Medium voltage cable based on thermoplastic polypropylene material and method of manufacture

Abstract

This invention relates to the field of medium-voltage cable technology, specifically to a medium-voltage cable based on thermoplastic polypropylene material, comprising, from the inside out, a conductor core, an insulation layer, and a sheath layer; the insulation layer includes: an antioxidant, a compatibilizer, an anti-interference material, and the remainder thermoplastic polypropylene, wherein the anti-interference material contains modified wave-transparent fibers and magnetic particles; the method for preparing this medium-voltage cable includes the following steps: S1, preparing an insulation layer, including: a first insulation layer, a second insulation layer, and a third insulation layer; S2, heating the sheath layer raw material to a molten state and extruding it onto the third insulation layer to obtain the medium-voltage cable; this application uses thermoplastic polypropylene as the insulation layer matrix, adds anti-interference material to the matrix, and designs a multi-layered insulation layer structure to improve the electromagnetic interference resistance and insulation properties of the insulation layer.

Description

Technical Field

[0001] This invention relates to the field of medium-voltage cable technology, specifically to a medium-voltage cable based on thermoplastic polypropylene material and its preparation method. Background Technology

[0002] Mutual inductance interference refers to the mutual influence between the current in a cable and the current in surrounding conductors, resulting in waveform distortion of the current and nonlinear changes in voltage. The main cause of mutual inductance interference is that the current in other conductors around the cable also induces current in the cable. This induced current interferes with the originally normal current waveform in the cable, causing waveform distortion. Simultaneously, the induced current also causes nonlinear changes in the voltage within the cable, interfering with surrounding electronic equipment.

[0003] Compared to cross-linked polyethylene (XLPE) insulated medium-voltage power cables, thermoplastic polypropylene (PP) insulated medium-voltage power cables do not produce cross-linking byproducts such as cumyl alcohol and acetophenone. The manufacturing process is simpler, energy consumption is lower, and carbon emissions can be significantly reduced throughout their lifespan. However, PP has weaker electromagnetic interference resistance. Therefore, this invention aims to design a medium-voltage cable based on PP and its preparation method. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a medium-voltage cable based on thermoplastic polypropylene material and its preparation method.

[0005] A medium-voltage cable based on thermoplastic polypropylene material, comprising, from the inside out, a conductor core, an insulation layer, and a sheath layer;

[0006] The insulating layer, by weight percentage, comprises: 1-2% antioxidant, 3-5% compatibilizer, 0.5-0.8% anti-interference material, and the balance thermoplastic polypropylene, wherein the anti-interference material contains modified wave-transparent fibers and magnetic particles in a mass ratio of 1:8-15.

[0007] Furthermore, the thermoplastic polypropylene is any one of homopolymer polypropylene, random copolymer polypropylene, and block copolymer polypropylene.

[0008] Note: The above-mentioned thermoplastic polypropylene materials do not require cross-linking and degassing during the co-extrusion process, and no cross-linking byproducts such as cumyl alcohol and acetophenone are generated.

[0009] Furthermore, the conductor core is made of copper alloy.

[0010] Note: Copper alloys have high electrical conductivity and excellent mechanical properties.

[0011] Furthermore, the sheath layer is made of polyvinyl chloride material.

[0012] Note: Polyvinyl chloride has good flame retardancy and aging resistance.

[0013] Furthermore, the antioxidant is antioxidant 1010, and the compatibilizer is any one of maleic anhydride-grafted SBS, maleic anhydride-grafted polypropylene, and dopamine.

[0014] Note: The antioxidants and compatibilizers mentioned above have excellent high-temperature stability and good compatibility with various matrices.

[0015] Furthermore, the method for preparing the anti-interference material is as follows:

[0016] The microwave-transparent fiber was placed in a high-density microwave plasma processor. Oxygen was introduced into the fiber for 10-15 minutes, followed by glow discharge at a vacuum of 25-45 Pa for 3-5 minutes. The fiber was then removed and immersed in a modification solution at a solid-liquid ratio of 1 g: 20-30 ml. The fiber was then impregnated at 45-65 °C and atmospheric pressure for 1-3 hours to obtain the modified microwave-transparent fiber.

