0.6~110kv hollow copper tube graphene composite cable

Abstract

The application discloses a 0.6kV-110kV high and low voltage general hollow copper tube graphene composite cable, which is characterized by systematic integration of mature materials and process systems and overall architecture innovation, and adopts hollow copper tube, silicone rubber support, graphene interface filling, layered insulation and integrated design of shielding structure to form a new overall architecture system.The cable comprises, from inside to outside, silicone rubber center filling, TP2 oxygen-free hollow copper tube conductor, graphene conductive composite layer, silicone rubber main insulation layer, 28 mu superimposed insulation layer, semi-conductive shielding layer and PVC outer sheath, and adopts three-core cabling for cables with a cross section of less than 150 square millimeters and single-core structure for cables with a cross section of more than 185 square millimeters.The matching connector adopts copper rod plug-in connection, graphene filling and silicone rubber integral injection molding process, which can save 43.3%-53.0% of copper materials, realizes low resistance, low partial discharge, high insulation, long-term sealing and long-term stable operation, and meets the needs of high-end power transmission and distribution engineering.

Description

Technical Field

[0002] 0001 This invention belongs to the field of power cable manufacturing technology, specifically relating to a high and low voltage universal composite cable with hollow copper tube conductor, graphene conductive composite, silicone rubber gradient insulation, nano-layered insulation, and cabled in different specifications. It is especially suitable for 0.6kV to 110kV transmission and distribution lines, and has the characteristics of large-scale production, standardized intermediate joint construction, and long-term stable operation. Background Technology

[0004] 0002 Traditional power cables generally use a solid copper core structure, which has problems such as high copper consumption, high cost, significant skin effect, poor heat dissipation of large cross-section conductors, and high joint temperature. Conventional hollow conductor cables have defects such as inconsistent structure, poor insulation matching, difficulty in implementing production processes, lack of standardized construction procedures for intermediate joints, and non-closed-loop data. At the same time, traditional cables have low dielectric strength of insulation layer, large partial discharge, and high joint failure rate, making it difficult to meet the requirements of long-distance, high-capacity, and high-reliability power transmission and distribution.

[0005] 0003 This invention achieves material savings, reduced consumption, and improved performance by superimposing and enhancing the overall architecture to form an integrated frame structure. It also systematically solves the above-mentioned industry pain points by combining a fixed structural system, unified dimensional parameters, segmented performance indicators, and mature production processes. At the same time, it is equipped with compatible construction processes to achieve high-performance, low-cost, and industrially feasible cable product design. Summary of the Invention

[0007] 0004 I. Overall Structural Design The core of this invention lies in the superposition and enhancement of the overall architecture to form an integrated frame structure. Through the coordinated cooperation of each functional layer and the closed-loop matching of parameters, it achieves material saving, consumption reduction and performance improvement. It is not a simple superposition of structures, but a systematic overall design.

[0008] 0005 The cable of this invention uses TP2 oxygen-free hollow copper tube as conductor. The conductor is densely filled with silicone rubber. The conductor is placed before the graphene layer. Graphene conductive composite layers are set on the inner and outer walls of the conductor. The outer side is sequentially set with a single-core silicone rubber main insulation layer, a 28μm superimposed insulation layer, a semi-conductive shielding layer, a three-core and multi-core cable structure, a tin-plated steel wire mesh braided shielding layer, and a polyvinyl chloride (PVC) outer sheath, forming a complete composite structure.

[0009] 0006 - ≤150mm² Specification: Three-core or multi-core cable structure, suitable for both high and low voltage applications. - ≥185mm² specification: Single-core independent structure, suitable for both high and low voltage applications. - High-voltage cable: includes a tin-plated steel wire braided shielding layer + a 28μm overlay insulation layer - Low-voltage cable: Excluding tinned steel wire braided shielding layer + 28μm superimposed insulation layer II. Specifications for 28μm Overlay Insulation Layer The 28μm superimposed insulation layer is a special composite structure for 6kV to 110kV high-voltage single-core cables of this invention. 28μm is the nominal value of the total thickness. It is composed of four layers of functional insulation materials stacked in sequence, and the total thickness is strictly controlled to be 28μm. This layer is not set in 0.6kV low-voltage cables, but is uniformly set in high-voltage cables.

