Medium voltage fire resistant flame retardant power cable

Abstract

The utility model relates to the technical field of power cable, more particularly to medium voltage fire -resistant flame -retardant power cable, including cable core, fire -resistant layer, inner sheath layer, armoring layer and outer sheath layer, the fire -resistant layer is covered in the outer wall of cable core, the inner sheath layer is extruded and is covered in the outer wall of cable core, the armoring layer is covered in the outer wall of inner sheath layer, the outer sheath layer extruded and is covered in the outer wall of armoring layer. The utility model adopts by baseband layer and in situ growth's inorganic ceramic insulation layer constitutes integrated metal ceramic composite tape as fire -resistant layer, replaces traditional mica tape, eliminates the risk of mica pulverization failure caused by the decomposition of organic baseband and adhesive under high temperature, and the inherent weak link of wrapping lap joint, and the in situ growth's ceramic layer and metal matrix binding force is extremely strong, avoids the interlayer peeling under high temperature, realizes high fire -resistant grade.

Description

Technical Field

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

[0002] Medium-voltage fire-resistant and flame-retardant power cables are the lifeline for ensuring continuous power supply to critical emergency systems in fire environments. In existing technologies, multi-layered composite structures are typically used to achieve high fire resistance. A typical structure involves sequentially placing a fire-resistant layer made of mica tape, a metal shielding layer, and a metal armor layer outside the cable core.

[0003] Mica tape, in particular, ensures circuit integrity by maintaining its insulation properties at high temperatures. However, mica tape is typically made with organic polymer films (such as polyester film) or fiberglass cloth as the base material, with mica paper attached by adhesives. Under continuous flame exposure, the organic base tape and adhesives rapidly decompose, carbonize, or melt, causing the mica paper to lose support, peel off, and pulverize, thus losing its insulating function. This makes the reliability of its fire resistance highly dependent on the temperature limit of the organic materials, posing a risk of failure. Furthermore, the spiral wrapping method of mica tape inevitably creates physical gaps at the overlaps, forming continuous weak points in the structure. High-temperature flames and smoke can easily penetrate directly along these paths, leading to premature insulation breakdown.

[0004] To overcome the above problems, existing technologies typically focus on developing more heat-resistant mica tape substrates or adhesives, or increasing the number of wrapping layers. However, this does not fundamentally solve the inherent structural problems of thermal mismatch at wrapping overlaps and multi-layer interfaces. Instead, it leads to increased cable outer diameter, higher costs, and reduced flexibility. Utility Model Content

[0005] To address the technical problems existing in fire-resistant and flame-retardant power cables in the prior art, the first aspect of this utility model proposes a technical solution: a medium-voltage fire-resistant and flame-retardant power cable, comprising a cable core, a fire-resistant layer, an inner sheath layer, an armor layer, and an outer sheath layer. The fire-resistant layer covers the outer wall of the cable core, the inner sheath layer is extruded and covers the outer wall of the cable core, the armor layer covers the outer wall of the inner sheath layer, and the outer sheath layer is extruded and covers the outer wall of the armor layer.

[0006] The refractory layer includes an integrated metal-ceramic composite tape refractory structure, which includes a base layer and an inorganic ceramic insulating layer on the surface of the base layer. The metal-ceramic composite tape refractory structure is a tubular structure formed by spiral wrapping.

[0007] The refractory layer comprises corrugated aluminum strips wrapped with a predetermined overlap ratio.

[0008] Preferably, a ceramic flame-retardant layer is formed on a local area of ​​one side surface of the wrinkled aluminum strip through anodizing treatment, and the non-anodized area on the surface of the wrinkled aluminum strip is completely covered by the overlapping area.

[0009] Preferably, the overlap ratio of the wrinkled aluminum strip is 35-45%.

[0010] Preferably, the flame-retardant filler rope includes a first filler rope near the core and a second filler rope near the fire-resistant layer, wherein the first filler rope is a ceramicized silicone rubber flame-retardant filler rope and the second filler rope is a glass fiber flame-retardant filler rope.

[0011] Preferably, the inner sheath layer comprises a low-smoke, halogen-free, flame-retardant polyolefin sheath layer.

