Medium voltage aluminium alloy power cable based on gradient insulation

Abstract

The utility model relates to the technical field of wire and cable, and concretely relates to medium voltage aluminum alloy power cable based on gradient insulation, which comprises: a cable core with a circular cross section, which is formed by wrapping a plurality of wire cores that are tangent to each other and a filling layer filled between the wire cores with a flame-retardant wrapping layer; an armor layer wrapped on the outer wall of the cable core; a flame-retardant layer wrapped on the outer wall of the armor layer; a reinforcing layer wrapped on the outer wall of the flame-retardant layer; and an outer sheath extruded on the outer wall of the reinforcing layer. The utility model sets a gradient insulation structure with soft inside and rigid outside, effectively disperses and absorbs the concentrated shear stress caused by thermal expansion mismatch through the continuous transition of material properties, inhibits the interface peeling and fatigue cracking of the insulation layer, and ensures the electrical integrity and thermal mechanical stability of the cable under frequent temperature cycles.

Description

Technical Field

[0001] This utility model relates to the field of wire and cable technology, and more specifically to medium-voltage aluminum alloy power cables based on gradient insulation. Background Technology

[0002] In industries such as chemical engineering, oil refining, and metallurgy, the power supply systems of core production facilities often operate under extremely complex conditions. These environments not only contain high concentrations of corrosive chemicals such as acids, alkalis, and solvents, but also, due to the continuous nature of production processes and the high load characteristics, cables must withstand severe temperature cycling caused by frequent start-ups, shutdowns, and equipment switching. These harsh conditions pose unprecedented challenges to the long-term operational reliability of cables, especially medium-voltage cables with aluminum alloy conductors, which are increasingly being used due to their lightweight and low-cost advantages.

[0003] Currently, these cables, which are composite structures made of layered metallic and polymeric materials, exhibit significant differences in their coefficients of thermal expansion during long-term service. When the cable undergoes drastic cyclical temperature changes, this thermal expansion mismatch between the materials generates alternating thermal stress at their interfaces. This stress, acting repeatedly over a long period, can easily lead to fatigue damage in the polymeric insulation material, ultimately causing fatal faults such as insulation breakdown and threatening the safety of the entire power supply system.

[0004] Therefore, existing cable structures are ill-suited to meet the stringent requirements for long-term thermomechanical stability in extreme industrial environments such as chemical plants. Utility Model Content

[0005] To address the technical problems existing in power cables for chemical equipment in the prior art, the first aspect of this utility model proposes a technical solution: a medium-voltage aluminum alloy power cable based on gradient insulation, comprising:

[0006] Multiple tangent wire cores and the filler layer between the wire cores are wrapped together by a flame-retardant wrapping layer to form a cable core with a circular cross-section.

[0007] An armor layer, covering the outer wall of the cable core;

[0008] A flame-retardant layer is wrapped around the outer wall of the armor layer;

[0009] A reinforcing layer is formed by covering the outer wall of the flame-retardant layer.

[0010] The outer sheath is extruded onto the outer wall of the reinforcing layer;

[0011] The wire core includes an aluminum alloy stranded conductor, a double-co-extruded semi-conductive conductor shielding layer outside the aluminum alloy stranded conductor, an inner insulation layer, a double-co-extruded intermediate insulation layer outside the inner insulation layer, and an outer insulation layer.

[0012] The intermediate insulation layer is a cross-linked polyethylene insulation layer. The elastic modulus of the inner insulation layer is lower than that of the intermediate insulation layer, which is used to buffer the strain of the aluminum alloy stranded conductor under temperature change environment. The tear resistance of the outer insulation layer is higher than that of the insulation layer. The outer insulation layer is used to inhibit the initiation and propagation of cracks.

[0013] Preferably, the inner insulation layer has a tensile modulus of elasticity of not more than 300 MPa and an elongation at break of more than 500% at 23°C, and the outer insulation layer has a tear resistance of not less than 30 kN / m.

