM> of the fixed cable part is arranged along an inner surface of the tower <NUM>. The movable cable part <NUM> of the power cable <NUM> extends from the central area of the tower, towards an inside wall of the tower and may be regarded as forming part of the same power cable loop.

The inner surface of the tower <NUM> may be formed by an inner wall surface of the turbine tower. The fixed power cable part <NUM> may be arranged in the vicinity of the inside wall of the wind turbine tower, thus maximizing the space available for the movable cable loop <NUM>. The fixed power cable part <NUM> may extend along the inside wall of the tower maintaining a substantially constant distance to the inside wall. The fixed power cable portion <NUM> may also be attached to at least one other fixed structure that is attached to the inside wall. Such a fixed structure might include parts of a ladder.

The upwards <NUM> and downwards portion <NUM> of the fixed power cable part <NUM> may be arranged along the inner surface of the tower e.g. using a plurality of cable cleats <NUM>. Cable cleats may herein be regarded as any mechanical assembly suitable for fixing, clamping and/or supporting cables.

In examples, like in <FIG>, the fixed vertical power cable loop may be fixed to an inside of a wind turbine tower using <NUM> - <NUM> cable cleats <NUM>.

In the example of <FIG>, one or more of the cable cleats 280may be connected to a mounting bracket <NUM> mounted to the inner surface of the tower. The brackets <NUM> may be configured to allow mounting the cable cleat <NUM> at a plurality of heights along the bracket using any suitable fasteners, like nuts and bolts. Such brackets may be attached to bosses of an inner surface of the tower.

In other examples, other cleats, cable clamps or assemblies for fixing the cable may be used, such as cable ladders or cable trays.

The first height H1 at which the fixed power cable loop <NUM> is arranged may be determined such that the power cable <NUM> arranged between the first height H1 and the nacelle <NUM> is configured to absorb a maximum amount of yaw of the nacelle in a single direction.

An electrical cable may have a specified torsion capability. For example, a power cable <NUM> may have a torsion capability of e.g. between <NUM> - <NUM>° per meter, and in the present example about <NUM>° per meter. The maximum torsion that the power cable <NUM> may have to withstand <NUM>° (<NUM> full revolutions of the nacelle) or <NUM>° (<NUM> full revolutions of the nacelle). The first height H1 where the power cable loop is arranged may be determined such that the length of the power cable between the nacelle and the first height is sufficient to absorb the maximum allowable torsion. The determination of the first height may further take a safety factor into account. The first height may e.g. be <NUM> meters or more below the nacelle, specifically at least <NUM> meters below the nacelle. The power cable loop <NUM> itself may not be able to absorb any torsion, so any torsion may need to be absorbed above the power cable loop <NUM>.

The wind turbine tower <NUM> may further comprise a platform <NUM> at or near the first height. The platform <NUM> may be configured to support personnel, and allow access of personnel for maintenance and installation purposes. Multiple platforms <NUM>, <NUM> may be arranged at different heights to allow personnel to carry out installation, inspection and/or maintenance tasks.

The platform <NUM> may include a cylindrical section <NUM> allowing the cables to pass through the platform. A geometric center of the cylindrical section <NUM> may substantially coincide with a geometric section of the wind turbine tower at the height of the platform <NUM>.

Also shown in the example of <FIG>, an elevator shaft <NUM> (in which also ladder may be arranged, as may be seen in <FIG>) can be formed next to the platform <NUM>, such that personnel can reach the platform <NUM> using the ladder <NUM> or elevator (not shown).

In the example of <FIG>, the platform <NUM> may include recesses <NUM>, <NUM> near an inner surface of the wind turbine tower for arranging the power cable <NUM>. In the example of <FIG>, a first substantially rectangular cut-out <NUM> is provided near a corner of platform <NUM>. The upwards portion <NUM> of the fixed cable part <NUM> is arranged through this cut-out <NUM>. Apart from the power cable <NUM>, further auxiliary cables (illustrated particularly with respect to <FIG>) may be arranged through the same cut-out <NUM>.

The downwards portion <NUM> of fixed cable part <NUM> may be guided through a smaller, substantially rectangular, cut-out <NUM>.

