Radial water-proof ceramicized silicone rubber insulated fire-resistant medium voltage cable and preparation method thereof

Abstract

The application discloses a radial waterproof type ceramicized silicon rubber insulation fire-resistant medium voltage cable and a preparation method thereof, which comprises at least two insulated cores, and the conductor 1 in the insulated core is sequentially coated with a vinyl semi-conductive shielding layer 2, a first ceramicized silicon rubber insulation fire-resistant layer 3, a first water-blocking coating layer 4 and a first aluminum plastic composite tape layer 5; the insulated core is sequentially provided with a filler layer 6, a cable tie 7 layer, a second ceramicized silicon rubber insulation fire-resistant layer 8, a second water-blocking coating layer 9, a second aluminum plastic composite tape layer 10, a copper fiber shielding layer 11 and a sheath 12. The ceramicized silicon rubber insulation fire-resistant layer and the water-blocking coating layer coated between the aluminum plastic composite tape layers can effectively improve the radial waterproof performance, especially the waterproof performance after the bonding part of the aluminum plastic composite tape layer is cracked after the cable is bent for many times in a long-term use process is also significantly improved, and the application is suitable for the new energy field.

Description

Technical Field

[0001] This invention relates to the field of new energy composite cable technology, and in particular to a radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable and its preparation method. Background Technology

[0002] New energy electric vehicles have received support from various countries and regions due to their advantages such as low energy consumption, low carbon emissions, and low noise. The rapid development of the electric vehicle industry has led to a surge in demand for electric vehicle charging pile cables. Medium-voltage cables are used in power systems to transmit voltage levels of 1-35kV, and are widely used in power distribution networks, industrial power supply, and new energy power plants. In most cable applications, cables are exposed to the elements, requiring not only excellent fire resistance but also excellent radial waterproofing. Water immersion in cables can easily lead to water treeing, severely degrading their electrical performance and ultimately causing voltage breakdown, affecting the safe and stable operation of the power grid. Direct water ingress can cause corrosion of the steel and copper strips, reducing insulation and shielding performance, easily leading to single-phase or three-phase faults, and even explosions causing injury. Therefore, some manufacturers have conducted research on radially waterproof cables.

[0003] Chinese patent CN105679418A discloses a radial waterproof cable, which consists of multiple cores forming a cable core. The gaps between the cores are filled with water-blocking material, and the surface of the core is secured with water-blocking tape. The outermost layer is an outer sheath, and a radial waterproof layer is provided between the water-blocking tape and the outer sheath. This radial waterproof layer is a seamless welded stainless steel strip (0.15-0.3mm thick, corrugated depth 1-3mm) and a corrugated tube-shaped sleeve. However, the stainless steel strip in this cable requires seamless welding, which is costly in terms of labor. Furthermore, the high temperature during welding can easily damage the inner structure, resulting in a low yield rate.

[0004] Chinese patent CN111584127A discloses an oil-resistant and UV-resistant B1-grade DC power cable, comprising a conductor, an insulation layer, a waterproof layer, a barrier layer, and a sheath layer. The insulation layer covers the conductor, the waterproof layer covers the insulation layer, the barrier layer (double-sided aluminum-plastic composite tape) covers the waterproof layer, and the sheath layer covers the barrier layer. This cable uses a conventional double-sided aluminum-plastic composite tape as the waterproof layer. However, during the cable manufacturing process, incomplete melting and closure are inevitable at the overlapping hot-melt portions of the double-sided aluminum-plastic composite tape. Furthermore, during cable winding, straightening, and cornering, the overlapping hot-melt portions are prone to cracking due to poor ductility, allowing water to enter through the cracks. Without an additional internal waterproof layer, this could lead to leakage during long-term use. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical defects and provide a radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable with good radial waterproof performance and fire resistance.

[0006] This invention is achieved through the following technical solution:

[0007] A radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable includes at least two insulated cores. The conductor 1 of the insulated core is sequentially covered with a vinyl semiconductive shielding layer 2, a first ceramicized silicone rubber insulated fire-resistant layer 3, a first water-proof coating 4, and a first aluminum-plastic composite tape layer 5. The insulated core is sequentially provided with a filler layer 6, a cable tie layer 7, a second ceramicized silicone rubber insulated fire-resistant layer 8, a second water-proof coating 9, a second aluminum-plastic composite tape layer 10, a copper fiber shielding layer 11, and a sheath 12.

