Cross-linked polyethylene insulated composite cable based on skin effect technology

Abstract

The invention discloses a crosslinked polyethylene insulated composite cable based on a skin effect technology, particularly relates to the technical field of electric power, and relates to the crosslinked polyethylene insulated composite cable based on the skin effect technology, which sequentially comprises an inner core conductor, an insulating layer protection layer and a welded pipe wrapping layer from inside to outside, the inner core conductor comprises the following components in parts by weight: 23.6-36.2 parts of an oxygen-free red copper wire and 0-2 parts of an optical cable; the insulating layer protective layer is prepared from the following components in parts by weight: 4.3 to 7.1 parts of low-melt-fat perfluoroplastic, 5.2 to 8.5 parts of enhanced low-melt-fat perfluoroplastic, 1.0 to 1.6 parts of two-way stretching modified polyester tape, 7.8 to 12.4 parts of high-tear-resistance silicon rubber, 1.8 to 2.9 parts of double-sided synthetic mica tape and 2.7 to 4.5 parts of filament alkali-free glass fiber; the welding pipe wrapping layer comprises the following components in parts by weight; 0-14.2 parts of a Q235 strip and 15 parts of crosslinked polyethylene; a multi-composite insulation structure is adopted, multiple materials are compounded to form a multi-layer barrier, external interference is blocked, molecular arrangement is optimized, insulation stability is remarkably improved, and high-voltage power transmission safety is guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and more particularly to a cross-linked polyethylene insulated composite cable based on skin effect technology. Background Art

[0002] With the continuous development of the power industry, the performance requirements for power cables are becoming increasingly higher. Cross-linked polyethylene insulated power cables have been widely used in power transmission due to their excellent electrical properties, high heat resistance and mechanical strength.

[0003] The power cable in the relevant technology is mainly composed of conductor, insulation layer, shielding layer and sheath; the conductor is the core of the cable and is used to conduct current. Copper, aluminum or alloy materials are commonly used; copper has good conductivity, high strength and corrosion resistance, and is used for medium and high-end cables; aluminum is light and low in cost, and is suitable for low-voltage or large-section transmission cables; alloys can optimize performance; the insulation layer can isolate the conductor, prevent leakage and short circuit, and provide mechanical protection. The materials include plastic, rubber, and PTFE; XLPE is resistant to high temperature and has high strength, and is the mainstream of medium and high voltage cables; PVC is low in cost and flame retardant, and is used for low-voltage cables; the shielding layer includes inner and outer shields. The inner shield uses semi-conductive material to fit tightly against the conductor to uniformly form the electric field. The outer shield consists of a semi-conductive layer plus a metal layer, which can uniformly form the electric field and resist interference. The metal layer can also serve as a short-circuit current channel; the sheath is used to protect the inside of the cable from mechanical damage, corrosion, water immersion, etc. The materials include PVC, PE, rubber, and metal; PVC is flame retardant and corrosion-resistant, and has low cost; the metal sheath has high sealing or strength and is suitable for special environments.

[0004] However, it still has some shortcomings in actual use, such as insufficient insulation performance, defects in the material chemical structure and environmental adaptability of traditional cables. Traditional cables use thermoplastic materials, and the molecular chains are arranged linearly. Molecular chains are prone to slippage under high temperature or electric field, resulting in a decrease in insulation resistance; its internal plasticizer will migrate and volatilize over time to form micropores, triggering local discharge and destroying insulation stability; poor temperature resistance. The poor temperature resistance of traditional cables is directly related to the thermal stability of their materials. The glass transition temperature of traditional cables is low. After exceeding this temperature, the activity of molecular chains increases, the material softens and deforms, and loses its insulation function; low mechanical strength is due to insufficient intrinsic properties and structural design of the material. Traditional cables use brittle polymer materials, which are prone to cracking at low temperatures and are prone to cracking when repeatedly bent or subjected to external force; they have poor creep resistance and are prone to permanent deformation after long-term stress. Summary of the Invention

[0005] In order to improve the above problems and reduce the problems of insufficient insulation performance, poor temperature resistance and low mechanical strength of power cables in related technologies, the present invention specially provides a cross-linked polyethylene insulated composite cable based on skin effect technology to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions: A cross-linked polyethylene insulated composite cable based on skin effect technology, which includes, from the inside out, an inner core conductor, an insulating layer, a protective layer, and a welded tube wrapping layer; The inner core conductor comprises the following components in parts by weight: 23.6-36.2 parts of oxygen-free copper wire and 0-2.0 parts of optical cable; The insulating layer protective layer comprises the following components in parts by weight: 4.3-7.1 parts of low-melting fat perfluoroplastic, 5.2-8.5 parts of reinforced low-melting fat perfluoroplastic, 1.0-1.6 parts of biaxially stretched modified polyester tape, 7.8-12.4 parts of high tear-resistant silicone rubber, 1.8-2.9 parts of double-sided synthetic mica tape and 2.7-4.5 parts of filament alkali-free glass fiber; The welded pipe wrapping layer comprises the following components in parts by weight: 0-14.2 parts of Q235 strip and 15 parts of cross-linked polyethylene.

[0007] Preferably, the steps for preparing the inner core conductor are as follows: S1. Use a 2.5mm diameter oxygen-free copper wire as the center. The first layer is 6 identical oxygen-free copper wires twisted clockwise at a pitch-to-diameter ratio of 12:1. The second layer is 12 identical oxygen-free copper wires twisted counterclockwise at a pitch-to-diameter ratio of 10:1. The third layer is 18 identical oxygen-free copper wires twisted clockwise at a pitch-to-diameter ratio of 12:1. The tension of each copper wire during twisting is controlled at 9N / strand. The outer diameter of the conductor after twisting is 14.8±0.1mm. This produces an inner core conductor. If an additional optical cable is required for the inner core conductor, a single-mode G.652D optical cable should be used. It should be placed in the gap between the center conductor and the first layer of twisted wires and fixed under a twisting tension of 10-12N to ensure that the optical cable is twisted synchronously with the conductor and is not damaged.

