B1-level flame-retardant cold-resistant medium-voltage power cable

Abstract

The utility model relates to the technical field of power cables, in particular to a B1-level flame-retardant cold-resistant medium-voltage power cable, which comprises a plurality of mutually twisted wire cores and a water-blocking filling layer which are fixed together by a wrapping layer to form a cable core with a circular cross section. The outer wall of the cable core is coated with the composite wrapping layer; the inner sheath layer is extruded on the outer wall of the composite wrapping layer; the outer wall of the inner sheath layer is coated with the armor layer; and the outer sheath is extruded on the outer wall of the armor layer. According to the composite wrapping layer provided by the utility model, the foaming structure layer and the flame-retardant structure layer are adopted, flame-retardant-cold-resistant synergistic enhancement is realized, copper / aluminum foil is utilized to construct the physical barrier layer, the foaming layer absorbs mechanical stress, functional integrity is maintained under extreme conditions, and meanwhile, a composite tape is used for replacing a traditional glass tape flame-retardant structure, so that the weight of the cable is reduced, and the cable is more environment-friendly. The bending performance is improved, and the use requirement in a low-temperature environment is met.

Description

Technical Field

[0001] This utility model relates to the field of power cable technology, and more specifically to a B1-grade flame-retardant and cold-resistant medium-voltage power cable. Background Technology

[0002] Medium-voltage power cables (6-35kV) are key power transmission carriers in urban power grids, rail transit, industrial facilities and other fields. Their safety and environmental adaptability requirements are becoming increasingly stringent, especially in special application scenarios such as densely populated high-rise building areas, underground integrated pipe corridors, and high-altitude cold regions, where high-level flame retardant performance and reliable operation in extreme low-temperature environments are required.

[0003] In cold regions or low-temperature operating environments, ordinary cables lack sufficient cold resistance. Their insulation and sheath materials harden and become brittle at low temperatures, significantly reducing their flexibility and mechanical properties. This makes them prone to cracking and damage, affecting normal cable operation and increasing the risk of power system failures. Moreover, when facing medium-voltage environments, the electrical performance of ordinary cables is insufficient to meet the requirements for long-term stable operation, making them susceptible to partial discharge, insulation breakdown, and other issues, thus reducing the stability and reliability of power transmission.

[0004] In conclusion, power cables with B1-level flame retardant properties, excellent cold resistance, and stable and reliable operation under medium-voltage conditions are of particular practical significance and necessity for ensuring the safe and stable operation of power systems and adapting to various complex working conditions. Utility Model Content

[0005] To address the technical problems existing in current medium-voltage power cables, this utility model proposes a B1-grade flame-retardant and cold-resistant medium-voltage power cable, comprising:

[0006] Multiple intertwined wire cores, together with a water-blocking filler layer, are wrapped and solidified into a cable core with a circular cross-section.

[0007] A composite wrapping layer is used to cover the outer wall of the cable core.

[0008] The inner sheath layer is extruded onto the outer wall of the composite wrapping layer;

[0009] An armor layer that covers the outer wall of the inner sheath layer;

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

[0011] The composite wrapping layer includes at least one layer of composite tape wrapping structure, the composite tape includes a foam layer and a flame-retardant layer that are fixed to each other, and the wrapping overlap rate of the composite tape is greater than 25%.

[0012] Preferably, the foaming layer comprises a silane cross-linked polyethylene foaming layer, and the flame retardant layer comprises an aluminum foil strip or a copper foil strip, the aluminum foil strip or copper foil strip being adhered to one side surface of the silane cross-linked polyethylene foaming layer.

[0013] Preferably, the thickness of the aluminum foil strip or copper foil strip is 0.05 to 0.2 mm.

[0014] Preferably, the density of the silane cross-linked polyethylene foam layer is 0.35–0.55 g / cm³. 3 Closed-cell ratio ≥95%.

[0015] Preferably, the silane cross-linked polyethylene foam layer is bonded to the aluminum foil strip or copper foil strip by a hot melt adhesive layer.

[0016] Preferably, the thickness ratio of the foamed layer to the flame-retardant layer is 3:1 to 5:1.

