Patent Description:
Wind turbine generators are an increasing popular source for generating electricity and may be deployed singly or in groups of several wind turbines, often referred to as a wind farm. To increase the efficiency, safety, and durability of wind turbines and wind farms, designers may incorporate various powered systems into the blades of the wind turbines, such as, for example, lights, de-icing systems, sensors, etc. These powered systems may receive operational power delivered via one or more electrical leads running along the length of the blade. These electrical leads carry power to the powered systems during normal operations, but also present a conductive path that lightning or other electrical discharges may take. Lightning strikes are a concern for wind turbine operators, as wind turbines are often the tallest objects in the vicinity and one or more of the electrical leads incorporated in the blades can offer a path of least impedance that passes through sensitive components.

<CIT> describes a wind turbine having a blade, and a device is provided for protecting electrical apparatus in the blade against damage caused by a lightning strike.

In one embodiment, a wind turbine blade is provided, which includes: a discharge filter, located in a root of the wind turbine blade, including a first cable wound into a first inductor using the root as a mandrel; a powered system, located in a body of the wind turbine blade; an electrical panel, located between the discharge filter and the powered system in the body of the wind turbine blade, wherein the first cable is configured to provide power to the powered system through the electrical panel.

In the present disclosure the expression "using the root as a mandrel" means that the cable is wound about the root of the wind turbine blade. The expression does not mean that the cable can only be wound onto the outside of the root. The cable can also be wound on the inside of the root. In other words, the inductor is supported by a diameter of the root.

In some embodiments, in combination with any wind turbine blade described above or below, wherein the mandrel is an exterior surface of the root or an interior surface of the root.

In some embodiments, in combination with any wind turbine blade described above or below, the first inductor is at least partially embedded in a material comprising the root.

In some embodiments, in combination with any wind turbine blade described above or below, the first cable is a bundled cable including a live line, a neutral line, and a protective earth line.

In some embodiments, in combination with any wind turbine blade described above or below, the discharge filter further includes: a second cable wound into a second inductor using the root as a mandrel and is intertwined with the first inductor; and a third cable wound into a third inductor using the root as a mandrel.

In some embodiments, in combination with any wind turbine blade described above or below, a pathway between the first cable and the powered system is linked via a surge protection device to a lightning protection system offering a lower impedance path to ground than the first cable.

In one embodiment, a wind turbine blade is provided, which includes: an electrical panel, receiving at an input: a first cable; a second cable; and a third cable; and a discharge filter located between a power source and the electrical panel in a root of the blade, the discharge filter comprising: a first inductor, comprising a portion of the first cable wound around the root as a mandrel; a second inductor, comprising a portion of the second cable wound around the root as a mandrel; and a third inductor, comprising a portion of the third cable wound around the root as a mandrel.

In some embodiments, in combination with any wind turbine blade described above or below, the root is a hollow cylinder and the mandrel is an interior surface of the root.

In some embodiments, in combination with any wind turbine blade described above or below, wherein the electrical panel further receives a fourth cable at the input, and the discharge filter further comprises: a fourth inductor, comprising a portion of the fourth cable wound around the root as a mandrel. In further embodiments, wherein the electrical panel further receives a fifth cable at the input, and the discharge filter further comprises: a fifth inductor, comprising a portion of the fifth cable wound around the root as a mandrel.

In some embodiments, in combination with any wind turbine blade described above or below, the first cable, the second cable, and the third cable are included in a single bundled cable wound into a bundled inductor.

In some embodiments, in combination with any wind turbine blade described above or below, the first inductor is intertwined with the second inductor.

In some embodiments, in combination with any wind turbine blade described above or below, the first inductor, the second inductor, and the third inductor are wound sequentially about the root.

A wind turbine may be provided which comprises a plurality of blades, wherein each blade of the plurality of blades is electrically connected to a power source via rotatable contacts in a nacelle from which a root of the blade extends towards a tip of the blade, each blade comprising: a first cable, electrically connected to the power source via the nacelle, and wound into a first inductor supported by a diameter of the root and connected to an input of an electrical panel; and a powered system, connected to an output of the electrical panel via an electrical lead and located tipward of the electrical panel;.

