Torsion-resistant and stretch-resistant flexible cable for wind power tower drum

Abstract

The invention discloses an anti-torsion and anti-tensile flexible cable for a wind power tower drum, and belongs to the field of flexible cables for wind power tower drums, the anti-torsion and anti-tensile flexible cable for the wind power tower drum comprises a cable core assembly, the cable core assembly is located in the center of the cable, an inner sheath is extruded outside the cable core assembly, and an outer sheath is sleeved outside the inner sheath. The outer sheath is made of a polymer elastomer matrix doped with conductive nano filler, the outer sheath has a piezoresistive characteristic, a plurality of spiral connecting ribs protruding towards the axis direction are integrally extruded and molded on the inner surface of the outer sheath, the spiral connecting ribs spirally extend in the axial direction, one end, far away from the outer sheath, of each spiral connecting rib abuts against the outer surface of the inner sheath, and the other end, far away from the outer sheath, of each spiral connecting rib abuts against the outer surface of the inner sheath. The problem that an existing cable sheath structure cannot give consideration to anti-torsion mechanical coupling and full-life-cycle state monitoring is solved. The problems that an existing tensile bearing structure is prone to causing mechanical damage to adjacent power wire cores; and the problem of friction heat generation between components in the existing cable and the insufficient volume compression allowance are solved.

Description

Technical Field

[0001] This invention relates to the field of flexible cables for wind turbine towers, and more specifically, to flexible cables for wind turbine towers that are resistant to torsion and tension. Background Technology

[0002] Wind power generation technology is developing towards larger capacity and taller towers. The power cables suspended inside the wind turbine towers, especially the twisted cable sections, are facing increasingly harsh operating environments. These cables are usually suspended vertically at a height of 100 meters and need to be twisted back and forth at an angle of ±720° or even greater with the wind turbine nacelle. Under long-term alternating stress, the structural stability and electrical reliability of the cables face enormous challenges. Existing cable sheath structures cannot simultaneously address both torsional mechanical coupling and full lifecycle condition monitoring. In terms of mechanical structure, existing cables typically use either tightly bonded or completely isolated sliding connections between the outer sheath and inner core. Tight connections, when the cable undergoes significant torsion, directly transfer the shear stress of the outer layer to the inner insulated core, easily leading to insulation fatigue cracking. While completely isolated connections reduce friction, under extreme torsional conditions, the outer sheath cannot effectively drive the inner layer to rotate synchronously, easily causing sheath wrinkling, accumulation, or even breakage due to uneven stress. Regarding condition monitoring, existing cables are mostly passive structures, lacking embedded sensing units. Maintenance personnel cannot obtain real-time information on the propagation of microcracks or the degree of fatigue aging in the sheath during cable operation; replacement is usually only possible after a short circuit or cable breakage, resulting in significant maintenance delays. Existing tensile load-bearing structures are prone to causing mechanical damage to adjacent power conductors. To address the self-weight tension problem caused by long-distance vertical suspension, current technologies typically fill the gaps inside the cable with aramid yarn, steel wire rope, or ordinary reinforcing cores. However, these load-bearing components usually have high elastic modulus and surface roughness. Under torsional conditions caused by frequent yaw of the wind turbine, severe relative sliding and compression will occur between the load-bearing components and the relatively soft ethylene propylene rubber insulation layer. Due to the lack of effective physical isolation measures, high-strength load-bearing components will exert continuous wear and cutting action on the power conductors. Long-term operation may lead to thinning or even breakage of the insulation layer, causing electrical short circuits. Existing cables suffer from problems such as frictional heat generation between internal components and insufficient volume compression allowance. The internal fillers of existing cables are mostly solid polypropylene mesh ropes or rubber strips, with the components primarily in sliding frictional contact. During repeated twisting, the frictional resistance between the cores and between the cores and the filler is high, accelerating not only the mechanical wear of the materials but also generating a large amount of frictional heat that is difficult to dissipate through the dense filler layer, thus accelerating the thermal aging of the insulation material. Furthermore, the solid filler structure lacks space for radial compression. When the cable is tightened, causing a reduction in the internal cross-sectional area, significant radial compressive force is generated between the internal components, further worsening the stress environment of the cores. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide a flexible cable for wind turbine towers that is resistant to torsion and tension, thereby solving the problem that the existing cable sheath structure cannot simultaneously achieve torsional mechanical coupling and full life cycle condition monitoring; solving the problem that the existing tensile load-bearing structure is prone to causing mechanical damage to adjacent power cores; and solving the problem of frictional heat generation between internal components and insufficient volume compression margin in existing cables.

