Flame-retardant fireproof high-voltage cable
Through the design of the split conductor structure and refractory layer, combined with the sintering and hardening of the ceramic silicone tape, a heat insulation layer is formed, which solves the problem of flammability of high-voltage cables, and achieves continuous operation and mechanical performance improvement in fires, providing a safe cable structure.
Patent Information
- Application Number
- CN202421784597.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-25
- Publication Date
- 2025-07-18
- Estimated Expiration
- 2034-07-25
AI Technical Summary
Existing high-voltage cables are prone to flammability in fires, resulting in power interruption, increasing fire risk, and have a bulky structure and poor softness, affecting laying and use.
It adopts a split conductor structure, a metal shield layer with copper wire sparse and copper tape reverse tie, a refractory mud extrusion-covered refractory layer and a low-smoke, halogen-free flame retardant sheath, combined with the sintering and hardening of the ceramicized silicone tape, a heat insulation layer is formed to enhance mechanical and fire resistance.
In the case of fire, delay heat transfer, protect the internal wire core, ensure the continuous operation of the power system, reduce the damage to equipment by the fire, and provide a safe cable structure.
Smart Images
Figure CN223123655U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of cables, in particular to a flame-retardant and fire-resistant high-voltage cable. Background Art
[0002] At present, the high-voltage cables produced by the vast majority of enterprises are of the structure of corrugated aluminum sheath + conventional plastic outer sheath, and mostly only have the flame-retardant function. The structure and process are relatively simple, mainly composed of a conductor, an insulation layer, a buffer layer, a metal aluminum sheath, and an outer sheath. Such cables do not have the fire-resistant function of continuing to operate in a fire. If the cable is prone to combustion, once it burns, it will cause power interruption and increase the fire risk; in addition, most of the existing cables adopt the corrugated aluminum sheath structure, which has a large bending radius, poor flexibility, and a large cable weight, affecting the loading logistics and on-site laying. Content of the Utility Model
[0003] The purpose of the utility model is to provide a cable structure that can ensure the continuous operation of the power system in case of a fire.
[0004] To achieve the above purpose, the utility model provides a flame-retardant and fire-resistant high-voltage cable, which includes a conductor, an insulating layer, a metal shielding layer, a moisture-proof layer, a fire-resistant layer, and a sheath:
[0005] The conductor adopts a segmented conductor structure. The conductor strand blocks are made by drawing and stranding copper rods, and the conductor strand blocks are separated by crepe paper;
[0006] The insulating layer is tightly coated on the surface of the conductor;
[0007] A semi-conductive buffer water-blocking tape is wound on the surface of the insulating layer to form a buffer layer, which is used to ensure good electrical contact between the insulating layer and the metal shielding layer;
[0008] The metal shielding layer adopts a structure of loosely winding copper wires and reverse binding with copper tape, and is arranged on the surface of the buffer layer;
[0009] The moisture-proof layer adopts a polyethylene coating structure and is arranged between the metal shielding layer and the fire-resistant layer;
[0010] The fire-resistant layer adopts a structure of extruding and coating fire-resistant mud, which is extruded and coated on the surface of the moisture-proof layer, and the fire-resistant mud is wound and fixed through a ceramicized silica gel tape; the fire-resistant mud and the ceramicized silica gel tape are sintered and hardened under the condition of high fire temperature to form a heat-insulating layer, which hinders most of the heat from transferring inward, and at the same time greatly improves the mechanical properties to protect the internal wire core; in addition, it can also maintain good performance under the action of various strong corrosive media such as acids, alkalis, and salts.
[0011] The sheath covers the outer surface of the refractory layer. The sheath uses a low-smoke and halogen-free flame-retardant sheath material, which has the characteristics of chemical corrosion resistance, halogen-free and low-smoke flame retardancy, preventing the fire from spreading over a long distance when on fire, and producing little or no smoke when burning.
[0012] Further, the conductor adopts a segmented conductor structure, and a first semi-conductive resistive water tape is wound around the conductor and tied tightly after winding to reduce the influence of skin effect in the conductor.
[0013] Further, a second semi-conductive resistive water tape is wound around the outer surface of the metal shielding layer; the moisture-proof layer adopts a polyethylene coating structure and is coated on the surface of the second semi-conductive resistive water tape.