[0008] Conductor 1 can be a copper wire, an aluminum wire, etc., and can be a single wire or multiple wires bundled together.

[0009] The thickness of the aluminum-plastic composite strip is ≥0.25mm.

[0010] The thickness of the vinyl semiconducting shielding layer is ≥0.35mm.

[0011] The thickness of the copper fiber shielding layer is ≥0.25mm.

[0012] The thickness of the ceramicized silicone rubber insulating refractory layer is ≥0.5mm.

[0013] The thickness of the sheath is ≥1.5mm.

[0014] The composition of the vinyl semiconductive shielding layer 2 includes 40-50 wt% polyethylene, 20-30 wt% ethylene-vinyl acetate copolymer, 20-30 wt% conductive carbon black, 0.5-1 wt% crosslinking agent, and 0.7-1.1 wt% peroxide crosslinking initiator.

[0015] The method for preparing the vinyl semiconducting shielding layer is as follows: after mixing the components, the mixture is melt-extruded through a twin-screw extruder, cooled, and pelletized, and then cross-linked by vulcanization to obtain vinyl semiconducting shielding layer particles; wherein, the melt extrusion temperature is 120-140℃; the vulcanization cross-linking process is as follows: hot-pressed in a flat vulcanizing machine at >15MPa and 110-125℃ for 5-10min, and then cross-linked at 170-180℃ for 10-20min to obtain a sheet-like vinyl semiconducting shielding layer.

[0016] The ceramicized silicone rubber insulating and fire-resistant layer comprises 35-45 wt% methyl vinyl silicone rubber, 2-5 wt% dimethyl silicone oil, 30-40 wt% ceramicized filler, 10-25 wt% flame retardant, and 0.3-1 wt% vulcanizing agent. The ceramicized filler is a compound of kaolin / chopped glass fiber / boron oxide in a weight ratio of (5-10):(5-10):1. The flame retardant is a compound of aluminum hydroxide / graphene in a weight ratio of (5-10):1. The vulcanizing agent is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, bis(2,4-dichlorobenzoyl) peroxide, and dicumyl peroxide.

[0017] The particle size range of kaolin, boron oxide, and aluminum hydroxide is 0.1-30 micrometers.

[0018] The preparation method of the ceramicized silicone rubber insulating and refractory layer is as follows: Methyl vinyl silicone rubber, dimethyl silicone oil, ceramicized filler and flame retardant are mixed evenly and kneaded at 80-110℃ for 1-3 hours. After cooling, vulcanizing agent is added and kneaded evenly at room temperature. Then, it is hot-vulcanized at 120-150℃ for 0.5-1 hours by molding, and then hot-vulcanized at 150-200℃ for 1-4 hours. Finally, it is sheared to obtain the ceramicized silicone rubber insulating and refractory layer tape.

[0019] The ceramicized silicone rubber insulating refractory layer can also be first hot vulcanized at 120-150℃ for 0.5-1 hours, then granulated, extruded in the cable manufacturing process (180-200℃), and then rapidly vulcanized with water vapor passing through 1.2-1.6MPa.

[0020] The waterproof coating comprises 40-50 wt% nano zinc oxide, 20-25 wt% fumed silica, 22-32 wt% dimethyl silicone oil, and 2-3 wt% dioctyl terephthalate. The thickness of the waterproof coating after drying and setting is 0.05-0.15 mm.

[0021] The preparation method of the water-resistant coating material is as follows: nano zinc oxide, fumed silica, dimethyl silicone oil, and dioctyl terephthalate are mixed in a certain proportion, and then 1-3 times the weight of solvent (such as hexane, petroleum ether, etc.) is added. The mixture is then ultrasonically treated for 10-30 minutes to obtain a water-resistant coating dispersion. After the solvent is sprayed onto the ceramicized silicone rubber insulating refractory layer of the cable, it evaporates by baking, forming a water-resistant coating.

[0022] The filler layer 6 is made of water-resistant glass yarn and / or fire-resistant filler.

[0023] One or more layers of semi-conductive terylene tape can be wrapped around the second aluminum-plastic composite tape layer 10, followed by a copper fiber layer, which can reduce the wear of the copper fiber layer on the second aluminum-plastic composite tape layer 10. An adhesive can also be applied.