[0012] Preferably, the armor layer includes an inner steel strip wrapping layer and an outer steel strip wrapping layer. The inner steel strip wrapping layer includes a first steel strip wrapping structure, and the outer steel strip wrapping layer includes a second steel strip wrapping structure. The first steel strip wrapping structure wraps around and covers the outer wall of the inner sheath layer, and the second steel strip wrapping structure wraps around the outer wall of the first steel strip wrapping structure.

[0013] Preferably, the first steel strip wrapping structure is formed by wrapping a first steel strip with a first wrapping overlap ratio to form a tubular structure, and the second steel strip wrapping structure is formed by wrapping a second steel strip with a second wrapping overlap ratio to form a tubular structure.

[0014] Preferably, the width of the second steel strip is 1 / 3 to 2 / 3 of the width of the first steel strip, the first wrapping overlap rate is 20 to 30%, and the second wrapping overlap rate is 0 to 10%.

[0015] Preferably, the surface of the first steel strip is provided with a plurality of protruding structures, and the second steel strip is provided with a plurality of movable parts. When the second steel strip is wound around the surface of the first steel strip, when the movable parts overlap with the protruding structures, the movable parts can be lifted by the protruding structures, forming a plurality of burrs protruding from the surface of the second steel strip.

[0016] Preferably, the outer sheath layer includes a flame-retardant polyolefin sheath layer, and a closed-cell foam layer is provided inside the flame-retardant polyolefin sheath layer.

[0017] Compared with the prior art, the advantages of this utility model are:

[0018] This invention uses a metal-ceramic composite tape, consisting of a base layer and an in-situ grown inorganic ceramic insulating layer, as a fire-resistant layer, replacing the traditional mica tape. This eliminates the risk of mica powdering failure caused by the decomposition of organic base tape and adhesive at high temperatures, as well as the inherent weak points of the wrapping overlap seams. Furthermore, the in-situ grown ceramic layer has extremely strong adhesion to the metal substrate, avoiding interlayer delamination at high temperatures and achieving a high fire resistance rating.

[0019] The metal-ceramic composite tape fire-resistant structure of this application achieves a continuous and seamless fire-resistant insulation barrier by spirally wrapping corrugated metal tape and using the interlocking of corrugations to realize mechanical interlocking. At the same time, the corrugated structure itself also gives the cable excellent flexibility. Furthermore, by locally treating the retained conductive area, the structure integrates metal shielding function, simplifying the cable structure. Attached Figure Description

[0020] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0021] Figure 1 This is a schematic diagram of the structure of the medium-voltage fire-resistant and flame-retardant power cable shown in this utility model;

[0022] Figure 2 This is a schematic diagram of the cross-sectional structure of the medium-voltage fire-resistant and flame-retardant power cable shown in this utility model;

[0023] Figure 3 This is a schematic diagram of the cross-sectional structure of the fire-resistant layer, inner sheath layer, armor layer and outer sheath layer shown in this utility model;

[0024] Figure 4 This is a schematic diagram showing the distribution of the ceramicized flame-retardant layer on the surface of the wrinkled aluminum strip as shown in this utility model;

[0025] Figure 5 This is a schematic diagram of the structure of the first steel strip shown in this utility model;

[0026] Figure 6 This is a schematic diagram of the structure of the second steel strip shown in this utility model. Detailed Implementation

[0027] To better understand the technical content of this utility model, specific embodiments are provided below in conjunction with the accompanying drawings.

[0028] {Example 1}

[0029] Combination Figure 1 and Figure 2The first aspect of this utility model proposes a technical solution: a medium-voltage fire-resistant and flame-retardant power cable, comprising a cable core 10, a fire-resistant layer 3, an inner sheath layer 4, an armor layer 5, and an outer sheath layer 6.

[0030] like Figure 2 As shown, the cable core 10 is formed by multiple pairs of tangent wire cores 1 and flame-retardant filler ropes 2 filling the spaces between the wire cores 1.

[0031] The wire core 1 includes a conductor 11, a conductor shielding layer 12, an insulation layer 13, an insulation shielding layer 14, and a metal shielding layer 15.

[0032] In an optional embodiment, conductor 11 may employ a type 2 stranded circular copper conductor structure to ensure flexibility and roundness. Conductor shielding layer 12, insulation layer 13, and insulation shielding layer 14 may be formed using a three-layer co-extrusion process and a cross-linked polyethylene material system. Metal shielding layer 15 may be formed by overlapping and wrapping copper strips.