In the example of <FIG>, the movable cable part extends substantially in a vertical longitudinal plane of the tower. In other examples, the movable cable loop may extend partially in an azimuthal direction as well (around the yaw axis or longitudinal axis of the tower). The entire movable cable part of the power cable loop is in these cases not arranged substantially in the same longitudinal plane. By combining a vertical extension with an azimuthal extension, the stretch of movable cable configured to absorb cable movement may be increased, or the vertical extension of the movable cable part can be reduced.

In the herein disclosed examples, the fixed cable part <NUM> is shown to be predominantly vertical, including upwards and downwards portions. However in other examples, the fixed cable part <NUM> may predominantly extend along an azimuthal plane rather than in a vertical direction. The fixed cable part <NUM> may be arranged to an inside wall of the tower at a substantially constant height.

Although not shown in the example of <FIG>, further auxiliary cables may be provided extending between the nacelle <NUM> and the bottom section of the tower, and further cable guiding assemblies <NUM> which guide the power cable <NUM> and the auxiliary cables. The cable guiding assemblies <NUM> may be arranged as a cable spacer, ensuring appropriate distance between different cables.

Beyond the fixed cable part <NUM> further in a direction of the bottom of the tower, the arrangement of the cables may be fixed. Fixed cable portion <NUM> of the power cable <NUM> and/or the auxiliary cables may generally be guided along the inside of the wind turbine tower. The fixed cable portion <NUM> may include different cables than the free-hanging portion <NUM> of the cables. The free-hanging or movable portion <NUM> of the cables as used throughout the present disclosure may be regarded as the portion of the cables that is configured to undergo and absorb movements and to this end has certain slack. as opposed to the fixed cable portion <NUM>, the free-hanging portion is not firmly fixed in place, but instead is allowed to move inside the tower in particular in response to yawing movements of the nacelle. Note that herein the fixed cable portion is indicated with reference number <NUM> as extending downwards from platform <NUM>, but the movable cable part <NUM> of the power cable loop may be arranged at least partially below the platform <NUM>.

The cable guiding assemblies may have a variety of different configurations, and sizes depending on the specific needs. Such a cable guiding assembly <NUM> may have a circular central part or through-hole with an outwardly facing convex surface and a number of fingers extending in a radial direction.

Between neighboring fingers, spaces may be arranged for receiving auxiliary cables. The auxiliary cables may include electrical cables for power supply for auxiliary systems of the wind turbine and/or communication cables. The auxiliary systems of the wind turbine receiving electrical power may include pitch systems, yaw systems, beacons, air conditioning systems and other. Communication cables may include fiber optic cables, signal cables and other.

In order to maintain such auxiliary cables firmly in the allocated spaces, clamps may be arranged inside the spaces. Depending on the type of cable arranged in each of the spaces, the number of clamps, and type of clamps may be adapted to firmly keep the cables in their position. Not all cables necessarily need to be clamped. A selection of the cables may be free inside their allocated spaces.

In examples, the power cable <NUM> is not restrained by the cable guiding assemblies, i.e. the power cable can twist and move vertically with respect to one or more of the cable guiding assemblies <NUM>, specifically all of the cable guiding assemblies <NUM>.

A plurality of cable guiding assemblies <NUM> may be arranged above each other. Generally, the cables may extend through the tower from (or to) the nacelle in a substantially central area of the wind turbine tower. The cable guiding assemblies <NUM> may have a distance between each other of e.g. <NUM> - <NUM>, specifically between <NUM> and <NUM> meter.

A selection of the cable guiding assemblies <NUM> above the first distance, i.e. along the free-hanging portion <NUM> of the cables, may be allowed to rotate (to absorb torsion) and translate along a vertical direction (to absorb shortening of the cables). A selection of the cable guiding assemblies <NUM> may only translate and not rotate. One or more of the cable guiding assemblies <NUM> may be fixed in place and may be arranged "floating" around the cables, i.e. they do not restrain the cables significantly and merely guide the cables.

For example, the cable guiding assembly <NUM> which is arranged to move along the cylindrical section <NUM> of platform <NUM>, may only be allowed to translate (move vertically).