[0014] Further, in the buffer layer, the semi-conductive buffer resistive water tape is evenly wound around the surface of the insulating layer by winding; the winding direction is to the right, and the overlap is 45%-50%.
[0015] Further, the insulating layer adopts a cross-linked polyethylene extrusion coating structure, which has the characteristics of high temperature resistance, strong insulation performance, non-melting, chemical corrosion resistance, high mechanical strength, environmental protection, etc.; a semi-conductive inner shielding layer is provided between the insulating layer and the conductor, and a semi-conductive outer shielding layer is provided between the insulating layer and the buffer layer. The semi-conductive inner shielding layer, insulating layer and semi-conductive outer shielding layer are simultaneously extruded under high pressure and tightly coated on the surface of the conductor to form an integral insulation structure.
[0016] Further, the metal shielding layer adopts a combined structure of loosely winding copper wires and reverse tying with copper tape, and is wound around the surface of the buffer layer; the copper wires are evenly wound around the surface of the buffer layer by loose winding, the loose winding direction is to the left, the loose winding pitch is 9-12 times, and the copper wires are reverse tied with copper tape outside.
[0017] Further, the moisture-proof layer adopts a serrated polyethylene coating structure. The medium-density polyethylene material is extruded through a special serrated die and coated on the surface of the second semi-conductive resistive water tape, so as to ensure that external water vapor and moisture will not enter the cable interior, causing oxidation of the copper wires and affecting the electrical performance. At the same time, the serrations can increase the contact area with the refractory mud and prevent the fireproof mud from falling off; the average coating thickness is not less than the nominal value, and the thickness of the thinnest point is not less than 90% of the nominal thickness; the serration length is not less than 2.5 mm.
[0018] Further, the serrated side of the moisture-proof layer is connected to the refractory layer. The refractory layer uses a grouting machine to extrude the refractory mud to coat the surface of the moisture-proof layer. Through a double-headed wrapping machine, the ceramicized silica gel tape is wound around the surface of the refractory mud in a way of intermittent wrapping. The wrapping direction of the ceramicized silica gel tape is rightward, and the overlapping degree is 45%-50%. Among them, the fireproof mud material is prepared by mixing magnesium hydroxide and glass water in a ratio of 7:3.
[0019] Further, the sheath adopts a halogen-free low-smoke flame-retardant polyolefin coating structure and is shrink-wrapped on the outer surface of the moisture-proof layer.
[0020] The preparation process of the flame-retardant and fire-resistant high-voltage cable of the present utility model is as follows:
[0021] 1) Conductor production process: The conductor is made by drawing and stranding copper rods. A water-blocking tape is longitudinally wrapped in the middle of each layer of single wires, and a first semiconductive water-blocking tape is wrapped around the conductor and tied tightly after wrapping. During the process, ensure that the surface of the conductor is smooth, free of oil stains, burrs and sharp edges that damage the insulation.
[0022] 2) Insulation layer production process: Crosslinked polyethylene together with the inner and outer shields is extruded under high pressure and tightly coated on the surface of the conductor to form an integrated insulation structure. Among them, the average value of the coating thickness is not less than the nominal value, the thickness of the thinnest point is not less than 90% of the nominal thickness, the eccentricity is not more than 10%, and the extrusion surface should be smooth without sharp corners, particles, burning, abrasion and other phenomena.
[0023] 3) Buffer layer production process: The semiconductive buffer water-blocking tape is evenly wound around the surface of the insulation layer by wrapping. Avoid moisture on the surface during wrapping. The wrapping direction is rightward, and the overlap is 45%-50% to ensure the tightness of the wrapping tape and the stability of the structure.
[0024] 4) Metal shielding layer production process: The copper wires are evenly wound around the surface of the buffer layer in a sparse winding manner. The sparse winding direction is leftward, and the sparse winding pitch is 9-12 times to ensure the uniform spacing of the copper wires and the stability of the structure. The copper wires are tied back with copper tape outside, and a second semiconductive water-blocking tape is wrapped outside the copper wire sparse winding layer.
[0025] 5) Moisture-proof layer production process: Medium-density polyethylene is extruded through a serrated die on the die sleeve and coated on the surface of the second semiconductive water-blocking tape. The average value of the coating thickness should not be less than the nominal value, the thickness of the thinnest point should not be less than 90% of the nominal thickness, the extrusion surface should be smooth without particles, burning, abrasion and other phenomena, and the serration length is not less than 2.5 mm.