[0004] To solve the above problems, the present invention adopts the following technical solution.

[0005] A torsion- and tensile-resistant flexible cable for wind turbine towers includes a core assembly located at the center of the cable. An inner sheath is extruded around the core assembly, and an outer sheath is fitted over the inner sheath. The outer sheath is made of a polymer elastomer matrix doped with conductive nanofillers and possesses piezoresistive characteristics. Multiple spiral connecting ribs protruding axially are integrally extruded onto the inner surface of the outer sheath. These spiral connecting ribs extend spirally along the axial direction, with the end of each spiral connecting rib away from the outer sheath abutting against the outer surface of the inner sheath.

[0006] At least two signal acquisition electrodes are embedded inside the outer sheath. The signal acquisition electrodes extend along the spiral trajectory and are located in the contact area between the spiral connecting rib and the outer sheath.

[0007] Furthermore, the cable core assembly includes a central skeleton with a multi-lobed cross-section. The internal material of the central skeleton is high-damping rubber. Power conductors are embedded in the recessed areas between the lobed structures of the central skeleton. The gaps between the power conductors and the inner sheath are filled with a filling system. The central skeleton isolates the power conductors to prevent direct rigid collisions between them during torsion. The high-damping material absorbs torsional impact energy through elastic shear deformation, maintaining the stability of the cable's geometric structure.

[0008] Furthermore, the filling system includes a protective tube disposed in the gap area between the power conductor and the inner sheath. A load-bearing cable is threaded through the middle of the protective tube. The outer diameter of the load-bearing cable is smaller than the inner diameter of the protective tube, and the load-bearing cable and the protective tube form a sliding fit gap. The load-bearing cable is used to bear the axial tensile load of the cable, and the protective tube is used to isolate the load-bearing cable from the adjacent power conductor. The load-bearing cable independently bears the self-weight of the cable, solving the problem of sag tension. The sliding fit between the protective tube and the load-bearing cable achieves mechanical decoupling, eliminating the sawing and abrasion of the adjacent insulated conductor by the rough load-bearing rope.

[0009] Furthermore, the filling system also includes a porous elastic filler strip that extends axially and has several longitudinally penetrating vents distributed in its cross-section. These vents provide volume compression margin and form a heat dissipation channel when the cable undergoes torsional deformation. The vents also provide volume clearance space when the cable is radially compressed, reducing the compressive stress on the power core. At the same time, the vents form an axial heat dissipation channel, which helps to reduce the internal temperature rise of the cable.

[0010] Furthermore, the gap between the cable core assembly and the inner sheath is filled with a first lubricating medium, which is a rolling composite grease. The rolling composite grease is composed of a high-viscosity thixotropic matrix and solid microspheres suspended therein. The solid microspheres are used to convert the sliding friction between the components into rolling friction. The solid microspheres create a fluid bearing effect between the components, converting the high-resistance sliding friction into the low-resistance rolling friction, reducing internal mechanical wear and frictional heat generation, and extending service life.

[0011] Furthermore, a second lubricating medium is provided between the outer surface of the inner sheath and the inner surface of the outer sheath. The second lubricating medium is a dry solid lubricating coating. The dry solid lubricating coating does not contain solid particles with a diameter of more than one millimeter, so as to ensure that the spiral connecting rib has compressible collapsing space under torsional conditions. The dry solid lubricating coating reduces the interlayer friction coefficient without occupying physical space, preventing solid particles from hindering the elastic collapsing action of the spiral connecting rib, and ensuring the effective operation of the double-layer sheath clutch mechanism.