In this respect, the cable guiding assembly <NUM>, which is configured to be received in and guided by cylindrical section <NUM> may be slightly different from other cable guiding assemblies arranged above it. In particular, the cable guiding assembly <NUM> may have a plurality of protrusions which are guided by slots of the cylindrical section <NUM> to impede rotational movement.

A wind turbine tower may be formed by a plurality of tower sections stacked on top of each other. These tower sections can be formed as substantially cylindrical sections or e.g. as frustoconical sections. In some case, the tower sections may have a polygonal perimeter. Cables, including the power cable <NUM> may be arranged at near a geometrical center of the tower at each cross-section between the power cable loop and the nacelle. Such a central arrangement is useful for absorbing the torsion caused by yawing of the nacelle.

In an aspect of the present disclosure, a method for guiding a power cable in a wind turbine is provided. The method comprises (with reference to <FIG>) connecting the power cable <NUM> to an electrical power component in a nacelle <NUM> of the wind turbine. The method then comprises arranging the power cable <NUM> through a central area of a bottom of the nacelle <NUM> such that the power cable <NUM> extends substantially vertically downwards from the nacelle <NUM> to a first height H1 along a central area of a tower <NUM>. The method further comprises directing the power cable from the central area of the tower to an inside wall of the tower near the first height H1 and attaching the power cable <NUM> to the inside wall of the tower to form a substantially vertical loop.

A part of the vertical loop may be attached to the inside wall of the tower. Another part of the vertical loop may be formed by a movable or free-hanging cable part.

In examples, directing the power cable <NUM> from the central area may comprise loosely arranging the power cable <NUM> through a portion of a platform <NUM>, and guiding the power cable towards the inside wall of the tower. The power cable <NUM> may be guided through a central portion <NUM> of platform <NUM> and then may be guided to the wall of the tower and upwards through a cut-out in the platform.

In examples, the method may further comprise arranging auxiliary cables substantially in parallel with the power cable along the central area of the tower, and guiding the power cable and the auxiliary cables in the same cable guiding assembly <NUM>.

At or near the first height H1, the auxiliary cables may include an auxiliary cables loop <NUM>, wherein the auxiliary cables loop <NUM> may be arranged separately from the power cable loop. The auxiliary power cables loop <NUM> may also be vertically arranged, and comprise upwards and downwards portions, and specifically these upwards and downwards portions may be mounted to an inside wall of the tower.

<FIG> schematically illustrates a further example of a cable arranged in a wind turbine tower. In the example of <FIG>, both a power cable, and auxiliary cables are shown.

In a further aspect of the present disclosure, and with reference to <FIG>, <FIG> and <NUM>, a wind turbine is provided. The wind turbine comprises a wind turbine rotor <NUM> including a plurality of rotor blades <NUM>, a generator <NUM> operatively coupled to the wind turbine rotor <NUM> for generating electrical power. The wind turbine further comprises a power electronic converter for converting the electrical power generated by the generator <NUM> to a converted AC power of predetermined frequency and voltage and a main wind turbine transformer having a low voltage side and a high voltage side for transforming the converted AC power to a higher voltage.

The wind turbine <NUM> comprises a nacelle <NUM> which includes or houses the generator <NUM>, the power electronic converter and the main transformer and a tower <NUM> for rotatably supporting the nacelle <NUM>.

The wind turbine <NUM> further comprises a power cable <NUM> for electrically connecting the high voltage side of the main wind turbine transformer to an electrical connection point in a lower portion of the tower <NUM>. The power cable <NUM> is arranged from the nacelle <NUM> downwards along a central area of the tower <NUM>, and the power cable <NUM> comprises a vertical power cable loop at least partially arranged along an inner surface of the tower <NUM>.

In this example, the power cable <NUM> is connected to a high voltage side of the main wind turbine transformer. The power cable <NUM> may be configured for transmitting electrical power of a voltage of 10kV or more, specifically 30kV or more, and more specifically 60kV or more as delivered on the high voltage side of the main wind turbine transformer.

The power cable <NUM> in any of the herein disclosed examples may include a single phase of the electrical connection, and in this particular example, the power cable may include multiple phases, e.g. three phases or six phases.