[0026] 6) Fire-resistant layer production process: Mix magnesium hydroxide and water glass into fire-resistant mud at a ratio of 7:3. Use a grouting machine to extrude the fire-resistant mud and coat it on the surface of the moisture-proof layer; the average coating thickness should not be less than the nominal value, and the thickness at the thinnest point should not be less than 90% of the nominal thickness; there should be no phenomena such as peeling or holes on the extruded surface; after the grouting machine extrudes, immediately carry out ceramicized silica gel wrapping through a double-head wrapping machine, and use the intermittent wrapping method to wind the ceramicized silica gel tape on the surface of the fire-resistant mud. The wrapping direction of the ceramicized silica gel is to the right, with an overlap of 45%-50%, ensuring the smoothness and flatness of the wrapping tape and the stability of the structure.
[0027] 7) Sheath production process: Extrude and stretch the halogen-free low-smoke flame-retardant polyolefin material to form a sheath structure, which shrinks and coats on the surface of the fire-resistant layer; among them, the average extrusion thickness should not be less than the nominal value, and the thickness at the thinnest point should not be less than 90% of the nominal thickness. The extruded surface should be smooth, without sharp corners, particles, charring, abrasions, etc.
[0028] Compared with the prior art, the advantages of the present utility model are as follows:
[0029] 1. By using polyethylene material to set the moisture-proof layer, the present utility model avoids external water vapor and moisture from entering the cable interior and causing copper wire oxidation, preventing the electrical performance from being affected; in addition, the connection end between the moisture-proof layer and the fire-resistant layer is serrated, increasing the contact area between the moisture-proof layer and the fire-resistant mud and preventing the fire-resistant mud from falling off.
[0030] 2. By setting the fire-resistant layer, the present utility model utilizes the fact that the fire-resistant mud and the ceramicized silica gel tape can quickly sinter and harden at high temperatures to form a heat-insulating layer, effectively hindering the transfer of heat to its interior, improving the mechanical properties, protecting the wire core inside the cable, and reducing the impact of strongly corrosive media on the cable, enabling the cable to maintain good performance under the action of various strongly corrosive media such as acids, alkalis, and salts, and having excellent fire resistance and corrosion resistance functions.
[0031] 3. The present utility model adopts a metal shielding structure of copper wire loose winding + copper tape reverse tying, improving the flexibility of the cable; using copper wire and copper tape instead of the conventional metal corrugated aluminum sheath not only increases the minimum bending radius of the cable but also has a greater current diversion ability for fault current than the conventional aluminum sheath.
[0032] 4. The present utility model adopts a segmented conductor structure to reduce the influence of the skin effect; through the process structures and connection relationships of the insulating layer, buffer layer, metal shielding layer, moisture-proof layer, fire-resistant layer, and halogen-free low-smoke flame-retardant polyolefin sheath, it not only effectively delays the erosion of the high-temperature flame to the interior but also ensures the continuous operation of the power system in case of a fire, reduces the damage of the fire to power equipment, and gains valuable time for personnel evacuation and fire fighting and rescue.
[0033] 5. The cable of the present utility model has a simple process, relatively light weight, good flexibility, is non-toxic, odorless, pollution-free, produces less smoke when burning, is environmentally friendly, safe, water-blocking, and has a larger loading capacity on the reel compared to high-voltage cables on the market. It is convenient and fast to construct and use. When stored in a natural indoor state, it will not have quality problems after being stored for more than 35 years and can be used normally. It can pass the Class C flame retardant standard specified in GB12666.5 and the fire resistance test of GB / T19666. BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Figure 1 It is a schematic diagram of the overall structure of the flame retardant and fire resistant high-voltage cable of the present utility model;
[0035] Figure 2 It is a process flow chart of the production of the flame retardant and fire resistant high-voltage cable of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0036] To make the objectives, technical solutions and advantages of the present utility model clearer, the technical solutions of the present utility model will be further described below.
