High-heat-dissipation aluminum tube core copper type single wire stranded conductor and preparation method thereof

Abstract

The invention discloses a high-heat-dissipation aluminum tube core copper type single wire stranded conductor and a preparation method thereof, and belongs to the technical field of power transmission conductors. The conductor comprises a central layer and an outer layer. The central layer is a circular hollow aluminum pipe and forms an axial heat dissipation channel. The outer layer is formed by twisting and pressing at least one layer of special-shaped metal single wires, and the side edge of each special-shaped metal single wire is provided with a concave-convex matching structure which enables the adjacent single wires to be meshed with each other so as to limit circumferential displacement. In-layer gapless dense laying is realized through the concave-convex matching structure, and the conductor simultaneously has high current-carrying capacity, excellent structural stability, excellent heat dissipation performance and surface quality by combining the active / passive heat dissipation design of the hollow aluminum pipe and optimized twisting process parameters. Compared with a traditional conductor of the same specification, the long-term allowable current-carrying capacity is improved by more than 15%, the compression coefficient is not lower than 0.97, and the cable is suitable for high-voltage, medium-voltage and low-voltage power cables.

Description

Technical Field

[0001] This invention relates to the field of power transmission conductor technology, specifically to a high-heat-dissipation aluminum core copper single-stranded conductor for high, medium and low voltage power cables and its preparation method. Background Technology

[0002] In power transmission systems, conductors, as the core carriers of energy transfer, directly affect transmission efficiency, operational safety, and cable lifespan. Currently, the second type of stranded conductors produced according to the national standard GB / T 3956 mostly adopt a circular single-wire stranded structure, which has the following inherent defects:

[0003] First, the unavoidable gaps between the circular single wires result in a conductor compaction coefficient generally below 0.90, insufficient effective conductive area, uneven current distribution, increased AC resistance, and significant line loss.

[0004] Secondly, the lack of an effective mechanical interlocking mechanism between individual wires makes them prone to relative sliding and creep displacement under cable bending, thermal cycling vibration, or long-term electromagnetic force, leading to loose and deformed conductor structure, burrs on the surface, threatening the safety of the insulation layer, and affecting the long-term reliability of the cable.

[0005] Third, traditional conductors often use solid metal cores (such as solid copper or aluminum rods), which have long heat dissipation paths, serious internal heat accumulation, and high operating temperatures. This is not only a major bottleneck limiting the improvement of current carrying capacity, but also accelerates the aging of insulation materials.

[0006] To address the aforementioned issues, existing technologies have undertaken some tentative improvements. For instance, patent document CN104064256B discloses an irregularly shaped stranded conductor, employing non-circular cross-section single wires to increase the fill factor. However, its irregular design does not adequately consider splicing compatibility, resulting in minute gaps between the single wires and failing to achieve truly gapless close-packing. Patent document CN203520993U discloses an aluminum core expanded diameter conductor, increasing the conductor's outer diameter through a hollow aluminum tube, but it does not address improvements in heat dissipation performance.

[0007] Furthermore, while there are precedents for using hollow tubes or irregularly shaped wires in some special cables (such as expanded diameter conductors and high-current busbars), these often focus on single performance indicators (such as reducing corona loss or improving mechanical strength) and fail to systematically combine heat dissipation design, structural interlocking, and electrical performance optimization. Existing irregularly shaped wire designs are mostly limited to simple trapezoidal, S-shaped, or Z-shaped designs, and their splicing mainly relies on line contact or small-area contact, lacking an effective three-dimensional interlocking mechanism, which may still lead to loosening under long-term dynamic loads.

[0008] Therefore, there is an urgent need in this field for a novel stranded conductor structure and its manufacturing method that can simultaneously resolve the contradictions of high current carrying capacity, high heat dissipation, and high stability. Summary of the Invention

[0009] 1. Purpose of the invention

[0010] To address the technical problems of existing stranded conductors, such as limited current carrying capacity, insufficient heat dissipation performance, and poor structural stability, the present invention aims to provide a high-heat-dissipation aluminum core copper-type single-wire stranded conductor and its preparation method. This conductor, through innovative structural design, combines active heat dissipation channels, mechanical interlocking splicing, and optimized stranding processes to achieve a comprehensive goal of significantly improved current carrying capacity, stable and reliable structure, and efficient heat dissipation. It can also flexibly adapt to various cable application scenarios from low voltage to high voltage.

[0011] 2. Technical Solution

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] Option 1: A stranded conductor

[0014] The conductor comprises a central layer and at least one outer layer.