[0033] Thus, the three-layer co-extrusion process ensures that there are no interface air gaps between the conductor shielding layer 12, the insulation layer 13, and the insulation shielding layer 14, and that the electric field distribution is uniform, which greatly improves the long-term electrical reliability of the medium-voltage cable. The outer metal shielding layer 15 is used to balance the electric field and carry short-circuit current.

[0034] Furthermore, the fire-resistant layer 3 is wrapped around the outer wall of the cable core 10.

[0035] Among them, the fire-resistant layer 3 includes an integrated metal-ceramic composite tape fire-resistant structure, which is composed of a base tape layer and an inorganic ceramic insulation layer grown in situ on its surface, so that the fire-resistant layer 3 can provide metal shielding and fire-resistant insulation for the cable core 10.

[0036] Inorganic ceramic insulation is an excellent high-temperature insulator that ensures fire resistance, while the metal base tape (such as aluminum tape) is a good conductor. By designing their local non-ceramic regions to contact each other, a continuous electrical path is formed, achieving the metal shielding function. This integrated design combines the traditionally separate mica fire-resistant layer and metal shielding layer into one, which not only simplifies the structure and reduces the cable diameter, but also eliminates the risk of peeling due to thermal mismatch between the two.

[0037] Furthermore, the refractory structure of the metal-ceramic composite belt is a tubular structure formed by spiral wrapping, and the metal-ceramic composite belt is a corrugated metal belt, which achieves mechanical interlocking through interlocking corrugations.

[0038] It should be understood that spiral wrapping is a mature continuous production process that is easy to implement to form a continuous refractory layer 3. The interlocking of the corrugations forms a mechanical lock, which makes the wrapping structure itself have extremely high integrity and stability. It significantly enhances the ability to resist external mechanical impact and internal thermal stress, avoids the loosening and unraveling that may occur with traditional smooth strip wrapping, and ensures the reliability of the refractory.

[0039] In an optional embodiment, combined with Figure 3 As shown, the fire-resistant layer 3 is formed by wrapping the corrugated aluminum strip 31 with a predetermined overlap rate. A local area on one side surface of the corrugated aluminum strip 31 is formed into a ceramic flame-retardant layer 32 through anodizing treatment. When the corrugated aluminum strip 31 is wrapped, the non-anodized area 311 on its surface is completely covered by the overlap area, so that the flame-retardant wrapping layer 3 provides metal shielding and fire-resistant insulation for the cable core 10.

[0040] As mentioned above, a ceramicized flame-retardant layer 32 is formed by localized anodizing of the corrugated aluminum strip 31. This area has flame-retardant, fire-resistant, and insulating properties. Figure 4 As shown, when the corrugated aluminum strip 31 is wrapped, the non-anodized area 311 is covered by the inner surface of the corrugated aluminum strip 31, so that the corrugated aluminum strip 31 can form a continuous conductor during wrapping, achieving a metal shielding effect. At the same time, the ceramic flame-retardant layer 32 on the outer side of the corrugated aluminum strip 31 is also continuously distributed, forming a fire barrier on the outer wall of the spiral tubular structure formed by the wrapping of the corrugated aluminum strip 31.

[0041] As mentioned above, the non-anodized region 311 forms a metal-metal contact at the overlap, ensuring longitudinal conductivity continuity and completing the metal shielding function, while the exposed ceramic flame-retardant layer 32 constitutes a continuous and complete inorganic ceramic protective sleeve, achieving good fire resistance and insulation.

[0042] In the above embodiments, the thickness of the ceramicized flame-retardant layer 32 is 10 to 50 micrometers.

[0043] In an optional embodiment, the overlap of the corrugated aluminum strip 31 is 35-45%.

[0044] Thus, by setting a larger wrapping overlap ratio, the corrugated structure of the corrugated aluminum strip 31 has more interlocking area to increase the tightness of the connection. On the other hand, a larger overlap ratio means a thicker protective layer and a longer flame penetration path, further improving the reliability of the fire barrier.

[0045] Furthermore, the flame-retardant filler rope 2 includes a first filler rope near the core 1 and a second filler rope near the fire-resistant layer 3. The first filler rope is a ceramicized silicone rubber flame-retardant filler rope, and the second filler rope is a glass fiber flame-retardant filler rope.

