Environment-friendly high-water-resistance impact-resistant medium-voltage power cable and preparation method thereof

Abstract

The invention discloses an environment-friendly high-water-resistance impact-resistant medium-voltage power cable and a preparation method thereof. The environment-friendly high-water-resistance impact-resistant medium-voltage power cable comprises a cable core, an aluminum-plastic composite belt and a sheath layer, wherein the aluminum-plastic composite belt and the sheath layer are arranged outside the cable core from inside to outside; the cable core is formed by twisting a plurality of insulated wire cores, and gaps among the insulated wire cores are filled with water-blocking filling ropes; each insulating wire core comprises a conductor, and a conductor shielding layer, an insulating layer, an insulating shielding layer and a metal composite shielding layer which are arranged outside the conductor from inside to outside; a water-blocking expansion layer is arranged between the insulation shielding layer and the metal composite shielding layer; the water-blocking expansion layer is composed of a super-absorbent fiber felt and water-blocking powder, and the water-blocking powder is sprayed on the surface of the polyester-based super-absorbent fiber felt through electrostatic spraying; the super-absorbent fiber felt is a polyester-based super-absorbent fiber felt; and a super-absorbent fiber felt layer is arranged between the cable core and the aluminum-plastic composite belt. The cable has the advantages of being good in water blocking effect and good in impact resistance.

Description

Technical Field

[0001] The invention relates to a power cable, in particular to an environmentally friendly high-resistance water-impact-resistant medium-voltage power cable and a preparation method thereof. Background Art

[0002] Power cables are used to transmit and distribute electrical energy. They are commonly used in urban underground power grids, power station outgoing lines, internal power supplies for industrial and mining enterprises, and underwater transmission lines across rivers and seas. The proportion of cables in power lines is gradually increasing. Power cables are used to transmit and distribute high-power electrical energy in the backbone lines of power systems. They include various voltage levels from 1 to 500 kV and above. They can be divided into medium and low voltage power cables (35 kV and below), high voltage cables (110 kV and above), extra-high voltage cables (275-800 kV), and ultra-high voltage cables (1000 kV and above). They can also be divided into AC cables and DC cables with various insulation types based on current. Medium voltage power cables are those that withstand power pressures of 35 kV and below. Currently, medium voltage power cables mostly use a structure consisting of a conductor, an insulation layer, a shielding layer, and an outer protective layer.

[0003] With the development of the economy, the application of power cables has become more extensive, and the performance indicators of power cables have become more stringent and diverse. For example, there are strict requirements for tensile strength, impact toughness, operating temperature, aging resistance, weather resistance and other indicators. Continuously improving the comprehensive performance of power cables is an urgent need for economic and social development. In high humidity environments, water-blocking belts are used to improve the water-blocking effect of power cables. However, most of these power cables have problems such as poor water-blocking effect, low strength, and poor impact toughness, which bring a lot of inconvenience to actual use and even threaten people's lives and property. Therefore, improvements are needed to adapt to the diverse needs of the power cable market. Summary of the Invention

[0004] The purpose of the present invention is to provide an environmentally friendly high water-resistance and impact-resistant medium-voltage power cable with good water-resistance and impact resistance and a preparation method thereof in response to the deficiencies of the existing technology.

[0005] The technical objectives of the present invention are achieved through the following technical solutions: Disclosed is an environmentally friendly, high-water-resistance, impact-resistant medium-voltage power cable, comprising a cable core, an aluminum-plastic composite tape and a sheath layer arranged outside the cable core from the inside to the outside; the cable core is formed by twisting a plurality of insulated wire cores, and the gaps between the insulated wire cores are filled with water-blocking filling ropes; the insulated wire core comprises a conductor and a conductor shielding layer, an insulating layer, an insulating shielding layer and a metal composite shielding layer arranged outside the conductor from the inside to the outside; a water-blocking expansion layer is provided between the insulating shielding layer and the metal composite shielding layer; the water-blocking expansion layer is composed of super absorbent fiber felt and water-blocking powder, and the water-blocking powder is electrostatically sprayed on the surface of a polyester-based super absorbent fiber felt; the super absorbent fiber felt is a polyester-based super absorbent fiber felt; a super absorbent fiber felt layer is provided between the cable core and the aluminum-plastic composite tape.

[0006] Preferably, the water-blocking powder is sodium acrylate-acrylamide copolymer powder.

