Low voltage insulated power cable

Abstract

The application discloses a low-voltage insulated power cable, which comprises a conductor, each group of the conductor is twisted by a plurality of metal wires, an outer side of each group of the conductor is covered by a shielding layer, an outer side of the shielding layer is covered by an insulation layer, and an inner surface of the insulation layer is provided with a plurality of grooves in an axial direction. By arranging the grooves in the inner surface of the insulation layer, micro heat bars are embedded in the grooves, a sintered copper powder capillary core layer is arranged on the inner wall of the micro heat bar, and the sintered copper powder capillary core layer is attached to the outer wall of the shielding layer. The micro heat bar utilizes the evaporation and condensation phase change of a working medium and capillary force to realize efficient heat transfer, and the equivalent heat conductivity coefficient is much higher than the heat conductivity coefficient of the insulation material itself. The structure establishes an efficient radial heat transfer channel in the insulation layer, so that the heat generated by the conductor can be transmitted to the outside of the insulation layer through the shielding layer and the micro heat bar with extremely low thermal resistance, and the limitation of the low heat conductivity coefficient of the insulation layer on the heat dissipation capacity of the cable is fundamentally broken.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and more specifically to a low-voltage insulated power cable. Background Technology

[0002] Low-voltage power cables are the most widely used type of cable in power transmission and distribution systems, and are extensively used in building power distribution, industrial power supply, municipal engineering, and residential power consumption. When transmitting electrical energy, the conductor of a low-voltage power cable generates Joule heat due to resistance. This heat must be conducted to the external environment through the insulation and sheath layers. When heat dissipation is insufficient, the conductor temperature rises, accelerating the thermal aging of the insulation material, and in severe cases, leading to insulation breakdown and shortening the cable's service life. Therefore, heat dissipation capacity is one of the key factors determining the cable's current carrying capacity and service life.

[0003] The heat dissipation of existing low-voltage power cables relies entirely on the thermal conduction of the insulation and sheath materials themselves. Currently, low-voltage power cables commonly use cross-linked polyethylene (XLPE) as the insulation material. XLPE has a low thermal conductivity, as does the polyvinyl chloride (PVC) sheath, making them poor conductors of heat. Heat transfer from the conductor surface to the cable's outer surface requires a long conduction path and significant thermal resistance, resulting in a substantial temperature difference between the conductor and the external environment. This problem is particularly pronounced under conditions of dense installation, high load operation, or high-temperature environments, severely limiting the cable's current-carrying capacity.

[0004] To improve the heat dissipation performance of cables, several solutions have been proposed in the existing technology: The first approach involves filling the space between the conductor and the insulation layer with thermally conductive powder to improve thermal conductivity at the conductor-insulator interface. However, this approach only improves the interfacial thermal resistance and does not change the low thermal conductivity of the insulation layer itself, resulting in limited heat dissipation.

[0005] The second approach involves placing thermally conductive filler strips between the insulated cores to increase longitudinal heat transfer channels. However, longitudinal heat transfer merely redistributes heat along the cable direction and does not fundamentally reduce radial thermal resistance, while also increasing the cable's outer diameter and weight.

[0006] Therefore, it is necessary to invent a low-voltage insulated power cable to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a low-voltage insulated power cable to overcome the aforementioned shortcomings in the technology.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a low-voltage insulated power cable, comprising a conductor, each group of the conductors being formed by stranding multiple metal wires, each group of the conductors being covered with a shielding layer on the outside, the shielding layer being covered with an insulating layer on the outside, the inner surface of the insulating layer being provided with a plurality of grooves along the axial direction, each groove being evenly distributed circumferentially along the inner surface of the insulating layer, each groove being embedded with a micro-heating strip, and each micro-heating strip being extended along the cable axial direction; Each of the micro-heating strips is a metal strip, and there is no gap between the outer wall of each micro-heating strip and the inner wall of the groove. The inner wall of each micro-heating strip is provided with a sintered copper powder capillary core layer, which is attached to the outer wall of the shielding layer. A heat collection and heat dissipation sleeve is provided on the outside of the insulating layer, and the outer surface of the heat collection and heat dissipation sleeve is provided with multiple protrusions along the axial direction. Each of the protrusions is evenly distributed circumferentially along the outer surface of the heat collection and heat dissipation sleeve and extends continuously in the axial direction. A cavity is formed between adjacent protrusions. The cavity is axially connected to the heat collection and heat dissipation sleeve. An outer protective sleeve covers the outside of the heat collection and heat dissipation sleeve and each protrusion.