[0046] Thus, in the early stages of a fire, the outer layer of glass fiber flame-retardant filling rope melts at high temperatures and fills all gaps, especially the possible gaps inside the fire-resistant layer 3, forming a glassy sealing layer that effectively achieves longitudinal flame retardancy and oxygen isolation. Meanwhile, the inner layer of ceramicized silicone rubber flame-retardant filling rope can be sintered at higher temperatures into a hard ceramic skeleton, providing mechanical support for the inner core 1 and the outer sealing layer, preventing the structure from collapsing at high temperatures, and jointly ensuring the integrity of the fire-resistant structure.

[0047] Furthermore, the inner sheath layer 4 is extruded and covered on the outer wall of the cable core 10, and the inner sheath layer 4 can be selected as a low-smoke halogen-free flame-retardant polyolefin sheath layer.

[0048] Thus, the inner sheath layer 4 provides a soft, insulating buffer layer between the armor layer 5 and the inner fire-resistant layer 3, protecting the brittle ceramic layer from direct impact from hard armor objects, while also adding an extra fire-resistant layer to the cable due to its low-smoke, halogen-free, and flame-retardant characteristics.

[0049] Furthermore, the armor layer 5 covers the outer wall of the inner sheath layer 4.

[0050] Combination Figure 3 As shown, the armor layer 5 includes an inner steel strip wrapping layer 51 and an outer steel strip wrapping layer 52. The inner steel strip wrapping layer 51 includes a first steel strip wrapping structure, and the outer steel strip wrapping layer 52 includes a second steel strip wrapping structure. The first steel strip wrapping structure wraps around and covers the outer wall of the inner sheath layer 4, and the second steel strip wrapping structure wraps around the outer wall of the first steel strip wrapping structure.

[0051] Specifically, the first steel strip wrapping structure is formed by wrapping the first steel strip 511 with the first wrapping overlap ratio to form a tubular structure, and the second steel strip wrapping structure is formed by wrapping the second steel strip 521 with the second wrapping overlap ratio to form a tubular structure.

[0052] Thus, the inner first steel strip 511 wraps around with a high overlap rate, mainly undertaking the basic functions of establishing continuous mechanical strength and protecting the inner sheath, while the outer second steel strip 521 wraps around with a low overlap rate, its main function being to interweave with the inner layer, cover the overlap seams of the inner steel strip, and form a more rigorous seamless protection.

[0053] The width of the second steel strip 521 is 1 / 3 to 2 / 3 of the width of the first steel strip 511. This makes the wrapping of the second steel strip 521 more flexible and better able to fit the uneven surface of the inner layer.

[0054] Optionally, the first wrapping overlap rate is 20-30%, and the second wrapping overlap rate is 0-10%.

[0055] Thus, the wrapping overlap rate of the first steel strip 511 is 20-30%, which can ensure the coverage strength and continuity of the foundation. The wrapping overlap rate of the second steel strip 521 is 0-10%, which can save materials and reduce weight. At the same time, it also reserves space for the embedding of the outer sheath, laying the foundation for the subsequent formation of a strong mechanical interlock.

[0056] Specifically, the surface of the first steel strip 511 is provided with multiple protruding structures 512, and the second steel strip 521 is provided with multiple movable parts 522. When the second steel strip 521 is wrapped around the surface of the first steel strip 511, when the movable parts 522 overlap with the protruding structures 512, the movable parts 522 can be lifted by the protruding structures 512, forming multiple burrs protruding from the surface of the second steel strip 521, so that when the outer sheath layer 6 is squeezed onto the surface of the outer steel strip wrapping layer 52, there is a stronger bonding force between it and the outer steel strip wrapping layer 52.

[0057] Thus, when the second steel strip 521 wraps around the first steel strip 511 with the raised structure 512, the movable part 522 is pushed up to form burrs. These burrs are embedded in the extruded outer sheath layer 6 (especially before the outer sheath layer 6 has cured), which can increase the bonding force and peel strength between the sheath and the armor layer, ensuring that the outer sheath will not fall off the armor in the event of fire, impact or bending deformation, thereby maintaining the structural integrity and durability of the cable protection system.

[0058] Furthermore, the outer sheath layer 6 is extruded and covered on the outer wall of the armor layer 5. The outer sheath layer 6 includes a flame-retardant polyolefin sheath layer, and a closed-cell foam layer is provided inside the flame-retardant polyolefin sheath layer.

