Flame-retardant fire-resistant control cable for nuclear power station

Abstract

The utility model relates to a flame-retardant fireproof control cable for a nuclear power station, and relates to the technical field of cables. The wrapping layer, the metal shielding layer, the heat insulation layer and the sheath are sequentially arranged outside the cable core from inside to outside, the cable core is formed by twisting a plurality of insulation wire cores, and an elastic ring is arranged between the sheath and the heat insulation layer. The flame-retardant cable material has relatively good flame-retardant performance.

Description

Technical Field

[0001] This application relates to the field of cables, and more particularly to a flame-retardant and fire-resistant control cable for nuclear power plants. Background Technology

[0002] As a crucial component of the modern energy system, the safe operation of nuclear power plants has a profound impact on socio-economic development. Cables, as key components for information transmission and power delivery within nuclear power plants, directly affect the safety and reliability of the plant.

[0003] Nuclear power plants have a large number of cables, and re-laying them would waste enormous manpower and resources, and would also require redoing related work such as fire sealing. Therefore, once cables are laid, it is difficult to re-lay them, and some areas are particularly difficult to work on, making cable replacement difficult or even impossible. In the event of a fire, the fire can ignite the cables and spread along them, increasing the fire's intensity and safety, thus requiring improvement. Utility Model Content

[0004] To address the issue of cables being susceptible to fire and prone to spreading, resulting in low safety, this application provides a flame-retardant and fire-resistant control cable for nuclear power plants.

[0005] This application provides a flame-retardant and fire-resistant control cable for nuclear power plants, which adopts the following technical solution:

[0006] A flame-retardant and fire-resistant control cable for nuclear power plants includes a cable core and a wrapping layer, a metal shielding layer, a heat insulation layer, and a sheath arranged sequentially from the inside to the outside of the cable core. The cable core is composed of multiple insulated wire cores twisted together, and the gaps between the insulated wire cores are filled with low-smoke halogen-free flame-retardant filler strips. An elastic ring is provided between the sheath and the heat insulation layer.

[0007] By adopting the above technical solution, the cable core is formed by stranding multiple insulated wire cores, thus ensuring the cable's flexibility and bendability. The low-smoke halogen-free flame-retardant filler strip has a low heat capacity, effectively reducing heat release during combustion; furthermore, the filler strip has good flame-retardant properties, improving the overall flame-retardant performance of the cable, preventing fire from spreading through the cable, and ensuring high safety. The elastic ring further increases the overall flexibility of the cable, giving it the ability to deform and making it less prone to breakage when bent by external forces, thus improving the cable's service life.

[0008] Optionally, the insulated core includes a conductor and an insulating layer covering the outer periphery of the conductor. The conductor is made of multiple strands of soft round copper wire twisted together with a twist pitch ratio ranging from 15 to 20, and the conductor cross-section ranges from 1.0 mm. 2 ~2.5mm 2 .

[0009] By employing the above technical solutions, the insulation layer isolates the conductor from the external environment, preventing short circuits or leakage caused by direct contact. Simultaneously, the insulation layer resists direct damage to the conductor from external forces, extending cable life. Furthermore, the insulation layer maintains circuit integrity and slows the spread of flames during a fire. Copper possesses excellent electrical properties and durability, while stranded tin-plated copper conductors improve conductivity, making them more corrosion-resistant and reducing the formation of CuO and Cu2O through oxidation, thus extending the overall lifespan of the conductor core. Stranded conductors are more flexible than solid conductors, improving the cable's bending performance.

[0010] Optionally, the conductor is fitted with a shape memory metal, which is used to shrink the conduit.

[0011] By adopting the above technical solution, when the cable is at high temperature, the shape memory metal will shrink and return to its original shape. At this time, radial compressive stress is applied to the conductor, which makes the conductor lattice denser, thereby reducing the resistivity. Although the shrinkage of the shape memory metal will slightly reduce the cross-section of the conductor, the change in resistivity will dominate the decrease in total resistance, thereby avoiding overheating and protecting the conductor.

[0012] Optionally, the insulation layer is made of low-smoke halogen-free silicone rubber insulation material, and the nominal thickness of the insulation layer is 0.8 mm.

[0013] By adopting the above technical solution, silicone rubber insulation can form a shell under flame conditions, and after burning, it can still completely wrap around the conductor, playing a good electrical insulation role and ensuring that the cable can still maintain normal power supply under flame conditions.