[0010] 0007 The order of the four layers of material from the inside out: 1. Nano-alumina modified epoxy-silane coupling primer (7μm) 2. High-resistivity insulating tape made of nano-boron nitride (h-BN) (7μm) 3. Nano-carbon black-polyimide semiconductive gradient layer (7μm) 4. Nano-zirconia-fluororubber composite resistive layer (7μm) Hierarchical order from inside to outside: 1. TP2 oxygen-free hollow copper tube conductor + graphene conductive composite layer 2. Single-core wire core-level silicone rubber main insulation layer 3. 28μm stacked insulating layers (four layers of insulating film / tape composite) 4. Semiconducting shielding layer 5. Three-core / multi-core cabling / single-core structure 6. Tin-plated steel wire mesh braided shielding layer (high voltage) 7. PVC outer sheath III. Summary Table of Core Specifications, Structure, and Processes Table A 120mm² Single Core High Voltage 1. Inner cavity silicone rubber filling layer, A40 silicone rubber, densely filled. 2. Inner wall graphene conductive layer, graphene composite layer, 0.024mm 3. TP2 hollow copper tube conductor, TP2 oxygen-free copper, outer diameter 12.4mm, wall thickness 2.12mm 4. Outer wall graphene conductive layer, graphene composite layer, 0.024mm 5. Four layers of composite insulation, each with a thickness of 28μm, totaling 0.028mm. 6. Colored semiconductor shielding layer, semiconductive shielding material, 1.0mm 7. Interface coupling agent, cable-specific coupling agent, uniformly coated. 8. Silicone rubber main insulation layer, high-temperature vulcanized silicone rubber, 3.0mm 9. Interface coupling agent, cable-specific coupling agent, uniformly coated. 10. Alkali-free fiberglass cloth, fiberglass tape, 0.2mm 11. Tin-plated steel wire mesh armor, φ0.35mm steel wire, weaving density ≥90%. 12. PVC outer sheath, sheath material, 2.3mm Table B 120mm² Single Core Low Voltage 1. Inner cavity silicone rubber filling layer, A40 silicone rubber, densely filled. 2. Inner wall graphene conductive layer, graphene composite layer, 0.024mm 3. TP2 hollow copper tube conductor, TP2 oxygen-free copper, outer diameter 12.4mm, wall thickness 2.12mm 4. Outer wall graphene conductive layer, graphene composite layer, 0.024mm 5. Silicone rubber main insulation layer, high-temperature vulcanized silicone rubber, 3.0mm 6. Interface coupling agent, cable-specific coupling agent, uniformly coated. 7. Color separation tape, marking tape, 0.2mm 8. Alkali-free fiberglass cloth, fiberglass tape, 0.2mm 9. PVC outer sheath, sheath material, 2.3mm Table C 120mm² Three-core / Multi-core Parallel High Voltage 1. Inner cavity silicone rubber filling layer, A40 silicone rubber, densely filled. 2. Inner wall graphene conductive layer, graphene composite layer, 0.024mm 3. TP2 hollow copper tube conductor, TP2 oxygen-free copper, outer diameter 12.4mm, wall thickness 2.12mm 4. Outer wall graphene conductive layer, graphene composite layer, 0.024mm 5. Four layers of composite insulation, each with a thickness of 28μm, totaling 0.028mm. 6. Colored semiconductor shielding layer, semiconductive shielding material, 1.0mm 7. Silicone rubber main insulation layer, high-temperature vulcanized silicone rubber, 3.0mm 8. Interface coupling agent, cable-specific coupling agent, uniformly coated. 9. Alkali-free fiberglass cloth, fiberglass tape, 0.2mm 10. Three cores in equilateral triangles are joined together to form a cable, arranged symmetrically with a gap of 5.8mm. 11. Secure the fiberglass cloth loosely and tightly. 12. One-piece silicone rubber filling molding, dense and gapless. 13. Alkali-free fiberglass cloth, reinforced wrapping, 0.2mm 14. Tin-plated steel wire mesh armor, φ0.35mm steel wire, weaving density ≥90%. 15. PVC outer sheath, sheath material, 2.3mm Table D 120mm² Three-core / Multi-core Parallel Low Voltage 1. Inner cavity silicone rubber filling layer, A40 silicone rubber, densely filled. 2. Inner wall graphene conductive layer, graphene composite layer, 0.024mm 3. TP2 hollow copper tube conductor, TP2 oxygen-free copper, outer diameter 12.4mm, wall thickness 2.12mm 4. Outer wall graphene conductive layer, graphene composite layer, 0.024mm 5. Silicone rubber main insulation layer, high-temperature vulcanized silicone rubber, 3.0mm 6. Interface coupling agent, cable-specific coupling agent, uniformly coated. 7. Color separation tape, marking tape, 0.2mm 8. Alkali-free fiberglass cloth, fiberglass tape, 0.2mm 9. Three cores in equilateral triangles are joined together to form a cable, arranged symmetrically with a gap of 5.8mm. 10. Secure the fiberglass cloth loosely and tightly. 11. One-piece silicone rubber filling molding, dense and gapless. 12. Alkali-free fiberglass cloth, reinforced wrapping, 0.2mm 13. PVC outer sheath, sheath material, 2.3mm Table E 185mm² Single Core High Voltage 1. Inner cavity silicone rubber filling layer, A40 silicone rubber, densely filled. 2. Inner wall graphene conductive layer, graphene composite layer, 0.028mm 3. TP2 hollow copper tube conductor, TP2 oxygen-free copper, outer diameter 15.4mm, wall thickness 2.63mm 4. Outer wall graphene conductive layer, graphene composite layer, 0.028mm 5. Four layers of composite insulation, each with a thickness of 28μm, totaling 0.028mm. 6. Colored semiconductor shielding layer, semiconductive shielding material, 1.0mm 7. Interface coupling agent, cable-specific coupling agent, uniformly coated. 8. Silicone rubber main insulation layer, high-temperature vulcanized silicone rubber, 4.0mm 9. Interface coupling agent, cable-specific coupling agent, uniformly coated. 10. Alkali-free fiberglass cloth, fiberglass tape, 0.2mm 11. Tin-plated steel wire mesh armor, φ0.35mm steel wire, weaving density ≥90%. 12. PVC outer sheath, sheath material, 2.3mm Table F 185mm² Single Core Low Voltage 1. Inner cavity silicone rubber filling layer, A40 silicone rubber, densely filled. 2. Inner wall graphene conductive layer, graphene composite layer, 0.028mm 3. TP2 hollow copper tube conductor, TP2 oxygen-free copper, outer diameter 15.4mm, wall thickness 2.63mm 4. Outer wall graphene conductive layer, graphene composite layer, 0.028mm 5. Silicone rubber main insulation layer, high-temperature vulcanized silicone rubber, 4.0mm 6. Interface coupling agent, cable-specific coupling agent, uniformly coated. 7. Color separation tape, marking tape, 0.2mm 8. Alkali-free fiberglass cloth, fiberglass tape, 0.2mm 9. PVC outer sheath, sheath material, 2.3mm IV. Key Parameter Table Table 1. Full Specifications and Dimensions of Hollow Copper Tubes Nominal cross-section copper tube outer diameter (mm) Wall thickness (mm) Inner diameter (mm) Copper material saving rate 25mm² 7.0±0.1 1.23±0.05 4.54±0.15 43.3% 35mm² 7.6±0.1 1.30±0.05 5.00±0.15 43.5% 50mm² 8.0±0.1 1.37±0.05 5.26±0.15 44.8% 70mm² 9.2±0.1 1.54±0.05 6.12±0.15 44.2% 95mm² 10.5±0.1 1.72±0.05 7.06±0.15 44.5% 120mm² 12.4±0.15 2.12±0.08 8.17±0.20 45.0% 150mm² 13.8±0.15 2.36±0.08 9.08±0.20 45.0% 185mm² 15.4±0.15 2.63±0.08 10.14±0.20 44.5% 240mm² 17.6±0.15 3.00±0.1 11.60±0.20 48.5% 300mm² 19.8±0.20 3.30±0.1 13.20±0.25 49.5% 400mm² 22.6±0.20 3.70±0.1 15.20±0.30 50.5% 500mm² 25.3±0.20 4.10±0.1 17.10±0.30 51.5% 630mm² 28.5±0.25 4.60±0.1 19.30±0.35 52.0% 800mm² 32.1±0.25 5.20±0.1 21.70±0.40 52.5% 1000mm² 35.8±0.30 5.80±0.1 24.20±0.40 53.0% 1200mm² 39.4±0.30 6.50±0.1 26.40±0.45 53.0% 1400mm² 42.5±0.30 7.00±0.1 28.50±0.50 53.0% 1600mm² 45.2±0.30 7.50±0.1 30.20±0.50 53.0% Table 2 Thickness parameters of graphene conductive composite layer Serial Number | Specification Range (mm²) | Graphene on Inner Wall of Copper Tube | Graphene on Outer Wall of Copper Tube 1 25~70 0.020mm 0.020mm 2 95~150 0.024mm 0.024mm 3 185~300 0.028mm 0.028mm 4 400~630 0.032mm 0.032mm 5 800~1600 0.036mm 0.036mm Table 3. Main Insulation Parameters of Single-Core Silicone Rubber Serial Number No. Nominal Cross-Section Range Insulation Thickness Shore Hardness 1 25~95mm² 2.0mm A45~A50 2 120~150mm² 3.0mm A45~A50 3 185mm² 4.0mm A55~A60 4 240~300mm² 5.0mm A55~A60 5 400~500mm² 6.0mm A55~A60 6 630~1600mm² 7.5mm A55~A60 Table 4. Parameters of Outer Silicone Rubber Insulation for Three-Core Cables Serial Number No. Nominal Cross-Section Range Insulation Thickness Shore Hardness 1 25~95mm² 1.8mm A50~A55 2 120mm² 2.5mm A50~A55 3 150mm² 3.5mm A50~A55 Table 5. Classification of High-Voltage Tinned Steel Wire Mesh Braided Shielding Layers Specification range (mm²) Wire diameter Braiding density 25~70 φ0.30mm ≥90% 95~150 φ0.35mm ≥90% 185~300 φ0.35mm ≥90% 400~630 φ0.40~0.50mm ≥90% 630~1600 φ0.65mm ≥90% V. Production Process Flow (Main Line, Core Inventions, Detailed and Complete Version) 1. Hollow conductor pretreatment: The TP2 oxygen-free copper hollow copper tube conductor is pretreated by cleaning, degreasing and drying before production. This thoroughly removes oil, oxide layer, dust and impurities from the conductor surface, ensuring that the conductor surface cleanliness meets the requirements of subsequent coating, extrusion and vulcanization, and ensuring that the bonding between each structural layer is firm, without delamination or bubbles.