[0007] The super absorbent fiber felt is a polyester-based super absorbent fiber felt with a gram weight of 60-80 g / m².

[0008] The sheath layer is a high-density polyethylene sheath layer.

[0009] Preferably, the sheath layer is made of a high-density polyethylene-based composite material; the high-density polyethylene-based composite material is made of the following components in parts by mass: 80-90 parts of high-density polyethylene, 10-15 parts of maleic anhydride grafted POE elastomer, 5-8 parts of nano-silica, 3-5 parts of sodium polyacrylate water-blocking agent, and 8-12 parts of halogen-free flame retardant.

[0010] A method for preparing the above-mentioned environmentally friendly high-resistance water-resistant and impact-resistant medium-voltage power cable, the method comprising the following process steps: S1. Making conductors: using a wire drawing machine to draw a round single wire, and using a frame-type stranding machine to make the conductors by regular stranding or irregular stranding; S2. Extruding a conductor shielding layer, an insulating layer, and an insulating shielding layer onto the conductor through a CCV catenary three-layer co-extrusion cross-linking machine to form a wire core; S3, after the wire core exits the die head, nitrogen pressurization is used to heat the conductor shielding layer, the insulation layer and the insulation shielding layer in a stepwise manner to reduce the heating temperature; S4, wrapping the water-blocking expansion layer on the surface of step S3; S5. On a copper wire shielding machine, 0.2-0.4 mm copper wire is sparsely wound on the water-blocking expansion layer to form a copper wire layer; then, a copper tape is wrapped around the outside of the copper wire layer to form a copper tape layer, ensuring that the wrapping direction of the copper tape is opposite to the sparse winding direction of the copper wire, to form a metal composite shielding layer; thus, an insulated wire core is obtained; S6: preparing a cable core, and cabling the insulated cores using a disc stranding machine; during cabling, gaps between the insulated cores are filled to form strands of water-blocking filling rope; S7: Wrap the cable core with a super absorbent fiber felt layer and an aluminum-plastic composite tape in sequence; S8. A sheath layer made of high-density polyethylene-based composite material is extruded outside the aluminum-plastic composite belt.

[0011] Preferably, the preparation method of the high-density polyethylene-based composite material in step 8 is as follows: 1) Mix high-density polyethylene and maleic anhydride grafted POE elastomer in an internal mixer at 180-190°C for 5 minutes; 2) Add nano-silica, sodium polyacrylate water-blocking agent and halogen-free flame retardant and continue mixing for 8 minutes; 3) Twin-screw extrusion granulation, extrusion temperature is controlled in sections: zone 1 160℃, zone 2 180℃, zone 3 190℃.

[0012] Preferably, the halogen-free flame retardant is a nitrogen-phosphorus intumescent flame retardant, and its composition is ammonium polyphosphate: melamine cyanurate = 2:1.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention incorporates a multi-layered, effective water-blocking structure, including a water-blocking filler rope between the insulated cores, a water-blocking expansion layer between the insulating shield and the metal composite shield, and a superabsorbent fiber felt layer between the cable core and the aluminum-plastic composite tape. These water-blocking structures work together to form a comprehensive water-blocking barrier, effectively preventing moisture from invading the cable interior through various pathways. The water-blocking expansion layer is composed of superabsorbent fiber felt and water-blocking powder. The superabsorbent fiber felt is a polyester-based superabsorbent fiber felt with excellent water absorption properties, rapidly absorbing intruding moisture and expanding to block potential water seepage channels. The water-blocking powder is electrostatically sprayed onto the surface of the superabsorbent fiber felt, further enhancing its water-blocking capabilities and enabling the water-blocking expansion layer to quickly form a solid water-blocking barrier when exposed to moisture. The superabsorbent fiber felt layer, located between the cable core and the aluminum-plastic composite tape, absorbs any small amount of moisture that may penetrate through the outer sheath, preventing further diffusion into the cable core. This enhances the synergistic effect of the cable's overall water-blocking system and significantly improves the cable's waterproof performance.

[0014] The aluminum-plastic composite tape also provides excellent impact cushioning. The water-blocking expansion layer and superabsorbent fiber felt layer, constructed from polyester-based superabsorbent fiber felt, offer excellent cushioning properties. Due to their flexibility and elasticity, they act as a cushion when impact forces act on the cable, effectively reducing the impact and protecting the cable's internal structure. This structure disperses the impact force, preventing it from being concentrated at a single point and causing fiber breakage, further enhancing the cable's overall impact resistance. This invention offers the advantages of both excellent water-blocking and impact resistance.

