High-dynamic-stability copper shielding rail transit cable and preparation method thereof

Abstract

The invention discloses a high-dynamic-stability copper shielding rail transit cable and a preparation method, and the preparation method comprises the following steps: putting an ethylene-vinyl acetate copolymer, an inorganic flame-retardant filler, layered silicate and a carboxylated carbon nanotube into a twin-screw extruder, carrying out melt blending, and carrying out underwater pelletizing to obtain a functional insulating material; a functional insulating material is extruded on the conductor to form a functional insulating layer; a conductor shielding layer and an insulation shielding layer are sequentially formed outside the functional insulation layer; forming a composite copper shielding layer outside the insulation shielding layer; a belting layer is wrapped outside the composite copper shielding layer, and an outer sheath layer is extruded outside the belting layer. Through surface pretreatment and a specific shearing process of the carboxylated carbon nanotubes, a controlled and discontinuous maximum conductive cluster is formed in the functionalized insulating layer, and the area proportion is less than or equal to 5%, so that the insulating resistance is ensured, and the performance degradation caused by local charge accumulation is avoided; and the structural stability and the partial discharge resistance of the insulating material under dynamic stress are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of cable technology, specifically relating to a high dynamic stability copper-shielded rail transit cable and its preparation method. Background Technology

[0002] The onboard electrical system of rail transit vehicles (such as high-speed trains and subways) is the nerve center for their safe operation. This system is located in a typical "electromagnetic-force" multi-physics field with strong electromagnetic interference, continuous mechanical vibration, and repeated bending stress coupling, which places stringent requirements on the cables transmitting signals: they must have extremely high initial shielding effectiveness to resist electromagnetic interference, and they must withstand tens of millions of vibration cycles over a service life of several decades without significant degradation in shielding performance.

[0003] The industry commonly uses simple copper strip wrapping or copper wire braiding structures, which are prone to problems such as loosening of the overlapping surface and displacement of braided wires under dynamic stress, resulting in a decrease in shielding effectiveness.

[0004] Currently, there are some improved shielding structures, such as composite shielding and bonded shielding layers, but their long-term shielding stability under high-frequency vibration is still not ideal, and the process control is difficult, making it hard to meet the stringent requirement in IEC 61373:2010 that the shielding effectiveness attenuation should not exceed 3dB after 10^7 axial vibration tests. Summary of the Invention

[0005] To address the problems in the prior art, the present invention aims to provide a high dynamic stability copper-shielded rail transit cable and its preparation method.

[0006] To achieve the above objectives and technical effects, the technical solution adopted by this invention is as follows: A method for preparing a high dynamic stability copper-shielded rail transit cable includes the following steps: S1. Preparation of functionalized insulating materials: Ethylene-vinyl acetate copolymer, inorganic flame retardant filler, layered silicate and carboxylated carbon nanotubes are fed into a twin-screw extruder and melt-blended and underwater pelletized under a shear mixing field consisting of a melt temperature of 130-160℃ and a screw speed of 200-400rpm to obtain a functionalized insulating material. S2. The functionalized insulating material obtained in step S1 is extruded onto the conductor to form a functionalized insulating layer; S3. A conductor shielding layer and an insulating shielding layer are formed sequentially outside the functionalized insulating layer; S4. Form a composite copper shielding layer outside the insulating shielding layer; S5. Wrap a wrapping tape layer around the composite copper shielding layer, and then extrude an outer sheath layer over the wrapping tape layer.

[0007] Furthermore, in step S1, the weight parts of the ethylene-vinyl acetate copolymer, inorganic flame retardant filler, layered silicate and carboxylated carbon nanotubes are 45-50 parts, 85-95 parts, 6-9 parts and 1-3 parts, respectively.

[0008] Furthermore, the VA content in the ethylene-vinyl acetate copolymer is 25%-30%; The inorganic flame-retardant filler is aluminum hydroxide or magnesium hydroxide with an average particle size D50≤1μm. The layered silicate is organo-modified montmorillonite.