A wind turbine may be provided, which includes: a plurality of blades, wherein each blade of the plurality of blades is electrically connected to a power source via rotatable contacts in a nacelle from which a root of the blade extends towards a tip of the blade, each blade comprising: a first cable, electrically connected to the power source via the nacelle, and wound into a first inductor supported by a diameter of the root and connected to an input of an electrical panel; a second cable, electrically connected to the power source via the nacelle, and wound into a second inductor supported by the diameter of the root and connected to the input of the electrical panel; a third cable, electrically connected to protective earth via the nacelle, and wound into a third inductor supported by the diameter of the root and connected to the input of the electrical panel; a powered system, connected to an output of the electrical panel via an electrical lead and located tipward of the electrical panel; and a lighting protection system, that is electrically isolated from the first cable, the second cable, and the third cable in the blade, that is connected to ground via the nacelle, and that is selectively connected to the electrical panel, wherein when connected to the electrical panel, the lightning protection system provides a lower impedance path to ground than the first cable, the second cable, and the third cable.

To protect a wind turbine that uses blades containing powered systems from lightning strikes or other electrical discharges, an operator may physically disconnect the electrical lead from the turbine when at risk of lightning (thus de-powering the powered systems) or may include a Lightning Discharge Filter System (LDFS) and surge protection devices on the cabling that supplies power to the powered systems in the blades to shunt the lightning current away from sensitive systems and to ground. An LDFS includes one or more inductors at the power input to the blade, which may include inductors on the live (single or multi-phase), neutral, and protective earth lines. Because the majority of the damage to wind turbine components associated with lightning strikes has been observed to be due to the higher frequency components of the lightning compared to the power supplied from the turbine to the blades, the inductors of the LDFS provide a low-pass filter that blocks the current from lightning strikes, but allows power of <NUM> (Hertz) or <NUM> to continue to flow to the powered systems.

Due to the mass of the inductors included in the LDFS, the inductors are preferably included in the base or root of each blade to reduce rotational stresses on the wind turbine. Although an LDFS may use off-the-shelf discrete inductors to provide low-pass filters to block lightning and permit power flow, such inductors are bulky, difficult to mount within a blade assembly intended to rotate, and have relatively poor heat transfer properties, and thus suffer from thermal issues when conducting continuous power. The present disclosure therefore provides LDFSs using large-scale fabricated inductors that are adapted to the dimensions of the root of the blade in which the LDFS is deployed. Each large-scale inductor forms a low-pass filter, and uses the physical structure of the blade for support, thus improving the ease and security of mounting and reducing the mass of the blade (and the associated rotational stresses). Additionally, as the structure of a blade root can be in excess of <NUM> (meter) in diameter, the large-scale inductors exhibit a surface area to volume ratio greater than prior LDFS inductors, and thus exhibit superior heat transfer properties.

<FIG> illustrates a diagrammatic view of an exemplary Wind Turbine Generator (WTG) <NUM>. Although the WTG <NUM> is illustrated as a horizontal-axis wind turbine, the principles and techniques described herein may be applied to other wind turbine implementations, such as vertical-axis wind turbines. The WTG <NUM> typically comprises a tower <NUM> and a nacelle <NUM> located at the top of the tower <NUM>. A rotor <NUM> may be connected with the nacelle <NUM> through a low-speed shaft extending out of the nacelle <NUM>. As shown, the rotor <NUM> comprises three rotor blades <NUM> mounted on a common hub <NUM>, which rotate in a rotor plane, but the rotor <NUM> may comprise any suitable number of blades <NUM>, such as one, two, four, five, or more blades <NUM>. The blades <NUM> (or airfoil(s)) typically each have an aerodynamic shape with a leading edge <NUM> for facing into the wind, a trailing edge <NUM> at the opposite end of a chord for the blades <NUM>, a tip <NUM>, and a root <NUM> for attaching to the hub <NUM> in any suitable manner.

For some embodiments, the blades <NUM> may be connected to the hub <NUM> using pitch bearings <NUM>, such that each blade <NUM> may be rotated around a respective longitudinal axis to adjust the blade's pitch. The pitch angle of a blade <NUM> relative to the rotor plane may be controlled by linear actuators, hydraulic actuators, or stepper motors, for example, connected between the hub <NUM> and the blades <NUM>.