[0012] Furthermore, the spiral helix angle of the spiral connecting rib is 15°-30°, and the spiral connecting rib undergoes elastic tilting deformation under torsion of less than 0° to absorb torsional stress, and is compressed into a solid state under torsion of more than 0° to transmit torque through mechanical interlocking, thus realizing nonlinear mechanical coupling: when the torsion is at a small angle, elastic deformation is used to buffer stress and protect the inner sheath; when the torsion is at a large angle, mechanical interlocking is used to force transmission to prevent the inner sheath from wrinkling and delaminating.

[0013] Furthermore, the signal acquisition electrode is a metal wire without an insulation layer, and the signal acquisition electrode is wrapped at the structural fusion point where the spiral connecting rib and the outer sheath are connected. The signal acquisition electrode is centrally symmetrically distributed on the cross-section of the cable. The root covering structure uses a thick base to prevent fatigue fracture of the signal acquisition electrode, and at the same time, it is positioned in the shear stress concentration area, which significantly improves the monitoring sensitivity of micro-deformation and crack propagation of the inner and outer sheaths.

[0014] Furthermore, the matrix material of the outer sheath is thermoplastic polyurethane, and the conductive nanofiller is carbon nanotube. The mass fraction of the conductive nanofiller is 1% to 5%, which makes the sheath material within the conductive percolation threshold range. The specific filler ratio makes the inner and outer sheaths within the conductive percolation threshold range, giving the material extremely high piezoresistive response characteristics, which can convert minute mechanical deformations into measurable resistance fluctuations in real time.

[0015] Furthermore, the cable is externally connected to an excitation source module, a signal processing unit, an opto-isolation module, and a monitoring system. The excitation source module is connected to the signal acquisition electrodes and is used to inject a constant micro-current into the conductive network inside the outer sheath. The signal processing unit is used to acquire the voltage signal between the two signal acquisition electrodes and calculate the real-time volume resistivity values ​​of the inner and outer sheaths. The opto-isolation module is connected in series between the signal processing unit and the external control terminal to achieve high and low voltage electrical isolation. The monitoring system is configured to output a cable fatigue early warning signal when the rate of change of the real-time volume resistivity value exceeds a preset threshold or irreversible drift occurs. This achieves proactive health monitoring throughout the cable's entire life cycle. Opto-isolation ensures the electrical safety of the low-voltage side control system and effectively realizes early fault warning.

[0016] Compared with the prior art, the advantages of this invention are: By integrally extruding spiral connecting ribs on the inner surface of the outer sheath with piezoresistive characteristics, the dual functions of nonlinear mechanical coupling and active health monitoring are achieved. The spiral connecting ribs elastically tilt under small-angle torsion to buffer shear stress, and are compressed into a solid state under large-angle torsion to force the inner sheath to rotate through mechanical interlocking, effectively solving the problems of sheath wrinkling and delamination. At the same time, a conductive network is constructed by using signal acquisition electrodes embedded in the root area of ​​the spiral connecting ribs. With the excitation source module and monitoring system, the microscopic deformation of the outer sheath can be converted into changes in volume resistivity in real time, thereby outputting fatigue warning signals before a fault occurs, overcoming the deficiency of existing cables in lacking condition sensing capabilities. By setting a tubular sliding bearing unit containing a protective tube and a bearing cable in the gap area between the power conductor core and the inner sheath, the problem of mechanical damage to adjacent conductor cores caused by the suspended load-bearing structure is completely solved. The bearing cable passes through the inside of the protective tube and the two form a sliding fit gap, which allows the bearing cable to independently bear the axial tensile load of the cable and freely release torsional stress. The protective tube, as a physical isolation barrier, effectively blocks the direct contact and friction between the rough surface of the high-modulus bearing cable and the relatively soft insulation layer of the power conductor core, fundamentally eliminating the hidden danger of the "sawing effect" caused by the load-bearing component to the power conductor core under long-term torsional conditions, and significantly improving the electrical safety and service life of the cable. By introducing a microsphere rolling lubrication system and a porous heat dissipation structure, the technical problems of severe frictional heat generation between internal cable components and insufficient volume compression margin are effectively solved. The rolling composite grease containing solid microspheres fills the tiny gaps in the cable core components. It utilizes the "fluid bearing" effect to transform the high-resistance sliding friction between components into low-resistance rolling friction, significantly reducing mechanical wear and frictional heat generation. At the same time, in conjunction with a porous elastic filler strip with longitudinally penetrating air holes distributed in the cross-section, the air holes provide crucial volume clearance space when the cable is radially compressed due to torsion, reducing the compressive stress on the power conductor core and constructing an axial heat dissipation channel, thereby effectively delaying the thermal aging process of the insulation material. Attached Figure Description