[0009] As a preferred embodiment of the present invention, the conductor is formed by twisting multiple metal wires into groups to form multiple fan-shaped cross sections, and the shielding layer is a semi-conductive shield, which tightly covers the outer surface of the conductor.

[0010] As a preferred embodiment of the present invention, the insulating layer is a thick-walled circular tube structure, the inner surface of the insulating layer is closely attached to the outer surface of the shielding layer, the cross-section of each groove is rectangular or trapezoidal, and the depth and width of each groove are adapted to the cross-sectional dimensions of the micro-heating strip.

[0011] As a preferred embodiment of the present invention, each of the micro-heating strips is uniformly distributed along the outer circumference of the insulating layer, the axis of each of the micro-heating strips extends radially along the insulating layer, the inner end of each of the micro-heating strips is provided with an outwardly protruding conical head, the conical head is embedded inside the shielding layer, and the outer end of each of the micro-heating strips is provided with annular fins extending radially outward.

[0012] As a preferred embodiment of the present invention, the sintered copper powder capillary core layer is formed by copper powder through a powder metallurgy sintering process, and the sintered copper powder capillary core layer has a uniformly distributed porous capillary channel structure, which is formed by the gaps between copper powder particles.

[0013] As a preferred embodiment of the present invention, the heat collection and heat dissipation sleeve completely wraps each micro-heat strip and the insulating layer, and each of the protrusions is distributed at equal intervals along the outer surface of the heat collection and heat dissipation sleeve, and the cross-section of each of the protrusions is arc-shaped.

[0014] As a preferred embodiment of the present invention, the cavity is formed by adjacent protrusions and the outer surface of the heat collection and heat dissipation sleeve, the cross section of the cavity is an inwardly concave arc shape, and the outer protective sleeve tightly covers the outer side of the heat collection and heat dissipation sleeve and each protrusion.

[0015] As a preferred embodiment of the present invention, the number of grooves is the same as the number of micro-heating strips, each groove is provided in a one-to-one correspondence with each micro-heating strip, and the outer surface of each micro-heating strip is flush with the outer surface of the protrusion of the insulating layer.

[0016] As a preferred embodiment of the present invention, the conductor is a plurality of conductors, each conductor is twisted together to form a cable core, a support frame is provided at the center position between adjacent conductors, and the support frame extends along the cable axis. At the same time, a central ventilation hole extending along the axis is provided at the center of the support frame.

[0017] The technical effects and advantages provided by the present invention in the above technical solution are as follows: By creating grooves on the inner surface of the insulation layer, embedding micro-heating strips within these grooves, and constructing a sintered copper powder capillary core layer on the inner wall of the micro-heating strips, which are then bonded to the outer wall of the shielding layer, efficient heat transfer is achieved through the evaporation-condensation phase change of the working fluid and capillary force. The equivalent thermal conductivity of these micro-heating strips is significantly higher than that of the insulation material itself. This structure establishes a highly efficient radial heat transfer channel within the insulation layer, allowing heat generated by the conductor to be transferred to the outside of the insulation layer with extremely low thermal resistance via the shielding layer and the micro-heating strips. This fundamentally overcomes the limitation imposed by the low thermal conductivity of the insulation layer on the cable's heat dissipation capacity.

[0018] Multiple micro-heating strips are evenly distributed circumferentially along the inner surface of the insulation layer, each working independently to form a uniform radial heat dissipation network. The heat collection and heat dissipation sleeve collects the heat from each micro-heating strip and redistributes it circumferentially, further eliminating temperature differences and preventing the formation of local hot spots. The micro-heating strips are embedded in grooves on the inner surface of the insulation layer, without occupying external space. The covering of the heat collection and heat dissipation sleeve and the outer protective sleeve does not change the overall outer diameter of the cable, which is conducive to dense laying. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0020] Figure 1 This is a perspective view of the overall structure of the present invention; Figure 2 This is an exploded view of the overall structure of the present invention; Figure 3 This is a perspective view of the insulating layer of the present invention; Figure 4 This is a perspective view of the heat collection and dissipation pipe of the present invention; Figure 5 This is a cross-sectional view of the overall structure of the present invention; Figure 6 This is a cross-sectional view of the overall structure of the present invention.