[0017] Ferric chloride, ferric nitrate, and a 50-55% (v / v) ethanol solution were mixed evenly at a solid-liquid ratio of 3g:1g:12-15g. The mixture was stirred for 5-10 minutes at 6-8 atm and 120-130°C. Melamine, with a mass ratio of 1:2.5-3 to ferric chloride, was added at 1-2 atm and 90-100°C. The mixture was stirred for another 20-30 minutes. The ethanol was then removed by placing the mixture in a vacuum rotary evaporator. The mixture was dried at 75-85°C for 10-12 hours and then kept at 280-320°C for 1.5-2.5 hours. The mixture was then ball-milled to obtain magnetic particles with a particle size of 50-350 nm.

[0018] The modified wave-transparent fiber and the magnetic particles are mixed at 30-40°C for 4-10 hours to obtain an anti-interference material.

[0019] Explanation: Magnetic particles complement the dielectric loss of modified transparent fibers through hysteresis loss, achieving broadband electromagnetic wave absorption. The eddy current effect of nanoscale magnetic particles attenuates high-frequency interference, while the wave transmission characteristics of the fibers reduce signal reflection, thus improving overall shielding effectiveness. Oxygen plasma treatment and glow discharge generate a large number of hydroxyl and polar groups on the surface of the transparent fibers, providing high-density active sites for subsequent silane coupling agent grafting. The modification liquid changes the fiber surface from hydrophilic to hydrophobic, reducing water absorption and enhancing its electrical insulation properties. The conductive network of magnetic particles and the fiber skeleton work together to homogenize the electric field distribution, suppress partial discharge, and increase the breakdown field strength, thereby enhancing the insulation performance of the insulation layer.

[0020] Furthermore, the wave-transparent fiber is a quartz fiber or a silicon nitride fiber, with a diameter of 5-10 μm and an aspect ratio of 2-6.

[0021] Note: The above-mentioned fibers have low dielectric loss and wide bandwidth transmission, and the specific surface area of ​​the wave-transparent fibers is small, resulting in a low high-temperature oxidation rate.

[0022] Furthermore, the modified liquid is a hydrolysis solution of a silane coupling agent with a mass concentration of 4-8%.

[0023] Explanation: The high-frequency signal penetration characteristics of the transparent fiber itself, together with the conductive network introduced by the silane coupling agent, form an impedance matching layer, reducing the electromagnetic wave reflectivity.

[0024] A method for preparing a medium-voltage cable based on thermoplastic polypropylene material as described in any of the above claims includes the following steps:

[0025] S1. Preparation of the insulating layer:

[0026] S1-1. The insulating layer is divided into a first insulating layer, a second insulating layer, and a third insulating layer from the inside out; the thermoplastic polypropylene is divided into a first material, a second material, and a third material with a mass ratio of 1:0.8:0.5 to 0.6; the anti-interference material is divided into material A with a particle size <100nm, material B with a particle size of 100 to 200nm, and material C with a particle size >200nm;

[0027] S1-2. After heating the first material at 220-230°C, add material A, antioxidant and compatibilizer to it and mix. After mixing evenly, extrude and coat it onto the core conductor to obtain the first insulation layer.

[0028] S1-3. After heating the second material at 200-205°C, add material B, antioxidant, and compatibilizer to it and mix. After mixing evenly, extrude and coat the mixture onto the first insulating layer to obtain the second insulating layer.

[0029] S1-4. After heating the third material at 175-180℃, add material C, antioxidant, and compatibilizer to it and mix. After mixing evenly, extrude and coat it onto the second insulating layer to obtain the third insulating layer.

[0030] The mass ratio of the antioxidants in the first, second, and third insulating layers is 1:0.5 to 1:0.4, and the mass ratio of the compatibilizers in the first, second, and third insulating layers is 1:0.8 to 1:1.5.

[0031] S2. After heating the sheathing material to a molten state, it is extruded and wrapped onto the third insulation layer to obtain a medium-voltage cable.