[0015] The central layer is a hollow metal tube, preferably a round hollow aluminum tube. Aluminum has good electrical conductivity and low cost, and its hollow structure naturally forms a continuous axial ventilation channel at the conductor's axis. This channel can achieve natural convection heat dissipation through thermal pressure difference, or it can be connected to a forced ventilation system at the cable terminal to efficiently and actively cool the conductor's interior through gas circulation (such as air or inert gas), thereby significantly reducing the conductor's operating temperature, improving long-term current carrying capacity, and possessing the potential for heat energy recovery and utilization.

[0016] The outer layer is composed of multiple irregularly shaped metal wires twisted together, preferably copper wires. The key innovation of this invention lies in the fact that the sides of the irregularly shaped metal wires are provided with a concave-convex mating structure that allows adjacent wires to mesh with each other to restrict circumferential displacement. This design overcomes the limitation of traditional irregularly shaped wires relying solely on shape fit for contact. Through the mechanical interlocking of the concave and convex teeth, the potential circumferential shear force is converted into a clamping force between the tooth surfaces, fundamentally suppressing the relative displacement between the wires.

[0017] In a preferred embodiment, the concave-convex mating structure is specifically designed as a complementary concave-convex toothed splicing structure. The apex of the tooth is located on the central arc (i.e., the equidistant line) between the inner and outer arc edges of a single line. The included angle of a single tooth is designed to be 90°±2°. The concave-convex teeth of adjacent single lines are centrally symmetrically and complementaryly distributed. This specific geometric design allows the convex teeth of adjacent single lines to be precisely embedded into the grooves of another single line, forming an interlocking structure similar to a mortise and tenon joint during twisting. This effectively resists circumferential shear force and radial creep, achieving a closed annular paving with no gaps or overlaps in the circumferential direction within the layer, while ensuring good processability and twisting assembly performance.

[0018] To further optimize conductor performance, the outer layer can consist of 1 to 4 layers. Each layer is made by twisting together several copper single wires of identical shape and size and then pressing them into a circle using a compaction mold. The number of single wires in each layer follows the rule that each layer has 4 to 6 more wires than its adjacent inner layer, in order to ensure a uniform transition and mechanical balance in the structure.

[0019] Regarding stranding process parameters, a non-rewinding stranding process is adopted to maintain the original characteristics of the single wire. The pitch ratio (the ratio of the stranding pitch to the outer diameter of the strand) of the outermost layer is controlled between 17 and 21, and the pitch ratio of the adjacent inner layers decreases by 8 to 12 (i.e., increases from the outside to the inside), with the maximum pitch ratio not exceeding 49. The stranding direction of adjacent strands is designed to be opposite (e.g., the inner layer is right-handed Z, and the outer layer is left-handed S). Through the coordinated design of the above stranding direction and pitch ratio, combined with the subsequent compaction process, the conductor can achieve extremely high compactness, with a compaction coefficient (the ratio of the actual metal cross-sectional area of ​​the conductor to the cross-sectional area of ​​its circumscribed circle) not less than 0.97.

[0020] The geometric dimensions of the copper single wire are precisely calculated to ensure a perfect fit: the radii of curvature of its inner and outer arc edges are precisely matched to the inner radius (D) of the preset stranded ring. N ) and outer radius (D) W The included angle A between the two sides satisfies the formula A = K × 360° / n (K = 0.985 ~ 0.995, n is the number of single lines). This range ensures a tight fit while leaving a small margin to avoid excessive compression during splicing. The height of a single line H = (D W -D N )×1.01 / 2; Average width W=π×(D W +D N )×0.99 / (2×n). In addition, all edges and corners are chamfered with a radius of 0.1mm to 0.2mm to avoid damaging the cable insulation layer.

[0021] Option 2: A method for preparing a stranded conductor ×

[0022] The method includes the following core steps: (1) providing a hollow metal tube (preferably a round hollow aluminum tube) as the center layer; (2) providing multiple irregularly shaped metal single wires (preferably copper single wires) with concave-convex mating structures (preferably complementary concave-convex toothed structures) on the sides; (3) using a non-rewinding stranding process, according to the set pitch ratio sequence and stranding direction, stranding the single wires layer by layer around the center layer to form at least one outer layer; (4) during the stranding process, controlling the elongation coefficient of the single wires within the range of 1.04 to 1.07 by stretching with a die to optimize its mechanical properties and adapt to stranding deformation, while promoting the mutual meshing of the concave-convex mating structures; (5) performing a compaction process on the stranded conductor (such as by a roll forming die or a rotary forging die) to make its compaction coefficient reach not less than 0.97 and meet the specified outer diameter dimensions.