[0014] Optionally, the wrapping layer is composed of ceramic fiber tape and halogen-free low-smoke high flame-retardant fabric tape, wherein the nominal thickness of the ceramic fiber tape and the halogen-free low-smoke high flame-retardant fabric tape in the wrapping layer are 0.3 mm respectively.

[0015] By adopting the above technical solutions, ceramic fiber tape, a high-temperature resistant material, exhibits low thermal conductivity and excellent heat insulation. The main raw material of halogen-free, low-smoke flame-retardant tape is inorganic, making it difficult to burn. The combined use of ceramic fiber tape and halogen-free, low-smoke flame-retardant tape forms a protective layer on the cable core, not only preventing the spread of flames within the core and improving the cable's flame-retardant performance, but also effectively reducing heat release and smoke production during combustion.

[0016] Optionally, the metal shielding layer is formed by wrapping a layer of copper strip, and the copper strip overlap rate of the metal shielding layer is not less than 20%.

[0017] By adopting the above technical solution, the copper tape can completely surround the cable core, resulting in better electromagnetic interference resistance. The high strength of the copper tape also allows it to act as a mechanical protective layer, protecting the internal cable core from mechanical damage during cable installation and use.

[0018] Optionally, the insulation layer is made of ceramic fiber tape wrapped around it, wherein the nominal thickness of the ceramic fiber tape in the insulation layer is 0.5 mm and the wrapping overlap rate is 30%.

[0019] By adopting the above technical solution, the ceramic fiber tape has low thermal conductivity and excellent heat insulation effect. Under fire conditions, it can prevent the transfer of flames and heat to the internal insulation layer, protect the integrity of the internal insulation layer, improve the fire resistance of the cable, and thus extend the time that electrical equipment can maintain normal power supply under fire conditions.

[0020] Optionally, the elastic ring includes a plurality of hollow circles, which are distributed along the circumferential direction of the heat insulation layer, and adjacent hollow circles are connected by hollow columns.

[0021] By adopting the above technical solution, when the cable is bent by external force, the elastic ring is stretched and deformed along the axial direction, so that the individual hollow circle becomes an ellipse. The hollow circle absorbs energy through elastic energy storage, and at the same time the hollow column is also stretched to prevent the hollow circles from separating, thereby achieving high ductility and tensile strength of the cable.

[0022] In summary, this application includes at least one of the following beneficial effects:

[0023] 1. The cable core is formed by twisting together multiple insulated wire cores, thus ensuring the cable's flexibility and bendability. The low-smoke halogen-free flame-retardant filler strip has a low heat capacity, effectively reducing heat release during combustion; furthermore, the filler strip has good flame-retardant properties, improving the overall flame-retardant performance of the cable, preventing fire from spreading through the cable, and ensuring high safety.

[0024] 2. When the cable is at high temperature, the shape memory metal will shrink and return to its original shape. At this time, radial compressive stress is applied to the conductor, which makes the conductor lattice denser, thereby reducing the resistivity. Although the shrinkage of the shape memory metal will slightly reduce the cross-section of the conductor, the change in resistivity will dominate the decrease in total resistance, thus avoiding overheating and protecting the conductor. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of a flame-retardant and fire-resistant control cable for a nuclear power plant, as described in an embodiment of this application.

[0026] In the diagram: 10, cable core; 11, insulated core; 111, conductor; 112, insulation layer; 20, wrapping layer; 30, metal shielding layer; 40, heat insulation layer; 50, sheath; 60, filler strip; 70, elastic ring; 71, hollow circle; 72, hollow column; 80, shape memory metal. Detailed Implementation

[0027] The following is in conjunction with the appendix Figure 1This application will be described in further detail.

[0028] This application discloses a flame-retardant and fire-resistant control cable for nuclear power plants. (Refer to...) Figure 1 The flame-retardant and fire-resistant control cable for nuclear power plants includes a cable core 10 and, from the inside out, a wrapping layer 20, a metal shielding layer 30, a heat insulation layer 40, and a sheath 50, which are sequentially wrapped around the cable core 10. The cable core 10 is composed of multiple insulated wire cores 11 twisted together. The wrapping layer 20 is made of ceramic fiber tape and halogen-free, low-smoke, high flame-retardant cloth tape. The metal shielding layer 30 is made of a layer of copper tape. The heat insulation layer 40 is made of ceramic fiber tape. The sheath 50 is extruded from halogen-free, low-smoke, flame-retardant polyolefin material. This design achieves the effect of improving the flame-retardant and fire-resistant properties of the cable and reducing the release of toxic gases.