[0024] The sheath 12 comprises 45-55 wt% polyethylene resin, 40-50 wt% aluminum hydroxide, 1-2 wt% maleic anhydride grafted polyethylene, 1-2 wt% peroxide crosslinking initiator, 0.5-1 wt% crosslinking agent, and 0.1-0.5 wt% lubricant.

[0025] The preparation method of the sheath raw material is as follows: the components are mixed evenly, and then melt-extruded, granulated, and cooled by a twin-screw extruder at 120-175℃.

[0026] The peroxidation crosslinking initiator is selected from any one of bis-tert-butyl peroxide diisopropylbenzene, diisopropylbenzene peroxide, lauroyl peroxide, diisopropylbenzene peroxide, and dibenzoyl peroxide; the crosslinking agent is selected from any one of triallyl cyanurate, triallyl isocyanurate, methyltriallyl isocyanurate, trimethylolpropane triacrylate, propoxytrimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, and dipropylene glycol diacrylate; the lubricant is selected from any one of calcium stearate, magnesium stearate, zinc stearate, ethylene bis-stearamide, and pentaerythritol stearate.

[0027] The method for preparing the radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable of the present invention includes the following steps:

[0028] Step A: The wire and the vinyl semiconductive shielding layer are co-extruded (extrusion temperature 180-200℃), and the whole process is heated, extruded, and cooled to form the final product;

[0029] Step B: Wrap the ceramicized silicone rubber insulating fire-resistant tape, then coat the ceramicized silicone rubber insulating fire-resistant layer with a water-proof coating, bake at 50-80℃ for 10-60 seconds, and then wrap the aluminum-plastic composite tape longitudinally along the axis of the insulating core. The plastic parts on the left and right sides of the aluminum-plastic composite tape are hot-melted and bonded together, with an overlap of not less than 3mm.

[0030] Step C: After filling the gaps in the cable core with filler, wrap the cable with a binding strap and a ceramicized silicone rubber insulating fire-resistant tape in sequence, then apply a water-proof coating, bake at 50-80℃ for 10-60 seconds, and then wrap with an aluminum-plastic composite tape layer and a copper fiber shielding layer.

[0031] Step D: Co-extrude the sheath layer to obtain a radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable.

[0032] The radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable of the present invention has the following beneficial effects:

[0033] First, the present invention improves radial waterproof performance by coating a water-resistant coating on the outside of the ceramicized silicone rubber insulating refractory layer, regardless of whether the ceramicized silicone rubber insulating refractory layer is co-extruded or wrapped (if wrapped, the water-resistant coating needs to have good ductility and permeability). In particular, it improves the waterproof performance after cracking at the weld (or bond) of the aluminum-plastic composite tape.

[0034] Secondly, the flame-retardant component in the insulation layer of the ceramic-silicone rubber composite tape contains a specific proportion of graphene, which can improve the adhesion of the waterproof coating and further improve the radial waterproof performance.

[0035] Third, the ceramicized filler in the ceramicized silicone rubber insulating refractory layer contains a specific ratio of kaolin / chopped glass fiber / boron oxide. Among them, the chopped glass fiber plays a supporting role, the kaolin is a ceramic-forming agent, and the specific content of boron oxide promotes ceramic formation.

[0036] Fourth, the ceramic-silicone rubber composite tape insulation layer of this invention transforms from a soft state to a sponge ceramic body during the fire resistance test. After hardening, cavities are generated inside the fire-resistant protective layer. This sponge ceramic body has significant fire resistance and high-temperature barrier properties, and the graphene carbon layer also significantly improves the flame retardant effect, thereby effectively preventing mechanical and electrical changes in the internal structure of the cable during the fire resistance test. The fire resistance performance is significantly higher than that of mica fire-resistant tapes commonly used in the field. Attached Figure Description

[0037] Figure 1 Schematic diagram of the cross-section of a radial waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable: 1. Conductor, 2. Vinyl semiconducting shielding layer, 3. First ceramicized silicone rubber insulated fire-resistant layer, 4. First waterproof coating, 5. First aluminum-plastic composite tape layer, 6. Filler layer, 7. Cable tie, 8. Second ceramicized silicone rubber insulated fire-resistant layer, 9. Second waterproof coating, 10. Second aluminum-plastic composite tape layer, 11. Copper fiber shielding layer, 12. Sheath. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] The raw material formulation and source for the vinyl semiconductive shielding layer are as follows:

[0040] Polyethylene: 45wt%, XJ710, purchased from Lotte Korea;

[0041] Ethylene-vinyl acetate copolymer: 25wt%, VS430, purchased from Lotte Korea;

[0042] Conductive carbon black: content 28wt%, specific surface area 50-80m² 2 / g, commercially available;

[0043] Crosslinking agent: 1 wt%, triallyl cyanurate, commercially available;

[0044] Peroxidation crosslinking initiator: 1 wt% dicumyl peroxide, commercially available;

[0045] The preparation process is as follows: after mixing the components, the mixture is melt-extruded through a twin-screw extruder, cooled, and pelletized, and then cross-linked by vulcanization to obtain vinyl semi-conductive shielding layer particles; wherein, the melt extrusion temperature is 120-140℃; the vulcanization cross-linking process is as follows: hot-pressed in a flat vulcanizing machine at 18MPa and 110℃ for 10min, and then cross-linked at 170-180℃ for 10min to obtain a sheet-like vinyl semi-conductive shielding layer.

[0046] The raw material formulation and source of the ceramicized silicone rubber insulating and refractory layer are as follows:

[0047] Methyl vinyl silicone rubber: grade 110-6, purchased from DJSilicone;

[0048] Dimethyl silicone oil: purchased from Shenzhen Jipeng Silicon Fluorine Materials Co., Ltd.;

[0049] Kaolin: particle size 0.3μm, purchased from Forsmann Technology (Beijing) Co., Ltd.;

[0050] Chopped fiberglass: Model ECS11-4.5-534A, purchased from Jushi Group Co., Ltd.;

[0051] Boron oxide: 1.4 μm particle size, commercially available;

[0052] Aluminum hydroxide: particle size 0.8μm, H-WF-10, purchased from China Aluminum;

[0053] Graphene: Sigma-Aldrich;

[0054] Crosslinking agent: 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, commercially available;

[0055]

[0056] The preparation method is as follows: Methyl vinyl silicone rubber, dimethyl silicone oil, ceramicized filler, and flame retardant are mixed evenly and kneaded at 100°C for 2 hours. After cooling, a vulcanizing agent is added and mixed evenly at room temperature. Then, the mixture is hot-cured at 130°C for 0.5 hours by molding, followed by hot-curing at 180°C for 3 hours. Finally, the ceramicized silicone rubber insulating and fire-resistant layer tape is obtained after shearing.

[0057] The raw material formula and source of the waterproof coating are as follows:

[0058] Nano zinc oxide: 50±10nm, commercially available;

[0059] Fumed silica: purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0060] Dimethyl silicone oil: purchased from Shenzhen Jipeng Silicon Fluorine Materials Co., Ltd.;

[0061] Dioctyl terephthalate: Commercially available;

[0062]

[0063] The preparation method is as follows: nano zinc oxide, fumed silica, dimethyl silicone oil, and dioctyl terephthalate are mixed in a certain proportion, then 1.5 times the weight of hexane is added, and the mixture is ultrasonically treated for 15 minutes to obtain a water-resistant coating dispersion. The solvent evaporates by baking after being coated onto the ceramicized silicone rubber insulating refractory layer of the cable.

[0064] Preparation method of cable samples A~H: Step A: Copper conductor and vinyl semiconductive shielding layer 2 (thickness 0.5mm) are co-extruded, and integrally heated, extruded, and cooled to form the sample; Step B: Ceramicized silicone rubber insulating fire-resistant tape (thickness 0.5mm) is wrapped around the sample, and then a water-proof coating is applied to the outside of the ceramicized silicone rubber insulating fire-resistant layer (sample I does not have a water-proof coating). The sample is baked at 60℃ for 40 seconds, and then an aluminum-plastic composite tape (thickness 0.25mm) is longitudinally wrapped along the axis of the insulating core. The plastic portions on both sides of the aluminum-plastic composite tape are hot-melted and bonded together, with an overlap of 3mm, resulting in... Step C: Fill the gaps in the cable core with glass water-blocking yarn, then wrap it with a binding tape and a ceramicized silicone rubber fire-resistant insulating tape (0.5 mm thick). Then apply a water-resistant coating (sample I does not have a water-resistant coating), bake at 60°C for 40 seconds, and then wrap it with an aluminum-plastic composite tape (0.25 mm thick) and a copper fiber shielding layer (0.25 mm thick). Step D: Extrude the sheath layer (1.8 mm thick) to obtain a radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable sample (fire resistance test).