<FIG> illustrates a diagrammatic view of typical components internal to the nacelle <NUM> and tower <NUM> of the WTG <NUM>. When the wind <NUM> is incident on the blades <NUM>, the rotor <NUM> rotates and rotates a low-speed shaft <NUM>. Gears in a gearbox <NUM> mechanically convert the low rotational speed of the low-speed shaft <NUM> into a relatively high rotational speed of a high-speed shaft <NUM> suitable for generating electricity using a generator <NUM>.

A controller <NUM> may sense the rotational speed of one or both of the low-speed shaft <NUM> and the high-speed shaft <NUM>. If the controller <NUM> determines that the shaft(s) are rotating too fast, the controller <NUM> may pitch the blades <NUM> out of the wind <NUM> or by increasing the torque from the generator <NUM> which slows the rotation of the rotor <NUM> - i.e., reduces the revolutions per minute (RPM). A braking system <NUM> may prevent damage to the components of the WTG <NUM> by keeping the hub <NUM> from rotating when the hub <NUM> is already at, or very close, to standstill. The controller <NUM> may also receive inputs from an anemometer <NUM> (providing wind speed) and/or a wind vane <NUM> (providing wind direction). Based on information received, the controller <NUM> may send a control signal to one or more of the blades <NUM> to adjust the pitch <NUM> of the blades <NUM>. By adjusting the pitch <NUM> of the blades <NUM>, the rotational speed of the rotor <NUM> (and therefore, the shafts <NUM>, <NUM>) may be increased or decreased. Based on the wind direction, for example, the controller <NUM> may send a control signal to an assembly comprising a yaw motor <NUM> and a yaw drive <NUM> to rotate the nacelle <NUM> with respect to the tower <NUM>, such that the rotor <NUM> may be positioned to face more (or, in certain circumstances, less) upwind.

<FIG> illustrates the relative placement of several electrical components of a wind turbine blade <NUM>, according to embodiments of the present disclosure. The body of a wind turbine blade <NUM> is generally hollow, which reduces the weight of the blade <NUM> and allows for various components to be fully or partially included inside of the blade <NUM>. For example, a sensor may be mounted to an exterior surface of the blade <NUM> and include wires running on an interior surface of the blade or in the material of the blade <NUM>.

The blade <NUM> includes an electrical panel <NUM>, which selectively provides power to one or more powered systems 320a-n (generally, powered system <NUM>) via associated electrical leads 330a-n (generally, electrical lead <NUM>). The electrical panel <NUM> is mounted internally to the blade <NUM>, near or in the root <NUM>. The powered systems <NUM> are located at various positions in the blade <NUM> tipward from the electrical panel <NUM>, and may include de-icing systems, wind sensors, rotational sensors, flexion sensors, lights, etc., that may be mounted externally, internally, embedded in the material, and through the surface of the blade <NUM>. The electrical leads <NUM> may include live and neutral lines for carrying power to/from associated powered systems <NUM>, and may include optical communications channels or electrical communications channels for carrying data from or command signals to the various powered systems. Each of the powered systems <NUM> may be connected in parallel to the electrical panel <NUM> via an associated electrical lead <NUM>, or several powered systems <NUM> may be connected in series with one another via a shared electrical lead <NUM>.

To protect the WTG that supplies power for the various powered systems <NUM> from lightning and other electrical discharges carried rootward along the electrical leads <NUM>, the root <NUM> includes an LDFS located rootward of the electrical panel <NUM> and one or more surge protection devices <NUM> to shunt the lightning current away to ground. For example, in a system supplying <NUM>-phase power to the blade <NUM>, the LDFS includes inductors <NUM> formed from the cables supplying, respectively, a live line (e.g., a powered path or "hot" wire), a neutral line (e.g., a return path), and a protective earth line (e.g., a grounding path). In other embodiments, more or fewer cables and associated inductors <NUM> carrying different power options are provided to the blade <NUM>, such as, for example: two-phases and ground, two-phases, neutral, and ground; three phases and ground; three phases, neutral, and ground; etc. In some aspects, several examples for how the individual inductors <NUM> for each cable in a three-cable system are formed and placed relative to one another are discussed in greater detail in regard to <FIG>. Several examples for how the individual cables for four-cable systems and five-cable systems are formed and placed relative to one another are discussed in greater detail in regard to <FIG> and <FIG>, respectively.