[0021] Explanation of reference numerals in the attached figures: 1. Conductor; 2. Shielding layer; 3. Insulating layer; 31. Groove; 4. Micro-heating strip; 41. Sintered copper powder capillary core layer; 5. Outer protective sleeve; 6. Heat collection and dissipation sleeve; 61. Protrusion; 7. Cavity. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0023] This invention provides, for example Figure 1-6 The low-voltage insulated power cable shown includes a conductor 1, each group of conductors 1 is made of multiple metal wires twisted together, each group of conductors 1 is covered with a shielding layer 2 on the outside, the shielding layer 2 is covered with an insulation layer 3 on the outside, the inner surface of the insulation layer 3 is provided with a plurality of grooves 31 along the axial direction, each groove 31 is evenly distributed circumferentially along the inner surface of the insulation layer 3, each groove 31 is embedded with a micro-heating strip 4, and each micro-heating strip 4 extends along the cable axial direction. Each micro-heating strip 4 is a metal strip. There is no gap between the outer wall of each micro-heating strip 4 and the inner wall of the groove 31. The inner wall of each micro-heating strip 4 is provided with a sintered copper powder capillary core layer 41. The sintered copper powder capillary core layer 41 is attached to the outer wall of the shielding layer 2. The outside of the insulating layer 3 is covered with a heat collection and heat dissipation sleeve 6. The outer surface of the heat collection and heat dissipation sleeve 6 is provided with multiple protrusions 61 along the axial direction. Each protrusion 61 is evenly distributed circumferentially along the outer surface of the heat collection and heat dissipation sleeve 6 and extends continuously in the axial direction. A cavity 7 is formed between adjacent protrusions 61. The cavity 7 is axially connected along the heat collection and heat dissipation sleeve 6. An outer protective sleeve 5 covers the outside of the heat collection and heat dissipation sleeve 6 and each protrusion 61.

[0024] In this embodiment, when the cable is energized, the current flowing through conductor 1 generates Joule heat, which is initially transferred from the surface of conductor 1 towards the outer diameter. Since there is no gap between the shielding layer 2 and the outer surface of conductor 1, heat can be conducted from conductor 1 to the shielding layer 2 with extremely low interfacial thermal resistance. The shielding layer 2, as the first-stage transition layer for heat conduction, gathers and homogenizes the unevenly distributed heat on the surface of conductor 1, making the heat flux density transferred to the insulation layer 3 more uniform.

[0025] The inner surface of the insulating layer 3 has a groove 31. The micro-heating strip 4 embedded in the groove 31 achieves thermal contact with the outer wall of the shielding layer 2 through a sintered copper powder capillary core layer 41. When the temperature of the outer wall of the shielding layer 2 exceeds the evaporation temperature of the working fluid inside the micro-heating strip 4, the working fluid absorbs heat at the inner end of the micro-heating strip 4 and undergoes a phase change, changing from a liquid state to a vapor state. Driven by the pressure gradient inside the micro-heating strip 4, the vapor working fluid migrates to the cooler outer end. Upon encountering the cooler wall surface at the outer end, it releases latent heat and condenses from a vapor state to a liquid state. The condensed liquid working fluid, under the capillary force generated by the sintered copper powder capillary core layer 41, flows back to the evaporation region at the inner end along the capillary channel, completing a complete phase change cycle. This phase change cycle continues, making the micro-heating strip 4 a highly efficient heat transfer bridge connecting the inner and outer surfaces of the insulating layer 3.

[0026] Furthermore, in the above technical solution, conductor 1 is formed by twisting multiple metal wires together to form multiple fan-shaped cross sections, and shielding layer 2 is a semi-conductive shield, which tightly covers the outer surface of conductor 1.

[0027] In this embodiment, conductor 1 is composed of multiple metal wires grouped and twisted together, with each group forming a conductor segment with a fan-shaped cross-section. The arc-shaped outer surface of each fan-shaped conductor segment faces outward, and the conductor segments support each other radially, forming a self-locking, tightly packed structure. This arrangement ensures that when conductor 1 is subjected to external radial pressure, there will be no relative slippage between the conductor segments, the conductor cross-sectional shape remains stable, and it will not deform due to external mechanical forces.

[0028] Because the outer surface of each sector-shaped conductor segment is an arc-shaped curved surface, the outer surface of conductor 1 after the conductor segments are combined presents an approximately circular outline. This approximately circular outer surface provides a good geometric basis for the uniform coverage of shielding layer 2. Shielding layer 2 can form a continuous layered structure with uniform thickness along the outer surface of conductor 1, avoiding the problem of uneven shielding layer thickness or local thinness caused by irregular conductor surface. Shielding layer 2 uses a semi-conductive material with a resistivity in the semi-conductive range between conductor and insulator. It can eliminate electric field spikes on the conductor surface through weak conductivity, uniformly distribute the electric field, and avoid forming a closed conductive loop that would generate circulating current loss.