[0014] Preferably, the filling layer includes a first filling structure and a second filling structure. The first filling structure includes a silicone rubber tube with a water-blocking paste layer inside. The second filling structure includes a flame-retardant filling rope and a water-blocking yarn, which are filled in the gap between the core, the silicone rubber tube and the flame-retardant wrapping layer in a mixed weaving manner.

[0015] Preferably, the flame-retardant wrapping layer comprises a double-layer glass ribbon wrapping layer, wherein the wrapping overlap rate of the inner glass ribbon wrapping layer is less than that of the outer glass ribbon wrapping layer.

[0016] Preferably, the armor layer comprises a repeatedly wrapped galvanized aluminum alloy armor layer.

[0017] Preferably, the armor layer includes a first aluminized alloy strip wrapping layer and a second galvanized aluminum alloy strip wrapping layer, wherein the wrapping direction of the first galvanized aluminum alloy strip wrapping layer is to the left and the wrapping direction of the second galvanized aluminum alloy strip wrapping layer is to the right.

[0018] Preferably, the flame-retardant layer includes an inner non-woven fabric wrapping layer and an outer non-woven fabric wrapping layer. The inner non-woven fabric wrapping layer includes a first non-woven fabric wrapping tape wrapped around the outer wall of the armor layer. The outer non-woven fabric wrapping layer includes a second non-woven fabric wrapping tape wrapped around the outer wall of the first non-woven fabric wrapping tape. The outer layer of the first non-woven fabric wrapping tape is provided with an inorganic flame-retardant particle coating, and the inner layer of the second non-woven fabric wrapping tape is provided with an inorganic flame-retardant particle coating, forming an inorganic flame-retardant layer between the inner and outer non-woven fabric wrapping layers.

[0019] Preferably, the aluminum alloy stranded conductor includes an inner conductor and an outer conductor, wherein the inner conductor is a trapezoidal aluminum alloy core stranded structure and the outer conductor is a Z-shaped aluminum alloy core stranded structure.

[0020] Preferably, the braiding angle of the aramid filament braided layer is 55-60°, and the braiding coverage of the aramid filament braided layer is greater than 50%.

[0021] Preferably, the reinforcing layer comprises an aramid filament braided layer, and the outer sheath comprises a halogen-free flame-retardant polyurethane sheath layer.

[0022] Compared with the prior art, the advantages of this utility model are:

[0023] This utility model features a gradient insulation structure that is flexible inside and rigid outside. Through the continuous transition of material properties, it effectively disperses and absorbs the concentrated shear stress caused by thermal expansion mismatch, suppresses interfacial peeling and fatigue cracking of the insulation layer, and ensures the electrical integrity and thermomechanical stability of the cable under frequent temperature cycles.

[0024] This utility model designs a structure with a double-layer non-woven fabric sandwiched with an inorganic flame-retardant layer. At high temperatures, it can be transformed into a continuous and hard ceramicized heat insulation shell, forming a seamless and durable fire barrier with the outer aramid reinforcement layer and halogen-free flame-retardant polyurethane sheath to prevent the spread of flames and achieve a high level of fire safety with low smoke and halogen-free properties, meeting the reliability and service life requirements of power supply in chemical environments. Attached Figure Description

[0025] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0026] Figure 1 This is a schematic diagram of the structure of a medium-voltage aluminum alloy power cable based on gradient insulation, as shown in this utility model.

[0027] Figure 2 This is a schematic diagram of the cross-sectional structure of the medium-voltage aluminum alloy power cable based on gradient insulation, as shown in this utility model.

[0028] Figure 3 This is a schematic diagram of the wire core structure shown in this utility model;

[0029] Figure 4 This is a schematic diagram of the structure of the flame-retardant layer shown in this utility model. Detailed Implementation

[0030] To better understand the technical content of this utility model, specific embodiments are provided below in conjunction with the accompanying drawings.

[0031] {Example 1}

[0032] Combination Figure 1 and Figure 2As shown, the first aspect of this utility model proposes a technical solution: a medium-voltage aluminum alloy power cable based on gradient insulation, comprising a cable core, an armor layer 4, a flame-retardant layer 5, a reinforcing layer 6, and an outer sheath 7. The armor layer 4 covers the outer wall of the cable core, the flame-retardant layer 5 covers the outer wall of the armor layer 4, the reinforcing layer 6 covers the outer wall of the flame-retardant layer 5, and the outer sheath 7 is extruded onto the outer wall of the reinforcing layer 6.