[0009] Furthermore, in step S1, the carboxylated carbon nanotubes are first ultrasonically dispersed in an ethanol solution for 20-40 minutes with 5%-8% of their weight of silane coupling agent before feeding and then subjected to surface pretreatment. The pretreated carbon nanotubes are then premixed with a portion of ethylene-vinyl acetate copolymer to form a masterbatch, and finally fed into a twin-screw extruder together with inorganic flame retardant filler, layered silicate and the remaining ethylene-vinyl acetate copolymer.

[0010] Furthermore, the pretreated carbon nanotubes are premixed with 20%-25% of the total ethylene-vinyl acetate copolymer to form a masterbatch, which is then fed into a twin-screw extruder along with inorganic flame-retardant fillers, layered silicates, and 75%-80% of the total ethylene-vinyl acetate copolymer.

[0011] Furthermore, in step S1, the functionalized insulating material satisfies: In the conductive extension mode of atomic force microscopy, the average area ratio of the largest continuous conductive clusters obtained by binarization within a 10μm×10μm observation area of ​​functionalized insulating materials does not exceed 5%.

[0012] Furthermore, in step S4, the composite copper shielding layer includes copper strips and copper wire braided layers arranged sequentially from the inside out. The step of forming the composite copper shielding layer outside the insulating shielding layer includes: S4.1 Copper tape wrapping: A copper tape with a thickness of 0.05-0.08mm is wrapped around the outside of the insulating shielding layer, with a wrapping overlap rate of 35%-45%, and the overlap rate fluctuation over any 1-meter length is ≤±2%; S4.2 High-density copper wire braiding: A copper wire braiding layer is formed by braiding on the outside of the copper strip, and the braiding density of the copper wire braiding layer is controlled at 94%-96%.

[0013] Furthermore, in step S4.2, a low-melting-point tin-bismuth alloy paste is first pre-coated on the surface of the copper strip, then woven on the outside of the copper strip, and then the low-melting-point tin-bismuth alloy paste is melted, leveled and solidified by a hot press roller.

[0014] Furthermore, in step S4.2, after the braiding is completed, an ultrasonic spot welding device is used to perform local spot welding along the longitudinal interval of the cable.