[0029] Furthermore, in the above technical solution, the insulating layer 3 is a thick-walled cylindrical structure, the inner surface of the insulating layer 3 is closely attached to the outer surface of the shielding layer 2, the cross-section of each groove 31 is rectangular or trapezoidal, and the depth and width of each groove 31 are adapted to the cross-sectional dimensions of the micro-heating strip 4.

[0030] In this embodiment, the insulating layer 3 is a thick-walled cylindrical structure. The thick-walled design gives the insulating layer 3 a large radial thickness, providing ample space for the groove 31, while ensuring that the insulating layer 3 still has sufficient remaining wall thickness to meet electrical insulation requirements after the groove 31 is created. The inner surface of the insulating layer 3 is tightly fitted to the outer surface of the shielding layer 2, with no gaps between them, avoiding the risk of partial discharge caused by air gaps.

[0031] The bottom surface of each groove 31 is flat, and the two sides are either parallel or inclined at a certain angle. When the two sides are parallel, the groove 31 has a rectangular cross-section. After the micro-heating strip 4 is embedded, it forms surface contact with both the side and bottom surfaces. Heat is conducted from the insulation layer 3 through the bottom surface and both sides of the groove to the micro-heating strip 4 simultaneously, resulting in a large heat transfer area and uniform heat transfer. When the two sides are inclined at a certain angle, the groove 31 has a trapezoidal cross-section, forming a wedge-shaped space that is wider at the top and narrower at the bottom. After the micro-heating strip 4 is embedded, it is subjected to radial clamping force from both sides. This clamping force increases with the increase of the cable operating temperature because the thermal expansion coefficient of the insulation layer 3 material is higher than that of the metal micro-heating strip 4. When the temperature rises, the outward expansion deformation of the insulation layer 3 is greater than that of the micro-heating strip 4, which further enhances the clamping force of the groove 31 on the micro-heating strip 4 and makes the thermal contact tighter. The dimensions of each groove 31 are adapted to the cross-sectional dimensions of the micro-heating strip 4 to ensure that a tight contact interface is formed between the micro-heating strip 4 and the groove 31 after it is embedded.

[0032] Furthermore, in the above technical solution, each micro-heating strip 4 is evenly distributed along the outer circumference of the insulating layer 3, the axis of each micro-heating strip 4 extends radially along the insulating layer 3, the inner end of each micro-heating strip 4 is provided with an outwardly protruding conical head, the conical head is embedded in the shielding layer 2, and the outer end of each micro-heating strip 4 is provided with annular fins extending radially outward.

[0033] In this embodiment, the micro-heating strips 4 are arranged at equal intervals along the inner circumference of the insulating layer 3, and the axis of each micro-heating strip 4 extends radially along the insulating layer 3. This equal-interval arrangement ensures that the heat transfer path from the surface of the conductor 1 to the outer surface of the insulating layer 3 is uniformly distributed in the circumferential direction. The heat generated by the conductor 1 is evenly distributed to each micro-heating strip 4 in the circumferential direction, avoiding local overheating caused by uneven heat transfer path distribution. The radially extending layout of each micro-heating strip 4 minimizes the heat conduction path from the conductor 1 to the outer surface of the insulating layer 3, resulting in the highest heat transfer efficiency.

[0034] Each micro-heating strip 4 has its inner end extending towards the conductor to form a tapered extension section, which is embedded inside the shielding layer 2. The tapered surface of the extension section forms a surface contact with the shielding layer 2, with a contact area much larger than that between the micro-heating strip 4 tube and the shielding layer 2. This larger contact area reduces contact thermal resistance, allowing the heat generated by the conductor 1 to be more smoothly conducted to the evaporation section of the micro-heating strip 4. The structure of the extension section embedded in the shielding layer 2 also serves a radial positioning function, anchoring the inner end of the micro-heating strip 4 within the shielding layer 2 and preventing radial displacement of the micro-heating strip 4 due to vibration or thermal expansion and contraction during cable operation.

[0035] Each micro-heating strip 4 extends outward from its outer end to form multiple annular extension structures. These extension structures are arranged circumferentially along the outer end of the micro-heating strip 4 and spaced apart axially along the micro-heating strip 4. The outer diameter of each extension structure is larger than the outer diameter of the tube of the micro-heating strip 4. They extend beyond the outer surface of the insulation layer 3 and embed into the inner surface area of ​​the heat-collecting and heat-dissipating sleeve 6. The extension structures increase the contact area between the condensation section of the micro-heating strip 4 and the heat-collecting and heat-dissipating sleeve 6, allowing the heat released from the condensation section to be conducted to the heat-collecting and heat-dissipating sleeve 6 more efficiently. Simultaneously, the radial extension of the extension structures also serves to position the outer end, anchoring the outer end of the micro-heating strip 4 within the heat-collecting and heat-dissipating sleeve 6, forming a double-end anchor with the inner tapered extension section, ensuring the stable position of the micro-heating strip 4 along the entire length of the cable.

