Complex environment direct-buried power cable with conductor built-in micro-channel cooling

Abstract

The invention discloses a complex environment direct burial power cable with a conductor built-in micro-channel cooling function, and belongs to the technical field of power cables. Comprising a conductor, a liquid cooling pipe, an isolation sleeve, an armor layer, an outer sheath layer and a nylon sheath layer. The conductor and the liquid cooling pipe are arranged in the isolation sleeve; the armor layer is arranged on the outer side of the isolation sleeve; the outer sheath layer is arranged on the outer side of the armor layer, and the nylon sheath layer is arranged on the outer side of the outer sheath layer; the conductor comprises a conductor monofilament; the conductor monofilament is provided with a spiral groove, and a micro-flow tube is arranged in the spiral groove. The cable solves the problems that the current-carrying capacity of a directly-buried cable is difficult to improve and fire disasters occur easily, improves the current-carrying capacity, and is environment-friendly and flame-retardant

Description

Technical Field

[0001] This invention relates to the field of power cable technology, and more specifically to a direct-buried power cable for complex environments with conductor-embedded microfluidic cooling. Background Technology

[0003] Urban power grids, as a crucial link in power transmission, mainly consist of two forms: traditional overhead lines and underground cables. However, traditional overhead transmission lines face numerous limitations in urban power grids, not only in their installation but also in their susceptibility to lightning strikes, endangering personal safety. With the deepening of urban power grid transformation in my country, the "earthwork" project has been gradually implemented, particularly in 110kV and below power distribution systems and urban centers. The undergrounding of power lines is carried out simultaneously with municipal engineering renovations, reducing project costs and improving power supply reliability. Among these methods, direct-buried cables, with their economic and low maintenance costs, are widely used in medium and low voltage lines below 35kV.

[0004] In recent years, my country's economy has continued to grow rapidly, leading to a surge in electricity demand and making the spatial layout of cable facilities increasingly problematic. The construction of new lines faces numerous constraints, including limited space, tight funding, and long construction periods, making it difficult to increase the current-carrying capacity of power transmission. In practice, cables often operate under low loads, far below their specified current-carrying capacity, resulting in low transmission efficiency and resource waste. Simultaneously, the laying environment is becoming increasingly complex, potentially posing safety hazards to otherwise safe cables and even causing fires, seriously threatening the stability of power supply. Therefore, ensuring a stable power supply while fully utilizing the transmission capacity of existing cables, guaranteeing the safe and reliable operation of power cable lines, and deeply exploring their transmission potential have become critical issues that urgently need to be addressed.

[0005] Current carrying capacity, a crucial indicator of cable transmission capacity, refers to the maximum current a cable conductor can withstand while continuously carrying current, provided the core temperature falls below a specified value due to various losses. The initial investment cost of buried cables is significantly higher than that of overhead lines, and maintenance is more complex. Design and operation must balance two requirements: firstly, to enhance the current-carrying capacity of the power grid, fully utilizing cable transmission capacity and enabling real-time dynamic adjustment based on demand; secondly, to strictly adhere to current-carrying limits to prevent current-induced aging of cable insulation, shortening its lifespan, or even causing fires. Data shows that fires caused by insulation damage due to long-term overloading of power cables account for 24.2% of all power cable fires, and the concealed location of these cables makes them extremely dangerous. To prevent such incidents, reducing the cable's transmission current is necessary, but this increases the number of cables and costs. Therefore, scientifically improving the current-carrying capacity of cables to ensure the safe and economical operation of buried cables is of paramount importance.

[0006] Since the current-carrying capacity of cables is closely related to heat generation and dissipation conditions, the temperature of commonly used cross-linked polyethylene (XLPE) cables will increase by 8% and their lifespan will be halved when the current-carrying capacity exceeds the limit by 6.5%. Under these circumstances, seeking new insulation materials to improve the current-carrying capacity of cables has become crucial to ensuring a stable power supply and promoting the sustainable development of the power industry. Summary of the Invention

[0007] To address the limitations of existing direct-buried cables in terms of space and cost, making it difficult to increase current-carrying capacity and posing a risk of fire due to overloading, this invention provides a direct-buried power cable for complex environments with a conductor featuring built-in microfluidic cooling. This solves the problems of difficulty in increasing current-carrying capacity and fire hazard associated with direct-buried cables, while also improving current-carrying capacity and being environmentally friendly and flame-retardant.

[0008] To achieve the above objectives, the present invention provides the following technical solution.