[0015] 2. This invention addresses the brittleness of high-density polyethylene (HDPE) through the synergistic effect of maleic anhydride-grafted POE elastomer toughening and nano-silica reinforcement, effectively improving the impact strength of the sheath layer. Using this HDPE-based composite sheath layer further enhances the impact resistance of this invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 yes Figure 1 Schematic diagram of the structure of the insulated wire core; Figure numerals: 1 - conductor; 2 - conductor shielding layer; 3 - insulation layer; 4 - insulation shielding layer; 5 - water-blocking expansion layer; 6 - copper wire layer; 7 - copper tape layer; 8 - water-blocking filling rope; 9 - super absorbent fiber felt layer; 10 - aluminum-plastic composite tape; 11 - sheath layer. DETAILED DESCRIPTION

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0019] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. In addition, the terms "first," "second," etc. are used only to distinguish the descriptions and are not to be understood as indicating or implying relative importance.

[0020] Example 1 like Figure 1 — Figure 2 The figure shows an environmentally friendly, high-water-resistance, impact-resistant medium-voltage power cable, comprising a cable core, an aluminum-plastic composite tape 10 disposed outside the cable core from the inside out, and a sheath 11. The cable core is composed of multiple twisted insulated wire cores, with the gaps between the insulated wire cores filled with a water-blocking filler rope 8. The insulated core comprises a conductor 1, a conductor shield 2, an insulating layer 3, an insulating shield 4, and a metal composite shield disposed outside the conductor 1 from the inside out. A water-blocking expansion layer 5 is disposed between the insulating shield 4 and the metal composite shield. The water-blocking expansion layer 5 is composed of a polyester-based superabsorbent fiber felt and water-blocking powder, which is electrostatically sprayed onto the surface of the superabsorbent fiber felt. A superabsorbent fiber felt layer 9 is disposed between the cable core and the aluminum-plastic composite tape 10. This technical measure effectively improves water-blocking and impact resistance. Specifically, the cable features multiple layers of effective water-blocking structures, including a water-blocking filler cord 8 between the insulating cores, a water-blocking expansion layer 5 between the insulating shield 4 and the metal composite shield, and a superabsorbent fiber felt layer 9 between the cable core and the aluminum-plastic composite tape 10. These water-blocking structures work together to form a comprehensive water-blocking barrier, effectively preventing moisture from invading the cable interior through various pathways.

[0021] The water-blocking expansion layer 5 is composed of super absorbent fiber felt and water-blocking powder. The super absorbent fiber felt is a polyester-based super absorbent fiber felt with excellent water absorption properties. It can quickly absorb intruding water and expand, blocking possible water seepage channels. The water-blocking powder is electrostatically sprayed on the surface of the super absorbent fiber felt, further enhancing the water-blocking ability, so that the water-blocking expansion layer 5 can quickly form a solid water-blocking barrier when encountering water. The super absorbent fiber felt layer 9 provided between the cable core and the aluminum-plastic composite tape 10 can absorb a small amount of water that may penetrate from the outer sheath, preventing the water from continuing to diffuse into the cable core, thereby enhancing the synergistic effect of the cable's overall water-blocking system and greatly improving the cable's waterproof performance. It is suitable for various humid environments, such as underground pipelines and places near water sources.

[0022] The aluminum-plastic composite tape 10 effectively cushions impacts. When the cable is subjected to external impacts, such as being struck by tools during construction or impacted by falling objects during operation, the aluminum-plastic composite tape 10 absorbs and disperses some of the impact energy, preventing sharp objects from directly piercing the cable and reducing direct damage to the cable's internal structure.

[0023] Furthermore, the water-blocking expansion layer 5 and superabsorbent fiber felt layer 9, made of polyester-based superabsorbent fiber felt, possess excellent cushioning properties. Their flexibility and elasticity act as a cushion when impact forces act on the cable, effectively reducing the impact and protecting the internal structure. This structure disperses the impact force, preventing it from being concentrated at a single point and causing fiber breakage, further enhancing the cable's overall impact resistance.

[0024] In specific implementation, the cable core is formed by twisting three insulated wire cores.