[0011] 2. Extrusion molding of the central support layer: A silicone rubber central filling layer is extruded inside the hollow copper tube conductor and cured by high-temperature vulcanization to form a continuous, dense, and gapless internal rigid support structure. This ensures that the conductor does not flatten, deform, bend, or crack during processing, stranding into cables, transportation, laying, and long-term operation, thus guaranteeing the overall roundness and structural stability of the cable.

[0012] 3. Preparation of graphene conductive composite layer: Graphene conductive composite slurry is uniformly coated on the inner and outer walls of the TP2 oxygen-free hollow copper tube conductor. The coating process ensures uniform thickness, full coverage, no missed coating, and no accumulation. After coating, it is sintered at low temperature to form a graphene conductive functional layer that is firmly bonded to the conductor, has continuous conductivity, and is corrosion-resistant. The thickness strictly follows the parameters in Table 2.

[0013] 4. Co-extrusion of insulation and shielding system: Co-extrusion is carried out from the inside out in sequence: single core-level silicone rubber main insulation layer, 28μm nano composite superimposed insulation layer (high voltage special), and outer semi-conductive shielding layer. Each layer is extruded synchronously, with tight bonding at the interface, no delamination, no air gaps, and no gaps, ensuring the overall electrical performance of the insulation system is stable.

[0014] 5. Insulation reinforcement and isolation layer fabrication: Wrapping with alkali-free fiberglass tape achieves mechanical reinforcement of the insulation layer, stable control of its shape and size, and electrical isolation between layers, preventing displacement, wear or electrical breakdown between functional layers, and improving the overall mechanical strength and insulation reliability of the cable.

[0015] 6. Single-core cable forming: After processes such as buffer layer longitudinal wrapping, outer diameter shaping, and appearance finishing, the single-core cable body is manufactured to ensure that the single-core cable has a round shape, uniform size, and smooth surface.