[0009] In a first aspect, the present invention provides a direct-buried power cable for complex environments with conductor-embedded microfluidic channel cooling, comprising a conductor, a liquid cooling pipe, an isolation sleeve, an armor layer, an outer sheath layer, and a nylon sheath layer; the conductor and the liquid cooling pipe are disposed inside the isolation sleeve; the armor layer is disposed outside the isolation sleeve; the outer sheath layer is disposed outside the armor layer, and the nylon sheath layer is disposed outside the outer sheath layer; the conductor comprises a conductor monofilament; the conductor monofilament is provided with a spiral groove, and the spiral groove contains a microfluidic channel.

[0010] As a further improvement of the present invention, the conductor is formed by twisting together several conductor monofilaments.

[0011] As a further improvement of the present invention, the liquid cooling tube is disposed between the two conductors.

[0012] As a further improvement of the present invention, a shielding layer is provided on the outside of the conductor.

[0013] As a further improvement of the present invention, the shielding layer includes a conductor shielding layer, an insulating layer, an insulating shielding layer, and a metal shielding layer; the conductor shielding layer is disposed on the outside of the conductor, the insulating layer is disposed on the outside of the conductor shielding layer, the insulating shielding layer is disposed on the outside of the insulating layer, and the metal shielding layer is disposed on the outside of the insulating shielding layer.

[0014] As a further improvement of the present invention, the insulating layer is made of polypropylene insulating material.

[0015] As a further improvement of the present invention, the outer sheath layer is made of a highly flame-retardant, low-smoke, halogen-free material.

[0016] As a further improvement of the present invention, the armor layer is made of steel wire armor.

[0017] As a further improvement of the present invention, the number of conductors is equal to the number of liquid cooling tubes.

[0018] As a further improvement of the present invention, the microfluidic tube is selected as an FEP microfluidic tube.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a spiral groove and built-in microfluidic tubes on the conductor monofilament to construct a structure comprising a conductor, liquid-cooled tubes, an insulating sleeve, an armor layer, an outer sheath layer, and a nylon sheath layer. Furthermore, it introduces a liquid-cooling circulation system. The cooling medium in the liquid-cooled tubes flows through the microfluidic tubes within the conductor, efficiently removing heat generated by the conductor. This cooling method is not limited by the external space of the cable or traditional heat dissipation structures. It does not require large-scale changes to the cable laying environment or the addition of extra heat dissipation equipment, achieving powerful heat dissipation within a relatively compact space. This significantly increases the cable's current carrying capacity, effectively meeting the ever-increasing demand for power transmission and providing reliable technical support for scenarios with high power capacity requirements, such as urban power grid upgrades and power supply for large industrial projects. Simultaneously, the conductor's built-in microfluidic cooling structure allows for real-time monitoring and control of the conductor's temperature. When the cable shows signs of overload, the liquid-cooling system immediately activates or increases the flow rate of the cooling medium to quickly dissipate excess heat, ensuring the conductor temperature remains within a safe range. This effectively prevents high-temperature accumulation caused by overload, eliminating the risk of fire at its source and greatly improving the safety and reliability of directly buried cables. Furthermore, this invention possesses significant advantages in terms of environmental friendliness and flame retardancy. Environmentally friendly materials are selected for each layer of the cable's structure, ensuring minimal environmental impact during production, use, and disposal, aligning with modern society's requirements for green energy and sustainable development. Simultaneously, the outer sheath and nylon sheath utilize materials with excellent flame-retardant properties, effectively preventing the spread of fire in the event of a fire, providing additional safety protection for the cable, and reducing losses caused by fire. Attached Figure Description

[0020] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. In the drawings: Figure 1 This is a schematic diagram of the structure of a direct-buried power cable for complex environments with conductor-embedded microfluidic cooling, according to the present invention. Figure 2 This is a schematic diagram of the conductor monofilament structure of the built-in microchannel cooling structure in a directly buried power cable in a complex environment, according to the present invention.

[0021] 1. Conductor; 11. Conductor monofilament; 12. Microfluidic tube; 2. Conductor shielding layer; 3. Insulation layer; 4. Insulation shielding layer; 5. Liquid cooling tube; 6. Metal shielding layer; 7. Isolation sleeve; 8. Armoring layer; 9. Outer sheath layer; 10. Nylon sheath layer. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] To address the limitations of existing direct-buried cables in terms of space and cost, difficulty in increasing current carrying capacity, and the risk of fire due to overloading, this invention provides a direct-buried power cable for complex environments with a conductor featuring built-in microchannel cooling. Figure 1 As shown, it includes conductor 1, liquid cooling pipe 5, isolation sleeve 7, armor layer 8, outer sheath layer 9, and nylon sheath layer 10.