[0037] This embodiment provides a flame retardant and fire resistant high-voltage cable, as Figure 1 shown, which includes a conductor 2, an insulating layer 6, a metal shielding layer, a moisture-proof layer 11, a fire resistant layer and a sheath 14. Among them, the conductor 2 adopts a segmented conductor structure. Conductor strand blocks are obtained by drawing and stranding copper rods. The conductor strand blocks are separated by crepe paper 3, as Figure 1 shown. A crepe paper rope 1 is also provided at the hole in the middle of the strand conductor. The crepe paper rope 1 is mainly used to fill the conductor gaps and support the conductor strand blocks; a first semi-conductive water-blocking tape 4 is wound around the outer surface of the conductor 2 and tied tightly after winding.
[0038] The outer surface of the first semi-conductive water-blocking tape 4 is connected to the insulating layer 6 through a semi-conductive inner shielding layer 5, so that the insulating layer 6 is tightly coated on the surface of the conductor 2. The insulating layer 6 adopts a cross-linked polyethylene extrusion coating structure and has characteristics such as high temperature resistance, strong insulation performance, non-melting, chemical corrosion resistance, high mechanical strength, and environmental friendliness. The outer surface of the insulating layer 6 is wound with a semi-conductive buffer water-blocking tape 8 through a semi-conductive outer shielding layer 7 to form a buffer layer. In the buffer layer, the semi-conductive buffer water-blocking tape 8 is evenly wound around the surface of the insulating layer 6 by a winding method; the winding direction is to the right, and the overlap is 45%-50%, which is used to ensure good electrical contact between the insulating layer 6 and the metal shielding layer.
[0039] In this embodiment, a semi-conductive inner shielding layer 5 is provided between the insulating layer 6 and the conductor 2, and a semi-conductive outer shielding layer 7 is provided between the insulating layer 6 and the buffer layer. The semi-conductive inner shielding layer 5, the insulating layer 6 and the semi-conductive outer shielding layer 7 are simultaneously extruded under high pressure and tightly coated on the surface of the conductor 2 to form an integral insulation structure.
[0040] AsFigure 1 As shown, a metal shielding layer is provided outside the buffer layer. The metal shielding layer is evenly wound around the surface of the buffer layer in a loose winding manner using copper wires and copper tapes 9; the loose winding direction is leftward, the loose winding pitch is 9 - 12 times, and the copper wires are reversely tied with copper tapes outside.
[0041] A second semiconductive resistive water tape 10 is wound around the outer surface of the metal shielding layer. The outer surface of the second semiconductive resistive water tape 10 is connected to a moisture-proof layer 11, such that the moisture-proof layer 11 is provided between the metal shielding layer and the fire-resistant layer.
[0042] In this embodiment, the moisture-proof layer 11 adopts a serrated polyethylene coating structure. After the medium-density polyethylene material is extruded through a special serrated die, it is coated on the surface of the second semiconductive resistive water tape 10, thereby preventing external water vapor and moisture from entering the cable interior, causing copper wire oxidation and affecting electrical performance. Among them, the average coating thickness is not less than the nominal value, and the thickness of the thinnest point is not less than 90% of the nominal thickness; the serration length is not less than 2.5 mm.
[0043] A fire-resistant layer is provided outside the moisture-proof layer 11. As Figure 1 shown, the serrated side of the moisture-proof layer 11 is connected to the fire-resistant layer through fire-resistant mud 12; through the serrated connection end, the contact area between the polyethylene moisture-proof layer 11 and the fire-resistant mud 12 is increased to prevent the fire-proof mud from falling off.
[0044] In this embodiment, the material of the fire-resistant mud 12 is prepared by mixing magnesium hydroxide and glass water in a ratio of 7:3. The fire-resistant layer is formed by extruding the fire-resistant mud 12 onto the surface of the moisture-proof layer 11 through a large grouting machine; and through a double-headed wrapping machine, the ceramicized silica gel tape 13 is wound around the surface of the fire-resistant mud 12 in an intermittent wrapping manner. Among them, the wrapping direction of the ceramicized silica gel tape 13 is rightward, and the overlap degree is 45% - 50%.