[0023] This method ensures stable mortise and tenon interlocking splicing of irregular single wires under moderate plastic deformation by precisely controlling the elongation coefficient, thus completely eliminating gaps within the layers.

[0024] 3. Beneficial effects

[0025] Compared with the prior art, the present invention has the following significant advantages:

[0026] (1) Significantly improved current carrying capacity and electrical performance: The hollow aluminum tube forms an efficient heat dissipation channel in the central layer. Combined with the high conductivity of copper, the gapless splicing achieved by the interlocking structure, and a high compression coefficient of not less than 0.97, the effective conductive cross section of the conductor is maximized, and the current distribution matches the skin effect characteristics, maximizing the material's effectiveness. Actual measurements show that, under the same operating conditions, the long-term allowable current carrying capacity of the conductor of this invention is 15% to 25% higher than that of traditional circular stranded compressed conductors of the same specification, and the AC resistance is reduced by more than 10%.

[0027] (2) Excellent heat dissipation efficiency and low operating temperature: The axial ventilation channel supports both natural convection and forced air cooling modes. Under forced air cooling, the conductor operating temperature can be reduced by 8℃~12℃, which significantly delays the thermal aging of the insulation material. Heat can be recovered through circulating gas, reflecting the concept of energy conservation and environmental protection.

[0028] (3) Excellent structural stability and mechanical strength: The concave-convex toothed splicing forms a three-dimensional mechanical interlock, which, combined with the internal stress balance generated by the reverse twisting of adjacent layers and the high compression coefficient, greatly suppresses the relative displacement, slippage and creep between single wires. The conductor has a compact overall structure, high tensile strength (tested to be more than 15% higher), and excellent bending and vibration resistance, making it particularly suitable for frequent bending or harsh vibration environments.

[0029] (4) Smooth and rounded surface quality: The non-twisting stranding and optimized pitch ratio design, combined with precise single wire shape and chamfering, make the outer surface of the conductor extremely smooth, with a surface roughness Ra of no more than 0.8μm (tested according to GB / T 10610). This not only reduces the skin effect and proximity effect of the current, but also effectively avoids insulation damage and improves the long-term operational reliability of the cable.

[0030] (5) Flexible design and wide application: It supports modular design of 1 to 4 layers. By adjusting the number of layers, the number of single wires and the size, it can flexibly cover a variety of standard cross sections from 120mm² to 400mm² and above, meet the requirements of national standards such as GB / T 3956 and GB / T 12706, and is suitable for power cables of various voltage levels from low voltage (0.6 / 1kV) to high voltage (such as 126kV). It has high practicality and promotion value. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the radial cross-sectional structure of the high heat dissipation aluminum core copper single-wire stranded conductor of the present invention.

[0032] Figure 2 This is a planar dimensioning diagram of a copper-type single-line (210) wire, clearly indicating the inner arc diameter (D). N ), outer arc diameter (D) W ), side angle (A), height (H), average width (W), and chamfer (R).

[0033] In the diagram: 100 - central layer (hollow aluminum tube), 200 - outer layer, 210 - copper type single wire. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that these embodiments are only for explaining the present invention and do not constitute a limitation on the scope of protection of the present invention. All equivalent transformations or improvements based on the technical concept of the present invention fall within the scope of protection of the present invention. Terminology: "Compression factor" = actual cross-sectional area of ​​the conductor / area of ​​the conductor's circumscribed circle; "Pitch ratio" = stranding pitch / outer diameter of the strand; "Extension factor" = length of a single wire after stranding / original length before stranding.

[0035] General manufacturing process: The manufacturing of the conductor of this invention mainly includes the following steps:

[0036] (1) Single wire preparation: According to the design cross section, the special-shaped copper single wire that meets the size requirements is processed by drawing die and forming roller, and the edges and corners are chamfered (R0.1mm~0.2mm).

[0037] (2) Core tube preparation: Cut aluminum tubes to a fixed length to serve as the core layer.

[0038] (3) Stranding: A non-reverse twisting frame stranding machine is used to strand the copper single wire layer by layer around the central aluminum tube according to the preset pitch ratio and stranding direction. During the stranding process, the elongation coefficient of the single wire is precisely controlled between 1.04 and 1.07 by adjusting the traction tension and the die to ensure that the single wire undergoes appropriate plastic deformation and achieves perfect meshing of the concave and convex tooth structure.