[0025] The insulated wire core comprises a conductor 1 and a conductor shielding layer 2, an insulating layer 3, an insulating shielding layer 4 and a metal composite shielding layer which are arranged outside the conductor 1 from the inside to the outside.

[0026] In a specific implementation, the conductor shielding layer 2 is a semi-conductive conductor shielding layer. The semi-conductive conductor shielding layer has a conductivity similar to that of the conductor 1, can closely adhere to the surface of the conductor 1, effectively uniformly distribute the electric field around the conductor 1, avoid electric field concentration, and reduce the risk of partial discharge.

[0027] In a specific embodiment, the insulation layer 3 is a cross-linked polyethylene (XLPE) insulation layer. This XLPE insulation layer has high breakdown strength and excellent electrical insulation properties, effectively isolating the conductor 1 from electrical contact with the outside world, ensuring stable and safe power transmission. XLPE also has high heat resistance, enabling long-term stable operation at higher temperatures, extending the cable's operating temperature range. XLPE also possesses excellent mechanical properties, including high tensile strength and elongation at break, enabling it to withstand the mechanical stresses that may be encountered during cable installation and use.

[0028] In a specific embodiment, the insulating shielding layer 4 is a semi-conductive insulating shielding layer. This layer has a conductivity similar to that of the insulating layer 3, closely adhering to the surface of the insulating layer 3 and effectively uniformizing the electric field distribution on the surface of the insulating layer 3, further reducing the risk of partial discharge. This prevents electrical treeing caused by electric field concentration on the surface of the insulating layer 3, thereby improving the insulation performance and service life of the cable.

[0029] In practice, the water-blocking expansion layer 5 is composed of superabsorbent fiber felt and water-blocking powder. The water-blocking powder is electrostatically sprayed onto the surface of a polyester-based superabsorbent fiber felt. The superabsorbent fiber felt is a polyester-based superabsorbent fiber felt. In actual use, the water-blocking powder side of the water-blocking expansion layer 5 serves as the inner layer, while the superabsorbent fiber felt side of the water-blocking expansion layer 5 serves as the outer layer. The superabsorbent fiber felt is a polyester-based superabsorbent fiber felt with a grammage of 60-80 g / m².

[0030] Specifically, the water-blocking powder is sodium acrylate-acrylamide copolymer powder. By using sodium acrylate-acrylamide copolymer powder as water-blocking powder, the water-blocking performance of the cable can be significantly improved. It can quickly absorb water and swell to form a gel-like substance to block the water seepage channel, thereby enhancing the waterproof reliability of the cable and is particularly suitable for humid environments. The gel-like substance formed after the sodium acrylate-acrylamide copolymer powder absorbs water and swells has a certain elasticity and toughness, and can play a buffering role when impacted, absorb and disperse impact energy, and reduce the damage of the impact force to the internal structure of the cable. After combining with polyester-based super absorbent fiber felt, the formed water-blocking expansion layer 5 has good impact resistance, can effectively resist external impacts and collisions, and protect the conductor 1 and insulation layer 3 of the cable.

[0031] Polyester-based super absorbent fiber felt is a super absorbent fiber material based on polyester, generally made of super absorbent fiber and polyester spun yarn. It has the advantages of strong water absorption, high tensile strength, moderate elongation, fast water absorption speed and high expansion rate.

[0032] In practice, the metal composite shielding layer includes a copper wire layer 6 and a copper tape layer 7. The copper wires of the copper wire layer 6 are sparsely wound on the water-blocking expansion layer 5, while the copper tape of the copper tape layer 7 is wrapped around the copper wire layer, with the sparse winding direction of the copper wires opposite to the winding direction of the copper tape. This technical measure strengthens the water barrier. The combination of the copper wire layer 6 and the copper tape layer 7 provides a solid physical barrier for the cable, further enhancing the cable's water-blocking capabilities. The tightly wrapped copper tape layer 7 effectively prevents moisture from penetrating the cable interior, forming a multi-layer water-blocking system together with the water-blocking expansion layer 5. High electrical conductivity and mechanical strength: Both the copper wire layer 6 and the copper tape layer 7 are made of copper, which has excellent electrical conductivity and high mechanical strength. The sparse winding structure of the copper wire layer 6 provides a certain degree of flexibility while also enhancing the cable's tensile strength. The tightly wrapped copper tape layer 7 further improves the cable's overall strength and rigidity, enabling it to withstand greater mechanical stress. The sparse winding direction of the copper wire 6 is opposite to the wrapping direction of the copper tape 7. This reverse wrapping method makes the copper wire layer 6 and the copper tape layer 7 more tightly bonded, enhancing the integrity and stability of the metal composite shielding layer and improving the cable's torsion resistance and bending fatigue resistance. The tight wrapping of the copper tape layer 7 can effectively disperse the impact force, preventing the impact force from being concentrated at a single point and causing damage to the cable. When the cable is impacted by an external force, the copper tape layer 7 can disperse the impact force over a larger area, reducing damage to the internal structure. Working synergistically with other structural layers such as the water-blocking expansion layer 5 and the aluminum-plastic composite tape 10, it forms an integrated protective system, improving the cable's impact resistance and ensuring that the cable can maintain good performance even when impacted by external forces.