Generally, the inductors <NUM> use the physical structure of the root <NUM> as a mandrel and as physical support. The inductors can be located on the exterior or the interior of the root, or embedded within the material of the root. The cables are wound into a desired number of coils about the root <NUM> to provide an inductance value capable of providing a low-pass filter between the electrical panel <NUM> and a power source connected via the cables through the nacelle <NUM>. The cables may be connected to the power source via various rotatable contacts in the nacelle <NUM>.

The inductance of a coil inductor, such as the inductors <NUM> described herein that are formed from the cabling to the electrical panel <NUM>, may be determined according to Formula <NUM>, where L is the inductance, µ is the permeability of the core material(s), N is the number of turns, r is the radius of the core, and ℓ is the length of the inductor. <MAT> Accordingly, using the structure of the root <NUM>, which may be greater than <NUM> in diameter, as a mandrel about which the cables are wound provides a similarly large value for r. By using a larger radius, the inductors <NUM> may be wound fewer times and thus extend for a shorter distance compared to a discrete inductor of a similar inductance but smaller radius, allowing a fabricator to place the mass of the inductor closer to the mounting point of the blade <NUM> and the hub <NUM>, thus reducing the moment of the blade <NUM>. The large radius of the inductors <NUM> wound about the root <NUM> also provides the inductors <NUM> with a greater ratio of surface area to volume compared to a discrete inductor of a smaller radius but equivalent inductance. The greater surface area to volume ratio provides the inductors <NUM> with superior heat dissipation characteristics compared to discrete inductors with a smaller radius.

In various embodiments, the value for µ is the value of free space permeability (e.g., when using an air core of the hollow space of the interior of root <NUM>), but may also include the permeability effects of the material of the root <NUM> (e.g., when the inductors <NUM> are wound around the exterior or embedded in the material of the root <NUM>) or the permeability effects of any other devices or cabling co-located in the root <NUM>. The coils may be arranged so that they form a common mode choke that presents a low impedance for the power from the hub <NUM> to the powered systems <NUM>, but a high impedance for the lightning transients from the blade <NUM> towards the hub <NUM>.

Depending on the radius of the root <NUM>, permeability of the core, and desired cutoff frequency for the low-pass filter, the fabricator can determine the associated length and number of coils to employ when designing and manufacturing the inductors <NUM> for the desired inductance. Additionally, depending on the placement of the individual inductors <NUM> relative to one another, the inductors <NUM> may exhibit mutual inductance, which the fabricator also accounts for when designing and manufacturing the inductors <NUM> for the desired cutoff frequency.

<FIG> is a block diagram of the circuitry <NUM> for supplying power to the powered systems <NUM> via an electrical panel <NUM> fed by an LDFS according to embodiments of the present disclosure. In the illustrated electrical panel <NUM>, the circuitry is configured for operation with three cables 410a-c (generally, cable <NUM>) supplying power and reference values, although in other examples, the electrical panel <NUM> may receive more cables that carry additional phases of power or reference values.

In one embodiment, the electrical panel <NUM> receives, at an input side, a live line via a first cable 410a wound into the first inductor 340a, a neutral line via a second cable 410b wound into the second inductor 340b, and a protective earth line via a third cable 410c wound into the third inductor 340c. The protective earth line supplies a ground reference to the electrical panel, while the live line and neutral line provide power and a return path to selectively activate one or more powered systems <NUM>. In other three-cable configurations, the electrical panel <NUM> and associated circuitry <NUM> receive a first phase of power via the first cable 410a, a second (different) phase of power via the second cable 410b, and protective earth via the third cable 410c. In a further embodiment, the electrical panel <NUM> and associated circuitry <NUM> receive four cables <NUM> wound into associated inductors <NUM> that provide two different phases of power, neutral, and ground references or three different phases of power and a ground reference. In another embodiment, the electrical panel <NUM> and associated circuitry <NUM> receive five cables <NUM> wound into associated inductors <NUM> that provide three different phases of power, neutral, and ground references. Although <FIG> is primarily discussed in relation to a live/neutral/ground configuration of a three-cable embodiment, the present disclosure envisions the deployment of large-scale inductors <NUM> formed from the cables <NUM> supplied to an electrical panel <NUM> in a blade <NUM> of a WTG <NUM> using various configurations of various numbers of cables.