[0039] (4) Compacting: The stranded conductor is compacted by a roller pressing die or a rotary forging die to achieve the specified compaction coefficient (≥0.97) and outer diameter, and to ensure that the conductor is round and symmetrical.

[0040] Example 1: 120mm² conductor (suitable for low-voltage cables)

[0041] (1) Structure: Central aluminum tube (inner diameter 3.20mm, outer diameter 6.40mm) + 2 layers of copper single wires (12 wires in the inner layer, 18 wires in the outer layer). (2) Single wire parameters: Inner layer single wire included angle A=29.7°, height H=1.69mm, average width W=2.09mm; outer layer single wire A=19.8°, H=1.69mm, W=1.97mm. Chamfer R0.1mm, elongation coefficient controlled at 1.05. (3) Process: No untwisting stranding, inner layer pitch ratio 17 (right-hand), outer layer pitch ratio 27 (left-hand). (4) Performance: Compaction coefficient 0.978, DC resistance ≤0.153Ω / km at 20℃, surface roughness Ra≤0.8μm. Under ambient air laying at 40℃, the long-term allowable current carrying capacity is increased by about 16% compared with traditional conductors.

[0042] Example 2: 150mm² conductor (suitable for medium voltage cables)

[0043] (1) Structure: Central aluminum tube (inner diameter 3.50mm, outer diameter 7.10mm) + 2 layers of copper single wires (12 wires in the inner layer, 18 wires in the outer layer). (2) Single wire parameters: Inner layer H=1.87mm, W=2.32mm; Outer layer H=1.87mm, W=2.19mm. Elongation coefficient 1.05. (3) Process: Inner layer diameter ratio 19 (right-hand), outer layer diameter ratio 29 (left-hand). (4) Performance: Compaction coefficient 0.977, DC resistance ≤0.124Ω / km at 20℃. After passing a 72-hour 125% rated current cycling test, the conductor structure showed no deformation.

[0044] Example 3: 185mm² conductor (suitable for medium voltage cables)

[0045] (1) Structure: Central aluminum tube (inner diameter 3.50mm, outer diameter 7.10mm) + 2 layers of copper single wires (12 wires in the inner layer, 18 wires in the outer layer). (2) Single wire parameters: inner layer H=2.25mm, W=2.42mm; outer layer H=2.25mm, W=2.38mm. Elongation coefficient 1.06. (3) Process: inner layer diameter ratio 20 (right-hand), outer layer diameter ratio 30 (left-hand). (4) Performance: compression coefficient 0.982, DC resistance at 20℃ ≤0.0991Ω / km, tensile strength ≥200MPa.

[0046] Example 4: 240mm² conductor (suitable for high-voltage cables)

[0047] (1) Structure: Central aluminum tube (inner diameter 4.00mm, outer diameter 8.00mm) + 2 layers of copper single wires (15 wires in the inner layer, 21 wires in the outer layer). (2) Single wire parameters: Inner layer included angle A=23.76°, H=2.60mm, W=2.19mm; Outer layer A≈16.97°, H=2.60mm, W=2.33mm. Elongation coefficient 1.04. (3) Process: Inner layer diameter ratio 18 (right-hand), outer layer diameter ratio 28 (left-hand). (4) Performance: Compaction coefficient 0.976, DC resistance ≤0.0754Ω / km at 20℃. Under forced air cooling (wind speed 1m / s), the temperature rise is 8~10℃ lower than that of traditional conductors without air cooling.

[0048] Example 5: 300mm² conductor (suitable for high-voltage cables)

[0049] (1) Structure: Central aluminum tube (inner diameter 4.00mm, outer diameter 8.00mm) + 2 layers of copper single wires (15 wires in the inner layer, 21 wires in the outer layer). (2) Single wire parameters: Inner layer H=3.11mm, W=2.30mm; Outer layer H=3.11mm, W=2.55mm. Elongation coefficient 1.05. (3) Process: Inner layer diameter ratio 21 (right-hand), outer layer diameter ratio 31 (left-hand). (4) Performance: Compressibility coefficient 0.981, DC resistance ≤0.0601Ω / km at 20℃, passed rigorous bending-thermal cycle test.