[0033] The sheath layer 11 is a high-density polyethylene (HDPE) layer. High-density polyethylene (HDPE) has high impact strength, effectively resisting external shocks. It prevents the sheath from rupturing or damaging when subjected to external forces such as impact and squeezing, thereby protecting the cable's internal structures. Its impact strength is typically above 50 kJ / m², making it capable of withstanding significant impact forces. HDPE's excellent flexibility and toughness allow the sheath to deform to a certain extent when impacted, thereby absorbing and dissipating the impact energy and reducing the direct impact on the cable's internal structure. The HDPE sheath layer 11 is typically used in conjunction with other structural layers, such as a metal composite shielding layer. The metal composite shielding layer provides additional mechanical strength and impact protection, forming an integrated protective system with the HDPE sheath layer 11. The combination of the rigidity of the metal shielding layer and the toughness of the HDPE sheath layer 11 provides enhanced resistance to external shocks and collisions, ensuring that the cable maintains good performance even when subjected to external impacts. The inclusion of a high-density polyethylene sheath layer further enhances the impact resistance of the present invention.

[0034] A method for preparing an environmentally friendly high-resistance water-impact resistant medium-voltage power cable comprises the following process steps: S1. Manufacturing conductor 1: using a wire drawing machine to draw a round single wire, and using a frame-type stranding machine to perform regular stranding or irregular stranding to manufacture conductor 1.

[0035] In this embodiment, a double-ended continuous annealing wire drawing machine is used to draw and shape φ8 copper rods through 6-8 passes of dies into 61 monofilaments with a diameter of 2.9 mm. These are then compressed and stranded in layers using a 60-bobbin frame stranding machine in a 1+6+12+18+24 configuration. The resulting round copper conductor has a diameter of 23.4 mm (compression coefficient ≥ 0.90) and a DC resistance of no greater than 0.0470 Ω / km. In actual implementation, the monofilament diameter, number of monofilaments, and stranding method are adjusted to suit the power cable specifications.

[0036] S2, the conductor shielding layer 2, the insulating layer 3 and the insulating shielding layer 4 are extruded and coated on the conductor 1 by a CCV catenary three-layer co-extrusion cross-linking machine, thereby forming a wire core; In this embodiment, the extrusion parameters are as follows: the temperature of the conductor shielding layer 2 is 120° C., the temperature of the insulating layer 3 is 125° C., and the temperature of the insulating shielding layer 4 is 120° C.; and the cross-linking temperature is nitrogen pressure of 1.0 MPa.

[0037] During extrusion, the conductor shield (ultra-smooth semi-conductive cross-linked polymer) with a nominal thickness of 0.8mm, cross-linked polyethylene insulation (ultra-clean XLPE, 10kV cable insulation thickness ≥4.5mm), and insulation shield (peelable semi-conductive layer) with a nominal thickness of 0.8mm are produced on the CCV catenary three-layer co-extrusion cross-linking production line.

[0038] S3. After the wire core leaves the die, nitrogen pressurization is used to heat the conductor shielding layer 2, the insulating layer 3 and the insulating shielding layer 4 in a step-by-step manner to effectively cross-link the conductor shielding layer 2; In this embodiment, the nitrogen pressurized zone heating cross-linking is divided into 8 sections, the water vapor transition section is 2 sections, and the water cooling area is 12 sections. The temperature of each section of the nitrogen pressurized cross-linking area is as follows: .