[0065] Radial Waterproofing Test Method: To illustrate the radial waterproofing performance of the ceramicized silicone rubber insulating fire-resistant layer / waterproof coating / aluminum-plastic composite tape layer of this invention, only the insulated core is tested. Before the test, a 2mm long slit is carefully scraped open at the overlapping portion of the first aluminum-plastic composite tape layer of the insulated core using a knife, without damaging the waterproof coating, forming a slit leading to the waterproof coating before the waterproofing test. Specifically: The insulated core is fixed in the pressure cylinder using a sealed mold (ensuring the scraped portion is submerged in water), with the length of both ends of the insulated core extending beyond the container ≥150mm. Water is injected to completely submerge the insulated core, and pressure is applied at room temperature to 3.0MPa±0.1MPa. The pressure is maintained for 10 days: 1. During this period, monitor whether water seeps into both ends of the insulated core; 2. After the test, measure the insulation resistance value before and after the test and observe whether there is a change; 3. After cutting each layer, observe whether the vinyl semiconducting shielding layer is damp. A pass is achieved if all three items are "no".

[0066] Fire resistance test: Fire resistance test shall be conducted in accordance with TICW8-2012. The cable shall be ignited by a double torch with a flame temperature >950℃ (test time 180min). An AC voltage shall be applied between the copper conductor and the copper fiber shield. Pass: Requirement (1) The rated voltage Uo (8.7kV) shall not break down during the entire test duration. Requirement (2) After the test, the cable shall be cooled for 15min and then 3.5Uo (30.5kV) shall be applied for 15min without breaking down. If (1) the cable breaks down, the 3.5Uo test shall not be conducted.

[0067]

[0068] As can be seen from samples A / B / I, the cable of the present invention can significantly improve radial waterproofness due to the waterproof coating, and the ceramicized silicone rubber insulating fire-resistant layer of the present invention has good fire resistance.

[0069] As can be seen from samples C / D / E / F, the fire resistance is poor when other components in the ceramicized silicone rubber insulating refractory layer are not within the scope of this invention. Furthermore, the radial waterproofing performance decreases when the ceramicized silicone rubber insulating refractory layer does not contain graphene, because the adhesion between the ceramicized silicone rubber insulating refractory layer E and the waterproof coating is insufficient, allowing water to slowly penetrate.

[0070] As can be seen from the G / H of the sample, when the filler ratio of the waterproof coating is not within the range of the present invention, the radial waterproof performance is poor. This is because the C / D ratio of the waterproof coating is poor in terms of extensibility, permeability, and water resistance. Water can penetrate the waterproof coating and the ceramicized silicone rubber insulating and fire-resistant layer, and then penetrate into the vinyl semi-conductive shielding layer, causing it to become damp. However, it does not penetrate, so the insulation resistance value remains unchanged. It is expected that after several more days of testing, it will penetrate the vinyl semi-conductive shielding layer.

Claims

1. A radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable, characterized in that, It includes at least two insulated wire cores. The conductor (1) in the insulated wire core is covered with a vinyl semiconducting shielding layer (2), a first ceramicized silicone rubber insulating and fire-resistant layer (3), a first water-proof coating (4), and a first aluminum-plastic composite tape layer (5) in sequence. The insulated wire core is provided with a filler layer (6), a cable tie layer (7), a second ceramicized silicone rubber insulating and fire-resistant layer (8), a second water-proof coating (9), a second aluminum-plastic composite tape layer (10), a copper fiber shielding layer (11), and a sheath (12) in sequence. The ceramicized silicone rubber insulating and fire-resistant layer comprises 35-45 wt% methyl vinyl silicone rubber, 2-5 wt% dimethyl silicone oil, 30-40 wt% ceramicized filler, 10-25 wt% flame retardant, and 0.3-1 wt% vulcanizing agent; the ceramicized filler is a compound of kaolin / chopped glass fiber / boron oxide in a weight ratio of (5-10):(5-10):1; the flame retardant is a compound of aluminum hydroxide / graphene in a weight ratio of (5-10):1; and the vulcanizing agent is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, bis(2,4-dichlorobenzoyl) peroxide, and dicumyl peroxide. The waterproof coating comprises 40-50 wt% nano zinc oxide, 20-25 wt% fumed silica, 22-32 wt% dimethyl silicone oil, and 2-3 wt% dioctyl terephthalate.