[0015] This invention also discloses a high dynamic stability copper shielded rail transit cable, which is prepared by the preparation method of a high dynamic stability copper shielded rail transit cable as described above. The high dynamic stability copper shielded rail transit cable includes a conductor, a functional insulation layer, a conductor shielding layer, an insulation shielding layer, a composite copper shielding layer, a wrapping layer, and an outer sheath layer arranged sequentially from the inside to the outside. The composite copper shielding layer includes a copper strip and a copper wire braided layer arranged sequentially from the inside to the outside.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) By pretreating the surface of carboxylated carbon nanotubes and using a specific shearing process, controlled and discontinuous maximum conductive clusters (area percentage ≤ 5%) are formed in the functionalized insulating layer. This ensures the insulation resistance and avoids the performance degradation caused by local charge accumulation, significantly improving the structural stability and resistance to partial discharge of the insulating material under dynamic stress. 2) The composite copper shielding layer achieves a strong mechanical bond and low-impedance electrical connection between layers through precise control of the wrapping overlap rate (35%-45%), high braiding density (94%-96%) and innovative interface enhancement technology, effectively suppressing the relative sliding between layers and the increase in contact resistance caused by vibration. 3) The cable as a whole has passed the stringent IEC 61373:2010 axial 10^7 vibration test, and the shielding effectiveness attenuation is ≤3dB at 1MHz, which proves its excellent stability of shielding performance under long-term dynamic conditions. It is particularly suitable for high reliability requirements of rail transit signaling, power and network systems. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail so that its advantages and features can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0019] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0020] like Figure 1As shown, this invention discloses a method for preparing a high dynamic stability copper-shielded rail transit cable, comprising the following steps: S1. Preparation of functionalized insulating materials: Ethylene-vinyl acetate copolymer (EVA), inorganic flame-retardant fillers, layered silicates, carboxylated carbon nanotubes, and additives are fed into a twin-screw extruder and melt-blended under a shear mixing field consisting of a melt temperature of 130-160℃ and a screw speed of 200-400rpm, followed by underwater pelletizing to obtain a functionalized insulating material. By controlling specific process parameters, the dispersion morphology of carboxylated carbon nanotubes in the functionalized insulating material matrix meets the following requirements: characterized by atomic force microscopy in conductivity spread mode (C-AFM), the average area ratio of the largest continuous conductive clusters obtained by binarization within a 10μm×10μm observation area does not exceed 5%; the volume resistivity of the functionalized insulating material is maintained at an extremely high insulation level of 1×10^15-5×10^15Ω·cm. In this step, the weight parts of ethylene-vinyl acetate copolymer, inorganic flame retardant filler, layered silicate and carboxylated carbon nanotubes are 45-50 parts, 85-95 parts, 6-9 parts and 1-3 parts, respectively. The VA content in the ethylene-vinyl acetate copolymer is 25%-30%; The inorganic flame-retardant filler is aluminum hydroxide or magnesium hydroxide with an average particle size D50≤1μm; Layered silicates are preferably organo-modified montmorillonite, etc. The additive is at least one of antioxidant, zinc stearate, and polyethylene wax, with the antioxidant, zinc stearate, and polyethylene wax in weight parts of 1-3 parts, 1-3 parts, and 1-5 parts, respectively. S2. Extrude the functionalized insulating material obtained in step S1 onto conductor 1 to form functionalized insulating layer 2, controlling the extrusion eccentricity to be ≤8%; S3. A conductor shielding layer 3 and an insulating shielding layer 4 are sequentially formed outside the functionalized insulating layer 2; S4. A composite copper shielding layer 5 is formed outside the insulating shielding layer 4; S5. Wrap a wrapping tape layer 6 around the composite copper shielding layer 5, and then extrude an outer sheath layer 7 over the wrapping tape layer 6.

[0021] In step S1, before feeding, the carboxylated carbon nanotubes are ultrasonically dispersed in an ethanol solution for 20-40 minutes with 5%-8% of a silane coupling agent by weight and then subjected to surface pretreatment. The pretreated carbon nanotubes are premixed with 20%-25% of the total amount of ethylene-vinyl acetate copolymer to form a masterbatch, which is then fed into a twin-screw extruder together with inorganic flame retardant fillers, layered silicates, and 75%-80% of the total amount of ethylene-vinyl acetate copolymer.

[0022] In step S4, the composite copper shielding layer 5 includes copper strips 8 and copper wire braided layers 9 arranged sequentially from the inside to the outside. The step of forming the composite copper shielding layer 5 outside the insulating shielding layer 4 includes: S4.1 Copper tape wrapping: With a tension of (25±5)N, wrap a copper tape 8 (preferably annealed soft copper tape) with a thickness of 0.05-0.08mm around the insulating shielding layer 4. The wrapping overlap rate is 35%-45%, and the overlap rate fluctuation over any 1-meter length is ≤±2%. S4.2 High-density copper wire braiding: A copper wire braiding layer 9 is formed by braiding outside the copper strip 8, and the braiding density of the copper wire braiding layer 9 is controlled at 94%-96%.

[0023] In step S4.2, a low-melting-point tin-bismuth alloy paste can be pre-coated onto the surface of the copper strip 8, followed by braiding. Then, a hot press roller is used to melt, level, and solidify the low-melting-point tin-bismuth alloy paste. This is one method of interface enhancement. Alternatively, after braiding, an ultrasonic spot welding device can be used to perform local spot welding along the longitudinal direction of the cable. This is another method of interface enhancement. Through interface enhancement, a stable low-resistance bonding interface can be formed between the copper strip 8 and the copper wire braided layer 9.