[0033] In an optional embodiment, the cable core is formed by multiple tangent cores 1 and a filler layer 2 between the cores 1 being wrapped and secured by a flame-retardant wrapping layer 3 to form a circular cross-section.

[0034] Combination Figure 3 As shown, the core 1 includes an aluminum alloy stranded conductor 11, a semi-conductive conductor shielding layer 12 co-extruded outside the aluminum alloy stranded conductor 11, an inner insulation layer 13, an intermediate insulation layer 14 co-extruded outside the inner insulation layer 13, and an outer insulation layer 15.

[0035] The aluminum alloy stranded conductor 11 includes an inner conductor 111 and an outer conductor 112. The inner conductor is a trapezoidal aluminum alloy core stranded structure, and the outer conductor 112 is a Z-shaped aluminum alloy core stranded structure.

[0036] Thus, the aluminum alloy stranded conductor 11 provides an extremely smooth, round, and stable cylindrical surface for subsequent insulation extrusion, greatly improving the electric field distribution, reducing internal micro-gap and electric stress concentration points from the source, and the stranded structure is more compact, with high mechanical strength of the conductor itself, which can better resist deformation caused by temperature changes and reduce mechanical stress on the insulation layer.

[0037] Furthermore, the wire core 1 is formed by two double-layer co-extrusion methods and is located on the outer layer of the aluminum alloy stranded conductor 11.

[0038] Specifically, the semiconducting conductor shielding layer 12 and the inner insulation layer 13 are co-extruded for the first time to ensure perfect fusion of the interface between the two without air gaps, which is conducive to the uniformity of the electric field and prevents partial discharge. Subsequently, the intermediate insulation layer 14 and the outer insulation layer 15 are co-extruded for the second time before the first co-extruded layer is cured. Through precise temperature control and cross-linking process, the four layers of materials diffuse and entangle with each other at the molecular level to form a quasi-integrated insulation system with gradually changing physical properties but blurred interfaces.

[0039] In this way, stress concentration and delamination risks caused by clear interfaces in traditional layered designs can be effectively avoided, and it is particularly suitable for frequent thermal cycling in chemical environments.

[0040] Optionally, the intermediate insulation layer 14 is a cross-linked polyethylene insulation layer, the elastic modulus of the inner insulation layer 13 is lower than that of the intermediate insulation layer 14, and the tear resistance of the outer insulation layer 15 is higher than that of the insulation layer 14.

[0041] Specifically, the inner insulation layer 13 is composed of an elastomer-modified cross-linked polyethylene composition, the tensile modulus of the inner insulation layer 13 at 23°C is not higher than 300 MPa, and the elongation at break is greater than 500%. The outer insulation layer 15 is composed of a cross-linked polyethylene composition reinforced with nanofillers, and the tear resistance of the outer insulation layer 15 is not lower than 30 kN / m.

[0042] In a specific embodiment, the inner insulation layer 13 is modified by elastomers such as POE and EVA to reduce the elastic modulus of cross-linked polyethylene and give it extremely high elongation at break, making the material extremely soft and elastic.

[0043] Thus, in the case of sudden temperature changes caused by frequent start-ups and shutdowns of chemical equipment, the thermal expansion / contraction of the aluminum alloy conductor is much greater than that of the outer intermediate insulation layer 14. At this time, the inner insulation layer 13 actively absorbs and accommodates most of the displacement and shear stress caused by the difference in thermal expansion coefficients between the conductor 11 and the intermediate insulation layer 14 through its own large deformation, thus preventing stress from concentrating on the more fragile interface.

[0044] In a specific embodiment, the intermediate insulation layer 14 is made of standard cross-linked polyethylene (XLPE) to maintain high purity and uniformity, thereby ensuring its extremely high volume resistivity and breakdown field strength.