[0016] 7. Three-core and multi-core cable assembly: Three qualified single-core cables are twisted into a cable in a symmetrical structure. The gaps between the cable cores are filled with special fillers to ensure the overall roundness of the cable. The cable core structure is fixed by wrapping with cable wrapping tape to prevent the cable core from loosening, shifting, or deforming.

[0017] 8. Tin-plated steel wire mesh braided shielding layer fabrication (high voltage only): Apply a tin-plated steel wire mesh braided shielding layer to high voltage cables. Select the wire diameter according to the parameters in Table 5. The braiding density should be ≥90% to improve the mechanical protection performance and electromagnetic shielding performance of the cable. This layer is not installed for low voltage cables.

[0018] 9. Outer sheath extrusion molding: Extruding polyvinyl chloride (PVC) outer sheath with uniform thickness, smooth surface, no scratches, and no bubbles, completing the overall cable structure fabrication.

[0019] 10. Finished product inspection: The finished cables are tested for all items including structural dimensions, power frequency withstand voltage, partial discharge, conductor DC resistance, mechanical properties, and sealing performance. Only after all indicators meet the design and national standard requirements can the cables be shipped out of the factory.

[0020] VI. Specific Production Examples Example 1: Production of 25mm² Three-Core High-Voltage Cable Example 2: Production of 185mm² Single-Core High-Voltage Cable Example 3: Production of 120mm² Three-Core Low-Voltage Cable VII. Production Process Details 1. Laying out and straightening: Laying out and straightening TP2 oxygen-free hollow copper tubes, conductor roundness ≥95%.

[0021] 2. Internal filler extrusion: The silicone rubber central filler layer is extruded, with a vulcanization temperature of 160-180℃, resulting in a dense and void-free product.

[0022] 3. Graphene coating: Coating at room temperature, sintering at high temperature, and the thickness must be strictly in accordance with Table 2.

[0023] 4. Main insulation extrusion: silicone rubber vulcanization molding, the thickness and Shore hardness shall be strictly in accordance with Table 3 and Table 4.

[0024] 5. Overlay insulation molding: Four layers of functional materials are composited, with the total thickness strictly controlled at 28μm.

[0025] 6. Cable forming / single core shaping: Three cores are symmetrically twisted, and the outer diameter of each core is shaped with a dimensional deviation of ≤ ±0.1mm.

[0026] 7. Shielding layer braiding: The high-voltage cable shall be braided according to the parameters in Table 5, with a density of ≥90%, and no broken wires or missing braids.

[0027] 8. Outer sheath extrusion: The PVC sheath is extruded uniformly, with no surface defects and the thickness meets the design requirements.

[0028] 9. Finished product inspection: After all items pass the inspection, the product is coded, coiled, packaged and put into storage.

[0029] VIII. Supporting Construction Techniques (Secondary Line - Application Adaptation) 8.1 Construction process of intermediate joint (general for high and low voltage, 15 steps) 1. Cable Stripping: Sequentially peel off the outer sheath, tinned steel wire braided shielding layer, and insulation layer of the cable to expose the internal TP2 hollow copper tube. Thoroughly clean any remaining filler adhesive and impurities from the inner and outer walls of the copper tube. 50mm of the TP2 hollow copper tube is stripped from each end, for a total of 100mm exposed, with a length deviation of ±1mm. The stripped area should be smooth and undamaged, with no broken strands or scratches on the conductor, meeting the requirements of GB / T 12706 cable manufacturing standards.

[0030] 2. Insulation Interface and Surface Treatment: The outer wall of the hollow copper tube is lightly polished, and the inner wall is thoroughly cleaned. The outer insulation interface layer of the TP2 copper tube is treated to ensure that there is no glue, oil, or oxidation impurities inside or outside the copper tube. The polishing length is 45mm, using 800-1200 grit sandpaper; the surface roughness Ra≤0.8μm, the insulation layer is undamaged, and it meets the interface treatment standards for high-voltage cable joints.

[0031] 3. Graphene Coating (Copper Tubes and Rods): A graphene conductive and anti-corrosion composite layer is uniformly coated on the inner and outer walls of TP2 hollow copper tubes, and the entire surface of solid copper rods is simultaneously coated with the same layer. The coating is uniform and continuous, with complete coverage and no missed areas or accumulation; the surface resistivity of the coating is ≤1×10⁻ 4 The contact resistance is Ω·cm, which meets the requirements.

[0032] 4. Pre-installation of the outer copper bushing: Pre-install the outer copper bushing onto one side of the cable and place it in a suitable position for later use. The outer copper bushing is 80mm long and 1.5mm thick; the dimensional accuracy conforms to the requirements of GB / T 1431 conductor connectors.

[0033] 5. Conductor alignment and butt joint: Align the graphene-coated solid copper rod with the hollow copper tubes on both sides coaxially to complete the centering and butt joint. The solid copper rod is 90mm long, and the coaxiality deviation of the butt joint is ≤0.1mm; the coaxiality of the butt joint is qualified and meets the coaxiality standard for conductor connection.

[0034] 6. Graphene Touch-up Coating in the Docking Area: After the conductors are docked, a layer of graphene conductive and anti-corrosion composite layer is applied to the entire outer surface of the docking area. The docking area is 100% covered, the coating is continuous, the conductive path is continuous and reliable, and there is no risk of electro-corrosion.

[0035] 7. Positioning the outer copper sleeve: Pull the pre-installed outer copper sleeve to the mating area, centering it completely with gaps at both ends. Leave a 5mm gap at each end of the outer copper sleeve, with a centering deviation ≤1mm; ensure accurate positioning, uniform stress in the crimping area, and compliance with joint structure requirements.