[0017] Figure 1 This is a partial cross-sectional perspective view of the present invention; Figure 2 This is a front view schematic diagram of the present invention.

[0018] Explanation of the labels in the diagram: 1. Central frame; 2. Inner sheath; 3. Spiral connecting rib; 4. Outer sheath; 5. Power conductor core; 6. Protective tube; 7. Bearing cable; 8. Elastic filler strip. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within a compatible component. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] This invention provides an embodiment 1 Please see Figure 1-2 A flexible cable for wind turbine towers with torsion and tensile strength resistance includes a core assembly located at the center of the cable. An inner sheath 2 is extruded around the core assembly, and an outer sheath 4 is fitted around the inner sheath 2. The outer sheath 4 is made of a polymer elastomer matrix doped with conductive nanofillers and has piezoresistive characteristics. Multiple spiral connecting ribs 3 protruding towards the axis are integrally extruded on the inner surface of the outer sheath 4. The spiral connecting ribs 3 extend spirally along the axial direction. The end of the spiral connecting rib 3 away from the outer sheath 4 abuts against the outer surface of the inner sheath 2. At least two signal acquisition electrodes are embedded inside the outer sheath 4. The signal acquisition electrodes extend along the spiral trajectory and are located in the contact area between the spiral connecting ribs 3 and the outer sheath 4. The cable core assembly includes a central skeleton 1, which has a multi-lobed cross-section. The internal material of the central skeleton 1 is high-damping rubber. The power conductors 5 are embedded in the recessed areas between the lobed structures of the central skeleton 1. The gap between the power conductors 5 and the inner sheath 2 is filled with a filling system. The central skeleton 1 isolates the power conductors 5 to prevent direct rigid collisions between the power conductors 5 during torsion. The high-damping material absorbs torsional impact energy through elastic shear deformation, maintaining the stability of the cable's geometric structure. The filling system includes a sheath 6 disposed in the gap area between the power conductor 5 and the inner sheath 2. A load-bearing cable 7 is threaded through the middle of the sheath 6. The outer diameter of the load-bearing cable 7 is smaller than the inner diameter of the sheath 6, and the load-bearing cable 7 and the sheath 6 form a sliding fit gap. The load-bearing cable 7 is used to bear the axial tensile load of the cable, and the sheath is used to isolate the load-bearing cable 7 from the adjacent power conductor 5. The load-bearing cable 7 independently bears the self-weight of the cable, solving the problem of sag tension. The sliding fit between the sheath 6 and the load-bearing cable 7 achieves mechanical decoupling and eliminates the sawing and wear of the rough load-bearing rope on the adjacent insulated conductor. The filling system also includes a porous elastic filler strip 8, which extends axially and has several longitudinally penetrating vents distributed in its cross-section. These vents provide volume compression margin and form a heat dissipation channel when the cable undergoes torsional deformation. The penetrating vents provide volume clearance space when the cable is radially compressed, reducing the compressive stress on the power core 5. At the same time, the vents form an axial heat dissipation channel, which helps to reduce the internal temperature rise of the cable. The gap between the cable core assembly and the inner sheath 2 is filled with a first lubricating medium, which is a rolling composite grease. The rolling composite grease is a mixture of a high-viscosity thixotropic matrix and solid microspheres suspended therein. The solid microspheres are used to convert the sliding friction between the components into rolling friction. The solid microspheres create a fluid bearing effect between the components, converting the high-resistance sliding