[0008] Preferably, the steps for preparing the insulating layer protective layer are as follows: S2. A single-screw extruder is used to place a low-melting fat perfluoroplastic in the extruder, and then extrusion is performed at an extrusion speed of 15 m / min, a pulling tension of 20 N, and an extrusion thickness of 1.0 ± 0.05 mm. During the extrusion, the temperature of each zone of the extruder is specifically 260-280° C. in the feeding section, 280-300° C. in the compression section, 300-320° C. in the homogenization section, and 310-330° C. in the die. After extrusion, the extrusion is heated and extruded at a melt flow rate of 5-10 g / 10 min, and then coated on the outer surface of the inner core conductor obtained in S1, and then cooled and shaped by circulating water at 20° C. to obtain an insulating layer protective layer 1. S3. On the outside of the insulating protective layer 1 obtained in S2, a reinforced low-melting fat perfluoroplastic is used for secondary extrusion through the same extruder, and the extrusion is carried out at an extrusion speed of 12 m / min, a pulling tension of 25 N, and an extrusion thickness of 1.2±0.08 mm. During the extrusion, the temperature of each zone of the extruder is specifically 270-290° C. in the feeding section, 290-310° C. in the compression section, 310-330° C. in the homogenizing section, and 320-340° C. in the die; after coating and cooling under the same conditions as S2, the insulating protective layer 2 is obtained; S4. The biaxially oriented modified polyester tape was wrapped on the insulating layer and protective layer 2 obtained in S3 by a wrapping machine in a left-hand overlapping manner, with a wrapping angle of 30°, an overlapping width of adjacent tapes of 1.5 mm, a wrapping tension of 8-12 N, and a wrapping speed of 18 m / min. The total thickness after wrapping was 0.225 mm, thereby obtaining an insulating layer and protective layer 3. S5. Place the high tear-resistant silicone rubber in an extruder and coat it on the insulating layer protective layer 3 obtained in S4 at an extrusion speed of 8 m / min, a pulling tension of 30 N, and an extrusion thickness of 2.5±0.1 mm. During this period, the extruder temperature settings are: 160-180° C. in the feeding section, 180-200° C. in the compression section, 200-220° C. in the homogenization section, and 210-230° C. in the die. After extrusion, enter a 15 m long vulcanization pipe and vulcanize at a temperature of 180-200° C. for 10-15 minutes to obtain the insulating layer protective layer 4. S6. Using a wrapping machine, wrap the double-sided synthetic mica tape over the insulating layer and protective layer 4 obtained in S5 in a right-hand overlapping manner, with a wrapping angle of 45°, an overlapping width of 2.0 mm for adjacent tapes, a wrapping tension of 3-5 N, and a wrapping speed of 10 m / min to obtain an insulating layer and protective layer 5. S7. The filament alkali-free glass fiber is braided on the insulating layer protective layer five obtained in S6 at a braiding angle of 50°, a spindle speed of 200 rpm, a braiding density of 85-95%, and a braiding tension of 2-4N. The thickness after braiding is 0.4 mm; then, the insulating layer protective layer six is obtained after degreasing at a high temperature of 500°C.

[0009] Preferably, the preparation steps of the welded pipe wrapping layer are as follows: S8. Use a Q235 strip with a thickness of 1mm and a width of 80mm, and roll it into a round tube with an inner diameter 3mm larger than the outer diameter of the cable by a tube reel. Weld it to the outside of the insulation layer protective layer obtained in S7 along the longitudinal direction with argon arc welding under the conditions of welding current 120-150A, voltage 18-22V, and speed 6-8mm / s. Then, convey the cross-linked polyethylene to the extruder hopper and convey it to the barrel through the screw at a speed of 18-22r / min; set the barrel temperature as 160℃ for zone 1, 175℃ for zone 2, 185℃ for zone 3, and 190℃ for zone 4, and the die temperature at 200℃. After the raw materials are fully melted and plasticized, the cable obtained in the above process is uniformly passed through the extruder die at a pulling speed of 15m / min. The inner diameter of the die is 2-3mm larger than the outer diameter of the cable. The cable is shaped and cooled by a vacuum sizing sleeve and a cooling water tank. Finally, a cross-linked polyethylene protective layer with a thickness of 0.8mm is extruded on the outermost layer of the cable to obtain a cross-linked polyethylene insulated composite cable based on skin effect technology.

[0010] Preferably, the purity of the oxygen-free copper wire is ≥99.97%, and the conductivity is ≥101% IACS.

[0011] Preferably, the single-mode G.652D optical cable has an outer diameter of 2.0 mm and contains two optical fibers and a Kevlar reinforcement core.

[0012] Preferably, the enhanced low-melting fat perfluoroplastic is specifically composed of low-melting fat perfluoroplastic and nano-SiO2 in a weight ratio of 2:98; The biaxially oriented modified polyester tape has a thickness of 0.075 mm, a tensile strength of 250 MPa, an elongation at break of 70%, and a surface treated with corona treatment; The high tear-resistant silicone rubber has a Shore hardness of 55A, a tensile strength of 10 MPa, and a tear strength of 30 kN / m; The double-sided synthetic mica tape is phlogopite, with a thickness of 0.15 mm, a temperature resistance of 1200°C / 1h and 1600°C / 5min, and a volume resistivity of 1×10¹³Ω・cm; The filament alkali-free glass fiber is specifically a filament alkali-free glass fiber with a single filament diameter of 9 μm and a breaking strength of 2200 MPa.

[0013] Technical effects and advantages of the present invention: The present invention adopts the principle of a multiple composite insulation structure, combining high-purity perfluoroplastic, modified polyester tape, high-temperature resistant silicone rubber and synthetic mica tape through precision extrusion and wrapping processes. Utilizing the material's own close molecular arrangement characteristics and the complementary protective effect between layers, a multi-layer insulation barrier is formed, effectively blocking the erosion of the insulation layer by moisture, impurities and electric field distortion. The carrier migration path is reduced from both the material molecular structure and physical stacking levels, and the volume resistivity and breakdown field strength of the insulation material are increased, thereby significantly enhancing the insulation stability of the cable in high-voltage environments and avoiding power transmission failures caused by insulation failure. This invention is based on the principle of combining high-temperature resistant materials and a thermal protection structure. It uses high and low temperature resistant perfluoroplastics, synthetic mica tape with a short-term resistance to 1600°C, and a metal sheath with balanced thermal conductivity. The molecular chain stability design of the inner insulation material resists temperature fluctuations from -85°C to 230°C. The middle mica tape forms a thermal insulation layer during high-temperature wrap welding to protect the inner structure. The outer metal sheath quickly dissipates heat generated during operation and resists external high-temperature invasion. These three layers work together to delay the thermal aging process of the insulation layer, allowing the cable to maintain its molecular structure integrity in long-term high-temperature or extreme low-temperature environments, solving the problem of material embrittlement and melting caused by rapid temperature fluctuations in traditional cables. The present invention utilizes the skin effect of multiple strands of oxygen-free copper wires twisted together with the outermost layer of cross-linked polyethylene, and the characteristic of charge aggregation towards the conductor surface under high-frequency current, so that the current is concentrated in the outer layer of the conductor, reducing the internal resistance loss of the conductor and improving the current-carrying efficiency of the cable. At the same time, it can be combined with the outer layer of highly conductive metal sheath to further optimize the current distribution, significantly reducing energy loss and enhancing transmission stability in high-frequency power transmission scenarios. DETAILED DESCRIPTION