[0036] 8. Crimping of the outer copper sleeve: Crim the outer copper sleeve in a centered position to ensure a firm conductor connection and continuous conductivity. The crimping should be in place, without loosening or deformation; the DC resistance of the joint should be ≤1.0 times the resistance of a conductor of the same cross-section (national standard ≤1.1 times).

[0037] 9. Surface treatment after crimping: Remove burrs and sharp edges from the crimped area, smooth and clean it. The surface should be smooth, without sharp edges, metal debris, or dust residue; there should be no risk of tip discharge, and the partial discharge amount should be ≤5pC, meeting national standards.

[0038] 10. High-voltage insulation tape wrapping: High-elasticity high-voltage insulation tape is used for uniform and sealed wrapping at the joints. The insulation tape is tightly and flat, with a 50% overlap between layers; it withstands a power frequency withstand voltage of 3.5U0 / 1min without breakdown, and the insulation strength meets operational requirements.

[0039] 11. Single-core insulation injection molding: Insulation injection is performed on the single-core joint area to restore the main insulation structure of the single-core wire. The injection is dense, without air bubbles or voids; the curing rate of the adhesive is ≥95%, the bonding strength is ≥1.5MPa, and the insulation performance is qualified.

[0040] 12. Three-core arrangement and point binding fixation: Arrange the three cores smoothly and secure them with binding tape. The three cores should be neatly arranged and firmly bound; the roundness of the three cores should be ≥95%, and the structural stability should meet the requirements.

[0041] 13. Integrated Injection Molding: Integrated injection molding is used for three-core and multi-core cables to restore their overall shape and structure. The filling is dense and seamless, without gaps or defects; the overall seal is reliable, and the waterproof, anti-fouling, and anti-aging properties meet standards.

[0042] 14. Restoration of Tin-plated Steel Wire Mesh Braided Shielding Layer: Straighten and smooth the existing tin-plated steel wire mesh braided shielding layer at both ends of the cable, and then overlap and butt-joint it flat. After butt-jointing, add an additional independent layer of tin-plated steel wire mesh for overall reinforcement. After smoothing the wrapping, use elastic self-locking steel straps for binding and fixing, evenly locking three fixing points in the binding area. The binding and wrapping width is 80-100mm, and the elastic self-locking steel straps fix three points; the shielding layer transition resistance is ≤0.1Ω, electrical continuity is continuous without breaks, and mechanical connections are firm and secure.

[0043] 15. Outer Sheath Restoration: Three layers of high-voltage insulating tape are wrapped around the outer sheath, and heat shrink tubing is used for sealing and protection. Both ends are overlapped to the outside of the original outer sheath. Protection rating: IP67; no water ingress at a depth of 1m for 24 hours; sealing performance is qualified.

[0044] 8.2 Completion Inspection / Experimental Data of Intermediate Joints (Revised Specification) 1. Conductor DC resistance: ≤0.95 times the body resistance (qualified) 2. Partial discharge level: ≤5pC (qualified) 3. Power frequency withstand voltage: 3.5U0 / 1min without breakdown (qualified) 4. Insulation resistance: ≥1000MΩ (Pass) 5. Shielding transition resistance: ≤0.1Ω (Pass) 6. Sealing test: No leakage at a water depth of 1m for 24 hours (passes) IX. Complete Construction Procedure for 120mm² High-Voltage Cable Termination Heads (National Standard Version - Final Draft) (Includes: Performance self-test form) I. Construction Preparation (in accordance with GB 50168 Cable Line Construction Specification) Tools prepared: circumferential cutter, wire strippers, 1200-grit wet sandpaper, anhydrous ethanol, cleaning non-woven cloth, 120mm² special crimping pliers, heat gun, torque wrench (0–50 N·m, calibrated and qualified); Materials are ready: 15mm inner clamp without ear, 15mm outer clamp with double ear, 40mm×4mm copper busbar, M12 bolt + flat washer + spring washer, high-voltage self-adhesive insulating tape, high-voltage self-adhesive waterproof tape, PVC tape, conductive graphene (hand-applied type), heat shrink tubing, 35kV cold shrink insulating tubing, high-voltage automatic spring shrink insulating tape, outer protective tape; All standard parts are available: - Copper tube (outer diameter φ12.4mm / wall thickness 2.12mm / inner diameter φ8.16mm / length 56mm) - Copper rod (diameter φ7.94mm / length 56mm) - 120mm² copper lug (inner hollow φ12.18mm, inner hollow length 56mm, total length 116mm) Cables are fixed vertically, with ends aligned, and surfaces cleaned of oil and dust. Safety precautions are in place, and the operation must comply with national standards for safe operation.

[0045] 0042 II. Outer Sheath Stripping (according to national standard dimensions and processes) Make a circumferential cut mark 600mm from the cable end, and cut the outer sheath along the mark (to a depth of 2 / 3 of the sheath thickness). After making a light longitudinal cut, peel off 600mm of the entire sheath. The cut should be smooth, burr-free, and without scratching the internal steel wire mesh shielding. Lightly wrap one round of PVC tape around the shielding cut to position it and prevent displacement during subsequent operations. This meets the national standard for stripping requirements.

[0046] 0043 III. Stripping and finishing of wire mesh shielding (in accordance with national standard shielding treatment specifications) Make a shielding ring cut mark 70mm forward from the 600mm sheath cut (530mm from the end). Cut the wire mesh shielding along the mark and peel off 530mm of the shielding layer backward, leaving only the front 70mm of shielding. Tightly wrap the end of the shielding with PVC tape for 2 turns to completely prevent loose threads from curling up and scratching the subsequent insulation layer. Make a mark at the midpoint of the 70mm shielding (505mm from the end). Lightly sand the shielding surface at this position and 10mm on both sides with 1200-grit sandpaper to remove the oxide layer and increase the clamping friction, which meets the national standard shielding treatment requirements.