friction into the low-resistance rolling friction, reducing internal mechanical wear and frictional heat generation, and extending service life. A second lubricating medium is provided between the outer surface of the inner sheath 2 and the inner surface of the outer sheath 4. The second lubricating medium is a dry solid lubricating coating. The dry solid lubricating coating does not contain solid particles with a diameter of more than one millimeter, so as to ensure that the spiral connecting rib 3 has a compressible collapsing space under torsional conditions. The dry solid lubricating coating reduces the interlayer friction coefficient without occupying physical space, preventing solid particles from hindering the elastic collapsing action of the spiral connecting rib 3, and ensuring the effective operation of the double-layer sheath clutch mechanism. The spiral helix angle of the spiral connecting rib 3 is 15°-30°. When the spiral connecting rib 3 is twisted at less than 20°, it undergoes elastic tilting deformation to absorb torsional stress. When the spiral helix angle is twisted at more than 20°, it is compressed into a solid state to transmit torque through mechanical interlocking, thus realizing nonlinear mechanical coupling: when the torsion angle is small, elastic deformation is used to buffer stress and protect the inner sheath 2; when the torsion angle is large, mechanical interlocking is used to force transmission to prevent the inner sheath 2 from wrinkling and delaminating. The signal acquisition electrode is a metal wire without insulation layer, and the signal acquisition electrode 6 is wrapped at the structural fusion point where the spiral connecting rib 3 and the outer sheath 4 are connected. The signal acquisition electrodes are centrally symmetrically distributed on the cross-section of the cable. The root covering structure uses a thick base to prevent fatigue fracture of the signal acquisition electrode, and at the same time, it is positioned in the shear stress concentration area, which significantly improves the monitoring sensitivity of the micro deformation and crack propagation of the inner sheath 2 and the outer sheath 4. The base material of the outer sheath 4 is thermoplastic polyurethane, and the conductive nanofiller is carbon nanotube. The mass fraction of the conductive nanofiller is 1% to 5%, which makes the sheath material within the conductive percolation threshold range. The specific filler ratio makes the inner sheath 2 and the outer sheath 4 within the conductive percolation threshold range, giving the material extremely high piezoresistive response characteristics, which can convert small mechanical deformations into measurable resistance fluctuations in real time. The cable is externally connected to an excitation source module, a signal processing unit, an opto-isolation module, and a monitoring system. The excitation source module is connected to the signal acquisition electrode and is used to inject a constant micro-current into the conductive network inside the outer sheath 4. The signal processing unit is used to acquire the voltage signal between the two signal acquisition electrodes and calculate the real-time volume resistance values ​​of the inner sheath 2 and the outer sheath 4. The opto-isolation module is connected in series between the signal processing unit and the external control terminal to achieve high and low voltage electrical isolation. The monitoring system is configured to output a cable fatigue early warning signal when the rate of change of the real-time volume resistance value exceeds a preset threshold or irreversible drift occurs, realizing active health monitoring of the cable throughout its entire life cycle. Opto-isolation ensures the electrical safety of the low-voltage side control system and effectively realizes early fault warning. This invention provides an embodiment 2 The cable is installed at a designated location on the wind turbine tower. When the wind turbine tower rotates the cable during daily operation, the support cable 7 provides support for the cable. At the same time, the