[0017] Preferably, the composite wrapping layer comprises two composite wrapping structures, with the inner composite wrapping structure wrapping in the forward direction at a wrapping angle of 30° to 45°, and the outer composite wrapping structure wrapping in the reverse direction at a wrapping angle of 30° to 45°.

[0018] Preferably, the wire core includes a conductor, a conductor shielding layer, a cross-linked polyethylene insulation layer, an insulation buffer layer, and an insulation shielding layer distributed from the inside out; the water-blocking filling layer includes multiple water-blocking ropes; and the wrapping layer includes longitudinally wrapped aluminum-plastic composite tape.

[0019] Preferably, the inner sheath layer comprises a low-smoke, halogen-free, flame-retardant polyolefin sheath layer, and the outer sheath comprises a cold-resistant polyurethane elastomer.

[0020] Preferably, the armor layer includes a galvanized steel wire loosely wound structure, and the outer layer of the galvanized steel wire loosely wound structure is provided with a water-blocking wrapping layer.

[0021] Compared with existing technologies, the significant advantages of this utility model's B1-grade flame-retardant and cold-resistant medium-voltage power cable are:

[0022] The B1-grade flame-retardant and cold-resistant medium-voltage power cable proposed in this utility model adopts a composite wrapping layer design, which achieves synergistic enhancement of flame retardancy and cold resistance through a foamed structural layer and a flame-retardant structural layer. A physical barrier layer is constructed using copper / aluminum foil, and the foamed layer absorbs mechanical stress to maintain functional integrity under extreme conditions. At the same time, the composite tape replaces the traditional glass ribbon flame-retardant structure, which reduces the weight of the cable and improves its bending performance, meeting the requirements for use in low-temperature environments. Attached Figure Description

[0023] 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.

[0024] Figure 1 This is a schematic diagram of the structure of the B1-grade flame-retardant and cold-resistant medium-voltage power cable shown in this utility model.

[0025] Figure 2 This is a schematic diagram of the composite wrapping layer shown in this utility model. Detailed Implementation

[0026] To better understand the technical content of this utility model, specific embodiments are provided below in conjunction with the accompanying drawings.

[0027] Combination Figure 1 As shown, the B1-grade flame-retardant and cold-resistant medium-voltage power cable of this utility model includes a cable core, a composite wrapping layer 4, an inner sheath layer 5, an armor layer 6, and an outer sheath 8. The cable core is formed into a circular cross-section by multiple twisted wire cores together with a water-blocking filling layer 2 and the wrapping layer 3.

[0028] Specifically, each wire core includes a conductor 11, a conductor shielding layer 12, a cross-linked polyethylene insulation layer 13, an insulation buffer layer 14, and an insulation shielding layer 15 distributed from the inside out. The water-blocking filling layer 2 includes multiple water-blocking ropes, and the wrapping layer 3 includes longitudinally wrapped aluminum-plastic composite tape.

[0029] Optionally, conductor 11 is made of Category 5 annealed copper conductor with a tightly packed circular stranded structure, and the surface of the copper wire is tin-plated. Conductor shielding layer 12 is made of semi-conductive shielding material, which is extruded onto the outer wall of conductor 11 to form a smooth cross-section to suppress partial discharge. Conductor shielding layer 12 and cross-linked polyethylene insulation layer 13 are formed by double-layer co-extrusion process. Insulating buffer layer 14 is formed by extrusion of polyethylene foam material. The thickness of insulating buffer layer 14 is less than the thickness of cross-linked polyethylene insulation layer 13. Insulating shielding layer 15 is formed by longitudinally wrapped copper-plastic composite tape.

[0030] Optionally, water-blocking ropes can be filled between multiple cores to make the cable round, and the cable core can be formed by wrapping it with longitudinal aluminum-plastic composite tape, which can achieve the effect of radial waterproofing and longitudinal water blocking.

[0031] Furthermore, the composite wrapping layer 4 covers the outer wall of the cable core. The composite wrapping layer 4 includes at least one layer of composite tape wrapping structure. The composite tape includes a foam layer 41 and a flame-retardant layer 42 that are fixedly connected to each other. The wrapping overlap rate of the composite tape is greater than 25%.