[0047] 0044 IV. S-shaped folding and double clamp fixing of the shielding layer (in accordance with national standard grounding structure specifications) Install a 15mm inner clamp without ears at the midpoint mark of the shield, tighten it evenly with pliers, and fix it to the main insulation without slipping or damaging the shield; fold the shield upwards from the inner clamp into an S-shape, smoothly adhering to the surface of the insulation layer, with a fold length of about 30mm, without wrinkles, sharp corners, or looseness; on the outside of the folded shield, install a 15mm outer clamp with double ears coaxially with the inner clamp, with the grounding ears facing outwards, and tighten it evenly so that the inner and outer clamps clamp the shield layer tightly, without loosening or breaking the shield wires, meeting the national standard requirements for shield fixing and grounding lead-out.

[0048] 0045 V. Shielding Grounding Connection and Insulation Covering (in accordance with national standard grounding and insulation specifications) Align the grounding lugs of the three-phase external clamps with 40mm×4mm copper busbars, insert M12 bolts + flat washers + spring washers, and tighten with a torque wrench to 30–35 N·m; connect the other end of the copper busbars to the field grounding trunk line to complete the shielding grounding, without short-circuiting with the steel armor; wrap the shielding and clamp area with 3–4 layers of high-voltage self-adhesive insulating tape in a semi-overlapping manner, covering the clamps, copper busbar joints and shielding folds, and then wrap the outer layer with 2 layers of PVC tape for fixation, forming insulation isolation to prevent interference from subsequent conductor processes. The shielding is now complete, meeting the national standard requirements for grounding and insulation wrapping.

[0049] 0046 VI. Main insulation stripping and copper tube exposure (in accordance with national standard main insulation treatment specifications) Mark the main insulation ring cut 56mm forward from the cable end. Cut the main insulation ring along the mark, and after peeling, expose 56mm of copper tubing. Use a knife to make a 2mm×45° chamfer on the insulation cut, remove burrs, and lightly grind the chamfer with 1200-grit sandpaper to prevent scratching the copper lug. Check that the surface of the copper tubing is free of scratches and damage, and that the dimensions meet the requirements of φ12.4mm outer diameter and φ8.16mm inner diameter, which meets the national standard requirements for main insulation stripping and chamfering.

[0050] 0047 VII. Cleaning of Copper Tubes and Rods (in accordance with national standard conductor cleaning specifications) Lightly sand the outer wall of the copper tube with 1200-grit wet sandpaper for 1-2 rounds to completely remove the surface nano-insulation layer and expose the fresh copper surface; use anhydrous ethanol to apply a cleaning non-woven cloth to repeatedly wipe the inner and outer walls of the copper tube and the entire surface of the copper rod to remove dust, oil, and debris, and let it air dry naturally until there is no moisture or residue. The inner wall of the copper tube should only be cleaned without sanding to maintain its original dimensions and smoothness, which meets the national standard for conductor cleaning requirements.

[0051] 0048 VIII. Hand-coated graphene conductive layer (specific process, according to uniform filling requirements) Take conductive graphene (hand-applied type) and apply it evenly by hand using non-woven fabric or gloves: ① Apply a thin coating to the entire inner wall of the copper tube, filling the 0.11mm gap on one side with the copper rod; ② Apply a thin coating to the entire outer wall of the copper tube, filling the 0.11mm gap on one side with the copper lug; ③ Apply the coating to the entire surface of the copper rod and the inner wall of the copper lug, controlling the thickness of the filling on one side to 0.10–0.15mm; After application, let it stand for 1–2 minutes to ensure there are no missed areas, no accumulation, no dripping, and that the conductive layer is continuous and complete, meeting the requirements for uniform filling.

[0052] 0049 IX. Assembly and crimping of the three-piece sandwich set (according to national standard crimping specifications) Slowly insert the graphene-coated copper rod into the copper tube, reaching the root, ensuring the gaps are completely filled with graphene without any gaps or voids; fit the graphene-coated copper lug onto the outer wall of the copper tube, pushing it to the root, ensuring the end face is flush with the copper tube and the three parts are coaxial without any skewing; use a 120mm² special pressure clamp to evenly press three points along the length of the copper lug, with consistent indentation spacing, stopping as soon as the parts are in place, ensuring the copper tube does not flatten or crack, and that the three parts are pressed firmly into one piece, with reliable conductivity and no loose connections, meeting the national standard crimping process requirements.

[0053] 0050 X. End waterproof sealing (in accordance with national standard waterproof sealing specifications) The crimping area and the tail of the copper lug are stretched to 2 / 3 of their original width with high-pressure self-adhesive waterproof tape. 5-8 layers are wrapped in a semi-overlapping manner from the copper lug port towards the main insulation direction, covering the entire crimping area and extending more than 30mm into the insulation layer, without gaps, wrinkles, or breaks. Two layers of PVC insulating tape are wrapped around the outer layer for fixation, preventing the waterproof layer from shifting, lifting, or falling off, ensuring long-term waterproof sealing, and meeting national standard waterproof sealing requirements.

[0054] 0051 XI. Installation of heat shrink tubing (in accordance with national standard heat shrink process specifications) Heat shrink tubing is applied to the waterproof sealing section. A hot air gun is used to heat the tubing evenly from the middle to both ends, causing it to shrink fully and tightly wrap the waterproof layer without bubbles, looseness, or wrinkles. This provides a flat and firm base for the subsequent cold shrink insulation tubing, meeting the national standard requirements for heat shrinking processes.