[0029] Reference Figure 1 The cable core 10 comprises multiple insulated cores 11 twisted together. Each insulated core 11 includes a conductor 111 and an insulation layer 112 covering the outer periphery of the conductor 111. The conductor 111 is composed of multiple strands of soft, round copper wire twisted together, with a twist pitch ratio ranging from 15 to 20, and a cross-sectional area ranging from 1.0 mm² to 2.5 mm². The twisted structure of the conductor 111 provides greater flexibility than a solid structure, making it easier to bend. The twisting method of the conductor 111 can be either concentric twisting or bundle twisting.

[0030] Conductors 111 with a pitch ratio of 15 to 20 exhibit good flexibility, resistance to bending fatigue, and uniform current distribution. Conductors 111 with a cross-section of 1.0 mm² to 2.5 mm² offer matched current carrying capacity, moderate mechanical strength, optimized cost, and compatibility with standard connectors.

[0031] The insulation layer 112 is made of low-smoke halogen-free silicone rubber insulation material with a nominal thickness of 0.8mm. Silicone rubber insulation material has excellent high-temperature resistance and can form a shell under flame conditions. After burning, it can still completely wrap around the conductor 111, providing excellent electrical insulation and ensuring that the cable can still maintain normal power transmission under flame conditions.

[0032] The 0.8mm thick insulation material offers excellent electrical properties, including high dielectric strength, low leakage current, and resistance to creepage.

[0033] To enhance the protection of conductor 111, a shape memory metal 80 is fitted onto conductor 111. In this embodiment, the shape memory metal 80 is a NiTi alloy. When the cable reaches a high temperature, the shape memory metal 80 shrinks and returns to its original shape. This applies radial compressive stress to conductor 111, causing the conductor 111 to densify its crystal lattice and thus reducing its resistivity. Although the shrinkage of the shape memory metal 80 slightly reduces the cross-section of conductor 111, the change in resistivity dominates the decrease in total resistance, thereby preventing overheating and protecting conductor 111.

[0034] The wrapping layer 20 is composed of ceramic fiber tape and halogen-free, low-smoke, high-flame-retardant fabric tape. The nominal thickness of both the ceramic fiber tape and the halogen-free, low-smoke, high-flame-retardant fabric tape is 0.3 mm. Ceramic fiber tape is a high-temperature resistant material with low thermal conductivity and good insulation properties; the main raw material of the halogen-free, low-smoke, high-flame-retardant fabric tape is inorganic and not easily combustible. The combined use of these two materials not only prevents the flame from spreading into the cable core 10, improving the cable's flame-retardant performance, but also effectively reduces heat release and smoke production during combustion. The ceramic fiber tape is spirally wrapped around the outer surface of the cable core 10, and the halogen-free, low-smoke, high-flame-retardant fabric tape is tightly wrapped around its outer side, with an overlap rate of not less than 50%, to ensure a tight bond between the two layers.

[0035] Reference Figure 1 The metal shielding layer 30 is composed of a layer of copper tape wrapped around the cable core 10, with an overlap rate of not less than 20%. The copper tape completely surrounds the cable core 10, providing better electromagnetic interference resistance. The high strength of the copper tape also allows it to act as a mechanical protection layer, protecting the internal cable core 10 from mechanical damage during cable installation and use. The copper tape can be made of 0.1mm thick soft copper foil, wrapped in a spiral or longitudinal manner to ensure the overlap rate between the copper tapes meets the specified requirements, thus forming a complete shielding layer. Furthermore, the surface of the copper tape can be coated with an anti-oxidation coating to extend its service life and enhance its corrosion resistance.

[0036] Reference Figure 1 The insulation layer 40 is made of ceramic fiber tape with a nominal thickness of 0.5 mm and an overlap rate of 30%. Ceramic fiber tape is a high-temperature resistant material with a temperature resistance rating above 1000℃, low thermal conductivity, and excellent insulation performance. Under fire conditions, the insulation layer 40 can prevent the transfer of flames and heat to the internal insulation layer 112, protecting the integrity of the internal insulation layer 112, improving the fire resistance of the cable, and thus extending the time that electrical equipment can maintain normal power supply under fire conditions.

[0037] Sheath 50 is extruded from halogen-free, low-smoke, flame-retardant polyolefin material, with a nominal thickness of not less than 1.5 mm. Halogen-free, low-smoke, flame-retardant polyolefin material possesses excellent flame-retardant properties and environmental characteristics, effectively inhibiting flame spread and reducing the release of toxic gases and fumes under flame conditions. Sheath 50 material can be modified polyethylene or cross-linked polyethylene, with flame retardants and stabilizers added to optimize its flame-retardant and heat-resistant properties. The extrusion process for sheath 50 can employ a single-screw extruder or a multi-screw extruder to ensure a tight bond between sheath 50 and the underlying material, forming a complete protective layer.