[0032] Thus, the foam layer 41 and the flame retardant layer 42 achieve fireproofing functions such as barrier, heat absorption and smoke suppression, while avoiding the problem of insulation becoming brittle at low temperatures after adding flame retardants in existing technologies, thereby increasing the impact toughness of the cable at low temperatures.

[0033] In an optional embodiment, the foam layer 41 includes a silane cross-linked polyethylene foam layer, and the flame retardant layer 42 includes an aluminum foil strip or a copper foil strip, which is adhered to one side of the silane cross-linked polyethylene foam layer.

[0034] The thickness of the aluminum foil strip or copper foil strip is preferably 0.05–0.2 mm. The density of the silane cross-linked polyethylene foam layer is 0.35–0.55 g / cm³. 3 Closed-cell ratio ≥95%.

[0035] Specifically, the silane cross-linked polyethylene foam layer is bonded to the aluminum foil or copper foil strip using a hot melt adhesive layer.

[0036] In the above embodiments, the thickness ratio of the foam layer 41 to the flame retardant layer 42 is 3:1 to 5:1.

[0037] Thus, due to the high thermal conductivity and ductility of copper or aluminum foil, the local temperature rise can be reduced through rapid heat diffusion when exposed to fire. At the same time, a dense metal barrier is formed to block the path of oxygen diffusion to the cable core and inhibit the decomposition and combustion of the insulation layer. The closed-cell structure of the foam layer 41 can effectively block the conduction of combustion heat flow to the internal insulation. Its low density characteristics reduce the mass of combustibles, and the carbonized layer structure helps to reduce smoke density during combustion.

[0038] In addition, since the microporous structure of the foam layer 41 can provide space for elastic deformation, it can absorb local stress concentration caused by cable bending at low temperatures, thus avoiding brittle cracking of the sheath.

[0039] Preferably, the composite wrapping layer 4 includes two composite wrapping structures, with the inner composite wrapping structure wrapping in the forward direction at a wrapping angle of 30° to 45°, and the outer composite wrapping structure wrapping in the reverse direction at a wrapping angle of 30° to 45°.

[0040] In this way, the multi-layer composite tape is wrapped alternately with opposite spiral angles to form a mesh-like compressive-shear resistant structure. The high ductility of the copper foil tape and the flexibility of the foam layer combine to form a low-temperature anti-delamination composite structure. The interlayer bonding force is enhanced by the repeated wrapping process, which suppresses the interfacial delamination caused by extreme temperature cycling.

[0041] In a specific embodiment, copper foil strip is used as flame retardant layer 42. The copper foil is rolled and annealed, and the surface is chemically passivated (passivation film thickness 50nm). During flame retardation, a dense copper oxide layer is generated. The foaming layer uses silane cross-linked polyethylene as the base material (MI = 1.2g / 10min), with 5wt% nano montmorillonite (interlayer spacing 1.2nm) and 3wt% ethylene-octene copolymer added. The foaming ratio is 3.5 times. It is extruded into a sheet by a foaming extruder. The microbubble pore size in the foaming layer is 80-150μm. Furthermore, the hot melt adhesive layer uses epoxy-modified EVA (epoxy value 0.12), which is pre-coated on the surface of the copper foil. During hot pressing, it forms a chemical cross-link with the foaming layer, making the foaming layer and copper foil strip difficult to peel off.

[0042] Furthermore, the inner sheath layer 5 is extruded onto the outer wall of the composite wrapping layer 4, and the armor layer 6 covers the outer wall of the inner sheath layer 5; the outer sheath 8 is extruded onto the outer wall of the armor layer 6.

[0043] Optionally, the inner sheath layer 5 includes a low-smoke halogen-free flame-retardant polyolefin sheath layer, the armor layer 6 includes a galvanized steel wire loosely wound structure, the outer layer of the galvanized steel wire loosely wound structure is provided with a water-blocking wrapping layer 7, and the outer sheath 8 includes a cold-resistant polyurethane elastomer.