[0036] Furthermore, in the above technical solution, the sintered copper powder capillary core layer 41 is formed by copper powder through a powder metallurgy sintering process. The sintered copper powder capillary core layer 41 has a uniformly distributed porous capillary channel structure, which is formed by the gaps between copper powder particles.

[0037] In this embodiment, the sintered copper powder capillary core layer 41 is formed of copper powder and contains a large number of interconnected micropores. These pores are formed by the gaps naturally created when copper powder particles are stacked together. The copper powder particles are interconnected to form a skeletal structure, and the gaps between the particles form an interconnected capillary channel network. The size of these capillary channels is at the micrometer level, which can generate a sufficiently large capillary force to overcome the flow resistance and gravity of the liquid working fluid in the channel, driving the liquid working fluid to flow back from the condensation region at the outer end to the evaporation region at the inner end.

[0038] The sintered copper powder capillary core layer 41 is integrated with the inner wall of the microheater strip 4, forming a strong structural bond. When the microheater strip 4 is filled with working fluid, the liquid working fluid permeates the porous structure of the sintered copper powder capillary core layer 41, forming a continuous liquid film within the capillary channels. In the evaporation section, the liquid film absorbs heat and evaporates, the vapor leaving the capillary channels and flowing towards the condensation section; in the condensation section, the vapor releases heat and condenses into a liquid state, the liquid working fluid re-permeates the capillary channels, and under capillary force, flows back to the evaporation section along the capillary channels. The porous structure of the sintered copper powder capillary core layer 41 also increases the surface area of ​​the inner wall of the microheater strip 4. The liquid working fluid is distributed on the surface of the porous structure to form a thin film, increasing the evaporation area and improving the evaporation efficiency, enabling the microheater strip 4 to transfer a larger heat flow rate with a smaller temperature difference.

[0039] Furthermore, in the above technical solution, the heat collection and heat dissipation sleeve 6 completely wraps each micro heat strip 4 and the insulation layer 3, and each protrusion 61 is distributed at equal intervals along the outer surface of the heat collection and heat dissipation sleeve 6, and the cross-section of each protrusion 61 is arc-shaped.

[0040] In this embodiment, the heat-collecting and heat-dissipating sleeve 6 completely encloses each micro-heating strip 4 and the insulating layer 3. The heat-collecting and heat-dissipating sleeve 6 is made of a high thermal conductivity metal, whose thermal conductivity is much higher than that of the insulating layer 3. The extended structure at the outer end of each micro-heating strip 4 is embedded in the inner surface area of ​​the heat-collecting and heat-dissipating sleeve 6, and the heat released by the condensation section of the micro-heating strip 4 is conducted to the heat-collecting and heat-dissipating sleeve 6 through the extended structure. Since the heat-collecting and heat-dissipating sleeve 6 is a continuous cylindrical structure, heat can diffuse simultaneously in the circumferential and axial directions inside the heat-collecting and heat-dissipating sleeve 6, so that the heat transferred from each micro-heating strip 4 is redistributed in the heat-collecting and heat-dissipating sleeve 6, eliminating the temperature difference between each micro-heating strip 4, and making the temperature distribution on the outer surface of the heat-collecting and heat-dissipating sleeve 6 more uniform.

[0041] The protrusions 61 are arranged at equal intervals along the circumference of the outer surface of the heat-collecting and heat-dissipating sleeve 6, and the outer edges of the protrusions 61 are arc-shaped. The presence of the protrusions 61 increases the contact area between the outer surface of the heat-collecting and heat-dissipating sleeve 6 and the outer protective sleeve 5. Heat is conducted from the heat-collecting and heat-dissipating sleeve 6 through the protrusions 61 to the outer protective sleeve 5, and then dissipated from the outer surface of the outer protective sleeve 5 to the external environment. The protrusions 61 extend continuously along the axial direction of the heat-collecting and heat-dissipating sleeve 6, forming a longitudinal strip structure. When the cable is bent, the transition area between the protrusions 61 can undergo slight elastic deformation, allowing the heat-collecting and heat-dissipating sleeve 6 to adapt to the bending radius of the cable and preventing structural damage or peeling from the insulation layer 3 due to bending.

