Fireproof power cable with insulating and flame-retardant sheath for rail transit

Abstract

The utility model relates to the technical field of power cable, and disclose insulating fire -retardant sheath fire -resistant power cable for rail transit, including copper -clad aluminium stranded conductor, the outer wrapping of copper -clad aluminium stranded conductor has zirconium fibre fire -resistant band, the outside of zirconium fibre fire -resistant band is provided with insulating protective layer, the outside of multiple insulating protective layers is provided with filling layer, the outside of filling layer is provided with cable buffer layer, the outer layer of cable buffer layer is provided with composite shielding layer, the outside of composite shielding layer is provided with protective layer, the outside of protective layer is provided with fire -retardant outer sheath, the utility model adopts high -purity zirconium fibre double -layered wrapping fire -resistant band high -efficient heat -insulating and keeps the continuity of electric conduction, and the inside and outside layer function synergy cross -linked polyethylene and weather -resistant polyolefin constitute insulating protective layer, and the matching anti -fatigue composite cable buffer layer, three -layer shielding structure and low -smoke halogen -free fire -retardant outer sheath realize the optimal balance and reliability promotion of rail transit cable in fire -resistant, insulating, weather -resistant, anti -vibration and light -weight on performance.

Description

Technical Field

[0001] This utility model relates to the field of power cable technology, specifically to fireproof power cables with insulating flame-retardant sheaths for rail transit. Background Technology

[0002] Urban rail transit, as a major artery of urban transportation, has developed rapidly in recent years, and its safe and stable operation is of paramount importance. DC power cables, as the core transmission channel for traction power, directly affect the safe and reliable operation of subway vehicles and the entire rail transit system. Since rail transit facilities are mostly located underground or in densely populated areas, cable failures can not only lead to operational disruptions but also pose a serious threat to passenger safety.

[0003] Traditional aluminum silicate fiber or mineral-insulated fireproof tapes have significant drawbacks: their upper temperature resistance limit is far below 1600℃, and their thickness fluctuates greatly (0.1-0.4mm). They are prone to decomposition and failure under high-temperature environments, resulting in weak thermal insulation performance and an inability to effectively block heat conduction to protect conductors from damage. Their insulation structure design is simplistic, with insufficient heat resistance of the main insulation layer (long-term operating temperature below 90℃), poor weather resistance, and susceptibility to oil and moisture corrosion. The outer layer lacks mechanical damage protection to withstand a wide temperature range of -40℃ to 90℃, leading to persistently high risks of leakage and aging. The shielding system lacks a gradient design, with loose overlaps in the aluminum-plastic tape resulting in poor water tightness. Furthermore, the absence of an efficient heat-conducting layer for heat dissipation, coupled with insufficient braided shielding density, results in low shielding effectiveness and difficulty in effectively resisting electromagnetic interference. The fireproof layer does not employ a gradient insulation scheme, resulting in a heavy structure at room temperature and a sharp decline in thermal insulation capacity at high temperatures, failing to significantly reduce the inner layer temperature in fire scenarios.

[0004] Therefore, the applicant proposed an insulated, flame-retardant, sheathed, fire-resistant power cable for rail transit, aiming to solve the problems existing in traditional power cables. Utility Model Content

[0005] The purpose of this utility model is to provide fire-resistant power cables with flame-retardant sheaths for rail transit, solving the following technical problems: Traditional aluminum silicate fiber or mineral-insulated fireproof tapes have obvious defects: the upper limit of temperature resistance is far below 1600℃, and the thickness fluctuates greatly (0.1-0.4mm). They are prone to decomposition and failure under high-temperature environments, have weak thermal insulation performance, and cannot effectively block heat conduction to protect the conductor from damage; the insulation structure design is simple, the heat resistance of the main insulation layer is insufficient (long-term operating temperature is below 90℃), the weather resistance is poor, and it is easily corroded by oil and moisture. The outer layer lacks mechanical damage protection that can adapt to a wide temperature range of -40℃ to 90℃, resulting in a high risk of leakage and aging. The shielding system lacks a gradient design, the aluminum-plastic tape overlap is not tight, resulting in poor water tightness, and there is no efficient heat-conducting layer to assist heat dissipation. In addition, the braided shielding density is insufficient, resulting in low shielding effectiveness and difficulty in effectively resisting electromagnetic interference; the fireproof layer does not adopt a gradient thermal insulation scheme, the structure is heavy at room temperature, and the thermal insulation capacity decreases sharply at high temperatures, failing to significantly reduce the inner layer temperature in fire scenarios.