[0045] In a specific embodiment, the outer insulation layer 15 is reinforced with nano-inorganic fillers (such as nano-silica or organic montmorillonite) to cross-linked polyethylene. The nanoparticles form a strong interfacial effect in the polymer matrix, which can effectively terminate the propagation of microcracks and hinder the slippage of molecular chains, thereby greatly improving the tear resistance and scratch resistance of the material to resist external mechanical stress, trace corrosion in chemical environment and environmental stress cracking during laying and operation.

[0046] As described above, the three-layer gradient design of the insulation layer of this utility model achieves a smooth transition from low modulus to high modulus. When thermal stress is transmitted from conductor 11 to the outside, it is first absorbed and buffered by the soft inner insulation layer 13. The remaining stress is then transmitted to the tough outer insulation layer 15 through the middle insulation layer 14. In this process, the stress is dispersed in a wide area with gradually changing performance, avoiding the formation of fatal stress peaks at any single interface, thereby reducing delamination stress.

[0047] Furthermore, the filling layer 2 includes a first filling structure 21 and a second filling structure 22. The first filling structure 21 includes a silicone rubber tube, and the inside of the silicone rubber tube is provided with a water-blocking paste layer 211. The second filling structure 22 includes a flame-retardant filling rope and a water-blocking yarn. The flame-retardant filling rope and the water-blocking yarn are filled in the gap between the core 1, the silicone rubber tube and the flame-retardant wrapping layer 3 in a mixed weaving manner.

[0048] Specifically, the surface of the silicone rubber tube has micropores. Water-blocking paste is filled into the filling layer by filling the entire silicone rubber tube, and the remaining space is filled by a mixture of flame-retardant filling rope and water-blocking yarn.

[0049] In this way, it can play a water-blocking role under normal conditions. In particular, after the water-blocking yarn absorbs water and expands, it can squeeze the silicone rubber tube, causing the water-blocking paste to be squeezed out from the silicone rubber tube and fill the excess gaps, thus achieving better radial and axial water-blocking capabilities. In a fire environment, the flame-retardant filling rope can play a heat insulation role. The evaporation of water absorbed in the water-blocking yarn can reduce heat, so as to work with the flame-retardant filling rope to prevent the flame from moving closer to the core 1.

[0050] As mentioned above, the design of the filling layer achieves dual protection under normal conditions and fire conditions. Under normal conditions, the water-blocking yarn expands rapidly when it comes into contact with water, first blocking the longitudinal channel; its expansion force will squeeze the silicone rubber tube, forcing the water-blocking paste inside to seep out through the micropores of the tube wall, further filling the micro gaps, and achieving active radial and longitudinal sealing.

[0051] Furthermore, the flame-retardant wrapping layer 3 includes a double-layer glass ribbon wrapping layer, wherein the wrapping overlap rate of the inner glass ribbon wrapping layer is less than that of the outer glass ribbon wrapping layer.

[0052] In this way, by wrapping with double-layer glass ribbon, the core 1 and the filling structure are secured into a circular cross-section. The outer layer of glass ribbon wrapping has a larger wrapping overlap, making the wrapping tighter. At the same time, the glass ribbon melts in a fire and forms a glassy state, filling the gap between the armor layer 4 and the flame-retardant filling rope, forming a dense isolation layer around the cable core to prevent flames and high temperatures from spreading to the core.

[0053] Furthermore, the armor layer 4 includes a repeatedly wrapped galvanized aluminum alloy armor layer.

[0054] Specifically, in combination Figure 4 As shown, the armor layer 4 includes a first aluminum-plated alloy strip wrapping layer 41 and a second zinc-plated aluminum alloy strip wrapping layer 42. The wrapping direction of the first zinc-plated aluminum alloy strip wrapping layer 41 is to the left, and the wrapping direction of the second zinc-plated aluminum alloy strip wrapping layer 42 is to the right.

[0055] In this way, the gaps in the first layer are covered by the solid part of the second layer of tape, which greatly reduces the gaps in electromagnetic leakage, provides a more continuous and complete shielding effect, and more effectively prevents flames, smoke or moisture from longitudinally penetrating into the cable through the lap joint.