[0042] Furthermore, in the above technical solution, the cavity 7 is formed by the adjacent protrusions 61 and the outer surface of the heat collection and heat dissipation sleeve 6. The cross-section of the cavity 7 is an inwardly concave arc shape, and the outer protective sleeve 5 tightly covers the outer side of the heat collection and heat dissipation sleeve 6 and each protrusion 61.

[0043] In this embodiment, the cavity 7 is formed by adjacent protrusions 61 and the outer surface of the heat collection and heat dissipation sleeve 6. Since the outer edges of each protrusion 61 have an arc-shaped transition, the top of each protrusion 61 protrudes outward, and the transition area between adjacent protrusions 61 is recessed inward, forming a space with an inwardly concave arc-shaped cross-section, i.e., the cavity 7. The cavity 7 extends along the axial direction of the heat collection and heat dissipation sleeve 6, forming a continuous longitudinal channel. The presence of the cavity 7 gives the outer surface of the heat collection and heat dissipation sleeve 6 a wavy, undulating profile. This wavy surface increases the contact area between the heat collection and heat dissipation sleeve 6 and the outer protective sleeve 5, while also providing additional structural flexibility to the heat collection and heat dissipation sleeve 6 when the cable is bent.

[0044] The outer protective sleeve 5 tightly covers the outer side of the heat-collecting and heat-dissipating sleeve 6 and each protrusion 61. During the covering process, the material of the outer protective sleeve 5 flows into the cavity 7 between the protrusions 61. The inner surface of the outer protective sleeve 5 not only adheres to the outer surface of each protrusion 61, but also partially embeds itself into the cavity 7, forming a mechanical interlocking structure. This mechanical interlocking ensures a strong bond between the outer protective sleeve 5 and the heat-collecting and heat-dissipating sleeve 6, preventing relative slippage or detachment of the outer protective sleeve 5 from the heat-collecting and heat-dissipating sleeve 6 under axial tensile or radial shear forces. The outer protective sleeve 5 is the outermost layer of the cable structure, sealing and protecting all internal structures, and isolating them from external moisture, chemicals, and mechanical damage.

[0045] Furthermore, in the above technical solution, the number of grooves 31 is the same as the number of micro-heating strips 4, each groove 31 is set in a one-to-one correspondence with each micro-heating strip 4, and the outer surface of each micro-heating strip 4 is flush with the outer surface of the boss of the insulating layer 3.

[0046] In this embodiment, the number of grooves 31 is the same as the number of micro-heating strips 4, with each groove corresponding to one micro-heating strip. This corresponding configuration ensures that each micro-heating strip 4 has an independent installation space and heat transfer path. The micro-heating strips 4 are separated from each other by the protrusions of the insulation layer 3, preventing them from contacting each other and allowing them to work independently. When the performance of one micro-heating strip 4 deteriorates or fails for any reason, the remaining micro-heating strips 4 are unaffected and continue to work normally. The overall heat dissipation capacity of the cable is only slightly affected, demonstrating good fault tolerance.

[0047] The outer surface of each micro-heating strip 4 and the outer surface of the protrusion of the insulating layer 3 are on the same cylindrical surface. This flush design ensures that when the heat-collecting and heat-dissipating sleeve 6 is fitted over the insulating layer 3, a complete cylindrical interface is formed between the inner surface of the heat-collecting and heat-dissipating sleeve 6 and the contact surface. The interface is composed of the outer surface of the micro-heating strip 4 and the outer surface of the protrusion of the insulating layer 3, both of which are on the same cylindrical surface without any unevenness. This continuous and flat contact interface allows the inner surface of the heat-collecting and heat-dissipating sleeve 6 to fit evenly against the contact surface, preventing deformation of the heat-collecting and heat-dissipating sleeve 6 due to stress concentration caused by local protrusions, and preventing the formation of thermal resistance bottlenecks due to poor contact caused by local depressions. This ensures the uniformity and continuity of heat transfer from the micro-heating strip 4 to the heat-collecting and heat-dissipating sleeve 6.

[0048] Furthermore, in the above technical solution, there are multiple conductors 1, each conductor 1 is twisted together to form a cable core, a support frame is provided at the center between adjacent conductors 1, and the support frame extends along the cable axis. At the same time, a central ventilation hole extending along the axis is provided at the center of the support frame.

[0049] In this embodiment, the cable adopts a multi-core structure, with multiple conductors 1, which are intertwined to form the cable core. Each conductor 1 is spirally wound in the cable core, and there are certain gaps between each conductor 1. These gaps provide space for the installation of the support structure and also provide channels for air circulation inside the cable core.