[0032] Compared with existing medium-voltage cables, the advantages of this invention are:

[0033] (1) This application uses thermoplastic polypropylene as the insulating layer matrix and adds anti-interference materials to the matrix. Magnetic particles complement the dielectric loss of modified transparent fibers through hysteresis loss, thereby achieving broadband electromagnetic wave absorption. The eddy current effect of nanoscale magnetic particles can attenuate high-frequency interference, while the wave transmission characteristics of the fibers reduce signal reflection and improve the overall shielding effectiveness. The dielectric constant of the modified transparent fibers is gradient matched with the thermoplastic polypropylene matrix, reducing interface polarization loss and reducing high-frequency signal transmission attenuation. The surface active groups of the transparent fibers after plasma treatment increase, and the binding with magnetic particles is enhanced. The conductive network of magnetic particles and the fiber skeleton work together to homogenize the electric field distribution, suppress partial discharge, and increase the breakdown field strength, thereby further enhancing the insulation performance of the thermoplastic polypropylene matrix.

[0034] (2) This application designs a multi-layered insulating layer on the surface of the conductor core. From the inside out, the layers are: an inner layer of low-porosity thermoplastic polypropylene combined with small-particle-size anti-interference material, which is closely attached to the conductor and suppresses partial discharge through nano-scale fillers; a middle layer of medium-porosity thermoplastic polypropylene combined with medium-particle-size anti-interference material to balance the electric field distribution; and an outer layer of high-porosity thermoplastic polypropylene combined with large-particle-size anti-interference material to absorb high-frequency pulse energy. The low-porosity structure can reduce microcracks, and the small-particle-size anti-interference material can improve carrier mobility and suppress partial discharge through quantum confinement effect. The two are tightly combined to avoid thermal expansion mismatch. The medium-particle-size anti-interference material is uniformly dispersed in the medium porosity and converts electromagnetic energy through eddy current loss and hysteresis loss. It can absorb thermal stress. The large-particle-size anti-interference material forms a multi-level reflection interface in the high porosity, expands the absorption frequency band, and improves the electromagnetic interference resistance of the insulating layer. Attached Figure Description

[0035] Figure 1 This is a comparison chart of the maximum voltage results in Experiment Example 1 of this invention;

[0036] Figure 2 This is a comparison chart of the shielding effectiveness results of Experiment Example 1 of this invention;

[0037] Figure 3 This is a comparison chart of the maximum voltage results in Experiment Example 2 of this invention;

[0038] Figure 4 This is a comparison chart of the shielding effectiveness results of Experiment Example 2 of this invention;

[0039] Figure 5 This is a comparison chart of the maximum voltage results in Experiment Example 3 of this invention;

[0040] Figure 6 This is a comparison chart of the shielding effectiveness results of Experiment Example 3 of this invention. Detailed Implementation

[0041] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0042] Example 1: A medium-voltage cable based on thermoplastic polypropylene material, comprising, from the inside out, a conductor core, an insulation layer, and a sheath layer;

[0043] The insulation layer, by weight percentage, includes: 1-2% antioxidant, 3-5% compatibilizer, 0.5-0.8% anti-interference material, and the balance thermoplastic polypropylene. The anti-interference material contains modified wave-transparent fibers and magnetic particles in a mass ratio of 1:8-15. The thermoplastic polypropylene is homopolymer polypropylene, the conductor core is made of brass alloy, the sheath layer is made of polyvinyl chloride, the antioxidant is antioxidant 1010, and the compatibilizer is maleic anhydride-grafted SBS.

[0044] The preparation method of the anti-interference material is as follows:

[0045] Wave-transparent fibers (quartz fibers) with a diameter of 8 μm and an aspect ratio of 4 were placed in a high-density microwave plasma processor. After oxygen was introduced into the wave-transparent fibers for 12 min, glow discharge was performed at a vacuum of 32 Pa for 4 min. The fibers were then removed and immersed in a modification solution with a solid-liquid ratio of 1 g: 25 ml. The modification solution was a hydrolysis solution of silane coupling agent with a mass concentration of 6%. The fibers were impregnated at 52 °C and atmospheric pressure for 2 h to obtain modified wave-transparent fibers.