[0006] The objective of this utility model can be achieved through the following technical solutions: Fireproof insulated flame-retardant sheathed power cable for rail transit includes a copper-clad aluminum stranded conductor, the copper-clad aluminum stranded conductor is wrapped with a zirconia fiber fireproof tape, the zirconia fiber fireproof tape is provided with an insulating protective layer, and multiple insulating protective layers are provided with a filler layer. The outer side of the filling layer is provided with a cable buffer layer, the outer layer of the cable buffer layer is provided with a composite shielding layer, the outer side of the composite shielding layer is provided with a fireproof layer, and the outer side of the fireproof layer is provided with a flame-retardant outer sheath. The composite shielding layer adopts a three-layer composite structure: the inner layer is an aluminum-plastic composite strip longitudinal wrapping layer, the middle layer is a graphene thermal conductive layer, and the outermost layer is a tin-plated copper wire braided layer.

[0007] As a further embodiment of this utility model: the stranding pitch of the copper-clad aluminum stranded conductor is controlled at 10-20 times the outer diameter of the conductor, and the copper layer thickness accounts for 15% of the total thickness of the copper-clad aluminum stranded conductor.

[0008] As a further aspect of this utility model: the thickness of the zirconia fiber fireproof strip is 0.18 mm, and the overlap rate is 65%.

[0009] As a further embodiment of this utility model: the insulating protective layer consists of cross-linked polyethylene and weather-resistant polyolefin from the inside out.

[0010] As a further embodiment of this invention: the inner annular array of the filling layer is provided with three sets of copper-clad aluminum stranded conductors.

[0011] As a further embodiment of this utility model: the cable buffer layer adopts a double-layer composite structure, including an inner buffer layer, which is a combination layer of rubber micro-foam and organosilicon modified layer, and an outer support layer is provided outside the inner buffer layer.

[0012] As a further embodiment of this utility model: the longitudinal wrapping layer of the aluminum-plastic composite strip is made of 0.1mm aluminum foil and 0.06mm polyethylene film, with a longitudinal overlap width of 18mm; the aluminum layer of the graphene thermal conductive layer has a thickness of 0.15mm, the plastic layer has a thickness of 0.06mm, and the longitudinal overlap width is 18mm; the tin-plated copper wire braided layer is made of 0.18mm diameter copper wire woven at a braiding density of 90%.

[0013] As a further embodiment of this utility model: the thickness of the aerogel layer of the fireproof layer is 1.2 mm, and the thickness of the expandable graphite layer is 0.6 mm.

[0014] The beneficial effects of this utility model are: (1) This utility model uses copper-clad aluminum stranded conductors to balance conductivity and light weight (weight reduction of more than 30%), reducing the difficulty and cost of laying; the cable buffer layer and composite shielding layer work together to improve vibration resistance, impact resistance and electromagnetic shielding performance (shielding effectiveness 88dB), which is suitable for high-frequency vibration scenarios in rail transit; the low-smoke halogen-free flame-retardant outer sheath reduces toxic fumes through a dual flame-retardant mechanism (oxygen index ≥38%), and with the lightweight and high flexibility design, it enhances safety protection while improving installation convenience and service life, fully meeting the stringent requirements of rail transit for power transmission safety, reliability and durability.

[0015] (2) This utility model uses high-purity zirconium oxide fiber (ZrO2 content ≥99.5%) to prepare by sol-gel method, and achieves a lightweight design with double-layer wrapping (inner layer 0.08mm + outer layer 0.1mm, total thickness 0.18mm), which is lighter than traditional mineral insulation fireproof tape. By precisely controlling the fiber diameter (5-15μm), wrapping pitch (10-15 times the cable outer diameter) and overlap rate (65%), while ensuring flexibility, it can reduce the conductor surface temperature by more than 60% under high temperature flame by utilizing its low thermal conductivity (≤0.1W / (m・K)) and high temperature resistance stability above 1600℃, effectively avoiding copper layer softening and aluminum core melting, and ensuring the continuity of conductivity in the early stage of fire; (3) This utility model adopts a double-layer composite system (1.2mm aerogel layer + 0.6mm expandable graphite layer) to achieve dynamic heat insulation of "lightweight at room temperature + expansion and strengthening at high temperature". At room temperature, the aerogel achieves basic heat insulation and lightweighting by relying on its extremely low thermal conductivity (≤0.015W / (m・K)); when the fire is at high temperature, the expandable graphite expands rapidly to form a dense barrier, further enhancing the heat insulation effect and increasing the temperature reduction of the inner layer to more than 70%, thus buying critical time for emergency power supply and personnel evacuation.