[0056] Furthermore, the flame retardant layer 5 includes a double-layer non-woven fabric wrapping layer and an inorganic flame retardant layer 52 disposed between the double-layer non-woven fabric wrapping layers.

[0057] Specifically, in combination Figure 4As shown, the flame-retardant layer 5 includes an inner non-woven fabric wrapping layer 51 and an outer non-woven fabric wrapping layer 53. The inner non-woven fabric wrapping layer 51 includes a first non-woven fabric wrapping tape wrapped around the outer wall of the armor layer 4. The outer non-woven fabric wrapping layer 53 includes a second non-woven fabric wrapping tape wrapped around the outer wall of the first non-woven fabric wrapping tape. The outer layer of the first non-woven fabric wrapping tape is provided with an inorganic flame-retardant particle coating, and the inner layer of the second non-woven fabric wrapping tape is provided with an inorganic flame-retardant particle coating. An inorganic flame-retardant layer 52 is formed between the inner non-woven fabric wrapping layer 51 and the outer non-woven fabric wrapping layer 53.

[0058] Specifically, flame-retardant particle coatings are respectively applied to the outer layer of the first non-woven fabric tape and the inner layer of the second non-woven fabric tape. This ensures that when the two layers of tape are wrapped and bonded together, the flame retardant is precisely positioned at the interface between the two non-woven fabric layers. This ensures that when a fire occurs, the ceramic reaction process takes place at the interface between the two skeleton layers, forming a uniform and efficient ceramic insulation layer.

[0059] In a preferred embodiment, the inorganic flame-retardant particle coating includes a water-blocking adhesive that can penetrate nonwoven fabric and inorganic flame-retardant particles dispersed in the water-blocking adhesive.

[0060] Optionally, the water-blocking adhesive can be a water-based silicone rubber-based or EVA-based adhesive that can penetrate the non-woven fabric, block the micropores between the fibers, and together with the double-layer non-woven fabric, form a solid longitudinal moisture barrier to prevent chemical products from migrating longitudinally along the cable and corroding the internal metal components.

[0061] Furthermore, the adhesive properties of the water-blocking adhesive firmly bond the inorganic flame-retardant particles to the non-woven fabric skeleton, preventing the particles from falling off and migrating when the cable is bent or vibrated, thus ensuring the long-term uniformity and reliability of the flame retardant distribution.

[0062] Optionally, the inorganic flame-retardant particles can preferably be aluminum hydroxide, magnesium hydroxide, or a compound system thereof, which decompose and absorb heat at high temperatures and generate high-temperature resistant metal oxides.

[0063] In this way, when the polymer matrix in the water-blocking adhesive is heated, it will carbonize or react with the decomposition products of inorganic flame-retardant particles, participating in the formation process of the ceramic body, strengthening the mechanical strength and density of the final ceramic body, and improving the heat insulation barrier.

[0064] Furthermore, the reinforcing layer 6 includes an aramid filament braided layer with a braiding angle of 55-60° and a braiding coverage of more than 50%.

[0065] In this way, the aramid fiber braided layer forms a high tensile strength and cut-resistant protective layer on the outside of the cable, which can work together with the armor layer 4 to bear external mechanical forces.

[0066] Furthermore, the outer sheath 7 includes a halogen-free flame-retardant polyurethane sheath layer. Halogen-free flame-retardant polyurethane combines excellent abrasion resistance, chemical corrosion resistance, high elasticity, and flame retardancy, meeting the usage requirements of chemical production environments.

[0067] {Example 2}

[0068] The above-mentioned method for preparing medium-voltage aluminum alloy power cables based on gradient insulation includes the following steps:

[0069] Step S1, Conductor stranding: Using a wire stranding device, trapezoidal aluminum alloy wire cores are first stranded to form the inner conductor 111, and then Z-shaped aluminum alloy wire cores are stranded to the outer layer to form a tightly stranded aluminum alloy wire conductor 11.

[0070] Step S2, First double-layer co-extrusion: The semi-conductive conductor shielding material and the modified flexible cross-linked polyethylene insulation material are simultaneously extruded on the outside of the conductor 11 through a double-head co-extrusion equipment to form a semi-conductive conductor shielding layer 12 and an inner insulation layer 13.