[0014] The present invention is further described in detail below in conjunction with the examples of the present invention. The raw materials used in the examples and embodiments of the present invention are all commercially available materials unless otherwise specified below. Preparation Examples 1-5 A cross-linked polyethylene insulated composite cable based on skin effect technology, the components and their corresponding proportions of which are shown in the following table, and which is prepared by the following preparation method: S1. Use a 2.5mm diameter oxygen-free copper wire as the center. The first layer is 6 identical oxygen-free copper wires twisted clockwise at a pitch-to-diameter ratio of 12:1. The second layer is 12 identical oxygen-free copper wires twisted counterclockwise at a pitch-to-diameter ratio of 10:1. The third layer is 18 identical oxygen-free copper wires twisted clockwise at a pitch-to-diameter ratio of 12:1. The tension of each copper wire during twisting is controlled at 9N / strand. The outer diameter of the conductor after twisting is 14.8±0.1mm. This produces an inner core conductor. If an additional optical cable is required for the inner core conductor, a single-mode G.652D optical cable should be used. It should be placed in the gap between the center conductor and the first layer of twisted wires and fixed under a twisting tension of 10-12N to ensure that the optical cable is twisted synchronously with the conductor and is not damaged. The purity of oxygen-free copper wire is ≥99.97%, and the conductivity is ≥101%IACS; The single-mode G.652D optical cable has an outer diameter of 2.0mm and contains two optical fibers and a Kevlar reinforcement core. S2. A single-screw extruder is used to place a low-melting fat perfluoroplastic in the extruder, and then extrusion is performed at an extrusion speed of 15 m / min, a pulling tension of 20 N, and an extrusion thickness of 1.0 ± 0.05 mm. During the extrusion, the temperature of each zone of the extruder is specifically 260° C. in the feeding section, 280° C. in the compression section, 300° C. in the homogenizing section, and 310° C. in the die. After extrusion, the extrusion is heated and extruded at a melt flow rate of 5 g / 10 min, and then coated on the outer surface of the inner core conductor obtained in S1, and then cooled and shaped by circulating water at 20° C. to obtain an insulating layer protective layer 1. S3. On the outside of the insulating protective layer 1 obtained in S2, a reinforced low-melting fat perfluoroplastic is used for secondary extrusion through the same extruder, and the extrusion is carried out at an extrusion speed of 12 m / min, a pulling tension of 25 N, and an extrusion thickness of 1.2±0.08 mm. During the extrusion, the temperature of each zone of the extruder is specifically 270° C. in the feeding section, 290° C. in the compression section, 310° C. in the homogenizing section, and 320° C. in the die; after coating and cooling under the same conditions as S2, the insulating protective layer 2 is obtained; The enhanced low-melting fat perfluoroplastic is specifically composed of low-melting fat perfluoroplastic and nano-SiO2 in a weight ratio of 2:98; S4. The biaxially oriented modified polyester tape was wrapped on the insulating layer and protective layer 2 obtained in S3 by a wrapping machine in a left-hand overlapping manner, with a wrapping angle of 30°, an overlapping width of adjacent tapes of 1.5 mm, a wrapping tension of 8 N, and a wrapping speed of 18 m / min. The total thickness after wrapping was 0.225 mm, thereby obtaining an insulating layer and protective layer 3. The biaxially oriented modified polyester tape has a thickness of 0.075 mm, a tensile strength of 250 MPa, an elongation at break of 70%, and a surface treated with corona treatment. S5. Place the high tear-resistant silicone rubber in an extruder and coat it on the insulating layer protective layer 3 obtained in S4 at an extrusion speed of 8 m / min, a pulling tension of 30 N, and an extrusion thickness of 2.5±0.1 mm. During this period, the extruder temperature settings are: 160° C. in the feeding section, 180° C. in the compression section, 200° C. in the homogenizing section, and 210° C. in the die. After extrusion, the rubber enters a 15 m long vulcanization pipe and is vulcanized at a temperature of 180° C. for 10 min to obtain the insulating layer protective layer 4. The high tear-resistant silicone rubber has a Shore hardness of 55A, a tensile strength of 10MPa, and a tear strength of 30kN / m. S6. Using a wrapping machine, wrap the double-sided synthetic mica tape over the insulating layer and protective layer 4 obtained in S5 in a right-hand overlapping manner, with a wrapping angle of 45°, an overlapping width of 2.0 mm for adjacent tapes, a wrapping tension of 3 N, and a wrapping speed of 10 m / min to obtain an insulating layer and protective layer 5. The double-sided synthetic mica tape is phlogopite with a thickness of 0.15mm, a temperature resistance of 1200℃ / 1h and 1600℃ / 5min, and a volume resistivity of 1×10¹³Ω・cm. S7, weaving the insulating layer protective layer 5 obtained in S6 with the filament alkali-free glass fiber through a braiding machine at a braiding angle of 50°, a spindle speed of 200 rpm, a braiding density of 85%, and a braiding tension of 2N, wherein the thickness after braiding is 0.4 mm; then degreasing the insulating layer protective layer 6 is obtained after high temperature degreasing at 500°C; The filament alkali-free glass fiber is specifically a filament alkali-free glass fiber with a monofilament diameter of 9 μm and a breaking strength of 2200 MPa; S8, using a Q235 strip with a thickness of 1mm and a width of 80mm, rolling it into a round tube with an inner diameter 3mm larger than the outer diameter of the cable by a tube reel, and welding it to the outside of the insulation layer protective layer obtained in S7 along the longitudinal direction with a welding current of 120-150A, a voltage of 18-22V, and a speed of 6-8mm / s. Then, the cross-linked polyethylene is conveyed to the extruder hopper and conveyed to the barrel by the screw at a speed of 18-22r / min; the barrel temperature is set as follows: 160℃ for zone 1, 175℃ for zone 2, 185℃ for zone 3, and 190℃ for zone 4, and the die temperature is 200℃. After the raw materials are fully melted and plasticized, the cable obtained by the above process is uniformly passed through the die of the extruder at a pulling speed of 15m / min. The inner diameter of the die is 2-3mm larger than the outer diameter of the cable. The cable is shaped and cooled by a vacuum sizing sleeve and a cooling water tank. Finally, a cross-linked polyethylene protective layer with a thickness of 0.8mm is extruded on the outermost layer of the cable to obtain a cross-linked polyethylene insulated composite cable based on skin effect technology; Table: Components and mass ratios of raw materials in Preparation Examples 1-5 (kg)