[0016] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings.

[0018] Figure 1 This is a cross-sectional structural diagram of the entire utility model; Figure 2 This is a structural schematic diagram of the copper-clad aluminum stranded conductor and other components of this utility model; Figure 3 This is a schematic diagram of the overall structure of this utility model.

[0019] In the diagram: 1. Copper-clad aluminum stranded conductor; 2. Zirconia fiber fireproof tape; 3. Insulation protective layer; 31. Cross-linked polyethylene; 32. Weather-resistant polyolefin; 4. Filler layer; 5. Cable buffer layer; 51. Inner buffer layer; 52. Outer support layer; 6. Aluminum-plastic composite tape longitudinal wrapping layer; 7. Graphene thermal conductive layer; 8. Tin-plated copper wire braided layer; 9. Fireproof layer; 10. Flame-retardant outer sheath. Detailed Implementation

[0020] The embodiments of this utility model are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0021] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0022] Example 1: Please refer to Figures 1-3 As shown, the fire-resistant insulated, flame-retardant, sheathed power cable for rail transit includes a copper-clad aluminum stranded conductor 1. This conductor 1 serves as the core for power transmission. The 15% copper layer ensures excellent conductivity, while the aluminum core significantly reduces conductor weight, achieving a reduction of over 30% compared to pure copper conductors. This makes installation easier, balancing conductivity and lightweight requirements. The stranding pitch of the copper-clad aluminum stranded conductor 1 is controlled at 10-20 times the conductor's outer diameter. For example, a conductor with a diameter of 1 can have a pitch of 100-200mm. By precisely controlling the copper layer thickness and stranding pitch, the copper-clad aluminum stranded conductor 1 achieves an optimal balance of performance, cost, and reliability while replacing pure copper conductors, becoming a highly efficient solution in the power transmission field.

[0023] The copper-clad aluminum stranded conductor 1 is wrapped with a zirconia fiber fireproof strip 2. Zirconia fiber itself has excellent high-temperature stability and can maintain its structural integrity in extreme high-temperature environments above 1600℃, which is far higher than the upper limit of the temperature resistance of traditional aluminosilicate fiber. When exposed to direct flame (such as 800℃ and above), its internal components will not decompose or fail rapidly. Instead, it can effectively block the transfer of heat to the conductor through its low thermal conductivity (thermal conductivity can be as low as 0.1W / (m・K) or less).

[0024] According to actual test data, under direct attack of high-temperature flames, the zirconia fiber fireproof strip 2 can reduce the surface temperature of copper-clad aluminum conductors by more than 60%, avoiding melting, oxidation or performance degradation of the conductor due to high temperature (such as softening of the copper layer and melting of the aluminum core), thereby ensuring the conductivity continuity of the conductor in the early stage of a fire and buying critical time for emergency power supply or personnel evacuation.

[0025] Zirconia fiber fireproof tape 2 is made of high-purity zirconia fiber (ZrO2 content ≥99.5%), prepared through a sol-gel method to form a polycrystalline structure. Its average fiber diameter is controlled at 5-15μm, with a white, cotton-like appearance, possessing both excellent flexibility and outstanding high-temperature stability. This fireproof tape adopts a double-layer wrapping design, with an inner layer thickness of 0.08mm and an outer layer thickness of 0.1mm, for a total thickness precisely controlled at 0.18mm. Compared to traditional mineral-insulated fireproof tapes (typically 0.1-0.4mm thick), it is thinner and lighter, effectively ensuring thermal insulation performance while achieving weight reduction. In the wrapping process, the pitch is set to 10-15 times the cable's outer diameter. For example, for a 10mm outer diameter cable, the pitch can be designed to be 100-150mm. In actual production, the overlap rate is 65%, avoiding insufficient coverage due to cable bending. Through this parameter optimization, the flexibility of the cable and the integrity of the fireproof structure are cleverly balanced.