[0025] The isolation sleeve 7 contains several conductors 1 and liquid cooling pipes 5, with the liquid cooling pipes 5 located in the gaps around two conductors 1, and the number of conductors 1 and liquid cooling pipes 5 is equal. The isolation sleeve 7 is provided with an armor layer 8 on the outside, an outer sheath layer 9 on the outside of the armor layer 8, and a nylon sheath layer 10 on the outside of the outer sheath layer 9.

[0026] By placing the liquid cooling pipes 5 in the gaps around the two conductors 1, and ensuring that the number of conductors 1 and liquid cooling pipes 5 are equal, this layout fully utilizes the unused space between the conductors 1. It eliminates the need for additional expansion of the overall cable size, achieving efficient cooling system integration within a compact direct-buried cable structure, effectively saving installation space and material costs. Simultaneously, the equal number of corresponding pipes ensures that each conductor 1 is precisely surrounded by adjacent liquid cooling pipes 5, forming a one-to-one efficient heat dissipation channel. This ensures that the heat generated by each conductor 1 is promptly and evenly dissipated, greatly improving heat dissipation efficiency and thus effectively increasing the cable's current carrying capacity and enhancing its power transmission capability. Furthermore, this orderly arrangement helps improve the overall stability and symmetry of the cable structure, reducing the risk of damage caused by uneven local stress or temperature differences, extending the cable's service life, and ensuring the long-term safe and stable operation of the direct-buried cable in complex environments.

[0027] Conductor 1 includes conductor monofilament 11.

[0028] like Figure 2 As shown, a spiral groove is laser-etched into the conductor filament 11, and a microfluidic tube 12 is embedded within the spiral groove. Several conductor filaments 11 are twisted together to form a conductor 1 with an embedded microfluidic cooling structure.

[0029] A spiral groove is laser-engraved into the conductor filament 11, and a microfluidic tube 12 is precisely embedded within the spiral groove. Several conductor filaments 11 are then twisted together to form the conductor 1 with an internal microfluidic cooling structure. Laser engraving of the spiral groove allows for extremely high precision control of the groove's size and shape, ensuring a perfect fit with the microfluidic tube 12. This significantly improves the stability and sealing of the microfluidic tube 12 installation, effectively preventing cooling medium leakage. The twisted conductor 1 not only maintains good conductivity, but the spiral groove structure also allows the microfluidic tubes 12 to be distributed spirally within the conductor, greatly increasing the contact area and contact time between the cooling medium and the conductor. This enables more efficient and uniform heat removal from the conductor, significantly improving heat dissipation and thus effectively increasing the cable's current carrying capacity. Simultaneously, this structure requires no additional external space, demonstrating its advantages in compact direct-buried cable installation environments. It also reduces the risk of high-temperature accumulation due to overload, fundamentally reducing fire hazards and providing a solid guarantee for the safe and stable operation of direct-buried cables.

[0030] A shielding layer is provided on the outside of conductor 1.

[0031] The shielding layer includes a conductor shielding layer 2, an insulating layer 3, an insulating shielding layer 4, and a metal shielding layer 6.

[0032] A conductor shielding layer 2 is provided on the outside of conductor 1, an insulating layer 3 is provided on the outside of conductor shielding layer 2, an insulating shielding layer 4 is provided on the outside of insulating layer 3, and a metal shielding layer 6 is provided on the outside of insulating shielding layer 4.

[0033] Insulation layer 3 will be made of polypropylene insulation material. Polypropylene insulation material is a thermoplastic that does not require cross-linking treatment, has environmentally friendly and recyclable characteristics, and has higher breakdown field strength and operating temperature.

[0034] Microfluidic tube 12 is an FEP microfluidic tube.

[0035] In summary, the liquid cooling pipes 5 are placed in the outer gaps of the two conductors 1 and are equal in number, making full use of the idle space, integrating a high-efficiency cooling system, saving installation space and cost, and improving heat dissipation efficiency, current carrying capacity and structural stability; the conductor monofilaments 11 are laser-engraved with spiral grooves and then twisted together after being fitted with FEP microfluidic tubes, ensuring that the microfluidic tubes 12 are installed stably and sealed, increasing the cooling contact area and time, achieving efficient heat dissipation without occupying external space, and reducing fire hazards; the conductor shielding layer 2, the insulation layer made of polypropylene material, the insulation shielding layer 4 and the metal shielding layer 6 are sequentially arranged on the outside of the conductors 1, further ensuring the insulation and shielding performance of the cable, and comprehensively improving the safe and stable operation capability and power transmission capability of the buried cable in complex environments.

[0036] The present invention will be further explained and illustrated below with reference to specific embodiments.