[0015] Preparation Example 6 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S2 is as follows: S2. Use a single-screw extruder to place low-melting fat perfluoroplastic in the extruder, and then extrude it at an extrusion speed of 15m / min, a pulling tension of 20N, and an extrusion thickness of 1.0±0.05mm. During this period, the temperature of each zone of the extruder is specifically 260℃ in the feeding section, 280℃ in the compression section, 300℃ in the homogenizing section, and 310℃ in the die. After extrusion, heat and extrude it at a melt flow rate of 7g / 10min and coat it on the outside of the inner core conductor obtained in S1. Then, cool it in circulating water at 20℃ and shape it to obtain an insulating layer protective layer 1.

[0016] Preparation Example 7 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S2 is as follows: S2. Use a single-screw extruder to place low-melting fat perfluoroplastic in the extruder, and then extrude it at an extrusion speed of 15m / min, a pulling tension of 20N, and an extrusion thickness of 1.0±0.05mm. During this period, the temperature of each zone of the extruder is specifically 260℃ in the feeding section, 280℃ in the compression section, 300℃ in the homogenizing section, and 310℃ in the die. After extrusion, heat and extrude it at a melt flow rate of 10g / 10min, and coat it on the outside of the inner core conductor obtained in S1. Then, cool it in circulating water at 20℃ and shape it to obtain the insulating layer protective layer 1.

[0017] Preparation Example 8 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S2 is as follows: S2. Use a single-screw extruder to place low-melting fat perfluoroplastic in the extruder, and then extrude it at an extrusion speed of 15m / min, a pulling tension of 20N, and an extrusion thickness of 1.0±0.05mm. During this period, the temperature of each zone of the extruder is specifically 270℃ in the feeding section, 290℃ in the compression section, 310℃ in the homogenizing section, and 320℃ in the die. After extrusion, heat and extrude it at a melt flow rate of 5g / 10min and coat it on the inner core conductor obtained in S1. Then, cool it in circulating water at 20℃ and shape it to obtain an insulating layer protective layer 1.

[0018] Preparation Example 9 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S2 is as follows: S2. Use a single-screw extruder to place low-melting fat perfluoroplastic in the extruder, and then extrude it at an extrusion speed of 15m / min, a pulling tension of 20N, and an extrusion thickness of 1.0±0.05mm. During this period, the temperature of each zone of the extruder is specifically 280℃ in the feeding section, 300℃ in the compression section, 320℃ in the homogenization section, and 330℃ in the die. After extrusion, heat and extrude it at a melt flow rate of 5g / 10min and coat it on the inner core conductor obtained in S1. Then, cool it in circulating water at 20℃ and shape it to obtain an insulating layer protective layer 1.

[0019] Preparation Example 10 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S3 is as follows: S3. In addition to the insulating protective layer 1 obtained in S2, a reinforced low-melting fat perfluoroplastic is used for secondary extrusion through the same extruder at an extrusion speed of 12 m / min, a pulling tension of 25 N, and an extrusion thickness of 1.2±0.08 mm. During the extrusion, the temperatures of the various zones of the extruder are specifically 280°C in the feeding section, 300°C in the compression section, 320°C in the homogenizing section, and 330°C in the die. After coating and cooling under the same conditions as S2, the insulating protective layer 2 is obtained.

[0020] Preparation Example 11 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S3 is as follows: S3. In addition to the insulating protective layer 1 obtained in S2, a reinforced low-melting fat perfluoroplastic is used for secondary extrusion through the same extruder at an extrusion speed of 12m / min, a pulling tension of 25N, and an extrusion thickness of 1.2±0.08mm. During the extrusion, the temperature of each zone of the extruder is specifically 290℃ in the feeding section, 310℃ in the compression section, 330℃ in the homogenizing section, and 340℃ in the die. After coating and cooling under the same conditions as S2, the insulating protective layer 2 is obtained.

[0021] Preparation Example 12 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S4 is as follows: S4. The biaxially oriented modified polyester tape is wrapped on the insulating layer protective layer 2 obtained in S3 by a wrapping machine in a left overlapping manner, with a wrapping angle of 30°, an overlapping width of adjacent tapes of 1.5 mm, a wrapping tension of 10 N, and a wrapping speed of 18 m / min. The total thickness after wrapping is 0.225 mm, and the insulating layer protective layer 3 is obtained.

[0022] Preparation Example 13 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S4 is as follows: S4. The biaxially oriented modified polyester tape is wrapped on the insulating layer protective layer 2 obtained in S3 by a wrapping machine in a left overlapping manner, with a wrapping angle of 30°, an overlapping width of adjacent tapes of 1.5 mm, a wrapping tension of 12 N, and a wrapping speed of 18 m / min. The total thickness after wrapping is 0.225 mm, and the insulating layer protective layer 3 is obtained.

[0023] Preparation Example 14 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S5 is as follows: S5. Place the high-tear resistant silicone rubber in the extruder and cover it on the insulating layer protective layer three obtained in S4 at an extrusion speed of 8 m / min, a pulling tension of 30 N, and an extrusion thickness of 2.5±0.1 mm. During this period, the extruder temperature settings are: feeding section 170°C, compression section 190°C, homogenization section 210°C, and die mouth 220°C; after extrusion, enter the 15m long vulcanization pipeline and be vulcanized at a temperature of 180°C for 10 minutes to obtain the insulating layer protective layer four.