2. The radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable according to claim 1, characterized in that, The composition of the vinyl semiconductive shielding layer includes 40-50 wt% polyethylene, 20-30 wt% ethylene-vinyl acetate copolymer, 20-30 wt% conductive carbon black, 0.5-1 wt% crosslinking agent, and 0.7-1.1 wt% peroxide crosslinking initiator.

3. The radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable according to claim 1, characterized in that, The filler layer (6) is glass water-blocking yarn and / or fireproof filler.

4. The radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable according to claim 1, characterized in that, A semi-conductive terylene strip layer and / or adhesive are also provided between the second aluminum-plastic composite strip layer (10) and the copper fiber shielding layer (11).

5. The radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable according to claim 1, characterized in that, The sheath (12) comprises 45-55 wt% polyethylene resin, 40-50 wt% aluminum hydroxide, 1-2 wt% maleic anhydride grafted polyethylene, 1-2 wt% peroxide crosslinking initiator, 0.5-1 wt% crosslinking agent, and 0.1-0.5 wt% lubricant.

6. The radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable according to claim 2 or 5, characterized in that, The peroxidation crosslinking initiator is selected from any one of bis-tert-butyl peroxide diisopropylbenzene, diisopropylbenzene peroxide, lauroyl peroxide, diisopropylbenzene peroxide, and dibenzoyl peroxide; the crosslinking agent is selected from any one of triallyl cyanurate, triallyl isocyanurate, methyltriallyl isocyanurate, trimethylolpropane triacrylate, propoxytrimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, and dipropylene glycol diacrylate.

7. The radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable according to claim 5, characterized in that, The lubricant is selected from any one of calcium stearate, magnesium stearate, zinc stearate, ethylene bis-stearamide, and pentaerythritol stearate.

8. The method for preparing the radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable according to any one of claims 1-7, characterized in that, Includes the following steps: Step A: The wire and the vinyl semiconductive shielding layer are co-extruded, and then heated, extruded, and cooled to form the whole structure; Step B: Wrap the ceramicized silicone rubber insulating fire-resistant tape, then coat the ceramicized silicone rubber insulating fire-resistant layer with a water-proof coating, bake at 50-80℃ for 10-60 seconds, and then wrap the aluminum-plastic composite tape longitudinally along the axis of the insulating core. The plastic parts on the left and right sides of the aluminum-plastic composite tape are hot-melted and bonded together, with an overlap of not less than 3mm. Step C: After filling the gaps in the cable core with filler, wrap the cable with a binding strap and a ceramicized silicone rubber insulating fire-resistant tape in sequence, then apply a water-proof coating, bake at 50-80℃ for 10-60 seconds, and then wrap with an aluminum-plastic composite tape layer and a copper fiber shielding layer. Step D: Co-extrude the sheath layer to obtain a radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable.

9. The method for preparing the radially waterproof ceramicized silicone rubber insulated fire-resistant medium-voltage cable according to claim 8, characterized in that, The method for preparing the vinyl semi-conductive shielding layer is as follows: the components are mixed and melt-extruded through a twin-screw extruder, cooled, and pelletized, and then cross-linked by vulcanization to obtain vinyl semi-conductive shielding layer particles; wherein, the melt extrusion temperature is 120-140℃; the vulcanization cross-linking process is as follows: hot-pressing in a flat vulcanizing machine at >15MPa and 110-125℃ for 5-10 minutes, and then cross-linking at 170-180℃ for 10-20 minutes to obtain a sheet-like vinyl semi-conductive shielding layer, wherein the composition of the vinyl semi-conductive shielding layer includes 40-50wt% polyethylene and ethylene-vinyl acetate. The composition includes 20-30 wt% copolymer, 20-30 wt% conductive carbon black, 0.5-1 wt% crosslinking agent, and 0.7-1.1 wt% peroxide crosslinking initiator. The preparation method of the sheath material is as follows: the components are mixed evenly, melt-extruded at 120-175℃ using a twin-screw extruder, granulated, and cooled. The sheath composition includes 45-55 wt% polyethylene resin, 40-50 wt% aluminum hydroxide, 1-2 wt% maleic anhydride grafted polyethylene, 1-2 wt% peroxide crosslinking initiator, 0.5-1 wt% crosslinking agent, and 0.1-0.5 wt% lubricant.

Images