protective tube 6 isolates the support cable 7 from the power conductor 5, preventing the support cable 7 from cutting and abrading the power conductor 5. When the cable rotates at a small angle, the spiral connecting rib 3 undergoes elastic tilting deformation, preventing the inner sheath 2 from rotating and reducing the number of rotations of the inner sheath 2. When the cable rotates at a large angle, the spiral connecting rib 3 is compressed into a solid state, causing the inner sheath 2 and the outer sheath 4 to rotate together, preventing delamination between the inner sheath 2 and the outer sheath 4. When the inner sheath 2 rotates, the elastic filling strip 8 squeezes the internal through-holes, thereby reducing the compressive stress on the power conductor 5. At the same time, the first lubricating medium further reduces the friction and compression of the outer insulation layer of the power conductor 5 inside the inner sheath 2, effectively increasing the cable's resistance to torsion and tension. In summary, this invention achieves the dual functions of nonlinear mechanical coupling and active health monitoring by integrally extruding a spiral connecting rib 3 on the inner surface of the outer sheath 4, which has piezoresistive characteristics. The spiral connecting rib 3 elastically tilts under small-angle torsion to buffer shear stress, and is compressed into a solid state under large-angle torsion to force the inner sheath 2 to rotate through mechanical interlocking, effectively solving the problems of sheath wrinkling and delamination. At the same time, a conductive network is constructed by using signal acquisition electrodes embedded in the root area of ​​the spiral connecting rib 3. Combined with the excitation source module and monitoring system, the microscopic deformation of the outer sheath 4 can be converted into changes in volume resistivity in real time, thereby outputting fatigue warning signals before a fault occurs, overcoming the deficiency of existing cables lacking condition sensing capabilities. By setting a tubular sliding bearing unit containing a protective tube 6 and a bearing cable 7 in the gap area between the power conductor core 5 and the inner sheath 2, the problem of mechanical damage to adjacent conductor cores caused by the suspended load-bearing structure is completely solved. The bearing cable 7 passes through the inside of the protective tube 6 and the two form a sliding fit gap, which allows the bearing cable 7 to independently bear the axial tensile load of the cable and freely release torsional stress. The protective tube 6, as a physical isolation barrier, effectively blocks the direct contact and friction between the rough surface of the high modulus bearing cable 7 and the relatively soft insulation layer of the power conductor core 5, fundamentally eliminating the hidden danger of the "sawing effect" caused by the load-bearing component to the power conductor core under long-term torsional conditions, and significantly improving the electrical safety and service life of the cable. By introducing a microsphere rolling lubrication system and a porous heat dissipation structure, the technical problems of severe frictional heat generation between internal cable components and insufficient volume compression margin are effectively solved. The rolling composite grease filled in the tiny gaps of the cable core components contains solid microspheres, which utilize the "fluid bearing" effect to transform the high-resistance sliding friction between components into low-resistance rolling friction, significantly reducing mechanical wear and frictional heat generation. At the same time, in conjunction with the porous elastic filler strip 8 with longitudinally penetrating air holes distributed in the cross-section, the air holes provide crucial volume clearance space when the cable is radially compressed due to torsion, reducing the compressive stress on the power conductor core 5 and constructing an axial heat dissipation channel, thereby effectively delaying the thermal aging process of the insulation material.