[0024] Preparation Example 15 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S5 is as follows: S5. Place the high-tear resistant silicone rubber in the extruder and cover it on the insulating layer protective layer three obtained in S4 at an extrusion speed of 8 m / min, a pulling tension of 30 N, and an extrusion thickness of 2.5±0.1 mm. During this period, the extruder temperature settings are: feeding section 180°C, compression section 200°C, homogenization section 220°C, and die mouth 230°C; after extrusion, enter the 15m long vulcanization pipeline and vulcanize at a temperature of 180°C for 10 minutes to obtain the insulating layer protective layer four.

[0025] Preparation Example 16 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S5 is as follows: S5. Place the high-tear resistant silicone rubber in the extruder and cover it on the insulating layer protective layer three obtained in S4 at an extrusion speed of 8 m / min, a pulling tension of 30 N, and an extrusion thickness of 2.5±0.1 mm. During this period, the extruder temperature settings are: feeding section 160°C, compression section 180°C, homogenization section 200°C, and die mouth 210°C; after extrusion, enter the 15m long vulcanization pipeline and be vulcanized at a temperature of 190°C for 12 minutes to obtain the insulating layer protective layer four.

[0026] Preparation Example 17 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S5 is as follows: S5. Place the high-tear resistant silicone rubber in the extruder and cover it on the insulating layer protective layer three obtained in S4 at an extrusion speed of 8 m / min, a pulling tension of 30 N, and an extrusion thickness of 2.5±0.1 mm. During this period, the extruder temperature settings are: feeding section 160°C, compression section 180°C, homogenization section 200°C, and die mouth 210°C; after extrusion, enter a 15m long vulcanization pipeline and vulcanize at a temperature of 200°C for 15 minutes to obtain the insulating layer protective layer four.

[0027] Preparation Example 18 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S6 is as follows: S6. The double-sided synthetic mica tape is wrapped on the insulating layer protective layer 4 obtained in S5 by a wrapping machine in a right-hand overlapping manner, with a wrapping angle of 45°, an overlapping width of adjacent tapes of 2.0 mm, a wrapping tension of 4 N, and a wrapping speed of 10 m / min to obtain the insulating layer protective layer 5.

[0028] Preparation Example 19 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S6 is as follows: S6. The double-sided synthetic mica tape is wrapped on the insulating layer protective layer 4 obtained in S5 by a wrapping machine in a right-hand overlapping manner, with a wrapping angle of 45°, an overlapping width of adjacent tapes of 2.0 mm, a wrapping tension of 5 N, and a wrapping speed of 10 m / min to obtain an insulating layer protective layer 5.

[0029] Preparation Example 20 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S7 is as follows: S7. The filament alkali-free glass fiber is weaved on the insulating layer protective layer five obtained in S6 under the conditions of a weaving angle of 50°, a spindle speed of 200 rpm, a weaving density of 90%, and a weaving tension of 3N. The thickness after weaving is 0.4 mm; then, the insulating layer protective layer six is obtained after degreasing at a high temperature of 500°C.

[0030] Preparation Example 21 A cross-linked polyethylene insulated composite cable based on skin effect technology, which is different from Preparation Example 1 in that the preparation method of S7 is as follows: S7. The filament alkali-free glass fiber is weaved on the insulating layer protective layer five obtained in S6 under the conditions of a weaving angle of 50°, a spindle speed of 200 rpm, a weaving density of 95%, and a weaving tension of 4N. The thickness after weaving is 0.4 mm; then, the insulating layer protective layer six is obtained after degreasing at a high temperature of 500°C.

[0031] Performance testing The cross-linked polyethylene insulated composite cables based on skin effect technology prepared in each embodiment were selected for testing. The test objects were 210 cross-linked polyethylene insulated composite cables based on skin effect technology, 10 in each group. The insulation performance, temperature resistance and mechanical strength were tested. The specific testing steps are as follows: Insulation performance: First, a sample of the cross-linked polyethylene insulated composite cable based on skin effect technology prepared in the embodiment was taken. A 1000V DC voltage was applied to two parallel surfaces of the sample using a high resistance meter. After standing for 1 minute, the resistance value was read and the volume resistance was calculated to characterize the insulation performance of the cross-linked polyethylene insulated composite cable based on skin effect technology. The test results and evaluation criteria are as follows: Volume resistivity>1×10 17 Ω・cm (considered to have strong insulation performance); Volume resistivity <1×10 17 Ω・cm (considered as weak insulation performance).

[0032] Temperature resistance: First, a sample of the cross-linked polyethylene insulated composite cable based on skin effect technology prepared in the embodiment was taken and aged in a heat aging oven at 135°C for 168 hours. After aging, the sample was taken out and cooled to room temperature. The volume resistivity change of the insulation layer was tested to characterize the temperature resistance of the cross-linked polyethylene insulated composite cable based on skin effect technology. The test results and evaluation criteria are as follows: Volume resistivity reduction rate ≤ 50% (considered to have strong heat resistance); The volume resistivity decrease rate is greater than 50% (considered as poor heat resistance).

[0033] Mechanical strength: First, a sample of the cross-linked polyethylene insulated composite cable based on skin effect technology prepared in the embodiment was taken and stretched at a speed of 50 mm / min using an electronic universal testing machine. The maximum tensile force and elongation at break were recorded to characterize the mechanical strength of the cross-linked polyethylene insulated composite cable based on skin effect technology. The test results and evaluation criteria are as follows: Tensile strength ≥600MPa (considered as strong mechanical strength); Tensile strength <600MPa (considered as mechanically weak).

[0034] It should be specifically noted that the above-mentioned cross-linked polyethylene insulated composite cable based on skin effect technology is a cross-linked polyethylene insulated composite cable based on skin effect technology produced in a normal production mode, and the defective cross-linked polyethylene insulated composite cable based on skin effect technology produced, the data of the cross-linked polyethylene insulated composite cable based on skin effect technology is discarded.

[0035] Examples 1-5 A cross-linked polyethylene insulated composite cable based on skin effect technology, and the corresponding relationship between the preparation methods used are shown in the following table.

[0036] Table: Comparison of usage of cross-linked polyethylene insulated composite cables based on skin effect technology in Examples 1-5

[0037] The cross-linked polyethylene insulated composite cables based on skin effect technology in Examples 1-5 above were selected, and their volume resistivity, volume resistivity reduction rate, and tensile strength were tested according to the above measurement steps and measurement standards. The average values of the test results were recorded in the following table.