[0037] Example Taking a conductor with a cross-sectional area of ​​400 mm² as an example, the current-carrying capacity of a cable with polypropylene insulation is calculated. The continuous allowable current-carrying capacity of a cable refers to the maximum allowable current when the cable is subjected to a continuous constant current (100% load rate). This can be calculated given the cable structure and laying conditions. The formula for calculating the cable current-carrying capacity is:

[0038] In the formula: This represents the highest permissible temperature for the conductor, and is set to 90℃. The ambient temperature is taken as 40℃. For cable dielectric loss; The AC resistance of the cable conductor at temperature is 0.0000621 Ω / m. This represents the loss coefficient of the metal sheath. This represents the loss coefficient of the armor layer. Thermal resistance of cable insulation layer; Thermal resistance of the cable insulation layer; Thermal resistance of the cable outer sheath; The thermal resistance of the coal surrounding the cable.

[0039] Cable dielectric loss

[0040] Thermal resistance of cable insulation

[0041] In the formula: The value is the thermal resistivity of the cable insulation layer; for polypropylene, it is taken as 6.

[0042] Thermal resistance of cable insulation layer

[0043] In the formula: is the thermal resistivity of the cable insulation layer; for low-smoke halogen-free polyolefins, it is taken as 6.

[0044] Cable outer sheath thermal resistance

[0045] In the formula: The thermal resistivity of the outer sheath is 6 for low-smoke halogen-free polyolefins.

[0046] Thermal resistance of air around the cable

[0047] In the formula: The equivalent heat dissipation coefficient of the cable in air is 9.

[0048] Loss factor of metal sheath

[0049] Due to the electric field shielding effect of the metallic shielding layer, the induced potential of the armor layer relative to ground can be approximated as zero. Therefore, the continuous allowable current carrying capacity of the cable is... 780.8A At an ambient temperature of 40℃, the current carrying capacity of a cross-linked polyethylene cable of the same specification is 690A, which is consistent with the characteristic that the current carrying capacity of a polypropylene cable of the same cross-sectional area is higher than that of a cross-linked polyethylene cable.

[0050] In summary, the conductor 1 incorporates a microfluidic tube 12 to control its operating temperature, and the gaps in the conductor 1 are filled with liquid cooling tubes 5 to reduce the impact of ambient temperature on the cable itself. The material of the liquid cooling tube 5 is a crucial factor determining the service life of the liquid-cooled cable. Currently, the main materials for liquid cooling tubes include thermoplastic polyolefin (TPO), thermoplastic elastomer (TPE), polyamide (PA), thermoplastic polyurethane elastomer (TPU), and perfluoroethylene propylene (FEP), and their hardness and temperature resistance ratings are shown in Table 1.

[0051] Table 1 Hardness and Temperature Resistance Rating of Cooling Pipe Materials

[0052] Cooling pipes must possess excellent compressive strength, thermal aging performance, oil resistance, and acid and alkali resistance. After comprehensive evaluation, FEP material demonstrates superior performance compared to other materials, making it the most suitable material for cooling pipes in liquid-cooled charging piles.

[0053] For the 8th layer of armor, steel wire armor is chosen. The core advantage of steel wire armor over steel strip armor lies in its superior tensile strength and dynamic adaptability. Through its spirally wound high-strength steel wire structure, it can effectively withstand longitudinal tension, such as the self-weight tension during steep slope laying, preventing cable slippage or deformation—a characteristic difficult to achieve with steel strip armor. Simultaneously, the three-dimensional mesh structure of the steel wire is more resilient to localized high pressure or sharp object puncture in rocky geological conditions—the steel wire disperses pressure through minute deformations, reducing the risk of crushing, while the planar hard layer of steel strip is prone to permanent deformation under point impact. Furthermore, the flexibility of steel wire armor makes it more adaptable to complex terrain such as uneven rock beds in trenches and dynamic environments such as geological subsidence or vibration, and it is also more resistant to friction damage during construction and traction.

[0054] The outer sheath layer 9 is made of highly flame-retardant, low-smoke, halogen-free material. The core advantage of using low-smoke, halogen-free sheathed cables in direct burial environments lies in balancing long-term reliability with safety in extreme scenarios. The material is halogen-free, significantly reducing the release of toxic and corrosive gases, such as hydrogen chloride, even if combustion occurs due to external fire or high temperatures from a short circuit, thus preventing soil contamination and corrosion of adjacent pipelines. Simultaneously, its ultra-low smoke emission characteristics delay the spread of smoke from underground manholes or tunnel entrances, buying valuable time for emergency response. The sheath itself possesses hydrolysis and chemical corrosion resistance, exhibiting a longer lifespan than traditional PVC in humid and acidic / alkaline soils, and demonstrating stronger resistance to environmental stress cracking, adapting to backfill pressure and geological settlement.