[0045] The fire-resistant layer adopts a fire-resistant mud extrusion coating structure, which is extruded and coated on the surface of the moisture-proof layer 11, and the fire-resistant mud 12 is wound and fixed through the ceramicized silica gel tape 13; under the action of high temperature, the fire-resistant mud 12 and the ceramicized silica gel tape 13 can quickly sinter and harden to form a heat-insulating layer, thereby hindering most of the heat from transferring to its interior, protecting the internal wire core, and effectively improving the mechanical performance. In addition, it can also maintain good performance under the action of various strong corrosive media such as acids, alkalis, and salts, making it have good corrosion resistance.
[0046] As Figure 1As shown in the figure, a sheath 14 is also provided outside the refractory layer. The sheath 14 uses a low-smoke and halogen-free flame-retardant sheath material and adopts a halogen-free low-smoke flame-retardant polyolefin coating structure. After the halogen-free low-smoke flame-retardant polyolefin material is extruded and stretched, a sheath structure is formed, which shrinks and wraps on the surface of the refractory layer, making it have the characteristics of chemical corrosion resistance, halogen-free low-smoke flame-retardant performance, preventing the spread of fire over a long distance during a fire, and producing little or no smoke during combustion.
[0047] The process preparation flow of the high-voltage cable in this embodiment is as Figure 2 shown, and includes the following steps:
[0048] 1) Conductor 2 production: Copper rods are drawn and stranded into conductor strand blocks, combined with copper tubes to form a cable. A water-blocking tape is longitudinally wrapped between the single wires of each layer. A first semiconductive water-blocking tape 4 is wrapped around the outside of the conductor 2, and after wrapping, it is tied tightly; during the process, it is ensured that the surface of the conductor 2 is smooth, free of oil stains, burrs and sharp edges that damage the insulation.
[0049] 2) Insulation layer 6 production: Crosslinked polyethylene, together with the inner shielding layer 5 and the outer shielding 7, are simultaneously extruded under high pressure and tightly wrapped on the surface of the conductor 2 to form an integral insulation structure; among them, the average value of the coating thickness is not less than the nominal value, the thickness of the thinnest point is not less than 90% of the nominal thickness, and the eccentricity is not more than 10%. The extrusion surface should be smooth, without sharp corners, particles, burning, abrasion and other phenomena.
[0050] 3) Buffer layer production: The semiconductive buffer water-blocking tape 8 is wrapped around the outside of the insulation layer 6 through the outer shielding layer 7 in a winding manner. During winding, moisture on the surface should be avoided. The winding direction is to the right, and the overlap is 45%-50%, ensuring the tightness of the tape and the stability of the structure.
[0051] 4) Metal shielding layer production: Copper wires 9 are evenly wound around the surface of the buffer layer in a sparse winding manner. The sparse winding direction is to the left, and the sparse winding pitch is 9-12 times, ensuring the uniform spacing of the copper wires 9 and the stability of the structure. The copper wires 9 are tied back with copper tape outside, and a second semiconductive water-blocking tape 10 is wound around the outside of the sparse winding layer of the copper wires 9.
[0052] 5) Moisture-proof layer 11 production process: Medium-density polyethylene is extruded through a saw-tooth-shaped die on the die sleeve and then wrapped on the surface of the second semiconductive water-blocking tape 10. The average value of the coating thickness should not be less than the nominal value, the thickness of the thinnest point should not be less than 90% of the nominal thickness, the extrusion surface should be smooth, without particles, burning, abrasion and other phenomena, and the saw-tooth length is not less than 2.5 mm.
[0053] 6) Production of refractory layer: Mix magnesium hydroxide and sodium silicate solution in a ratio of 7:3 to form refractory mud 12. Use a grouting machine to extrude the refractory mud 12 and coat it on the surface of the moisture-proof layer 11. The average coating thickness should not be less than the nominal value, and the thickness at the thinnest point should not be less than 90% of the nominal thickness. There should be no phenomena such as shedding and holes on the extruded surface. After the grouting machine extrudes, immediately wrap the ceramicized silica gel 13 through a double-head wrapping machine. Wind the ceramicized silica gel tape 13 around the surface of the refractory mud 12 in an intermittent wrapping manner. The wrapping direction of the ceramicized silica gel 13 is rightward, with an overlap of 45%-50%, ensuring the smoothness and flatness of the wrapping tape and the stability of the structure.