[0024] If a low-melting-point tin-bismuth alloy paste is used, 1%-3% of nano-copper powder with a particle size of 50-100nm is added to the alloy paste to enhance the interfacial conductivity and bonding strength. The temperature of the hot press roller is controlled at 150-180℃, the pressure is 0.5-1MPa, and the action time is 2-5s.

[0025] This invention also discloses a high dynamic stability copper shielded rail transit cable, which is prepared by the preparation method of the high dynamic stability copper shielded rail transit cable described above. The high dynamic stability copper shielded rail transit cable includes a conductor 1, a functional insulation layer 2, a conductor shielding layer 3, an insulation shielding layer 4, a composite copper shielding layer 5, a wrapping layer 6, and an outer sheath layer 7 arranged sequentially from the inside to the outside. The composite copper shielding layer 5 includes a copper strip 8 and a copper wire braided layer 9 arranged sequentially from the inside to the outside.

[0026] Conductor 1 is made of multiple copper or aluminum wires twisted together and is used to transmit current or signals.

[0027] The conductor shielding layer 3 uses a conventional cross-linked semi-conductive shielding material to eliminate electric field concentration and unevenness on the conductor surface, ensuring a uniform electric field.

[0028] The insulating shielding layer 4 uses a conventional cross-linked semi-conductive shielding material, and its function is similar to that of the conductor shielding layer 3, ensuring uniform potential on the outer surface of the insulating layer.

[0029] The outer sheath layer 7 is formed by extrusion of polyurethane elastomer material. Its surface has annular protrusions spaced along the axial direction, with a protrusion height of 0.3-0.8 mm, a width of 1-2 mm, and a spacing of 5-10 mm between adjacent protrusions. The annular protrusion structure of the outer sheath layer 7, together with the polyurethane material containing silicon carbide, not only provides excellent wear resistance, heat dissipation, and stress buffering performance, but also facilitates the directional laying and fixing of cables in confined spaces.

[0030] The high dynamic stability copper-shielded rail transit cable obtained by this invention has an insulation resistance on the order of 10^15 Ω·cm. After undergoing 10^7 axial vibration tests as described in IEC 61373:2010 Category 1 standard, the absolute value of the shielding effectiveness attenuation |ΔSE| is ≤3dB at a frequency of 1MHz. The transfer impedance of the composite copper shielding layer 5 is ≤5mΩ / m at a frequency of 100MHz. Moreover, the shielding effectiveness of the cable is ≥92dB in the frequency range of 1MHz to 3GHz.

[0031] Example 1 like Figure 1 As shown, a method for preparing a high dynamic stability copper-shielded rail transit cable includes the following steps: S1. Preparation of functionalized insulating materials: Ethylene-vinyl acetate copolymer (EVA), inorganic flame-retardant filler, layered silicate, commercially available carboxylated carbon nanotubes, and additives (1 part antioxidant 1010, 2 parts zinc stearate, and 3 parts polyethylene wax) were fed into a twin-screw extruder and melt-blended under a shear mixing field consisting of a melt temperature of 130°C and a screw speed of 350 rpm, followed by underwater pelletizing to obtain a functionalized insulating material. By controlling specific process parameters, the dispersion morphology of carboxylated carbon nanotubes in the functionalized insulating material matrix met the following requirements: characterized by atomic force microscopy conductivity spread mode (C-AFM), the average area ratio of the largest continuous conductive clusters within a 10 μm × 10 μm observation area, after binarization, was 3.5%; the volume resistivity of the functionalized insulating material remained at an extremely high insulation level of 1 × 10^15 - 5 × 10^15 Ω·cm. In this step, the weight parts of ethylene-vinyl acetate copolymer, inorganic flame retardant filler, mechanized montmorillonite and carboxylated carbon nanotubes are 47 parts: 90 parts: 7 parts: 2 parts, respectively. The VA content in the ethylene-vinyl acetate copolymer is 28%; The inorganic flame-retardant filler is aluminum hydroxide with an average particle size D50 = 0.8 μm; S2. The functionalized insulating material obtained in step S1 is extruded onto conductor 1 to form functionalized insulating layer 2, and the extrusion eccentricity is controlled at 6%; S3. A conductor shielding layer 3 and an insulating shielding layer 4 are sequentially formed outside the functionalized insulating layer 2; S4. A composite copper shielding layer 5 is formed outside the insulating shielding layer 4; S5. Wrap a wrapping tape layer 6 around the composite copper shielding layer 5, and then extrude an outer sheath layer 7 over the wrapping tape layer 6.