[0026] Zirconia fiber fireproof strip 2 has a fireproof layer 9 on the outermost side of the power cable. It adopts a composite system of "expandable graphite + aerogel". The aerogel layer is 1.2mm thick and the expandable graphite layer is 0.6mm thick. Aerogel (thermal conductivity ≤0.015W / (m・K)) is used as the bottom layer and expandable graphite is used as the outer layer, forming a gradient heat insulation of "lightweight at room temperature + expansion and strengthening at high temperature", which increases the temperature reduction of the inner layer to more than 70%. At room temperature: Lightweight basic thermal insulation is achieved by relying on the extremely low thermal conductivity of aerogel (≤0.015W / (m・K)). The aerogel itself is lightweight, which can reduce the overall structural load, and at the same time, the heat conduction is greatly reduced through the nanoscale porous structure.

[0027] High-temperature stage: The outer expandable graphite expands rapidly when exposed to high temperatures, forming a dense heat insulation barrier, which enhances the heat insulation effect at high temperatures and achieves the synergistic effect of "lightweighting at room temperature + expansion enhancement at high temperature".

[0028] To verify the heat insulation effect of zirconia fiber fireproof strip 2 and fireproof layer 9, and to ensure that the conductor temperature is reduced by more than 60% during a fire and that the conductivity continuity is not affected.

[0029] Take a 2m long test sample, peel off the flame-retardant outer sheath 10 and the outer layer of the fireproof layer 9 (retaining the composite shielding layer and internal structure), and connect the temperature sensor and the continuity tester at both ends of the conductor.

[0030] A propane torch (flame temperature 800-1000℃) was used to continuously burn the middle part of the cable (burning distance 10cm, burning time 60min), and the temperature change and conductivity status of the conductor surface were recorded in real time.

[0031] Judgment criteria: The conductor surface temperature decreases by ≥60% compared to the flame temperature during the burning process; the conductor remains conductive for 60 minutes (conductivity change ≤10%), with no melting or oxidation failure.

[0032] Example 2: Based on Example 1, the zirconia fiber fireproof strip 2 is provided with an insulating protective layer 3 on its exterior. The insulating protective layer, from the inside out, consists of cross-linked polyethylene 31 and weather-resistant polyolefin 32. The inner cross-linked polyethylene 31 serves as the main insulating layer and possesses excellent electrical insulation properties: breakdown strength ≥25kV / mm, volume resistivity ≥1×10⁻⁶. 14 Ω・cm, can reliably isolate the conductor from the external environment, avoiding the risk of leakage or short circuit from the source; at the same time, after cross-linking treatment, its heat resistance is significantly improved, the long-term working temperature can reach 90℃, and the short-term overload temperature can reach 130℃, which can fully meet the temperature rise requirements of the cable during operation, and has excellent chemical stability, and is not easily corroded by oil, moisture and other substances. The outer layer of weather-resistant polyolefin 32 exhibits multiple practical properties: Tests show a tensile strength retention rate of ≥85% and an elongation at break retention rate of ≥80%, enabling long-term stable operation in a wide temperature range of -40℃ to 90℃. It effectively copes with complex climatic conditions such as outdoor sun and rain, and large diurnal temperature variations, significantly extending the cable's outdoor service life. Simultaneously, this material possesses high tensile strength and impact resistance, resisting mechanical damage such as scratches, compression, and collisions during laying, installation, and use, preventing direct exposure and damage to the inner cross-linked polyethylene 31 insulation layer. Furthermore, its good flexibility allows for a bending radius of ≥12 times the cable's outer diameter, meeting the needs of complex laying paths and reducing the likelihood of cracking or fatigue damage during long-term bending. This dual-layer structure, through functional division and performance synergy, ensures insulation reliability in high-temperature environments while significantly improving overall mechanical strength, further enhancing the comprehensive protective performance of the conductor assembly.