[0055] 0052 XII. Installation of 35kV cold-shrink insulation tubing (in accordance with national high-voltage insulation specifications) Slowly stretch the 35kV cold-shrink insulation tube from the cable end to the 600mm outer sheath cut, overlapping it with the outer sheath by 20mm to ensure full coverage of the stripped section; remove the internal support strip to allow the cold-shrink tube to shrink naturally and evenly, fitting tightly without any exposed areas, wrinkles, or gaps, seamlessly connecting with the previously shielded insulation area, restoring the high-voltage insulation completely, and meeting the national standard requirements for high-voltage insulation installation.

[0056] 0053 XIII. Overall Insulation Reinforcement and Outer Sheath Finishing (in accordance with national standard outer sheath specifications) The cold shrink tubing is then wrapped with 4-6 layers of high-voltage automatic retractable insulating tape in a semi-overlapping manner to enhance the high-voltage insulation performance, ensuring no breaks or weak points. Finally, outer sheath tape is wrapped neatly and semi-overlappingly along the entire length from the copper lug end to the 600mm outer sheath cut, covering the cable smoothly, evenly, without steps or exposed areas, restoring the overall cable shape, and ensuring a neat and standardized appearance that meets the national standard requirements for outer sheath finishing.

[0057] 0054 XIV. Copper Lug Wiring and Final Tightening (in accordance with national standard wiring specifications) Clean the oxide layer and debris in the connection hole of the copper nose to ensure the contact surface is clean; insert the matching terminal or busbar, and align the mounting holes; use M12 bolts + flat washers + spring washers, and tighten with a torque wrench to 35–40 N·m to ensure tight contact, reliable conduction, no looseness, and no virtual connection, meeting the national standard wiring and tightening requirements.

[0058] 0055 XV. Final overall inspection and closed-loop acceptance (in accordance with national standard acceptance specifications) Comprehensive item-by-item inspection: ① The shielding closing is complete without loose wires, the grounding connection is reliable and the torque meets the standard; ② The graphene coating is uniform, the gap is filled, and the conduction is continuous; ③ The crimping is firm without deformation or cracks; ④ The waterproof seal is complete without leakage; ⑤ There is no exposed high-voltage insulation and no weak points; ⑥ The appearance is round without steps or burrs; ⑦ The wiring is tightened and the conduction is reliable; all items are qualified, and the entire set of terminal head processes are all completed in a closed loop, meeting the national standard construction and acceptance specifications, and can be directly put into operation.

[0059] 0056 Attachment: Performance self-inspection form for 120 mm² high-voltage cable terminal head (revised version · unified specifications) I. Core structure and dimension inspection Inspection items Design parameters Self-inspection results Judgment Diameter of copper rod φ7.94 mm Qualified Qualified Length of copper rod 56 mm Qualified Qualified Inner diameter of copper tube φ8.16 mm Qualified Qualified Outer diameter of copper tube φ12.4 mm Qualified Qualified Length of copper tube 56 mm Qualified Qualified Inner hole of copper nose φ12.18 mm Qualified Qualified Length of inner hole of copper nose 56 mm Qualified Qualified Single-sided gap between copper rod and copper tube 0.11 mm Qualified Qualified Single-sided gap between copper tube and copper nose 0.11 mm Qualified Qualified Graphene filling thickness 0.10–0.15 mm Qualified Qualified II. Conductive performance inspection Inspection items National standard requirements Self-inspection results (theory) Judgment Contact resistance ≤10 μΩ ≤5 μΩ Qualified (better than national standard) Electrical continuity Conductive without breakpoints 100% conductive Qualified III. Grounding performance inspection Inspection items National standard requirements Self-inspection results (theory) Judgment Grounding resistance ≤4 Ω ≤0.5 Ω Qualified (better than national standard) The shielding is continuous, without breaks or sharp corners, and is in good condition. IV. Insulation Performance Testing The national standard requires self-test results (theoretical) for the following testing items: Judgment Power frequency withstand voltage (35kV class): 42kV / 1min without breakdown; 42kV / 1min pass / fail. Overall insulation resistance ≥1000MΩ ≥1000MΩ Pass V. Sealing and Mechanical Protection Testing National standards for testing items require self-inspection result determination Waterproof sealing with no leakage is qualified. The mechanical strength of the crimping is qualified as long as there is no deformation or cracks. The outer protective layer is intact, with no exposed areas or steps, and meets the requirements. VI. Self-inspection of process flow Testing items require self-test result interpretation The construction sequence from outside to inside → pressing → protection from inside to outside is correct and qualified. The main processes conform to national standards and are qualified (compliant with GB 50168). Innovative structure embedded sandwich + graphene filling in place and qualified VII. Overall Conclusion The entire structure is dimensionally matched, the procedures are compliant, and all performance indicators meet the standards. Key performance indicators are superior to national standards, meet design requirements, and can be put into construction and operation.

[0060] 0057 Table 6 Performance Benchmark Table for Finished Products Compared with traditional solid copper cables, the finished cable of this invention improves performance. Copper usage is 100%, with a reduction of 47.0% to 56.7%, resulting in savings of 43.3% to 53.0%. Equivalent conductivity (IACS) at 100% IACS: 102%–107% IACS improvement of +2%–+7%. Insulation dielectric strength ≥28kV / mm ≥38kV / mm, increase by +35%. Partial discharge level ≤10pC ≤5pC: Reduced by 50% The connector contact resistance is ≤1.1 times that of the body and ≤0.95 times that of the body, resulting in a more stable connection. Joint temperature rise ≤10K ≤2K, reduced by 80%. Corrosion resistance levels are significantly improved from level 5 to 6, and level 9. Design lifespan extended by 50% to 20-30 years. The expected failure rate is ≤0.1 times / km·year or ≤0.01 times / km·year, a reduction of 90%. Beneficial effects

[0061] 0058 This invention achieves material savings, reduced consumption, and improved performance by superimposing and enhancing the overall architecture to form an integrated frame structure. At the same time, through unified structure, solidified parameters, mature production process, standardized terminal head construction, and closed-loop data throughout the entire process, it enables the large-scale production and engineering application of hollow copper tube cables. It has significant advantages in saving copper materials, improving conductivity, reducing temperature rise, improving insulation reliability, extending service life, and ensuring long-term stable operation of joints, and fully meets the requirements for high and low voltage power transmission and distribution.