[0046] Ferric chloride, ferric nitrate, and a 53% ethanol solution were mixed evenly at a solid-liquid ratio of 3g:1g:13g. The mixture was stirred for 8 minutes at 7 atm and 125°C. Melamine with a mass ratio of 1:2.8 to ferric chloride was added at 1.5 atm and 95°C. The mixture was stirred for another 25 minutes. The mixture was then placed in a vacuum rotary evaporator to remove the ethanol. The mixture was dried at 80°C for 11 hours and then kept at 300°C for 2 hours. The mixture was then ball-milled to obtain magnetic particles with a particle size of 90–320 nm.

[0047] Modified wave-transparent fibers and magnetic particles were mixed at 35°C for 7 hours in a certain proportion to obtain an anti-interference material.

[0048] Example 2: A method for preparing a medium-voltage cable based on thermoplastic polypropylene material as described in Example 1, comprising the following steps:

[0049] S1. Preparation of the insulating layer:

[0050] S1-1. The insulation layer is divided into a first insulation layer, a second insulation layer, and a third insulation layer from the inside out; the thermoplastic polypropylene is divided into a first material, a second material, and a third material with a mass ratio of 1:0.8:0.55; the anti-interference material is divided into material A with a particle size <100nm, material B with a particle size of 100-200nm, and material C with a particle size >200nm.

[0051] S1-2. After heating the first material at 225°C, add material A, antioxidant, and compatibilizer to it and mix. After mixing evenly, extrude and coat the core conductor to obtain the first insulation layer.

[0052] S1-3. After heating the second material at 203°C, add material B, antioxidant, and compatibilizer to it and mix. After mixing evenly, extrude and coat the mixture onto the first insulating layer to obtain the second insulating layer.

[0053] S1-4. After heating the third material at 178°C, add material C, antioxidant, and compatibilizer to it and mix. After mixing evenly, extrude and coat it onto the second insulating layer to obtain the third insulating layer.

[0054] The mass ratio of the antioxidants in the first, second, and third insulating layers is 1:0.8:0.4, and the mass ratio of the compatibilizers in the first, second, and third insulating layers is 1:0.9:1.5.

[0055] S2. After heating the sheathing material to a molten state, it is extruded and wrapped onto the third insulation layer to obtain a medium-voltage cable.

[0056] Example 3: This example differs from Example 1 in that the insulation layer, by weight percentage, includes: 1% antioxidant, 3% compatibilizer, 0.8% anti-interference material, and the balance thermoplastic polypropylene. The anti-interference material contains modified wave-transparent fibers and magnetic particles in a mass ratio of 1:8, and the compatibilizer is maleic anhydride-grafted polypropylene.

[0057] Example 4: This example differs from Example 1 in that the insulating layer, by weight percentage, includes: 2% antioxidant, 5% compatibilizer, 0.5% anti-interference material, and the balance thermoplastic polypropylene. The anti-interference material contains modified wave-transparent fibers and magnetic particles in a mass ratio of 1:15, and the compatibilizer is dopamine.

[0058] Example 5: The difference between this example and Example 1 is that a microwave-transparent fiber (silicon nitride fiber) with a diameter of 5 μm and an aspect ratio of 2 is placed in a high-density microwave plasma processor, oxygen is introduced into the microwave-transparent fiber for 10 min, and then glow discharge is performed for 3 min under a vacuum of 25 Pa.

[0059] Example 6: The difference between this example and Example 1 is that a microwave-transparent fiber (quartz fiber) with a diameter of 10 μm and an aspect ratio of 6 is placed in a high-density microwave plasma processor, oxygen is introduced into the microwave-transparent fiber for 15 min, and then glow discharge is performed for 5 min under a vacuum of 45 Pa.

[0060] Example 7: The difference between this example and Example 1 is that the solid-liquid ratio of 1g:30ml is used to soak the sample in the modified solution, which is a hydrolysis solution of silane coupling agent with a mass concentration of 4%, and the sample is soaked at 45°C and normal pressure for 1 hour.