[0071] Step S3, Second Double-Layer Co-Extrusion: Before the first co-extruded layer enters the cross-linking pipeline, the standard cross-linked polyethylene insulation material and the nano-modified high-toughness cross-linked polyethylene insulation material are extruded simultaneously through the second double-head co-extrusion equipment to form the intermediate insulation layer 14 and the outer insulation layer 15; then, the wire core enters the cross-linking pipeline for unified vulcanization and cross-linking, so that the four layers of materials form a gradient insulation whole.

[0072] Step S4, cabling and wrapping: multiple cores 1 are twisted together with the first filling structure 21 and the second filling structure 22 to form a circular cable core; then, the inner glass ribbon is wrapped with a smaller overlap rate first, and the outer glass ribbon is wrapped with a larger overlap rate to form a flame-retardant wrapping layer 3.

[0073] Step S5, Armor layer wrapping: First, wrap the first galvanized aluminum alloy strip 41 to the left outside the cable core, and then wrap the second galvanized aluminum alloy strip 42 to the right to form the armor layer 4.

[0074] Step S6, Flame retardant layer preparation and coating: A slurry made of water-based adhesive and inorganic flame retardant particles is pre-coated on one side of the non-woven fabric tape and dried; during wrapping, the first non-woven fabric tape with the coated side facing outward is first wrapped to form the inner non-woven fabric wrapping layer 51, and then the second non-woven fabric tape with the coated side facing inward is wrapped to the outer layer to form the outer non-woven fabric wrapping layer 53, so that the two coated sides are facing each other and sandwiched in the middle to form the inorganic flame retardant layer 52;

[0075] Step S7, Reinforcing Layer Weaving and Outer Sheath Extrusion: Aramid filaments are woven at a weaving angle of 55-60° outside the flame-retardant layer 5 to form the reinforcing layer 6; finally, halogen-free flame-retardant polyurethane material is extruded onto the outer layer of the reinforcing layer 6 to form the outer sheath 7.

[0076] In steps S2 and S3, the co-extrusion of the conductor shielding layer 12 and the inner insulation layer 13 ensures that the interface between the two is originally gapless. Then, before the first co-extrusion layer has cooled and cross-linked, a second co-extrusion is performed. At this time, the molecular chains of the inner insulation layer 13 and the intermediate insulation layer 14 diffuse and entangle with each other under high temperature and high pressure, and form covalent bonds in the subsequent vulcanization cross-linking.

[0077] Ultimately, the resulting four-layer structure forms a gradient structure with blurred interfaces and interconnected layers. This chemical and physical fusion achieved through manufacturing processes results in an interface bonding strength far exceeding that of traditional adhesive-based laminated interfaces, enabling it to meet the long-term thermomechanical stability requirements of extreme industrial environments such as chemical processing.

[0078] In step S6, flame-retardant particle coatings are respectively applied to the outer layer of the first nonwoven fabric tape and the inner layer of the second nonwoven fabric tape. This ensures that when the two layers of tape are wrapped and bonded together, the flame retardant is precisely positioned at the interface between the two nonwoven fabric layers. This ensures that when a fire occurs, the ceramic reaction process occurs at the interface between the two skeleton layers, forming a uniform and efficient ceramic insulation layer.

[0079] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Those skilled in the art to which this invention pertains can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of this invention shall be determined by the claims.

Claims

1. A medium-voltage aluminum alloy power cable based on gradient insulation, characterized in that, include: Multiple tangent wire cores (1) and a filler layer (2) between the wire cores (1) are wrapped together by a flame-retardant wrapping layer (3) to secure the cable core with a circular cross-section. Armor layer (4) covers the outer wall of the cable core; A flame-retardant layer (5) covers the outer wall of the armor layer (4); A reinforcing layer (6) is attached to the outer wall of the flame-retardant layer (5); The outer sheath (7) is extruded onto the outer wall of the reinforcing layer (6); The core (1) includes an aluminum alloy stranded conductor (11), a semiconducting conductor shielding layer (12) co-extruded on the aluminum alloy stranded conductor (11) and an inner insulation layer (13), an intermediate insulation layer (14) co-extruded on the inner insulation layer (13) and an outer insulation layer (15). The intermediate insulation layer (14) is a cross-linked polyethylene insulation layer. The elastic modulus of the inner insulation layer (13) is lower than that of the intermediate insulation layer (14), which is used to buffer the strain of the aluminum alloy stranded conductor (11) under temperature change environment. The tear resistance of the outer insulation layer (15) is higher than that of the insulation layer (14), and the outer insulation layer (15) is used to suppress the initiation and propagation of cracks.