[0038] Table: Performance test results of volume resistivity, volume resistivity reduction rate, and tensile strength of Examples 1-5

[0039] As can be seen from the above table, the preparation process of cross-linked polyethylene insulated composite cables based on skin effect technology in Examples 1-5 has a good effect on improving the production effect of cross-linked polyethylene insulated composite cables based on skin effect technology. The oxygen-free copper wire adopts multiple concentric positive and negative phase wrapped twisting. Its high purity and good conductivity ensure efficient current transmission. The twisted structure enhances the tensile and bending resistance and balances the current distribution; the optical cable is used for fault point location and Internet of Things monitoring to achieve remote monitoring; the low-melting fat perfluoroplastic is extruded to form an insulating protective layer, which has a temperature range of -85 The high-strength silicone rubber extrusion layer not only continues the characteristics of perfluoroplastics, but also gives the cable flexibility, elasticity and high-pressure resistance, and lays the foundation for the shrinking process after the outer layer is wrapped and welded; the double-sided synthetic mica tape wrapping layer can withstand temperatures up to 1200°C. The Q235 is used as the outer layer of the welded pipe, which reduces static electricity and provides safety protection through the inner magnetic layer and the outer anti-corrosion layer, ensuring the stable operation of the cable in complex environments. The skin effect of the twisted strands of oxygen-free copper wires and the outer layer of cross-linked polyethylene is used to utilize the characteristics of charge accumulation on the conductor surface under high-frequency current, so that the current is concentrated on the outer layer of the conductor, reducing the internal resistance loss of the conductor and improving the current carrying efficiency of the cable. At the same time, it can cooperate with the outer layer of high-conductivity metal sheath to further optimize the current distribution, significantly reducing energy loss and enhancing transmission stability in high-frequency power transmission scenarios. This achieves the purpose of improving the production effect of cross-linked polyethylene insulated composite cables based on skin effect technology. The volume resistivity of the cross-linked polyethylene insulated composite cable prepared in Experimental Examples 1-5 based on the skin effect technology is 2.51-2.62×10 17 Ω・cm, which is considered to have strong insulation performance; the volume resistivity decrease rate is 40.6-41.6%, which is considered to have strong heat resistance. The tensile strength of the cross-linked polyethylene insulated composite cables based on the skin effect technology prepared in Experimental Examples 1-4 is 627-640MPa, which is considered to have strong mechanical strength. The tensile strength of the cross-linked polyethylene insulated composite cables based on the skin effect technology prepared in Experimental Example 5 is low due to the lack of a welded tube wrapping layer; It can be seen that when the production raw materials are certain, the production effect of cross-linked polyethylene insulated composite cables based on skin effect technology can be increased by adjusting the proportion of raw materials. Combined with the data in the above table, it is not difficult to see that when preparing cross-linked polyethylene insulated composite cables based on skin effect technology, 32.8 parts of oxygen-free copper wire, 6.4 parts of low-melting fat perfluoroplastic, 7.9 parts of enhanced low-melting fat perfluoroplastic, 1.5 parts of biaxially oriented modified polyester tape, 11.2 parts of high-tear silicone rubber, 2.6 parts of double-sided synthetic mica tape, 4.1 parts of filament alkali-free glass fiber, 20.3 parts of Q235 tape and 15 parts of cross-linked polyethylene are used to prepare the cross-linked polyethylene insulated composite cables based on skin effect technology. The cross-linked polyethylene insulated composite cable has the strongest insulation performance and temperature resistance. The reason for this is that the reinforced low-melting fat perfluoroplastic used in the cable significantly improves the electrical insulation network structure inside the material by adding specific nanomaterials, reduces the carrier migration path, and thus enhances the volume resistivity. At the same time, the material itself has excellent basic high-temperature resistance performance, and is matched with a synthetic mica tape wrapping layer with a higher high-temperature resistance grade. It can effectively block heat transfer in a high-temperature environment, delay the thermal aging process of the insulation layer, and enable the material to maintain a stable molecular structure and insulation properties at high temperatures, thereby achieving synergistic optimization of insulation and temperature resistance, as obtained in Examples 1-5.

[0040] It can be seen that when the production raw materials are certain, the production effect of cross-linked polyethylene insulated composite cables based on skin effect technology can be increased by adjusting the proportion of raw materials. Combined with the data in the above table, it is not difficult to see that when preparing cross-linked polyethylene insulated composite cables based on skin effect technology, 36.2 parts of oxygen-free copper wire, 7.1 parts of low-melting fat perfluoroplastic, 8.5 parts of enhanced low-melting fat perfluoroplastic, 1.6 parts of biaxially oriented modified polyester tape, 12.4 parts of high-tear silicone rubber, 2.9 parts of double-sided synthetic mica tape, 4.5 parts of filament alkali-free glass fiber, 23.1 parts of Q235 tape and 15 parts of cross-linked polyethylene are used to prepare cross-linked polyethylene insulated composite cables based on skin effect technology. The cable has the strongest mechanical strength. The reason is that its conductor is twisted with more high-quality oxygen-free copper wire. This structural design effectively improves the overall tensile strength and bending resistance of the conductor. The outer layer uses metal materials with high mechanical strength and Q235 tapes with excellent corrosion resistance to form a sheath structure, which provides strong structural support and deformation resistance. While enhancing corrosion resistance, it further strengthens the overall rigidity of the sheath. Combined with the elastic buffering and reinforcement of the middle layer of high-tear resistant silicone rubber and the filament alkali-free glass fiber braided layer, a multi-level mechanical reinforcement system from the inside to the outside is formed, which significantly improves the stability and reliability of the cable under mechanical effects such as stretching and bending, as obtained by Examples 1-5.

[0041] Example 6-21 A cross-linked polyethylene insulated composite cable based on skin effect technology, and the corresponding relationship between the preparation methods used are shown in the following table.

[0042] Table: Comparison of usage of cross-linked polyethylene insulated composite cables based on skin effect technology in Examples 6-21

[0043] The cross-linked polyethylene insulated composite cables based on skin effect technology in the above Examples 6-21 were selected, and their volume resistivity, volume resistivity reduction rate and tensile strength were tested according to the above measurement steps and measurement standards. The average value of the test results was recorded in the following table.