[0061] Example 8: The difference between this example and Example 1 is that the solid-liquid ratio of 1g:20ml is used to soak the sample in the modified solution, which is a hydrolysis solution of silane coupling agent with a mass concentration of 8%, and the sample is soaked at 65°C and normal pressure for 3 hours.

[0062] Example 9: The difference between this example and Example 1 is that ferric chloride, ferric nitrate, and 50% ethanol solution are mixed evenly at a solid-liquid ratio of 3g:1g:12ml, and stirred for 5min at 6atm and 120℃.

[0063] Example 10: The difference between this example and Example 1 is that ferric chloride, ferric nitrate, and 55% ethanol solution are mixed evenly at a solid-liquid ratio of 3g:1g:15ml, and stirred for 10min at 8atm and 130℃.

[0064] Example 11: The difference between this example and Example 1 is that melamine with a mass ratio of 1:2.5 to ferric chloride is added at 1 atm and 90°C, and stirring is continued for 20 minutes.

[0065] Example 12: The difference between this example and Example 1 is that melamine with a mass ratio of 1:3 to ferric chloride is added at 2 atm and 100°C, and stirring is continued for 30 minutes.

[0066] Example 13: This example differs from Example 1 in that the particles are dried at 75°C for 10 hours and then kept at 280°C for 1.5 hours, followed by ball milling to obtain magnetic particles with a particle size of 320-350 nm.

[0067] Example 14: This example differs from Example 1 in that the particles are dried at 85°C for 12 hours and then kept at 320°C for 2.5 hours, followed by ball milling to obtain magnetic particles with a particle size of 50-90 nm.

[0068] Example 15: The difference between this example and Example 1 is that the modified transparent fiber and magnetic particles are mixed at 30°C for 4 hours in a certain proportion.

[0069] Example 16: This example differs from Example 1 in that the modified transparent fiber and magnetic particles are mixed at 40°C for 10 hours in a certain proportion.

[0070] Example 17: This example differs from Example 2 in that the thermoplastic polypropylene is divided into a first material, a second material, and a third material in a mass ratio of 1:0.8:0.5; the antioxidants in the first, second, and third insulating layers have a mass ratio of 1:0.5:0.4; and the compatibilizers in the first, second, and third insulating layers have a mass ratio of 1:0.8:1.5.

[0071] Example 18: This example differs from Example 2 in that the thermoplastic polypropylene is divided into a first material, a second material, and a third material in a mass ratio of 1:0.8:0.6; the antioxidants in the first, second, and third insulating layers have a mass ratio of 1:1:0.4; and the compatibilizers in the first, second, and third insulating layers have a mass ratio of 1:1:1.5.

[0072] Example 19: This example differs from Example 2 in that, in step S1-2, the first material is heated at 220°C; in step S1-3, the second material is heated at 205°C; and in step S1-4, the third material is heated at 180°C.

[0073] Example 20: This example differs from Example 2 in that, in step S1-2, the first material is heated at 230°C; in step S1-3, the second material is heated at 200°C; and in step S1-4, the third material is heated at 175°C.

[0074] Experimental Example: The description of this experimental example is based on the scheme described in Example 2, and aims to illustrate the practical application effect of the present invention.

[0075] The insulation performance and electromagnetic interference resistance of the medium-voltage cables prepared in each embodiment were tested. The insulation performance was reflected by testing the maximum voltage that the medium-voltage cable could withstand per unit thickness. The lower the maximum voltage, the better the insulation performance. The electromagnetic interference resistance was reflected by testing the shielding effectiveness of the medium-voltage cable. The greater the shielding effectiveness, the better the electromagnetic interference resistance.

[0076] Investigation 1: Investigate the influence of the composition ratio of the insulation layer on the insulation performance and electromagnetic interference resistance of medium-voltage cables.