[0055] Furthermore, this invention adds a nylon sheath layer 10 to the outer sheath layer 9. The nylon material of the sheath layer 10 has a hardness ≥65D, a smooth surface when used as a protective layer, and formic acid resistance, preventing termites and rodents from biting and thus achieving the purpose of prevention and control. This solves the problem of environmental pollution and ecological damage caused by toxic substances in chemical methods of rodent and termite control. It can guarantee long-term effective rodent and termite control performance, eliminating the need for additional construction methods for rodent and termite control.

[0056] In summary, this invention provides a power cable with a conductor monofilament featuring a built-in microfluidic cooling structure. It utilizes laser-engraved Ф2.94mm soft copper wire, with microfluidic tubes wound around the wires in slots, and the monofilaments are tightly stranded into a conductor in a "1+6+12+18+23" configuration. Ethylene glycol liquid is introduced into the microfluidic tubes, and the conductor's operating temperature is controlled by adjusting the flow rate. The conductor with the built-in microfluidic cooling structure effectively controls its operating temperature. The insulation layer uses polypropylene insulation, which generates no waste during production and is recyclable after the cable's lifespan. Furthermore, its electrical performance and temperature resistance are superior to traditional XLPE, resulting in higher current carrying capacity. The outer sheath employs a low-smoke halogen-free sheath + nylon sheath structure, providing flame retardancy and environmental friendliness.

[0057] Many embodiments and applications beyond the examples provided will be apparent to those skilled in the art upon reading the foregoing description. Therefore, the scope of this teaching should not be determined by reference to the foregoing description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed inventive subject matter.

[0058] The above content provides a further detailed description of the present invention. It should not be construed that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection of the present invention as defined by the submitted claims.

Claims

1. A direct-buried power cable for complex environments with conductor-embedded microfluidic cooling, characterized in that, It includes a conductor (1), a liquid cooling pipe (5), an isolation sleeve (7), an armor layer (8), an outer sheath layer (9), and a nylon sheath layer (10); The conductor (1) and the liquid cooling pipe (5) are disposed inside the isolation sleeve (7); The armor layer (8) is provided on the outside of the isolation sleeve (7); the outer sheath layer (9) is provided on the outside of the armor layer (8); and the nylon sheath layer (10) is provided on the outside of the outer sheath layer (9). The conductor (1) includes a conductor monofilament (11); The conductor monofilament (11) is provided with a spiral groove, and a microfluidic tube (12) is built into the spiral groove.

2. The direct-buried power cable for complex environments with conductor-embedded microchannel cooling according to claim 1, characterized in that, The conductor (1) is formed by twisting together several conductor monofilaments (11).

3. The direct-buried power cable for complex environments with conductor-embedded microchannel cooling according to claim 1, characterized in that, The liquid cooling pipe (5) is disposed between the two conductors (1).

4. The direct-buried power cable for complex environments with conductor-embedded microchannel cooling according to claim 1, characterized in that, The conductor (1) is provided with a shielding layer on the outside.

5. A direct-buried power cable for complex environments with conductor-embedded microchannel cooling as described in claim 4, characterized in that, The shielding layer includes a conductor shielding layer (2), an insulating layer (3), an insulating shielding layer (4), and a metal shielding layer (6). The conductor (1) is provided with a conductor shielding layer (2) on the outside, the conductor shielding layer (2) is provided with an insulating layer (3) on the outside, the insulating shielding layer (3) is provided with an insulating shielding layer (4) on the outside, and the insulating shielding layer (4) is provided with a metal shielding layer (6) on the outside.

6. A direct-buried power cable for complex environments with conductor-embedded microchannel cooling as described in claim 5, characterized in that, The insulating layer (3) is made of polypropylene insulating material.

7. A direct-buried power cable for complex environments with conductor-embedded microchannel cooling as described in claim 1, characterized in that, The outer sheath layer (9) is made of a high flame retardant, low smoke, and halogen-free material.

8. A direct-buried power cable for complex environments with conductor-embedded microchannel cooling as described in claim 1, characterized in that, The armor layer (8) is made of steel wire armor.

9. A direct-buried power cable for complex environments with conductor-embedded microchannel cooling as described in claim 1, characterized in that, The number of conductors (1) is equal to the number of liquid cooling pipes (5).

10. A direct-buried power cable for complex environments with conductor-embedded microchannel cooling according to claim 1, characterized in that, The microfluidic tube (12) is an FEP microfluidic tube.

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