[0038] To increase the overall flexibility of the cable and prevent cable breakage, an elastic ring 70 is provided between the sheath 50 and the heat insulation layer 40. The elastic ring 70 includes a plurality of hollow circles 71, which are distributed along the circumference of the heat insulation layer 40. Adjacent hollow circles 71 are connected by hollow columns 72, thereby forming a stretchable spring-like microstructure inside the sheath 50.

[0039] When the cable is bent by an external force, the elastic ring 70 is stretched and deformed along the axial direction, so that the individual hollow circle 71 becomes an ellipse. The hollow circle 71 absorbs energy through elastic energy storage, and at the same time the hollow column 72 is also stretched to prevent the hollow circles 71 from separating, thereby achieving high ductility and tensile strength of the cable.

[0040] The implementation principle of a flame-retardant and fire-resistant control cable for nuclear power plants according to an embodiment of this application is as follows: through multi-layer structural design and material optimization, the flame-retardant, fire-resistant, and environmentally friendly performance of the cable is significantly improved. Specifically, the cable core 10 adopts a stranded structure of multiple insulated cores 11, which improves the cable's flexibility and bendability; the wrapping layer 20 is composed of ceramic fiber tape and halogen-free, low-smoke, high-flame-retardant fabric tape, effectively preventing the spread of flames into the cable core 10 and reducing heat release; the metal shielding layer 30 not only provides electromagnetic shielding but also plays a mechanical protection role; the heat insulation layer 40 is wrapped with ceramic fiber tape, which significantly improves the cable's fire resistance; the sheath 50 is made of halogen-free, low-smoke, flame-retardant polyolefin material, further enhancing the overall flame-retardant performance of the cable. These designs enable the cable to meet the stringent standards of the nuclear power plant's fire safety system for flame-retardant performance and additional requirements, providing a reliable guarantee for the safe operation of the nuclear power plant.

[0041] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A flame-retardant, fire-resistant control cable for nuclear power plants, characterized in that, It includes a cable core (10) and a wrapping layer (20), a metal shielding layer (30), a heat insulation layer (40) and a sheath (50) arranged sequentially from the inside to the outside of the cable core (10). The cable core (10) is composed of multiple insulated wire cores (11) twisted together. An elastic ring (70) is provided between the sheath (50) and the heat insulation layer (40).

2. The flame-retardant and fire-resistant control cable for nuclear power plants according to claim 1, characterized in that, The insulated core (11) comprises a conductor (111) and an insulating layer (112) covering the conductor (111), the conductor (111) is twisted by multiple soft round copper wires, and the pitch range of the twisted conductor (111) is 15-20, the cross-section range of the conductor (111) is 1.0mm 2 ~2.5mm 2 .

3. A flame and fire retardant control cable for nuclear power plants according to claim 2, characterized in that, The conductor (111) is fitted with a shape memory metal (80), which is used to shrink the conduit.

4. The flame and fire-retardant control cable for nuclear power plants according to claim 2, characterized in that, The insulation layer (112) is made of low-smoke halogen-free silicone rubber insulation material, and the nominal thickness of the insulation layer (112) is 0.8 mm.

5. The flame and fire-retardant control cable for nuclear power plants according to claim 1, characterized in that, The wrapping layer (20) is made of ceramic fiber tape and halogen-free low-smoke high flame-retardant cloth tape, and the nominal thickness of the ceramic fiber tape and the halogen-free low-smoke high flame-retardant cloth tape in the wrapping layer (20) is 0.3 mm respectively.

6. The flame and fire-retardant control cable for nuclear power plants according to claim 1, characterized in that, The metal shielding layer (30) is formed by wrapping a layer of copper strip, and the copper strip wrapping overlap rate of the metal shielding layer (30) is not less than 20%.

7. The flame and fire-retardant control cable for nuclear power plants according to claim 1, characterized in that, The heat insulation layer (40) is made of ceramic fiber tape wrapped around it. The nominal thickness of the ceramic fiber tape in the heat insulation layer (40) is 0.5 mm, and the wrapping overlap rate is 30%.

8. The flame and fire-retardant control cable for nuclear power plants according to claim 1, characterized in that, The elastic ring (70) includes a plurality of hollow circles (71), which are distributed along the circumferential direction of the heat insulation layer (40), and adjacent hollow circles (71) are connected by hollow columns (72).

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