[0044] Table: Performance test results of volume resistivity, volume resistivity reduction rate, and tensile strength of Examples 1, 6-21

[0045] As can be seen from the above table, the preparation process of cross-linked polyethylene insulated composite cables based on skin effect technology in Examples 1-5 has a good effect on improving the production effect of cross-linked polyethylene insulated composite cables based on skin effect technology. The oxygen-free copper wire adopts multiple concentric positive and negative phase wrapped twisting. Its high purity and good conductivity ensure efficient current transmission. The twisted structure enhances the tensile and bending resistance and balances the current distribution; the optical cable is used for fault point location and Internet of Things monitoring to achieve remote monitoring; the low-melting fat perfluoroplastic is extruded to form an insulating protective layer, which has a temperature range of -85 The high-strength silicone rubber extrusion layer not only continues the characteristics of perfluoroplastics, but also gives the cable flexibility, elasticity and high-pressure resistance, and lays the foundation for the shrinking process after the outer layer is wrapped and welded; the double-sided synthetic mica tape wrapping layer can withstand temperatures up to 1200°C. The Q235 is used as the outer layer of the welded pipe, which reduces static electricity and provides safety protection through the inner magnetic layer and the outer anti-corrosion layer, ensuring the stable operation of the cable in complex environments. The skin effect of the twisted strands of oxygen-free copper wires and the outer layer of cross-linked polyethylene is used to utilize the characteristics of charge accumulation on the conductor surface under high-frequency current, so that the current is concentrated on the outer layer of the conductor, reducing the internal resistance loss of the conductor and improving the current carrying efficiency of the cable. At the same time, it can cooperate with the outer layer of high-conductivity metal sheath to further optimize the current distribution, significantly reducing energy loss and enhancing transmission stability in high-frequency power transmission scenarios. This achieves the purpose of improving the production effect of cross-linked polyethylene insulated composite cables based on skin effect technology. Its volume resistivity is 2.58-2.63×10 17 Ω・cm, considered as strong insulation performance; the volume resistivity decrease rate is 40.6-41.0%, considered as strong heat resistance performance; the tensile strength is 632-637MPa, considered as strong mechanical strength; It can be seen that when the production raw materials are certain, the production effect of the cross-linked polyethylene insulated composite cable based on the skin effect technology can be increased by adjusting the preparation conditions. Combined with the data in the above table, it is not difficult to see that when preparing the cross-linked polyethylene insulated composite cable based on the skin effect technology, the extruder temperature melt flow rate in the process of preparing the insulating layer protective layer one, the extruder temperature in the process of preparing the insulating layer protective layer two, the wrapping tension in the process of preparing the insulating layer protective layer three, the extruder temperature in the process of preparing the insulating layer protective layer four, the vulcanization temperature, the vulcanization time, the wrapping tension in the process of preparing the insulating layer protective layer five, the braiding density and the braiding tension in the process of preparing the insulating layer protective layer six are increased. The insulation performance, temperature resistance and mechanical strength of the cross-linked polyethylene insulated composite cable based on the skin effect technology prepared are improved. The reason for this is that the melt flow rate is accelerated, the material is plasticized more evenly and fully, the internal defects of the insulating layer are reduced and a denser structure is formed, thereby improving the insulation performance. At the same time, the dense structure can better resist the damage to the molecular chain of the material in the high temperature environment and enhance the heat resistance. Increasing the extruder temperature in the process of the protective layer two can improve the melt fluidity, so that the protective layer material can more tightly and evenly cover the inner layer, further strengthening The electrical insulation and adaptability of the insulation layer to temperature changes; increasing the wrapping tension during the third process of the protective layer can make the wrapping material more tightly wound, forming a compact mechanical support structure, directly improving the mechanical strength of the cable such as tensile strength and bending resistance, and moderate tension will not damage the inner layer insulation; increasing the extruder temperature during the fourth process of the protective layer can promote the full melting of the material and its firm bonding to the inner layer. Combined with the adjustment of the vulcanization temperature and time, the molecular chains of materials such as silicone rubber can be more fully cross-linked, increasing the cross-linking density, thereby improving the temperature resistance through a stable network structure and enhancing the overall mechanical strength of the material through the enhancement of intermolecular forces; Increasing the wrapping tension during the fifth protective layer process can make materials such as high-temperature resistant mica tape fit closely, better play a thermal protection role in a high-temperature environment, indirectly improve the temperature resistance, and at the same time provide a more stable support for the inner layer, helping to enhance mechanical stability; increasing the weaving density and tension during the sixth protective layer process can form a stronger glass fiber braided layer, effectively resist external mechanical impact and wear, significantly improve the mechanical strength of the cable, and the tight weaving structure can evenly disperse external forces, avoiding damage to the insulation layer due to stress concentration, thereby having a positive protective effect on the insulation performance and temperature resistance, which is obtained from Examples 1, 6-21.

[0046] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A cross-linked polyethylene insulated composite cable based on skin effect technology, characterized in that: From the inside out, it includes the inner core conductor, the insulation layer, and the welded pipe wrapping layer; The inner core conductor comprises the following components in parts by weight: 23.6-36.2 parts of oxygen-free copper wire and 0-2.0 parts of optical cable; The insulating layer protective layer comprises the following components in parts by weight: 4.3-7.1 parts of low-melting fat perfluoroplastic, 5.2-8.5 parts of reinforced low-melting fat perfluoroplastic, 1.0-1.6 parts of biaxially stretched modified polyester tape, 7.8-12.4 parts of high tear-resistant silicone rubber, 1.8-2.9 parts of double-sided synthetic mica tape and 2.7-4.5 parts of filament alkali-free glass fiber; The welded pipe wrapping layer comprises the following components in parts by weight: 0-14.2 parts of Q235 strip and 15 parts of cross-linked polyethylene.