[0033] The outer wall of the insulating protective layer 3 is provided with a filling layer 4. Multiple copper-clad aluminum stranded conductors 1 are arranged in a ring array inside the filling layer 4. In this embodiment, the number of conductor assemblies 1 is three sets. The filling layer 4 is made of halogen-free flame-retardant polyolefin, which has excellent flame-retardant and fire-resistant properties, effectively slowing the spread of flames and blocking the release of smoke. Simultaneously, the filling layer 4 also supports the internal structure of the cable, maintaining the relative stability of the multiple copper-clad aluminum stranded conductors 1. When the cable is bent or subjected to external force, the filling layer can evenly distribute stress, preventing damage to the conductors due to excessive localized stress.

[0034] A cable buffer layer 5 is provided outside the filling layer 4. The cable buffer layer 5 adopts a double-layer composite structure design to achieve the dual functions of efficient buffering and structural support. This buffer layer is made of high-density polyethylene (HDPE) foam material. Long-term high-frequency vibration of rail transit (such as vibration of subway tunnels) may cause fatigue damage to the foamed closed-cell structure. It is necessary to verify the performance retention rate after more than 100,000 vibration cycles. Therefore, the inner buffer layer 51 is made of "EPDM rubber micro-foam + organosilicon modification" material to improve weather resistance (-50℃~120℃) and fatigue resistance, ensuring that the energy absorption rate still remains at 75% after 100,000 vibration cycles. This structure has excellent elastic recovery performance. The cable buffer layer 5 is surrounded by an outer support layer 52, which is made of high-density polyethylene (HDPE) foam. The outer support layer 52 incorporates 2% carbon nanotubes, enhancing rigidity and thermal conductivity to aid heat dissipation. With a foaming ratio of 3-5 times, its Shore hardness is increased to 60-70D, resulting in stronger structural rigidity. Its closed-cell structure is uniform and stable, exhibiting excellent puncture resistance and protecting against scratches and compression from sharp objects. Working synergistically with the inner buffer layer 51, it maintains a mechanical vibration energy absorption rate of over 80% for the entire cable buffer layer 5, covering a temperature range of -40℃ to 80℃, comprehensively ensuring the structural stability of the conductor assembly in complex environments. The outer layer of the cable buffer layer 5 is equipped with a composite shielding layer. The composite shielding layer adopts a three-layer composite structure. The inner layer is an aluminum-plastic composite tape longitudinal wrapping layer 6, which is made of 0.1mm aluminum foil and 0.06mm polyethylene film. The longitudinal wrapping overlap width is 18mm to ensure longitudinal water tightness. The middle layer is a graphene thermally conductive layer 7, with an aluminum layer thickness of 0.15mm and a plastic layer thickness of 0.06mm. The longitudinal wrapping overlap width is 18mm to ensure longitudinal water tightness. The outer layer is a tin-plated copper wire braided layer 8, which is made of 0.18mm copper wire with a braiding density of 90% to form an electromagnetic shielding barrier with a shielding effectiveness of 88dB.

[0035] The fireproof layer 9 is provided with a flame-retardant outer sheath 10, which is made of low-smoke halogen-free flame-retardant polyolefin composite material. This material is made of 55%-60% of ultrafine magnesium hydroxide (particle size ≤2μm) and aluminum hydroxide composite flame-retardant system, and is combined with melamine cyanurate (MCA) as a synergist to form a dual mechanism of "condensed phase flame retardancy + gas phase flame retardancy", so that the oxygen index of the material reaches ≥38%. When a fire occurs, inorganic flame retardants decompose upon heating, absorbing heat and releasing moisture, effectively inhibiting flame propagation; MCA, on the other hand, captures free radicals in the gas phase, blocking the combustion chain reaction. Because the material does not contain halogen elements such as chlorine and bromine, the production of toxic smoke and corrosive gases during combustion is significantly reduced. This characteristic is particularly important in densely populated areas such as subways, high-rise buildings, and hospitals, as it reduces the risk of smoke asphyxiation and mitigates corrosion damage to fire-fighting equipment and surrounding facilities. Through extrusion, the flame-retardant outer sheath 10 can tightly wrap around the outside of the fireproof layer 9, forming a continuous and smooth sheath surface. This ensures a tight fit with the inner structure without air bubbles, enhancing the overall sealing of the cable and reducing the intrusion of moisture, dust, and other impurities. Simultaneously, its relatively light density does not excessively increase the cable's weight, and its good flexibility allows it to meet the needs of complex laying paths. While maintaining high-strength protective performance, it significantly improves the cable's installation convenience and usage flexibility. Example 3: Based on Examples 1 and 2, this utility model cable uses copper-clad aluminum stranded conductor 1 as the transmission core. The outer layer is successively blocked by zirconia fiber fireproof tape 2, double-layer insulation protective layer 3 to ensure electrical safety and mechanical strength, multiple sets of conductors are fixed by halogen-free flame-retardant filling layer 4, and double-layer cable buffer layer 5 to resist vibration and impact. The composite shielding layer achieves water tightness, heat dissipation and electromagnetic shielding. The gradient fireproof layer 9 is reinforced by aerogel and expandable graphite to enhance thermal insulation at normal and high temperatures. The outermost low-smoke halogen-free flame-retardant outer sheath 10 is fire-retardant and smoke-suppressing and enhances sealing. All layers work together to achieve the comprehensive functions of power transmission, fire prevention and flame retardancy, insulation safety and environmental adaptability.