[0050] A support structure is provided in the central area between adjacent conductors 1, extending along the length of the cable. Each arm of the support structure extends into the gap between adjacent conductors 1, radially separating them and preventing deformation due to their own weight or external pressure after winding. The support structure also withstands the radial mechanical forces experienced by the cable during laying and use, protecting each conductor 1 from external mechanical damage. A ventilation channel runs along the length of the support structure in its central area. This ventilation channel connects to the gaps between conductors 1, forming a network of ventilation channels from the center of the cable core to both ends of the cable. When the cable is energized, the air inside the cable core expands due to heat, decreasing in density. Driven by the thermo-pressure effect, it flows along the ventilation channels towards both ends of the cable. Cooler external air enters the cable core from both ends, creating natural convection. This natural convection carries away some of the heat from inside the cable core, assisting the heat dissipation of the micro-heating strips 4 and further reducing the cable's operating temperature. The ventilation channels also facilitate the removal of moisture from inside the cable core, maintaining a dry environment and extending the service life of the insulation layer 3.

[0051] The low-voltage insulated power cable provided by this invention operates as follows: When the cable is energized, current flows through conductor 1. Due to the resistance of conductor 1, Joule heating is generated when the current passes through conductor 1. Joule heating raises the temperature of conductor 1, and the heat is transferred from the surface of conductor 1 towards the outer diameter.

[0052] Since there is no gap between the shielding layer 2 and the outer surface of the conductor 1, the heat generated on the surface of the conductor 1 can be conducted to the shielding layer 2 with extremely low interfacial thermal resistance. As the first-level transition layer for heat conduction, the shielding layer 2 can concentrate and homogenize the unevenly distributed heat on the surface of the conductor 1 because the shielding layer 2 is tightly attached to all parts of the conductor 1 surface. This makes the heat flux density transferred to the direction of the insulating layer 3 more uniform and avoids the formation of hot spots caused by excessively high local heat flux density.

[0053] The inner surface of the insulation layer 3 is provided with a groove 31. The micro-heating strip 4 embedded in the groove 31 achieves thermal contact with the outer wall of the shielding layer 2 through the sintered copper powder capillary core layer 41. When the cable is running under rated load, the temperature of the outer wall of the shielding layer 2 gradually increases. When the temperature exceeds the evaporation temperature of the working fluid inside the micro-heating strip 4, the phase change heat transfer process inside the micro-heating strip 4 is automatically started.

[0054] The phase change heat transfer process inside the micro-heater 4 includes the following four stages: In the evaporation section of the inner end region of the micro-heater strip 4, heat from the outer wall of the shielding layer 2 is conducted to the liquid working fluid inside the micro-heater strip 4 through the sintered copper powder capillary core layer 41. After absorbing heat, the liquid working fluid's temperature rises. When the temperature reaches the evaporation temperature, the liquid working fluid undergoes a phase change, transforming from a liquid state to a vapor state. During this process, the working fluid absorbs a large amount of latent heat of vaporization, which is stored in the vapor state of the working fluid.

[0055] Vapor migration stage: Driven by the pressure gradient inside the micro-heater strip 4, the vapor working fluid migrates from the higher-temperature inner region to the lower-temperature outer region. Since the inner end of the micro-heater strip 4 is close to the conductor 1 and has a higher temperature, while the outer end is close to the outer surface of the insulating layer 3 and has a lower temperature, there is a temperature difference between the two. This temperature difference drives the vapor working fluid to flow from the inner end to the outer end.

[0056] Condensation stage: After the vapor working fluid reaches the condensation section at the outer end of the micro-heater strip 4, it encounters a cooler wall surface and releases latent heat, condensing from vapor to liquid. The released latent heat is conducted through the outer wall and annular fins of the micro-heater strip 4 to the heat collection and dissipation sleeve 6, and then dissipated into the external environment through the heat collection and dissipation sleeve 6 and the outer protective sleeve 5.

[0057] Liquid working fluid reflux stage: Under the capillary force generated by the sintered copper powder capillary core layer 41, the condensed liquid working fluid flows back from the outer condensation area to the inner evaporation area along the capillary channel, providing liquid working fluid replenishment for the next evaporation process.

[0058] The protrusions 61 on the outer surface of the heat-collecting and heat-dissipating sleeve 6 increase the contact area between the heat-collecting and heat-dissipating sleeve 6 and the outer protective sleeve 5. Heat is conducted from the heat-collecting and heat-dissipating sleeve 6 through the protrusions 61 to the outer protective sleeve 5, and then dissipated from the outer surface of the outer protective sleeve 5 to the surrounding environment. The protrusions 61 extend continuously along the axial direction of the heat-collecting and heat-dissipating sleeve 6, forming a longitudinal heat dissipation fin structure, which further increases the heat dissipation area. The cavity 7 formed between adjacent protrusions 61 is axially continuous. The air in the cavity 7 expands when heated at the cable operating temperature, generating weak natural convection along the axial direction, which assists in the axial transfer and dissipation of heat.