[0032] In step S1, before feeding, the carboxylated carbon nanotubes are ultrasonically dispersed in an ethanol solution for 20 minutes with 5% by weight of silane coupling agent and subjected to surface pretreatment. The pretreated carbon nanotubes are premixed with 20% of the total amount of ethylene-vinyl acetate copolymer to form a masterbatch, which is then fed into a twin-screw extruder together with inorganic flame retardant filler, layered silicate, and 80% of the total amount of ethylene-vinyl acetate copolymer.

[0033] In step S4, the composite copper shielding layer 5 includes copper strips 8 and copper wire braided layers 9 arranged sequentially from the inside to the outside. The step of forming the composite copper shielding layer 5 outside the insulating shielding layer 4 includes: S4.1 Copper tape wrapping: With a tension of (25) N, wrap a copper tape 8 (annealed soft copper tape) with a thickness of 0.05 mm around the insulating shielding layer 4. The wrapping overlap rate is 38%, and the overlap rate fluctuation over any 1-meter length is ≤ ±1.5%. S4.2 High-density copper wire braiding: A copper wire braiding layer 9 is formed by braiding outside the copper strip 8, and the braiding density of the copper wire braiding layer is controlled at 95%.

[0034] In step S4.2, a low-melting-point tin-bismuth alloy paste is first pre-coated onto the surface of the copper strip 8, then woven onto the outside of the copper strip 8, and finally melted, leveled, and solidified by a hot press roller. Through interface enhancement treatment, a stable low-resistance bonding interface can be formed between the copper strip 8 and the copper wire braided layer 9.

[0035] When using a low-melting-point tin-bismuth alloy paste, an additional 1% of nano-copper powder with a particle size of 50nm is added to the alloy paste to enhance interfacial conductivity and bonding strength; the temperature of the hot press roller is controlled at 150℃, the pressure is 1MPa, and the action time is 5s.

[0036] A high dynamic stability copper shielded rail transit cable is prepared by the preparation method of a high dynamic stability copper shielded rail transit cable as described above. The high dynamic stability copper shielded rail transit cable includes a conductor 1, a functional insulation layer 2, a conductor shielding layer 3, an insulation shielding layer 4, a composite copper shielding layer 5, a wrapping layer 6, and an outer sheath layer 7 arranged sequentially from the inside to the outside. The composite copper shielding layer 5 includes a copper strip 8 and a copper wire braided layer 9 arranged sequentially from the inside to the outside.

[0037] Conductor 1 is made of multiple stranded copper wires and is used to transmit current or signals.

[0038] The conductor shielding layer 3 uses a conventional cross-linked semi-conductive shielding material to eliminate electric field concentration and unevenness on the conductor surface, ensuring a uniform electric field.

[0039] The insulating shielding layer 4 uses a conventional cross-linked semi-conductive shielding material, and its function is similar to that of the conductor shielding layer 3, ensuring uniform potential on the outer surface of the insulating layer.

[0040] The outer sheath layer 7 is formed by extrusion of polyurethane elastomer material. Its surface has annular protrusions spaced along the axial direction, with a protrusion height of 0.3 mm, a width of 1 mm, and a spacing of 5 mm between adjacent protrusions. The annular protrusion structure of the outer sheath layer 7 and the polyurethane material with added silicon carbide not only provide excellent wear resistance, heat dissipation, and stress buffering performance, but also facilitate the directional laying and fixing of the cable in confined spaces.