The electrical panel <NUM> selectively provides, on an output side, an associated live line and neutral line for each powered system <NUM> as a respective primary lead <NUM> and secondary lead <NUM> of the electrical leads <NUM> that provide live/neutral electrical inputs or different phases of power as electrical inputs. For example, a first powered system 320a includes a first primary lead 440a and a first secondary lead 450a connecting the first powered system 320a to the electrical panel <NUM>, which selectively provides power to the first powered system 320a. Similarly, an nth powered system <NUM>n includes an nth primary lead <NUM>n and an nth secondary lead <NUM>n connecting the nth powered system <NUM>n to the electrical panel <NUM>, which selectively provides power to the nth powered system <NUM>n.

Additionally, the electrical panel <NUM> may receive control signals or output status signals to a control unit <NUM>, either located internally to the electrical panel <NUM> or as a separate device. The control unit <NUM> can relay data to the powered systems <NUM>, receive data from the powered systems <NUM>, and monitor and control various components of the electrical panel <NUM>. In various embodiments, the control unit <NUM> is a computing device including a processor, a memory storage device (e.g., a hard drive) that is included in each blade <NUM> for controlling systems thereof, that is included in the WTG <NUM> for controlling the systems thereof and in several blades <NUM>, or that is included in a wind farm for controlling the systems thereof and in several WTGs <NUM>.

Internally, the electrical panel <NUM> includes a primary path 313a connecting the first cable 410a to the primary leads 440a-n of the powered systems 320a-n and a secondary path 313b connecting the second cable 410b to the secondary leads 450a-n of the powered systems 320a-n. Generally, the primary path 313a and the secondary path 313b may be referred to as internal paths <NUM> (along with a tertiary path, quaternary path, etc., connected to the third, fourth, etc., cables respectively (not illustrated)). The primary path 313a includes a first selective switch 311a (generally, selective switch <NUM>) and a first circuit breaker 312a (generally, circuit breaker <NUM>). Similarly, the secondary path 313b includes a second selective switch 311b and a second circuit breaker 312b. The selective switches <NUM> are selectively controlled (e.g., via signals from the control unit <NUM>) to open or close to establish or disconnect an associated internal path to the powered systems 320a-n. The circuit breakers <NUM> are controlled by the thermal and/or electrical properties experienced on the internal paths to automatically open and disconnect an associated internal path <NUM> to the powered systems 320a-n. In various embodiments, the relative positions of the selective switches <NUM> and the circuit breakers <NUM> may be swapped from the order illustrated in <FIG> or the selective switches <NUM> and circuit breakers <NUM> on a given internal path <NUM> may be combined into one component (e.g., a selectively switched circuit breaker).

Each powered system 320a-n is connected to two or more internal paths <NUM> by respective system switches 314a-n that may be controlled to selectively provide power to individual powered systems 320a-n.

Each internal path <NUM> is connected by one or more surge protection devices <NUM> to a lightning protection system <NUM> for the blade <NUM>. A lightning protection system <NUM> provides an alternative, lower-impedance, path for lightning striking the blade <NUM> to run than the higher-impedance path offered by the cables <NUM> and the associated inductors <NUM>. The lightning protection system <NUM> is a conductive pathway that runs from the tip <NUM> of the blade <NUM> (e.g., via a solid metal contact or a conductive cap at the tip <NUM>) to the root <NUM> of the blade <NUM> (e.g., to a ferrule or conductive band that is electrically isolated from the cables <NUM>) and is connected via a lightning current transfer unit <NUM> to ground via a conductive path through the tower <NUM>.