[0059] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A low-voltage insulated power cable, comprising a conductor (1), characterized in that: Each conductor (1) is made of multiple metal wires twisted together. Each conductor (1) is covered with a shielding layer (2) on the outside. The shielding layer (2) is covered with an insulating layer (3) on the outside. The inner surface of the insulating layer (3) is provided with multiple grooves (31) along the axial direction. Each groove (31) is evenly distributed circumferentially along the inner surface of the insulating layer (3). Each groove (31) is embedded with a micro-heating strip (4). Each micro-heating strip (4) extends along the cable axial direction. Each of the micro-heating strips (4) is a metal strip. There is no gap between the outer wall of each of the micro-heating strips (4) and the inner wall of the groove (31). The inner wall of each of the micro-heating strips (4) is provided with a sintered copper powder capillary core layer (41). The sintered copper powder capillary core layer (41) is attached to the outer wall of the shielding layer (2). The outer side of the insulating layer (3) is covered with a heat collection and heat dissipation sleeve (6). The outer surface of the heat collection and heat dissipation sleeve (6) is provided with a plurality of protrusions (61) along the axial direction. Each of the protrusions (61) is evenly distributed circumferentially along the outer surface of the heat collection and heat dissipation sleeve (6) and extends continuously in the axial direction. A cavity (7) is formed between adjacent protrusions (61). The cavity (7) is axially connected to the heat collection and heat dissipation sleeve (6). The outer side of the heat collection and heat dissipation sleeve (6) and each protrusion (61) is covered with an outer protective sleeve (5).

2. The low-voltage insulated power cable according to claim 1, characterized in that: The conductor (1) is formed by twisting multiple metal wires into groups to form multiple cross sections in a fan shape. The shielding layer (2) is a semi-conductive shield and is tightly wrapped around the outer surface of the conductor (1).

3. A low-voltage insulated power cable according to claim 1, characterized in that: The insulating layer (3) is a thick-walled cylindrical structure. The inner surface of the insulating layer (3) is closely attached to the outer surface of the shielding layer (2). The cross-section of each groove (31) is rectangular or trapezoidal. The depth and width of each groove (31) are adapted to the cross-sectional dimensions of the micro-heating strip (4).

4. A low-voltage insulated power cable according to claim 1, characterized in that: Each of the micro-heating strips (4) is evenly distributed along the outer circumference of the insulating layer (3). The axis of each of the micro-heating strips (4) extends radially along the insulating layer (3). The inner end of each of the micro-heating strips (4) is provided with an outwardly protruding conical head. The conical head is embedded inside the shielding layer (2). The outer end of each of the micro-heating strips (4) is provided with annular fins extending radially outward.

5. A low-voltage insulated power cable according to claim 1, characterized in that: The sintered copper powder capillary core layer (41) is formed by copper powder through powder metallurgy sintering process. The sintered copper powder capillary core layer (41) has a uniformly distributed porous capillary channel structure, which is formed by the gaps between copper powder particles.

6. A low-voltage insulated power cable according to claim 1, characterized in that: The heat collection and heat dissipation sleeve (6) completely wraps each micro heat strip (4) and the insulation layer (3). Each of the protrusions (61) is distributed at equal intervals along the outer surface of the heat collection and heat dissipation sleeve (6), and the cross section of each of the protrusions (61) is arc-shaped.

7. A low-voltage insulated power cable according to claim 1, characterized in that: The cavity (7) is formed by the outer surface of the adjacent protrusions (61) and the heat collection and heat dissipation sleeve (6). The cross section of the cavity (7) is an inwardly concave arc shape. The outer protective sleeve (5) tightly covers the heat collection and heat dissipation sleeve (6) and the outer side of each protrusion (61).

8. A low-voltage insulated power cable according to claim 1, characterized in that: The number of grooves (31) is the same as the number of micro-heating strips (4). Each groove (31) is set in a one-to-one correspondence with each micro-heating strip (4). The outer surface of each micro-heating strip (4) is flush with the outer surface of the boss of the insulating layer (3).

9. A low-voltage insulated power cable according to claim 1, characterized in that: The conductor (1) consists of multiple strands, each of which is twisted together to form a cable core. A support frame is provided at the center between adjacent conductors (1), and the support frame extends along the cable axis. At the same time, a central ventilation hole extending along the axis is provided at the center of the support frame.

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