2. The medium-voltage aluminum alloy power cable based on gradient insulation according to claim 1, characterized in that, The inner insulation layer (13) has a tensile elastic modulus of not more than 300 MPa at 23°C and an elongation at break of more than 500%, and the outer insulation layer (15) has a tear resistance of not less than 30 kN / m.

3. The medium-voltage aluminum alloy power cable based on gradient insulation according to claim 1, characterized in that, The filling layer (2) includes a first filling structure (21) and a second filling structure (22). The first filling structure (21) includes a silicone rubber tube, and the inside of the silicone rubber tube is provided with a water-blocking paste layer (211). The second filling structure (22) includes a flame-retardant filling rope and a water-blocking yarn. The flame-retardant filling rope and the water-blocking yarn are filled in the gap between the core (1), the silicone rubber tube and the flame-retardant wrapping layer (3) in a mixed weaving manner.

4. The medium-voltage aluminum alloy power cable based on gradient insulation according to claim 1, characterized in that, The flame-retardant wrapping layer (3) includes a double-layer glass ribbon wrapping layer, wherein the wrapping overlap rate of the inner glass ribbon wrapping layer is less than that of the outer glass ribbon wrapping layer.

5. The medium-voltage aluminum alloy power cable based on gradient insulation according to claim 1, characterized in that, The armor layer (4) includes a repeatedly wrapped galvanized aluminum alloy armor layer.

6. The medium-voltage aluminum alloy power cable based on gradient insulation according to claim 1, characterized in that, The armor layer (4) includes a first galvanized aluminum alloy strip wrapping layer (41) and a second galvanized aluminum alloy strip wrapping layer (42). The wrapping direction of the first galvanized aluminum alloy strip wrapping layer (41) is to the left, and the wrapping direction of the second galvanized aluminum alloy strip wrapping layer (42) is to the right.

7. The medium-voltage aluminum alloy power cable based on gradient insulation according to claim 1, characterized in that, The flame-retardant layer (5) includes an inner non-woven fabric wrapping layer (51) and an outer non-woven fabric wrapping layer (53). The inner non-woven fabric wrapping layer (51) includes a first non-woven fabric wrapping tape wrapped around the outer wall of the armor layer (4). The outer non-woven fabric wrapping layer (53) includes a second non-woven fabric wrapping tape wrapped around the outer wall of the first non-woven fabric wrapping tape. The outer layer of the first non-woven fabric wrapping tape is provided with an inorganic flame-retardant particle coating. The inner layer of the second non-woven fabric wrapping tape is provided with an inorganic flame-retardant particle coating. An inorganic flame-retardant layer (52) is formed between the inner non-woven fabric wrapping layer (51) and the outer non-woven fabric wrapping layer (53).

8. The medium-voltage aluminum alloy power cable based on gradient insulation according to claim 1, characterized in that, The aluminum alloy stranded conductor (11) includes an inner conductor (111) and an outer conductor (112). The inner conductor is a trapezoidal aluminum alloy core stranded structure, and the outer conductor (112) is a Z-shaped aluminum alloy core stranded structure.

9. The medium-voltage aluminum alloy power cable based on gradient insulation according to claim 1, characterized in that, The reinforcing layer (6) includes an aramid filament braided layer, and the outer sheath (7) includes a halogen-free flame-retardant polyurethane sheath layer.

10. The medium-voltage aluminum alloy power cable based on gradient insulation according to claim 9, characterized in that, The braiding angle of the aramid filament braided layer is 55~60°, and the braiding coverage of the aramid filament braided layer is greater than 50%.

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