The higher impedance presented by the inductors <NUM> offers a less attractive path to ground for the lightning than the lower impedance presented by the lightning protection system <NUM>. The surge protection devices <NUM> are selectively activated or nonlinear devices that shunt current flow from the electrical leads <NUM> to the lightning protection system <NUM> in the event of a lightning strike or other electrical discharge to the blade <NUM>. The surge protection devices <NUM> include one or more of: spark gaps, metal oxide varistors, gas discharge tubes, Transient Voltage Suppression (TVS) diodes, or other non-linear devices to shunt the current of a lightning strike or other electrical discharge away from the cables to the lightning protection system <NUM> when the voltage across the inductors <NUM> is sufficiently high.

The inductors <NUM> provide a common mode choke connection between the electrical panel <NUM> and the power source. As common mode chokes that are wound around a shared core, the inductors provide potential electrical paths with opposing impedances that cancel out to appear as a zero impedance link from the perspective of the power source, but appear as a high impedance link to the perspective of a powered system <NUM> or a lightning strike tipward of the electrical panel <NUM>.

<FIG> illustrate various cross-sectional views of an LDFS that highlight various relative positions and arrangements of the inductors <NUM> in relation to the section of the root <NUM> used as a mandrel and the portions of the cables used to define the inductors <NUM>. <FIG> illustrate the inductors <NUM> using the internal surface of the root <NUM> as a mandrel. <FIG> illustrate the inductors <NUM> using the external surface of the root as a mandrel. The portion of the root <NUM> illustrated in cross section in <FIG> is hollow and generally cylindrical in shape, although other shapes are contemplated and various supports and other components may be included in other portions of the root <NUM>. <FIG> illustrate winding patterns using three cables 410a-c to produce three corresponding inductors 340a-c. In various embodiments, each of the individual three cables 410a-c may provide electrical inputs of a phase of power, a neutral line, or a ground line to an electrical panel <NUM>, and a fabricator may select a winding pattern and designate any cable <NUM> to handle a particular electrical input according to the power requirements of the powered systems <NUM> in the blade <NUM>.

<FIG> and <FIG> illustrate arrangements of the inductors <NUM> that are intertwined in which the inductors <NUM> are free from the material of the root <NUM> and at least partially secured by the material of the root <NUM>, respectively. The first cable 410a, the second cable 410b, and the third cable 410c are wound into coils on the inner surface of the root <NUM> as a mandrel to form the respective inductors <NUM>, and are wound sequentially to each other to produce intertwined inductors <NUM>.

<FIG> and <FIG> illustrate arrangements of the inductors <NUM> that wind the third cable <NUM> separately from the first and second cables 410a, 420b in which the inductors <NUM> are free from the material of the root <NUM> and at least partially secured by the material of the root <NUM>, respectively. The first and second cables 410a,b are intertwined with one another, and the third cable 430c is wound separately. Winding the inductors <NUM> on an internal surface of the root <NUM>, as in <FIG>, results in a diameter D (and associated radii) for the inductors <NUM> based on the internal diameter of the root <NUM> and the diameters of the first, second, and third cables 410a-c.

<FIG> and <FIG> illustrate arrangements of the inductors <NUM> that employ a bundled cable <NUM> that includes the first, second, and third cables 410a-c as sub-cables defined therein. The bundled cable <NUM> is wound internally to the root <NUM> as a mandrel and imparts coils to each of the included first, second, and third cables 410a-c to form the inductors 340a-c. The interior distances between the individual cables 410within the bundled cable <NUM> define individual diameters and associated radii that determine the inductance for the inductors <NUM> (i.e., D1 for the first cable 410a, D2 for the second cable 420b, and D3 for the third cable 430c). In various embodiments, D1=D2=D3, but in other embodiments, different diameters can be defined for the various cables <NUM> by altering the placement of the cables within the bundled cable <NUM> or altering the individual sizes of the cables <NUM>.

In various embodiments, such as in <FIG>, <FIG>, and <FIG>, one or more cable clamps (not illustrated) mounted to or built into the inner surface of the root <NUM> hold the wound cables in place to define the inductors. In other embodiments, such as in <FIG>, <FIG>, and <FIG>, the body of the root <NUM> may secure a portion or all of the inductors <NUM>. For example, <FIG> (or <FIG> or <FIG>) may be an alternative point of view of the cross section presented in <FIG> (or <FIG> or <FIG>, respectively) rotated by a predefined angle of view.