[0077] The difference between Comparative Example 1 and Example 1 is that the insulating layer does not include anti-interference material;

[0078] The difference between Comparative Example 2 and Example 1 is that the anti-interference material does not include modified wave-transparent fibers;

[0079] Depend on Figure 1 and Figure 2 The results show that Comparative Example 1 lacks anti-interference materials, and the thermoplastic polypropylene matrix has weak electromagnetic interference resistance and lacks the effect of homogenizing the electric field with the anti-interference materials, resulting in reduced insulation performance. Comparative Example 2 lacks modified transparent fibers, so it lacks the complementarity with the magnetic hysteresis loss of magnetic particles, and the electromagnetic wave absorption range is weakened. Therefore, compared with Examples 1 and 3-4, Comparative Example 1 and Comparative Example 2 have weakened the insulation and electromagnetic interference resistance of the medium-voltage cable.

[0080] Comparing Examples 1 and 3-4, it can be seen that if the proportion of modified wave-transparent material in the anti-interference material is too small or too large, it will lead to an increase in the maximum voltage of the medium-voltage cable and a decrease in the shielding effectiveness. Therefore, from a comprehensive perspective, the parameter effect of Example 1 is relatively better.

[0081] Investigation 2: Investigate the influence of the preparation parameters of anti-interference materials on the insulation performance and electromagnetic interference resistance of medium-voltage cables.

[0082] The difference between Comparative Example 3 and Example 1 is that the wave-transparent fibers are not subjected to plasma treatment;

[0083] Depend on Figure 3 and Figure 4 The results show that, due to the lack of plasma treatment, the dielectric constant of the transparent fiber surface and the thermoplastic polypropylene matrix in Comparative Example 3 is significantly different, which leads to enhanced reflection of electromagnetic waves at the interface. Therefore, compared with Examples 1 and 5-16, Comparative Example 3 has reduced insulation and electromagnetic interference resistance of its medium-voltage cable.

[0084] Comparing Examples 1 and 5-16, it can be seen that excessively small or large plasma treatment parameters, excessively small or large modified impregnation parameters, excessively small or large mixed parameters of ferric chloride and ethanol, excessively small or large parameters of melamine addition, excessively small or large calcination parameters of magnetic particles, and excessively small or large mixed parameters of modified transparent fiber and magnetic particles will all lead to an increase in the maximum voltage of the medium-voltage cable and a decrease in shielding effectiveness. Therefore, from a comprehensive perspective, the parameter effect of Example 1 is relatively better.

[0085] Investigation 3: Investigate the influence of the manufacturing parameters of medium-voltage cables on their insulation performance and electromagnetic interference resistance.

[0086] The difference between Comparative Example 4 and Example 2 is that material C is added to the first insulating layer and material A is added to the third insulating layer;

[0087] The difference between Comparative Example 5 and Example 2 is that all the raw materials of the insulating layer are mixed evenly to form a single insulating layer, and it does not have a multi-layer structure.

[0088] Depend on Figure 5 and Figure 6The results show that Comparative Example 4, which swaps and combines anti-interference materials of different particle sizes corresponding to high and low porosity, shows that the large-particle-size anti-interference material is prone to forming microstructural inhomogeneity in the low-porosity thermoplastic polypropylene matrix, causing electric field concentration. Comparative Example 5, with its uniformly mixed insulation layer, lacks the deep trap energy level design in the multilayer structure and has insufficient ability to capture space charge. Therefore, compared with Examples 2 and 17-20, Comparative Example 4 and Comparative Example 5 have reduced the insulation and electromagnetic interference resistance of the medium-voltage cable.

[0089] Comparing Examples 2 and Examples 17-20, it can be seen that if the mass difference of thermoplastic polypropylene in the multilayer structure is too small or too large, and the heating temperature of each layer of thermoplastic polypropylene is too small or too large, it will lead to an increase in the maximum voltage of the medium-voltage cable and a decrease in the shielding effectiveness. Therefore, from a comprehensive point of view, the parameter effect of Example 2 is relatively better.