[0041] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 did not use carboxylated carbon nanotubes, the wrapping overlap rate of copper strip 8 was 20%, the braiding density of copper wire braid layer 9 was 85%, and no interface reinforcement treatment was performed.

[0042] The rest is the same as in Example 1.

[0043] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 did not use copper strip 8 and did not undergo interface enhancement treatment.

[0044] The rest is the same as in Example 1.

[0045] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the braiding density of the copper wire braided layer 9 in Comparative Example 3 is 90%.

[0046] The rest is the same as in Example 1.

[0047] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the carboxylated carbon nanotubes in Comparative Example 4 have an insufficient weight fraction, only 0.5 parts, and the maximum continuous cluster area accounts for <1%.

[0048] The rest is the same as in Example 1.

[0049] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the carboxylated carbon nanotubes in Comparative Example 5 are in excess by weight, up to 3.5 parts, and the maximum continuous cluster area accounts for >15%.

[0050] The rest is the same as in Example 1.

[0051] The high dynamic stability copper-shielded rail transit cables obtained in Example 1 and Comparative Examples 1-5 were subjected to performance testing. The shielding effectiveness (SE) of all samples was tested according to IEC 62153-4-7 (triaxial method), and the dynamic vibration test strictly followed IEC 61373:2010 Category 1 (axial, 5-150Hz, 5 m / s). 2 (1×10^7 cycles). Transfer impedance (Z_T) was tested according to IEC62153-4-3, and volume resistivity (ρ_v) was tested according to GB / T 1410-2006. The results are shown in Table 1.

[0052] Table 1 Comparative Example 5 did not complete the dynamic test because its insulation resistance ρ_v was less than 1×10^15 Ω·cm, which did not meet the safety specifications.

[0053] Define the synergistic gain coefficient η = [(ΔSE of the control sample) - (ΔSE of the embodiment)] / (ΔSE of the control sample) × 100%.

[0054] Based on Comparative Example 1 (conventional technology): η = (5.5-1.4) / 5.5×100% = 74.5%.

[0055] Based on Comparative Example 3 (parameter deviation): η = (4.5-1.4) / 4.5×100% = 68.9%.

[0056] Based on Comparative Example 4 (CNT morphology deviation): η = (4.0 - 1.4) / 4 × 100% = 65%.

[0057] The exceptional dynamic stability (ΔSE = 1.4 dB) and comprehensive high performance exhibited in Example 1 are the inevitable result of the precise synergy between the composite shielding layer with specific parameters and the functionalized insulating layer with specific microstructures. The synergistic gain coefficient η is greater than 65% in all cases, demonstrating that the performance improvement brought about by the complete technical solution of this invention is far more than a linear sum of the effects of each improved part; rather, it produces a huge and unexpected synergistic effect. The overall technical effect far exceeds the sum of the effects of each part, successfully achieving the intended purpose of this invention.

[0058] Any parts or structures not specifically described in this invention can be made using existing technologies or products, and will not be elaborated upon here.

[0059] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a high dynamic stability copper-shielded rail transit cable, characterized in that, Includes the following steps: S1. Preparation of functionalized insulating materials: Ethylene-vinyl acetate copolymer, inorganic flame retardant filler, layered silicate and carboxylated carbon nanotubes are fed into a twin-screw extruder and melt-blended and underwater pelletized under a shear mixing field consisting of a melt temperature of 130-160℃ and a screw speed of 200-400rpm to obtain a functionalized insulating material. S2. The functionalized insulating material obtained in step S1 is extruded onto the conductor to form a functionalized insulating layer; S3. A conductor shielding layer and an insulating shielding layer are formed sequentially outside the functionalized insulating layer; S4. Form a composite copper shielding layer outside the insulating shielding layer; S5. Wrap a wrapping tape layer around the composite copper shielding layer, and then extrude an outer sheath layer over the wrapping tape layer.