2. The cross-linked polyethylene insulated composite cable based on skin effect technology according to claim 1, characterized in that: The steps for preparing the inner core conductor are as follows: S1. Use a 2.5mm diameter oxygen-free copper wire as the center. The first layer is 6 identical oxygen-free copper wires twisted clockwise at a pitch-to-diameter ratio of 12:

1. The second layer is 12 identical oxygen-free copper wires twisted counterclockwise at a pitch-to-diameter ratio of 10:

1. The third layer is 18 identical oxygen-free copper wires twisted clockwise at a pitch-to-diameter ratio of 12:

1. The tension of each copper wire during twisting is controlled at 9N / strand. The outer diameter of the conductor after twisting is 14.8±0.1mm. This produces an inner core conductor. If an additional optical cable is required for the inner core conductor, a single-mode G.652D optical cable should be used. It should be placed in the gap between the center conductor and the first layer of twisted wires and fixed under a twisting tension of 10-12N to ensure that the optical cable is twisted synchronously with the conductor and is not damaged.

3. The cross-linked polyethylene insulated composite cable based on skin effect technology according to claim 1, characterized in that: The steps for preparing the insulating layer protective layer are as follows: S2. A single-screw extruder is used to place a low-melting fat perfluoroplastic in the extruder, and then extrusion is performed at an extrusion speed of 15 m / min, a pulling tension of 20 N, and an extrusion thickness of 1.0 ± 0.05 mm. During the extrusion, the temperature of each zone of the extruder is specifically 260-280° C. in the feeding section, 280-300° C. in the compression section, 300-320° C. in the homogenization section, and 310-330° C. in the die. After extrusion, the extrusion is heated and extruded at a melt flow rate of 5-10 g / 10 min, and then coated on the outer surface of the inner core conductor obtained in S1, and then cooled and shaped by circulating water at 20° C. to obtain an insulating layer protective layer 1. S3. On the outside of the insulating protective layer obtained in S2, a reinforced low-melting fat perfluoroplastic is used for secondary extrusion through the same extruder at an extrusion speed of 12 m / min, a pulling tension of 25 N, and an extrusion thickness of 1.2 ± 0.08 mm. During the extrusion, the temperature of each zone of the extruder is specifically 270-290° C. in the feeding section, 290-310° C. in the compression section, 310-330° C. in the homogenizing section, and 320-340° C. in the die; After being coated and cooled under the same conditions as S2, the second insulating protective layer is obtained; S4. The biaxially oriented modified polyester tape was wrapped on the insulating layer and protective layer 2 obtained in S3 by a wrapping machine in a left-hand overlapping manner, with a wrapping angle of 30°, an overlapping width of adjacent tapes of 1.5 mm, a wrapping tension of 8-12 N, and a wrapping speed of 18 m / min. The total thickness after wrapping was 0.225 mm, thereby obtaining an insulating layer and protective layer 3. S5. Place the high tear-resistant silicone rubber in an extruder and coat it on the insulating layer protective layer 3 obtained in S4 at an extrusion speed of 8 m / min, a pulling tension of 30 N, and an extrusion thickness of 2.5±0.1 mm. During this period, the extruder temperature settings are: 160-180° C. in the feeding section, 180-200° C. in the compression section, 200-220° C. in the homogenization section, and 210-230° C. in the die. After extrusion, enter a 15 m long vulcanization pipe and vulcanize at a temperature of 180-200° C. for 10-15 minutes to obtain the insulating layer protective layer 4. S6. Using a wrapping machine, wrap the double-sided synthetic mica tape over the insulating layer and protective layer 4 obtained in S5 in a right-hand overlapping manner, with a wrapping angle of 45°, an overlapping width of 2.0 mm for adjacent tapes, a wrapping tension of 3-5 N, and a wrapping speed of 10 m / min to obtain an insulating layer and protective layer 5. S7. The filament alkali-free glass fiber is braided on the insulating layer protective layer five obtained in S6 at a braiding angle of 50°, a spindle speed of 200 rpm, a braiding density of 85-95%, and a braiding tension of 2-4N. The thickness after braiding is 0.4 mm; then, the insulating layer protective layer six is obtained after degreasing at a high temperature of 500°C.

4. The cross-linked polyethylene insulated composite cable based on skin effect technology according to claim 1, characterized in that: The control preparation steps of the welded pipe wrap layer are as follows: S8, using Q235 strip with a thickness of 1mm and a width of 80mm, roll it into a round tube with an inner diameter 3mm larger than the outer diameter of the cable through a tube reel, and weld it to the insulating layer protective layer obtained in S7 along the longitudinal direction with a welding current of 120-150A, a voltage of 18-22V, and a speed of 6-8mm / s. Then, the cross-linked polyethylene is transported to the extruder hopper and transported to the barrel through the screw at a speed of 18-22r / min; the barrel temperature is set as follows: 160℃ for zone 1, 175℃ for zone 2, 185℃ for zone 3, and 190℃ for zone 4, and the die temperature is 200℃. After the raw materials are fully melted and plasticized, the cable obtained in the above process is uniformly passed through the extruder die at a pulling speed of 15m / min. The inner diameter of the die is 2-3mm larger than the outer diameter of the cable. It is shaped and cooled through a vacuum sizing sleeve and a cooling water tank, and finally extruded into the outermost layer of the cable with a thickness of 1000mm. A 0.8mm cross-linked polyethylene protective layer is provided to obtain a cross-linked polyethylene insulated composite cable based on skin effect technology.

5. The cross-linked polyethylene insulated composite cable based on skin effect technology according to claim 2, characterized in that: The purity of the oxygen-free copper wire is ≥99.97%, and the conductivity is ≥101% IACS.

6. The cross-linked polyethylene insulated composite cable based on skin effect technology according to claim 2, characterized in that: The single-mode G.652D optical cable has an outer diameter of 2.0 mm and contains two optical fibers and a Kevlar reinforcement core.

7. The cross-linked polyethylene insulated composite cable based on skin effect technology according to claim 3, characterized in that: The enhanced low-melting fat perfluoroplastic is specifically composed of low-melting fat perfluoroplastic and nano-SiO2 in a weight ratio of 2:98; The biaxially oriented modified polyester tape has a thickness of 0.075 mm, a tensile strength of 250 MPa, an elongation at break of 70%, and a surface treated with corona treatment; The high tear-resistant silicone rubber has a Shore hardness of 55A, a tensile strength of 10 MPa, and a tear strength of 30 kN / m; The double-sided synthetic mica tape is phlogopite, with a thickness of 0.15 mm, a temperature resistance of 1200°C / 1h and 1600°C / 5min, and a volume resistivity of 1×10¹³Ω・cm; The filament alkali-free glass fiber is specifically a filament alkali-free glass fiber with a single filament diameter of 9 μm and a breaking strength of 2200 MPa.

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