[0050] Example 6: 400mm² conductor (suitable for high-capacity high-voltage cables)

[0051] (1) Structure: Central aluminum tube (inner diameter 5.00mm, outer diameter 9.00mm) + 3 layers of copper single wires (12 wires in the inner layer, 18 wires in the middle layer, and 24 wires in the outer layer). (2) Single wire parameters: The height of each of the three layers of single wires is H=2.36mm, and the widths are W=2.94mm (inner layer), 2.76mm (middle layer), and 2.68mm (outer layer), respectively. The elongation coefficient is 1.06. (3) Process: The pitch ratios are 19 (right-hand), 29 (left-hand), and 39 (right-hand). (4) Performance: The compression coefficient is 0.973, the DC resistance at 20℃ is ≤0.0470Ω / km, and the current carrying capacity and mechanical stability are outstanding.

[0052] The above embodiments fully verify the effectiveness and superiority of the technical solution of the present invention. Through the systematic synergy of hollow aluminum tube heat dissipation design, copper single-wire interlocking structure, and optimized stranding and pressing process, a stranded conductor with high heat dissipation, high current carrying capacity, and high stability has been successfully produced, which can meet the stringent requirements of cables of different voltage levels for conductors and has broad prospects for industrial application.

Claims

1. A stranded conductor, characterized in that, include: The central layer is a hollow metal tube; as well as At least one outer layer is formed by twisting together multiple irregularly shaped metal single wires; wherein, the sides of the irregularly shaped metal single wires are provided with a concave-convex mating structure that enables adjacent single wires to mesh with each other to restrict circumferential displacement.

2. The stranded conductor according to claim 1, characterized in that: The central layer is a hollow aluminum tube; the irregularly shaped metal wire is a copper wire; the outer layer includes 1 to 4 layers, each layer consisting of several copper wires of the same shape and size twisted and pressed into a circle.

3. The stranded conductor according to claim 2, characterized in that: The number of copper single wires in each layer is 4 to 6 more than that in the adjacent layers; the stranding direction of the adjacent layers is opposite; the pitch ratio of the outermost layer is 17 to 21, the pitch ratio of the adjacent layers increases by 8 to 12, and the maximum pitch ratio is not greater than 49.

4. The stranded conductor according to claim 2, characterized in that: The copper mold single wire has an irregular pentagonal tile-like structure; the concave-convex mating structure is a complementary concave-convex toothed splicing structure, with the apex of the tooth shape located on the central arc between the inner and outer arc sides of the copper mold single wire; the included angle of the tooth shape is 90°±2°.

5. The stranded conductor according to claim 4, characterized in that: The curvatures of the inner arc edge and the outer arc edge of the copper type single wire respectively match the inner diameter (D N ) and the outer diameter (D W ) of the preset circular ring; the included angle A between the two side edges of the copper type single wire satisfies A=K×360° / n, wherein the value range of K is 0.985 to 0.995, and n is the number of the layer of copper type single wires; a chamfer with a radius of 0.1mm to 0.2mm is arranged at the corner of the copper type single wire.

6. The stranded conductor according to claim 5, characterized in that: The height H of the copper mold single wire satisfies: H=(D W -D N )×1.01 / 2; The average width W of the copper mold single wire satisfies: W=π×(D W +D N )×0.99 / (2×n).

7. The stranded conductor according to claim 2, characterized in that: The compaction factor of the conductor is not less than 0.97, wherein the compaction factor is defined as the ratio of the actual metal cross-sectional area of ​​the conductor to the cross-sectional area of ​​its circumscribed circle.

8. A method for preparing a stranded conductor, characterized in that, Includes the following steps: (1) Provide a hollow metal tube as the central layer; (2) Provide multiple irregularly shaped metal single wires with concave-convex mating structures on the sides; (3) The irregular metal single wires are stranded around the periphery of the central layer using a non-returning twisting process to form at least one outer layer; (4) Among them, the extension coefficient of a single wire during the twisting process is controlled to be in the range of 1.04 to 1.

07.

9. The preparation method according to claim 8, characterized in that, Also includes: The stranded conductors are compacted to achieve a compaction coefficient of not less than 0.

97. The stranding process parameters are controlled so that the pitch ratio of the outermost layer is 17 to 21, the pitch ratio of adjacent layers increases by 8 to 12 and does not exceed 49, and the stranding directions of adjacent layers are opposite.

10. The preparation method according to claim 8, characterized in that: The central layer is a hollow aluminum tube; the irregular metal single wire is a copper single wire, and the concave-convex mating structure on its side is a complementary concave-convex tooth splicing structure; by controlling the extension coefficient and twisting parameters of the single wire, the concave-convex mating structures of adjacent single wires are interlocked to achieve gapless dense laying within the layer.

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