2. The method for preparing a high dynamic stability copper-shielded rail transit cable according to claim 1, characterized in that, In step S1, the weight parts of the ethylene-vinyl acetate copolymer, inorganic flame retardant filler, layered silicate and carboxylated carbon nanotubes are 45-50 parts, 85-95 parts, 6-9 parts and 1-3 parts, respectively.

3. A method for preparing a high dynamic stability copper-shielded rail transit cable according to claim 1 or 2, characterized in that, The VA content in the ethylene-vinyl acetate copolymer is 25%-30%; The inorganic flame-retardant filler is aluminum hydroxide or magnesium hydroxide with an average particle size D50≤1μm. The layered silicate is organo-modified montmorillonite.

4. The method for preparing a high dynamic stability copper-shielded rail transit cable according to claim 1, characterized in that, In step S1, the carboxylated carbon nanotubes are first ultrasonically dispersed in an ethanol solution for 20-40 minutes with 5%-8% of their weight of silane coupling agent before feeding and then subjected to surface pretreatment. The pretreated carbon nanotubes are then premixed with a portion of ethylene-vinyl acetate copolymer to form a masterbatch, and finally fed into a twin-screw extruder together with inorganic flame retardant filler, layered silicate and the remaining ethylene-vinyl acetate copolymer.

5. The method for preparing a high dynamic stability copper-shielded rail transit cable according to claim 4, characterized in that, The pretreated carbon nanotubes are premixed with 20%-25% of the total ethylene-vinyl acetate copolymer to form a masterbatch, which is then fed into a twin-screw extruder along with inorganic flame-retardant fillers, layered silicates, and 75%-80% of the total ethylene-vinyl acetate copolymer.

6. The method for preparing a high dynamic stability copper-shielded rail transit cable according to claim 1, characterized in that, In step S1, the functionalized insulating material satisfies: In the conductive extension mode of atomic force microscopy, the average area ratio of the largest continuous conductive clusters obtained by binarization within a 10μm×10μm observation area of ​​functionalized insulating materials does not exceed 5%.

7. The method for preparing a high dynamic stability copper-shielded rail transit cable according to claim 1, characterized in that, In step S4, the composite copper shielding layer includes copper strips and copper wire braided layers arranged sequentially from the inside out. The step of forming the composite copper shielding layer outside the insulating shielding layer includes: S4.1 Copper tape wrapping: A copper tape with a thickness of 0.05-0.08mm is wrapped around the outside of the insulating shielding layer, with a wrapping overlap rate of 35%-45%, and the overlap rate fluctuation over any 1-meter length is ≤±2%; S4.2 High-density copper wire braiding: A copper wire braiding layer is formed by braiding on the outside of the copper strip, and the braiding density of the copper wire braiding layer is controlled at 94%-96%.

8. The method for preparing a high dynamic stability copper-shielded rail transit cable according to claim 7, characterized in that, In step S4.2, a low-melting-point tin-bismuth alloy paste is first pre-coated on the surface of the copper strip, then woven on the outside of the copper strip, and then the low-melting-point tin-bismuth alloy paste is melted, leveled and solidified by a hot press roller.

9. The method for preparing a high dynamic stability copper-shielded rail transit cable according to claim 7, characterized in that, In step S4.2, after the braiding is completed, an ultrasonic spot welding device is used to perform local spot welding along the longitudinal interval of the cable.

10. A high dynamic stability copper-shielded rail transit cable, characterized in that, The high dynamic stability copper shielded rail transit cable is prepared by any one of the preparation methods of claims 1-9. The high dynamic stability copper shielded rail transit cable includes a conductor, a functionalized insulation layer, a conductor shielding layer, an insulation shielding layer, a composite copper shielding layer, a wrapping layer and an outer sheath layer arranged in sequence from the inside to the outside. The composite copper shielding layer includes a copper strip and a copper wire braided layer arranged in sequence from the inside to the outside.

Images