<FIG> and <FIG> illustrate arrangements of the inductors <NUM> that are intertwined in which the inductors <NUM> are free from the material of the root <NUM> and at least partially secured by the material of the root <NUM>, respectively. The first cable 410a, the second cable 410b, and the third cable 410c are wound into coils on the outer surface of the root <NUM> as a mandrel to form the respective inductors <NUM>, and are wound sequentially to each other to produce intertwined inductors <NUM>.

<FIG> and <FIG> illustrate arrangements of the inductors <NUM> that wind the third cable <NUM> separately from the first and second cables 410a,b in which the inductors <NUM> are free from the material of the root <NUM> and at least partially secured by the material of the root <NUM>, respectively. The first and second cables 410a,b are intertwined with one another, and the third cable 410c is wound separately. Winding the inductors <NUM> on an outer surface of the root <NUM>, as in <FIG>, results in a diameter D (and associated radii) for the inductors <NUM> based on the external diameter of the root <NUM> and the diameters of the first, second, and third cables 410a-c.

<FIG> and <FIG> illustrate arrangements of the inductors <NUM> that employ a bundled cable <NUM> that includes the first, second, and third cables 410a-c as sub-cables defined therein. The bundled cable <NUM> is wound externally to the root <NUM> as a mandrel and imparts coils to each of the included first, second, and third cables 410a-c to form the inductors <NUM>. The interior distances between the individual cables 410a-c within the bundled cable <NUM> define individual diameters and associated radii that determine the inductance for the inductors <NUM> (i.e., D1 for the first cable 410a, D2 for the second cable 410b, and D3 for the third cable 410c). In various embodiments, D1=D2=D3, but in other embodiments, different diameters can be defined for the various cables 410a-c by altering the placement of the cables within the bundled cable <NUM> or altering the individual sizes of the cables <NUM>.

In various embodiments, such as in <FIG>, <FIG>, and <FIG>, one or more cable clamps (not illustrated) mounted to or built into the outer surface of the root <NUM> hold the wound cables in place to define the inductors <NUM>. In other embodiments, such as in <FIG>, <FIG>, and <FIG>, the body of the root <NUM> may secure a portion or all of the inductors <NUM>. For example, <FIG> (or <FIG> or <FIG>) may be an alternative point of view of the cross section presented in <FIG> (or <FIG> or <FIG>, respectively) rotated by a predefined angle of view. Although not illustrated, the externally wound inductors <NUM> may be covered by a protective cap and/or covered by a cowl or other portion of the hub <NUM> when the root <NUM> is installed to the hub <NUM>, and are electrically isolated from the lightning protection system <NUM>. The cables 410a-c of the externally defined inductors <NUM> may enter and exit the blade <NUM> via various through-holes (not illustrated) defined in the body of the root <NUM>.

A fabricator may determine whether to install the cables <NUM> internally (e.g., as in <FIG>) or externally (e.g., as in <FIG>) based on the different potential internal/external diameters for the inductors <NUM>, the structural strength of the root <NUM> (e.g., including the effect of through-holes on structural soundness), mounting hardware used between the blade root <NUM> and the hub <NUM>, the permeability of the material used for the root <NUM>, etc., to result in inductors <NUM> of a desired inductance and with desired physical properties. Accordingly, a fabricator can deploy large-scale inductors <NUM> made from the cables <NUM> supplying an electrical panel <NUM> as an LDFS with greater heat dissipation potential, a lower rotational moment, and less material than an LDFS using internal discrete inductors.

<FIG> illustrate additional cable winding patterns for an LDFS using four cables 410a-d to produce four corresponding inductors 340a-d. As will be appreciated, the cable winding patterns shown in <FIG> do not show the relative positions of the cables <NUM> of the root <NUM> used as a mandrel for the inductors <NUM>; the cable winding patterns may be used with internal windings (e.g., as in <FIG>) or external windings (e.g. as in <FIG>), and may be fully, partially, or not captured in the material of the root <NUM> in various embodiments. In various embodiments, each of the individual four cables 410a-d may provide electrical inputs of a phase of power, a neutral line, or a ground line to an electrical panel <NUM>, and a fabricator may select a winding pattern and designate any cable <NUM> to handle a particular electrical input according to the power requirements of the powered systems <NUM> in the blade <NUM>.