A minimum bending radius of the power cable <NUM> in the free-hanging or flexible portion in any of the herein disclosed examples may be at least <NUM> meters, specifically at least <NUM>,<NUM> meter, and even <NUM> meter or more. Because of the minimum bending radius of the power cable <NUM>, there may not be enough space at height H1 to arrange a classical cable saddle. A cable power loop <NUM> which respects the minimum bending radius may be arranged along the inner surface of the tower.

The vertical power cable loop comprises upwards and downwards portions, and wherein one or more of the upwards and downwards portions of the power cable loop may be attached to the inner surface of the tower e.g. with cable cleats mounted on brackets. The fixed cable part <NUM> in this case includes upwards and downwards portions of the power cable loop. The brackets may be attached to one or more bosses at the inner surface of the tower. Other fasteners may also be used.

Auxiliary cables may generally be arranged in parallel to the power cable <NUM> along free-hanging portion <NUM> of the cables, i.e. specifically above platform <NUM>, and generally along a central area of the tower. All torsion and shortening of cables can be absorbed by the free-hanging portion <NUM>.

At or near the platform <NUM>, the auxiliary cables on the one hand and power cable <NUM> on the other may be separated from each other. The auxiliary cables may have a different, and particularly, a smaller minimum bending radius than power cable <NUM>. The auxiliary cables may thus have a different cable loop, and particularly a vertical auxiliary cables loop <NUM>. A downwards portion <NUM> of the auxiliary cables may be guided along the tower, and in a specific example along or near an elevator shaft.

In the fixed portion <NUM> of the cables, specifically below the cable loops, the power cable <NUM> may be arranged in parallel with the auxiliary cables. A plurality of clamps or cleats may be arranged with the wind turbine tower to fix the power cable and auxiliary cables in position.

In a plurality of locations along the wind turbine tower, and/or in a plurality of locations along a substantially horizontal direction (particularly between the nacelle and the platform in the vicinity of the cable loop), cable organizers (also known as "cable spacers"), or cable guiding assemblies may be arranged in which the power cables are arranged substantially parallel to one another.

Throughout the present disclosure, reference has been made to power cables. Dimensions and materials of the power cables may vary. For example, a cable (MVhigh-cable, <NUM>-<NUM> kV) for the higher middle voltage power transmission made of copper may have a cross section of e.g. <NUM> - <NUM><NUM>. A minimum bending radius of the power cable may depend particularly on the voltage rating and on the insulation material that is required for a particular power and/or voltage rating. A minimum bending radius may be e.g. <NUM> or more, specifically <NUM> or more, and even <NUM> meter or more. These minimum bending radii may apply to a free-hanging or movable portion of the cable. The minimum bending radius of the same power cable may be smaller for a fixed portion of the cable. Such a minimum bending radius may be e.g. <NUM> or more, specifically <NUM> or more, and more specifically <NUM> or more.

According to an additional or alternative embodiment, electrical energy as generated by the generator having a voltage of <NUM> V to <NUM> V is guided through the tower to an electrical power component, switches and/or to a transformer for being transformed to medium voltage (<NUM> - <NUM> KV) by said components located at a lower position than the nacelle.

Claim 1:
A tower (<NUM>) for a wind turbine comprising:
a top section (<NUM>) supporting a nacelle (<NUM>) of the wind turbine about a yaw axis (<NUM>), wherein the nacelle (<NUM>) comprises an electric power component; and
a power cable (<NUM>) for electrically connecting the electric power component to an electrical connection point in a lower section of the tower, wherein
the power cable (<NUM>) extends downwards from the nacelle (<NUM>) along a substantially central area of the tower (<NUM>), and at a first height (H1) between the nacelle and the electrical connection point, the power cable comprises a power cable loop, including an upwards curve, and a downwards curve, wherein
the power cable loop comprises a movable cable part (<NUM>), and a fixed cable part (<NUM>), and the fixed cable part (<NUM>) comprises at least a portion of the downwards curve, wherein
the fixed cable part (<NUM>) comprises at least an upwards portion (<NUM>) and a downwards portion (<NUM>), characterized in that
the upwards portion (<NUM>) of the fixed cable part (<NUM>) is arranged along an inner surface of the tower (<NUM>).