[0054] 7) Production of sheath 14: Extrude and stretch the halogen-free low-smoke flame-retardant polyolefin material to form the sheath 14 structure, which shrinks and wraps around the surface of the refractory layer. Among them, the average extrusion thickness should not be less than the nominal value, and the thickness at the thinnest point should not be less than 90% of the nominal thickness. The extruded surface should be smooth without phenomena such as sharp corners, particles, charring, and abrasions.
[0055] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any person skilled in the art, within the scope of the technical solution of the present invention, makes any form of equivalent substitution or modification and other changes to the technical solution and technical content disclosed in the present invention, which are still within the content of the technical solution of the present invention and still fall within the protection scope of the present invention.
Claims
1. A flame-retardant and fire-resistant high-voltage cable, characterized in that, It includes a conductor, an insulating layer, a metal shielding layer, a moisture-proof layer, a fire-resistant layer and a sheath: The conductor adopts a segmented conductor structure, and the conductor strand blocks are separated by crepe paper; the insulating layer is tightly coated on the surface of the conductor; a semi-conductive buffer water-blocking tape is wound on the surface of the insulating layer to form a buffer layer; the metal shielding layer is arranged on the outer surface of the buffer layer; The moisture-proof layer adopts a polyethylene coating structure and is arranged between the metal shielding layer and the fire-resistant layer; the fire-resistant layer adopts a fire-resistant mud extrusion coating structure, is extruded and coated on the surface of the moisture-proof layer, and the fire-resistant mud is wound and fixed by a ceramicized silica gel tape; the fire-resistant mud and the ceramicized silica gel tape are sintered and hardened at high temperature to form a heat-insulating layer; the sheath is coated on the outer surface of the fire-resistant layer.
2. The flame-retardant and fire-resistant high-voltage cable according to claim 1, wherein A first semi-conductive water-blocking tape is wound around the conductor.
3. The flame-retardant and fire-resistant high-voltage cable according to claim 1, characterized in that, A second semi-conductive water-blocking tape is wound on the outer surface of the metal shielding layer; the moisture-proof layer adopts a polyethylene coating structure and is coated on the surface of the second semi-conductive water-blocking tape.
4. The flame-retardant and fire-resistant high-voltage cable according to claim 1, wherein In the buffer layer, the semi-conductive buffer water-blocking tape is evenly wound on the surface of the insulating layer by a winding method; the winding direction is rightward, and the overlap is 45%-50%.
5. The flame-retardant and fire-resistant high-voltage cable according to claim 1, wherein, The insulating layer adopts a cross-linked polyethylene extrusion coating structure. A semi-conductive inner shielding layer is arranged between the insulating layer and the conductor, and a semi-conductive outer shielding layer is arranged between the insulating layer and the buffer layer. The semi-conductive inner shielding layer, the insulating layer and the semi-conductive outer shielding layer are simultaneously extruded under high pressure and tightly coated on the surface of the conductor to form an integral insulation structure.
6. The flame-retardant and fire-resistant high-voltage cable according to claim 1, wherein, The metal shielding layer is wound on the surface of the buffer layer by a loose winding method of copper wires; the copper wires are evenly wound on the surface of the buffer layer by a loose winding method, the loose winding direction is leftward, the loose winding pitch is 9-12 times, and the outside of the copper wires is tied back by a copper tape.
7. The flame-retardant and fire-resistant high-voltage cable according to claim 3, wherein, The moisture-proof layer adopts a serrated polyethylene coating structure and is coated on the surface of the second semi-conductive water-blocking tape; the average coating thickness is not less than the nominal value, and the thickness of the thinnest point is not less than 90% of the nominal thickness; the serration length is not less than 2.5 mm.
8. The flame-retardant and fire-resistant high-voltage cable according to claim 7, wherein, The serrated side of the moisture-proof layer is connected to the fire-resistant layer. The fire-resistant layer extrudes and coats the fire-resistant mud on the surface of the moisture-proof layer through a grouting machine; through a double-head winding machine, the ceramicized silica gel tape is wound on the surface of the fire-resistant mud in an intermittent winding manner, and the winding direction of the ceramicized silica gel tape is rightward, and the overlap degree is 45%-50%.
9. The flame-retardant and fire-resistant high-voltage cable according to claim 1, characterized in that, The sheath adopts a halogen-free low-smoke flame-retardant polyolefin coating structure and is shrink-wrapped on the outer surface of the moisture-proof layer.