[0039] S4, wrapping the water-blocking expansion layer 5 on step S3, In this embodiment, the water-blocking expansion layer 5 is produced by spraying an acrylic water-blocking powder (particle size ≤ 50 μm) onto the inner layer of a polyester-based superabsorbent fiber felt. Furthermore, a sodium acrylate-acrylamide copolymer (particle size 30 μm) is electrostatically sprayed (thickness 0.2 mm). The polyester-based superabsorbent fiber felt has an overlap ratio ≥ 30% and a tension of 15 N.

[0040] S5. On a copper wire shielding machine, 0.2-0.4 mm copper wire is sparsely wound on the water-blocking expansion layer 5 to form a copper wire layer 6. Subsequently, a copper tape is wrapped around the outside of the copper wire layer 6 to form a copper tape layer 7, ensuring that the wrapping direction of the copper tape is opposite to the sparse winding direction of the copper wire, to form a metal composite shielding layer; thus, an insulated wire core is obtained. S6: Prepare the cable core and use a disc stranding machine to cable the insulated cores; when cabling, water-blocking filling ropes 8 are placed in the gaps between the insulated cores; S7: wrapping the cable core with a super absorbent fiber felt layer 9 and an aluminum-plastic composite tape 10 in sequence; S8. Extruding a sheath layer 11 outside the aluminum-plastic composite tape 10.

[0041] The medium voltage power cable adopts green manufacturing technology. The entire cable production process is halogen-free and the waste sheath can be recycled (recycling rate ≥ 90%).

[0042] Example 2 The rest of this embodiment is the same as that of embodiment 1, except that: The sheath layer 11 is made of a high-density polyethylene-based composite material. That is, S8, the sheath layer 11 made of a high-density polyethylene-based composite material is extruded outside the aluminum-plastic composite strip 10.

[0043] The high-density polyethylene-based composite material is made of the following components in parts by mass: 80-90 parts of high-density polyethylene, 10-15 parts of maleic anhydride grafted POE elastomer, 5-8 parts of nano-silica, 3-5 parts of sodium polyacrylate water-blocking agent, and 8-12 parts of halogen-free flame retardant.

[0044] Preferably, the high-density polyethylene-based composite material is made of the following compositions in parts by mass: High-density polyethylene (Yangzi Petrochemical 5000S) 85kg, maleic anhydride grafted POE elastomer 12kg, nano-silica 6kg, sodium polyacrylate water repellent 4kg, halogen-free flame retardant 10kg The preparation method of the high-density polyethylene-based composite material comprises: 1) Mix high-density polyethylene and maleic anhydride grafted POE elastomer in an internal mixer at 180-190°C for 5 minutes; 2) Add nano-silica, sodium polyacrylate water-blocking agent and environmentally friendly flame retardant and continue mixing for 8 minutes; 3) Twin-screw extrusion granulation, extrusion temperature is controlled in sections: zone 1 160℃, zone 2 180℃, zone 3 190℃.

[0045] The halogen-free flame retardant is a nitrogen-phosphorus intumescent flame retardant with a composition of ammonium polyphosphate: melamine cyanurate (2:1). Nitrogen-phosphorus intumescent flame retardants are halogen-free and do not release toxic or corrosive gases such as hydrogen halide during combustion, reducing environmental pollution and harm to human health, thus meeting environmental protection requirements. This flame retardant formulation exhibits excellent processing properties during the processing of high-density polyethylene (HDPE) composite sheaths, without affecting the sheath's molding process. Extrusion and injection molding can be performed on conventional processing equipment, improving production efficiency and reducing costs. It can be used synergistically with other additives (such as anti-aging agents and lubricants) without adverse reactions, enhancing the cable's overall performance and meeting the performance requirements of various application scenarios. Performance testing of the FS-YJAY 8.7 / 10kV 3×400 cable is shown in Table 1.

[0046] Table 1: FS-YJAY 8.7 / 10kV 3×400 cable performance test Water immersion aging test: Test conditions: 85℃ water temperature + 15kV AC voltage, lasting 30 days Results: The water tree growth length was ≤50μm (microscope observation) and the dielectric loss increment was ≤0.0005.

[0047] The synergistic effect of maleic anhydride-grafted POE elastomer toughening and nano-silica reinforcement solves the brittleness problem of high-density polyethylene and effectively improves the impact strength of the sheath layer 11. The use of this high-density polyethylene-based composite sheath layer 11 can further improve the impact resistance of the power cable.