Claims

1. A 0.6kV~110kV hollow copper tube graphene composite cable, characterized in that, The design employs an integrated, superimposed, and reinforced overall architecture to form a unified frame structure, achieving material savings, reduced consumption, and improved performance. From the inside out, it includes: a silicone rubber central filling layer, a TP2 oxygen-free hollow copper tube conductor, a graphene conductive composite layer on the inner wall of the copper tube, a graphene conductive composite layer on the outer wall of the copper tube, a single-core silicone rubber main insulation layer, a 28μm superimposed insulation layer, a semi-conductive shielding layer, a three-core / multi-core cable structure, a tin-plated steel wire braided shielding layer, and a polyvinyl chloride (PVC) outer sheath. With 150mm² as the dividing line, cables ≤150mm² are three-core / multi-core cable structures, while those ≥185mm² are single-core independent structures. High-voltage cables include a tin-plated steel wire braided shielding layer and a 28μm superimposed insulation layer, while low-voltage cables do not. All specifications are suitable for both high and low voltage applications.

2. The cable according to claim 1, characterized in that, The thickness of the graphene conductive composite layer is set in segments according to specifications: 0.020mm for 25-70mm², 0.024mm for 95-150mm², 0.028mm for 185-300mm², 0.032mm for 400-630mm², and 0.036mm for 800-1600mm², with the inner and outer wall thicknesses being consistent.

3. The cable according to claim 1, characterized in that, The 28μm superimposed insulation layer is a special structure for high-voltage single-core cables. It is composed of four layers of functional insulation materials, with a total thickness strictly controlled at 28μm. It is used uniformly across all specifications, regardless of voltage level or cross-sectional size. The four materials, from the inside out, are: nano-alumina modified epoxy-silane coupling primer, nano-boron nitride high-resistance insulation tape, nano-carbon black-polyimide semi-conductive gradient layer, and nano-zirconia-fluororubber composite resistive layer. Each layer is 7μm thick.

4. The cable according to claim 1, characterized in that, The main insulation parameters of single-core silicone rubber are as follows: 25-95mm² thickness 2.0mm, Shore hardness A45-A50; 120-150mm² thickness 3.0mm, Shore hardness A45-A50; 185mm² thickness 4.0mm, Shore hardness A55-A60; 240-300mm² thickness 5.0mm, Shore hardness A55-A60; 400-500mm² thickness 6.0mm, Shore hardness A55-A60; 630-1600mm² thickness 7.5mm, Shore hardness A55-A60.

5. The cable according to claim 1, characterized in that, The outer silicone rubber insulation parameters for three-core and multi-core cabling are as follows: 25-95mm² thickness 1.8mm, Shore hardness A50-A55; 120mm² thickness 2.5mm, Shore hardness A50-A55; 150mm² thickness 3.5mm, Shore hardness A50-A55.

6. The cable according to claim 1, characterized in that, The tinned steel wire mesh braided shielding layer of high-voltage cables uses tinned round steel wire, with the following specifications: 25-70mm² using φ0.30mm, 95-150mm² using φ0.35mm, 185-300mm² using φ0.35mm, 400-630mm² using φ0.40-0.50mm, and 630-1600mm² using φ0.65mm, with a braiding density ≥90%.

7. The cable according to claim 1, characterized in that, TP2 oxygen-free hollow copper tube conductors cover all specifications from 25 to 1600 mm², with a copper material saving rate of 43.3% to 53.0%. Dimensions, wall thickness, and inner diameter are implemented according to unified standards, and correspond one-to-one with insulation parameters, shielding parameters, and graphene parameters in a closed loop.

8. The cable according to claim 1, characterized in that, The finished product performance indicators are as follows: equivalent conductivity 102%~107%IACS, main insulation dielectric strength ≥38kV / mm, high voltage partial discharge ≤5pC, joint temperature rise ≤2K, joint failure rate ≤0.01 times / km·year, and design life of 30 years.

9. A method for producing the cable according to claim 1, characterized in that: The production process is as follows: silicone rubber filling inside hollow copper tube → graphene conductive composite layer coating and sintering → extrusion of single-core silicone rubber main insulation layer → forming of 28μm superimposed insulation layer → semi-conductive shielding and wrapping → three-core and multi-core cabling / single-core forming → tin-plated steel wire mesh braided shielding layer production → outer sheath extrusion; among which, after graphene coating, it is sintered under nitrogen protection at 160~180℃, and the silicone rubber vulcanization temperature is 160~180℃.

10. A method for constructing an intermediate joint of the cable according to claim 1, characterized in that: The construction process is as follows: cable stripping → interface treatment → coating of three-sided graphene conductive composite layer → copper connecting rod centering and insertion → copper connecting sleeve crimping → insulation delamination repair → restoration of tin-plated steel wire mesh braided shielding layer → overall sealing and performance testing. The data and structure of the whole process are completely matched in a closed loop. Among them, the coaxiality deviation between the copper connecting rod and the hollow copper tube is ≤0.1mm, and the DC resistance of the joint is ≤1.0 times the body resistance.