<FIG> illustrates that the four cables 410a-d may be co-wound about the mandrel to produce the four inductors 340a-d. <FIG> illustrates that a first cable 410a (e.g., carrying a ground electrical input) may be wound separately into a first inductor 340a about a shared mandrel from the second through fourth cables 410b-d (e.g., carrying two phases of power and neutral, or three phases of power), which are co-wound about the mandrel with one another to produce the second through fourth inductors 340b-d. <FIG> illustrates that a first and a second cable 410a,b may be co-wound about a shared mandrel to form a first common mode choke with the first and second inductors 340a,b separately from a third and a fourth cable 410c,d that are co-wound with one another about the mandrel to form a second common mode choke with the third and fourth inductors 340c,d. <FIG> illustrates that a bundled cable <NUM> may include the first through fourth cables 410a-d as sub-cables thereof, which are wound about the mandrel to produce the inductors <NUM>.

<FIG> illustrate additional cable winding patterns for an LDFS using five cables 410a-e to produce five corresponding inductors 340a-e. As will be appreciated, the cable winding patterns shown in <FIG> do not show the relative positions of the cables <NUM> of the root <NUM> used as a mandrel for the inductors <NUM>; the cable winding patterns may be used with internal windings (e.g., as in <FIG>) or external windings (e.g. as in <FIG>), and may be fully, partially, or not captured in the material of the root <NUM> in various embodiments. In various embodiments, each of the individual five cables 410a-e may provide electrical inputs of a phase of power, a neutral line, or a ground line to an electrical panel <NUM>, and a fabricator may select a winding pattern and designate any cable <NUM> to handle a particular electrical input according to the power requirements of the powered systems <NUM> in the blade <NUM>.

<FIG> illustrates that the five cables 410a-e may be co-wound about the mandrel to produce the five inductors 340a-e. <FIG> illustrates that a first cable 410a (e.g., carrying a ground electrical input) may be wound separately into a first inductor 340a about a shared mandrel from the second through fifth cables 410b-e (e.g., carrying three phases of power and neutral), which are co-wound about the mandrel with one another to produce the second through fifth inductors 340b-e. <FIG> illustrates that a first and a second cable 410a,b may be co-wound about a shared mandrel to form a first common mode choke with the first and second inductors 340a,b separately from the third through fifth cables 410c-e that are co-wound with one another about the mandrel to form a second common mode choke with the third through fifth inductors 340c-e. <FIG> illustrates that the five cables <NUM> may be wound into the associated inductors <NUM> in three separate groups, in which the first cable 410a is wound into a first inductor 340a by itself, the second and third cables 410b,c are co-wound to form a first common mode choke with the second and third inductors 340b,c, and the fourth and fifth cables 410d,e are co-wound to form a second common mode choke with the fourth and fifth inductors 340d,e. <FIG> illustrates that a bundled cable <NUM> may include the first through fifth cables 410a-e as sub-cables thereof, which are wound about the mandrel to produce the inductors <NUM>. Throughout the present disclosure, reference is made to embodiments presented. However, the scope of the present disclosure is not limited to specific described embodiments. Instead, any combination of the features and elements provided above, whether related to different embodiments or not, is contemplated to implement and practice contemplated embodiments. Furthermore, although embodiments disclosed herein may achieve advantages over other possible solutions or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the scope of the present disclosure. Thus, the aspects, features, embodiments, and advantages described herein are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s).

Claim 1:
A wind turbine blade (<NUM>), comprising:
a discharge filter, located in a root (<NUM>) of the wind turbine blade (<NUM>), including a first cable (410a) wound into a first inductor (340a) using the root (<NUM>) as a mandrel;
a powered system (<NUM>), located in a body of the wind turbine blade (<NUM>);
an electrical panel (<NUM>), located between the discharge filter and the powered system (<NUM>) in the body of the wind turbine blade (<NUM>), wherein the first cable (410a) is configured to provide power to the powered system (<NUM>) through the electrical panel (<NUM>).