[0048] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. An environmentally friendly high-resistance water-impact resistant medium-voltage power cable, characterized in that: It includes a cable core, an aluminum-plastic composite tape and a sheath layer arranged outside the cable core from the inside to the outside; The cable core is formed by twisting a plurality of insulating cores, and the gaps between the insulating cores are filled with water-blocking filling ropes; The insulated wire core includes a conductor and a conductor shielding layer, an insulating layer, an insulating shielding layer and a metal composite shielding layer arranged outside the conductor from the inside to the outside; a water-blocking expansion layer is provided between the insulating shielding layer and the metal composite shielding layer; The water-blocking expansion layer is composed of super absorbent fiber felt and water-blocking powder, and the water-blocking powder is electrostatically sprayed on the surface of the polyester-based super absorbent fiber felt; the super absorbent fiber felt is a polyester-based super absorbent fiber felt; a super absorbent fiber felt layer is provided between the cable core and the aluminum-plastic composite tape.

2. The environmentally friendly high-resistance water-resistant and impact-resistant medium-voltage power cable according to claim 1, characterized in that: The water-blocking powder is sodium acrylate-acrylamide copolymer powder.

3. The environmentally friendly high-resistance water-resistant and impact-resistant medium-voltage power cable according to claim 1, characterized in that: The super absorbent fiber felt is a polyester-based super absorbent fiber felt with a gram weight of 60-80 g / m².

4. The environmentally friendly high-resistance water-impact resistant medium-voltage power cable according to claim 1, characterized in that: The sheath layer is a high-density polyethylene sheath layer.

5. The environmentally friendly high-resistance water-resistant and impact-resistant medium-voltage power cable according to claim 1, characterized in that: The sheath layer is made of a high-density polyethylene-based composite material; the high-density polyethylene-based composite material is made of the following components in parts by mass: 80-90 parts of high-density polyethylene, 10-15 parts of maleic anhydride grafted POE elastomer, 5-8 parts of nano-silica, 3-5 parts of sodium polyacrylate water-blocking agent, and 8-12 parts of halogen-free flame retardant.

6. A method for preparing an environmentally friendly high-resistance water-resistant and shock-resistant medium-voltage power cable according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following process steps: S1. Making conductors: using a wire drawing machine to draw a round single wire, and using a frame-type stranding machine to make the conductors by regular stranding or irregular stranding; S2. Extruding a conductor shielding layer, an insulating layer, and an insulating shielding layer onto the conductor through a CCV catenary three-layer co-extrusion cross-linking machine to form a wire core; S3, after the wire core exits the die head, nitrogen pressurization is used to heat the conductor shielding layer, the insulation layer and the insulation shielding layer in a stepwise manner to reduce the heating temperature; S4, wrapping the water-blocking expansion layer on the surface of step S3; S5. On a copper wire shielding machine, 0.2-0.4 mm copper wire is sparsely wound on the water-blocking expansion layer to form a copper wire layer; then, a copper tape is wrapped around the outside of the copper wire layer to form a copper tape layer, ensuring that the wrapping direction of the copper tape is opposite to the sparse winding direction of the copper wire, to form a metal composite shielding layer; thus, an insulated wire core is obtained; S6: preparing a cable core, and cabling the insulated cores using a disc stranding machine; during cabling, gaps between the insulated cores are filled to form strands of water-blocking filling rope; S7: Wrap the cable core with a super absorbent fiber felt layer and an aluminum-plastic composite tape in sequence; S8. A sheath layer made of high-density polyethylene-based composite material is extruded outside the aluminum-plastic composite belt.

7. The method for preparing the environmentally friendly high-resistance water-resistant and shock-resistant medium-voltage power cable according to claim 6, characterized in that: The preparation method of the high-density polyethylene-based composite material in step 8 is as follows: 1) Mix high-density polyethylene and maleic anhydride grafted POE elastomer in an internal mixer at 180-190°C for 5 minutes; 2) Add nano-silica, sodium polyacrylate water-blocking agent and halogen-free flame retardant and continue mixing for 8 minutes; 3) Twin-screw extrusion granulation, extrusion temperature is controlled in sections: zone 1 160℃, zone 2 180℃, zone 3 190℃.

8. The method for preparing the environmentally friendly high-resistance water-resistant and shock-resistant medium-voltage power cable according to claim 7, characterized in that: The halogen-free flame retardant is a nitrogen-phosphorus intumescent flame retardant, and its composition is ammonium polyphosphate: melamine cyanurate = 2:1.

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