Claims

1. A medium voltage cable based on a thermoplastic polypropylene material, characterized in that, From the inside out, it includes the conductor core, insulation layer, and sheath layer; The insulating layer, by weight percentage, comprises: 1-2% antioxidant, 3-5% compatibilizer, 0.5-0.8% anti-interference material, and the balance thermoplastic polypropylene, wherein the anti-interference material contains modified wave-transparent fibers and magnetic particles in a mass ratio of 1:8-15. The method for preparing the anti-interference material is as follows: The microwave-transparent fiber is placed in a high-density microwave plasma processor. The microwave-transparent fiber is a quartz fiber or a silicon nitride fiber with a diameter of 5-10 μm and an aspect ratio of 2-6. After oxygen is introduced into the microwave-transparent fiber for 10-15 min, glow discharge is performed at a vacuum of 25-45 Pa for 3-5 min. Then, the fiber is taken out and immersed in a modification solution at a solid-liquid ratio of 1 g: 20-30 ml. The modification solution is a hydrolysis solution of silane coupling agent with a mass concentration of 4-8%. The fiber is then impregnated at 45-65 °C and atmospheric pressure for 1-3 h to obtain the modified microwave-transparent fiber. Ferric chloride, ferric nitrate, and a 50-55% (v / v) ethanol solution were mixed evenly at a solid-liquid ratio of 3g:1g:12-15g. The mixture was stirred for 5-10 minutes at 6-8 atm and 120-130°C. Melamine with a mass ratio of 1:2.5-3 to ferric chloride was added at 1-2 atm and 90-100°C. The mixture was stirred for another 20-30 minutes. The ethanol was then removed by placing the mixture in a vacuum rotary evaporator. The mixture was dried at 75-85°C for 10-12 hours and then kept at 280-320°C for 1.5-2.5 hours. The mixture was then ball-milled to obtain magnetic particles with a particle size of 50-350 nm. The modified wave-transparent fiber and the magnetic particles are mixed at 30-40°C for 4-10 hours to obtain an anti-interference material.

2. A medium voltage cable based on thermoplastic polypropylene material according to claim 1, characterized in that, The thermoplastic polypropylene is any one of homopolymer polypropylene, random copolymer polypropylene, and block copolymer polypropylene.

3. A medium-voltage cable based on thermoplastic polypropylene material as described in claim 1, characterized in that, The conductor core is made of copper alloy.

4. A medium-voltage cable based on thermoplastic polypropylene material as described in claim 1, characterized in that, The sheath layer is made of polyvinyl chloride.

5. A medium-voltage cable based on thermoplastic polypropylene material as described in claim 1, characterized in that, The antioxidant is antioxidant 1010, and the compatibilizer is any one of maleic anhydride-grafted SBS, maleic anhydride-grafted polypropylene, and dopamine.

6. A method for preparing a medium-voltage cable based on thermoplastic polypropylene material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Preparation of the insulating layer: S1-1. The insulating layer is divided into a first insulating layer, a second insulating layer and a third insulating layer from the inside out; Thermoplastic polypropylene is divided into three materials: a first material, a second material, and a third material, with a mass ratio of 1:0.8:0.5~0.6; the anti-interference material is divided into material A with a particle size <100nm, material B with a particle size of 100~200nm, and material C with a particle size >200nm. S1-2. After heating the first material at 220~230℃, add material A, antioxidant and compatibilizer to it and mix. After mixing evenly, extrude and coat it onto the core conductor to obtain the first insulation layer. S1-3. After heating the second material at 200~205℃, add material B, antioxidant and compatibilizer to it and mix. After mixing evenly, extrude and coat it onto the first insulating layer to obtain the second insulating layer. S1-4. After heating the third material at 175~180℃, add material C, antioxidant and compatibilizer to it and mix. After mixing evenly, extrude and coat it onto the second insulating layer to obtain the third insulating layer. The mass ratio of the antioxidants in the first, second, and third insulating layers is 1:0.5 to 1:0.4, and the mass ratio of the compatibilizers in the first, second, and third insulating layers is 1:0.8 to 1:1.

5. S2. After heating the sheathing material to a molten state, it is extruded and wrapped onto the third insulation layer to obtain a medium-voltage cable.

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