[0023] The above description is merely a preferred embodiment of the present invention; however, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concepts, should be covered within the scope of protection of the present invention.

Claims

1. A flexible cable for wind turbine towers that is resistant to torsion and tension, characterized in that: The cable core assembly is located at the center of the cable. The cable core assembly is extruded with an inner sheath (2). An outer sheath (4) is fitted on the outside of the inner sheath (2). The outer sheath (4) is made of a polymer elastomer matrix doped with conductive nanofillers. The outer sheath (4) has piezoresistive characteristics. The inner surface of the outer sheath (4) is integrally extruded with a plurality of spiral connecting ribs (3) protruding in the axial direction. The spiral connecting ribs (3) extend in a spiral shape along the axial direction. The end of the spiral connecting rib (3) away from the outer sheath (4) abuts against the outer surface of the inner sheath (2).

2. The torsion- and tensile-resistant flexible cable for wind turbine towers according to claim 1, characterized in that: The cable core assembly includes a central skeleton (1), the central skeleton (1) has a multi-lobed cross-section, the internal material of the central skeleton (1) is high-damping rubber, the recessed areas between the lobed structures of the central skeleton (1) are inlaid with power wire cores (5), and the gap area between the power wire cores (5) and the inner sheath (2) is filled with a filling system.

3. The torsion- and tensile-resistant flexible cable for wind turbine towers according to claim 2, characterized in that: The filling system includes a sheath (6) disposed in the gap area between the power conductor (5) and the inner sheath (2). A load-bearing cable (7) is inserted through the middle of the sheath (6). The outer diameter of the load-bearing cable (7) is smaller than the inner diameter of the sheath (6), and the load-bearing cable (7) and the sheath (6) form a sliding fit gap. The load-bearing cable (7) is used to bear the axial tensile load of the cable, and the sheath is used to isolate the load-bearing cable (7) from the adjacent power conductor (5).

4. The torsion- and tensile-resistant flexible cable for wind turbine towers according to claim 3, characterized in that: The filling system also includes a porous elastic filler strip (8), which extends axially and has several longitudinally penetrating air holes distributed in its cross-section, which are used to provide volume compression margin and form a heat dissipation channel when the cable undergoes torsional deformation.

5. The torsion- and tensile-resistant flexible cable for wind turbine towers according to any one of claims 2-4, characterized in that: The gap between the cable core assembly and the inner sheath (2) is filled with a first lubricating medium, which is a rolling composite grease. The rolling composite grease is a mixture of a high-viscosity thixotropic matrix and solid microspheres suspended therein. The solid microspheres are used to convert the sliding friction between the components into rolling friction.

6. The torsion- and tensile-resistant flexible cable for wind turbine towers according to claim 1, characterized in that: A second lubricating medium is provided between the outer surface of the inner sheath (2) and the inner surface of the outer sheath (4). The second lubricating medium is a dry solid lubricating coating. The dry solid lubricating coating does not contain solid particles with a diameter of more than one millimeter, so as to ensure that the spiral connecting rib (3) has compressible collapsible space under torsion conditions.

7. The torsion- and tensile-resistant flexible cable for wind turbine towers according to claim 1, characterized in that: At least two signal acquisition electrodes are embedded inside the outer sheath (4). The signal acquisition electrodes extend along the spiral trajectory and are located in the contact area between the spiral connecting rib (3) and the outer sheath (4). The spiral helix angle of the spiral connecting rib (3) is 15°-30°. The spiral connecting rib (3) undergoes elastic tilting deformation under a torsion of less than 20° to absorb torsional stress, and is compressed to a solid state under a torsion of more than 20° to transmit torque through mechanical interlocking.

8. The torsion- and tensile-resistant flexible cable for wind turbine towers according to claim 7, characterized in that: The signal acquisition electrode is a metal wire without insulation layer, and the signal acquisition electrode (6) is covered at the structural fusion point where the spiral connecting rib (3) and the outer sheath (4) are connected, and the signal acquisition electrode is centrally symmetrically distributed on the cross-section of the cable.

9. The torsion- and tensile-resistant flexible cable for wind turbine towers according to claim 1, characterized in that: The base material of the outer sheath (4) is thermoplastic polyurethane, the conductive nanofiller is carbon nanotube, and the mass fraction of the conductive nanofiller is 1% to 5%, so that the sheath material is in the conductive permeation threshold range.

10. The torsion- and tensile-resistant flexible cable for wind turbine towers according to claim 7, characterized in that: The cable is externally connected to an excitation source module, a signal processing unit, an opto-isolation module, and a monitoring system. The excitation source module is connected to the signal acquisition electrode and is used to inject a constant micro-current into the conductive network inside the outer sheath (4). The signal processing unit is used to acquire the voltage signal between the two signal acquisition electrodes and calculate the real-time volume resistance values ​​of the inner sheath (2) and the outer sheath (4). The opto-isolation module is connected in series between the signal processing unit and the external control terminal to achieve high and low voltage electrical isolation. The monitoring system is configured to output a cable fatigue warning signal when the rate of change of the real-time volume resistance value exceeds a preset threshold or irreversible drift occurs.

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