[0044] Specifically, the armor layer 6 is made of galvanized steel wire with a diameter of 0.8 mm and a spacing of 2 mm, which balances mechanical strength and electromagnetic shielding capability.

[0045] In conjunction with the above embodiments, the composite wrapping layer proposed in this utility model adopts a foamed structural layer and a flame-retardant structural layer to achieve synergistic enhancement of flame retardancy and cold resistance. A physical barrier layer is constructed using copper / aluminum foil, and the foamed layer absorbs mechanical stress to maintain functional integrity under extreme conditions. At the same time, the composite tape replaces the traditional glass ribbon flame-retardant structure, thereby reducing the weight of the cable, improving its bending performance, and meeting the usage requirements of low-temperature environments.

[0046] 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 B1-class flame-retardant cold-resistant medium-voltage power cable, characterized in that, include: Multiple intertwined wire cores, together with the water-blocking filling layer (2), are wrapped and solidified into a circular cross-section cable core by the sheath (3); A composite wrapping layer (4) is wrapped around the outer wall of the cable core; The inner sheath layer (5) is extruded onto the outer wall of the composite wrapping layer (4); The armor layer (6) covers the outer wall of the inner sheath layer (5); The outer sheath (8) is extruded onto the outer wall of the armor layer (6); The composite wrapping layer (4) includes at least one layer of composite tape wrapping structure, the composite tape includes a foam layer (41) and a flame retardant layer (42) that are fixedly connected to each other, and the wrapping overlap rate of the composite tape is greater than 25%.

2. The B1 flame-retardant cold-resistant medium voltage power cable according to claim 1, characterized in that, The foam layer (41) includes a silane cross-linked polyethylene foam layer, and the flame retardant layer (42) includes an aluminum foil strip or a copper foil strip, which is bonded to one side of the silane cross-linked polyethylene foam layer.

3. The B1 flame-retardant cold-resistant medium voltage power cable according to claim 2, characterized in that, The thickness of the aluminum foil strip or copper foil strip is 0.05~0.2mm.

4. The B1 flame-retardant cold-resistant medium voltage power cable according to claim 2, characterized in that, The density of the silane cross-linked polyethylene foam layer is 0.35~0.55 g / cm³, and the closed-cell rate is ≥95%.

5. The B1 flame-retardant cold-resistant medium voltage power cable according to claim 2, characterized in that, The silane cross-linked polyethylene foam layer is bonded to the aluminum foil strip or copper foil strip by a hot melt adhesive layer.

6. The B1 flame-retardant cold-resistant medium voltage power cable according to claim 1, characterized in that, The thickness ratio of the foamed layer (41) to the flame-retardant layer (42) is 3:1 to 5:

1.

7. The B1 flame-retardant cold-resistant medium voltage power cable according to claim 1, characterized in that, The composite wrapping layer (4) includes two composite wrapping structures. The inner composite wrapping structure wraps in the forward direction with a wrapping angle of 30°~45°, and the outer composite wrapping structure wraps in the reverse direction with a wrapping angle of 30°~45°.

8. The B1 flame-retardant cold-resistant medium voltage power cable according to claim 1, characterized in that, The core includes a conductor (11), a conductor shielding layer (12), a cross-linked polyethylene insulation layer (13), an insulation buffer layer (14), and an insulation shielding layer (15) distributed from the inside out. The water-blocking filling layer (2) includes multiple water-blocking ropes, and the wrapping layer (3) includes longitudinally wrapped aluminum-plastic composite tape.

9. The B1 flame-retardant cold-resistant medium voltage power cable according to claim 1, characterized in that, The inner sheath layer (5) includes a low-smoke halogen-free flame-retardant polyolefin sheath layer, and the outer sheath (8) includes a cold-resistant polyurethane elastomer.

10. The B1 flame-retardant cold-resistant medium voltage power cable according to claim 1, characterized in that, The armor layer (6) includes a galvanized steel wire loose winding structure, and the outer layer of the galvanized steel wire loose winding structure is provided with a water-blocking wrapping layer (7).

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