[0036] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A fire-resistant, flame-retardant, sheathed insulated power cable for rail transit, comprising a copper-clad aluminum stranded conductor (1), characterized in that, The copper-clad aluminum stranded conductor (1) is wrapped with a zirconia fiber fireproof strip (2), and an insulating protective layer (3) is provided on the outside of the zirconia fiber fireproof strip (2). A filler layer (4) is provided on the outside of the plurality of insulating protective layers (3). The outer side of the filling layer (4) is provided with a cable buffer layer (5), the outer layer of the cable buffer layer (5) is provided with a composite shielding layer, the outer side of the composite shielding layer is provided with a fireproof layer (9), and the outer side of the fireproof layer (9) is provided with a flame-retardant outer sheath (10). The composite shielding layer adopts a three-layer composite structure, with the inner layer being an aluminum-plastic composite strip longitudinal wrapping layer (6), the middle layer being a graphene thermal conductive layer (7), and the outermost layer being a tin-plated copper wire braided layer (8).

2. The fire-resistant, flame-retardant, sheathed power cable for rail transit according to claim 1, characterized in that, The stranding pitch of the copper-clad aluminum stranded conductor (1) is controlled at 10-20 times the outer diameter of the conductor, and the copper layer thickness accounts for 15% of the total thickness of the copper-clad aluminum stranded conductor (1).

3. The fire-resistant, flame-retardant, sheathed power cable for rail transit according to claim 1, characterized in that, The zirconia fiber fireproof strip (2) has a thickness of 0.18 mm and an overlap rate of 65%.

4. The fire-resistant, flame-retardant, sheathed power cable for rail transit according to claim 1, characterized in that, The insulating protective layer (3) consists of cross-linked polyethylene (31) and weather-resistant polyolefin (32) from the inside out.

5. The fire-resistant, flame-retardant, sheathed power cable for rail transit according to claim 1, characterized in that, The inner annular array of the filling layer (4) is provided with three sets of copper-clad aluminum stranded conductors (1).

6. The fire-resistant, flame-retardant, sheathed power cable for rail transit according to claim 1, characterized in that, The cable buffer layer (5) adopts a double-layer composite structure, including an inner buffer layer (51) and an outer support layer (52) is provided on the outside of the inner buffer layer (51).

7. The fire-resistant, flame-retardant, sheathed power cable for rail transit according to claim 1, characterized in that, The longitudinal wrapping layer (6) of the aluminum-plastic composite strip is made of 0.1mm aluminum foil and 0.06mm polyethylene film, with a longitudinal overlap width of 18mm; the aluminum layer of the graphene thermal conductive layer (7) has a thickness of 0.15mm, the plastic layer has a thickness of 0.06mm, and the longitudinal overlap width is 18mm; the tin-plated copper wire braided layer (8) is made of 0.18mm diameter copper wire woven at a braiding density of 90%.

8. The fire-resistant, flame-retardant, sheathed power cable for rail transit according to claim 1, characterized in that, The fireproof layer (9) has an aerogel layer thickness of 1.2 mm and an expandable graphite layer thickness of 0.6 mm.

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