[0059] In this way, the sealed foam layer can prevent flames from spreading out from the gaps where the sheath and armor separate, and prevent high-temperature fumes from directly scorching the armor layer, thus slowing down the transfer of heat to the inside of the cable.

[0060] Understandably, the built-in sealed foam layer forms a stable gas phase insulation layer with a thermal conductivity far lower than that of solid plastic. It can effectively block the heat of external flames, significantly reduce the temperature transferred to the armor layer and inside the cable, effectively alleviate the heat accumulation effect from a structural perspective, and provide a longer safety window for the internal fire-resistant layer.

[0061] {Example 2}

[0062] The above-mentioned method for preparing medium-voltage fire-resistant and flame-retardant power cables includes the following steps:

[0063] Step S1: Twist multiple annealed soft round copper wires in layers according to a certain direction and pitch to form conductor 11;

[0064] Step S2: The conductor shielding material, the insulating material, and the insulating shielding material are extruded simultaneously in the same die head to form a three-layer co-extruded conductor shielding layer 12, insulating layer 13, and insulating shielding layer 14.

[0065] Step S3: Repeatedly wrap copper tape around the surface of the insulating shielding layer 14 to form a metal shielding layer 15, thus completing the preparation of the wire core 1;

[0066] Step S4: Wrap the corrugated aluminum strip 31 with ceramic flame retardant layer 32 around the outside of multiple wire cores 1 and flame retardant filler rope 2 according to the predetermined wrapping overlap rate to form a fire-resistant layer 3.

[0067] Step S5: Extrude low-smoke halogen-free flame-retardant polyolefin on the outside of the refractory layer 3 to form the inner sheath layer 4;

[0068] Step S6: Wrap the first steel strip 511 around the outer wall of the inner sheath layer 4 according to the first wrapping overlap ratio, and then wrap the second steel strip 521 around the surface of the first steel strip 511 with the second wrapping overlap ratio to form the armor layer 5.

[0069] Step S7: Extrude flame-retardant polyolefin onto the outer wall of the armor layer 5 to form the outer sheath layer 6;

[0070] In step S4, the aluminum alloy strip is rolled into a wrinkled shape, so that the whole roll of aluminum strip passes continuously through the micro-arc oxidation electrolytic cell and a specific area is covered, so that the target area is exposed in the micro-arc oxidation electrolytic cell and a ceramic flame retardant layer 32 is formed in situ in a predetermined pulse electric field and electrolyte environment.

[0071] Among these techniques, precision masking technology can be used to cover non-oxidized areas.

[0072] Optionally, the thickness of the ceramicized flame-retardant layer 32 is between 10 micrometers and 50 micrometers. If the thickness is greater than 50 micrometers, the ceramicized flame-retardant layer 32 may undergo brittle cracking due to stress when the corrugated aluminum strip 31 is wrapped around it. Preferably, it is 20 to 40 micrometers to achieve a balance between fire-resistant insulation properties and mechanical durability.

[0073] Furthermore, in step S6, when wrapping the double-layer steel strip, the pitch and overlap rate of the two wrapping devices are precisely controlled so that the gap of the second steel strip 521 precisely covers the overlap of the first steel strip 511, achieving staggered shielding of the armor layer and greatly improving the tightness of the armor. At the same time, the interaction between the protrusions and the movable parts is determined in the design stage and can be automatically realized in production, laying the foundation for the firm attachment of the final sheath.

[0074] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Those skilled in the art to which this invention pertains can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of this invention shall be determined by the claims.

Claims

1. A medium-voltage fire-resistant and flame-retardant power cable, characterized in that, It includes a cable core (10), a fire-resistant layer (3), an inner sheath layer (4), an armor layer (5) and an outer sheath layer (6). The cable core (10) is formed by multiple pairs of tangent wire cores (1) and flame-retardant filler ropes (2) filled between the wire cores (1). The fire-resistant layer (3) covers the outer wall of the cable core (10), the inner sheath layer (4) is extruded and covers the outer wall of the cable core (10), the armor layer (5) covers the outer wall of the inner sheath layer (4), and the outer sheath layer (6) is extruded and covers the outer wall of the armor layer (5). The refractory layer (3) includes an integrated metal-ceramic composite strip refractory structure, which includes a base layer and an inorganic ceramic insulating layer on the surface of the base layer. The metal-ceramic composite strip refractory structure is a tubular structure formed by spiral wrapping. The refractory layer (3) comprises a corrugated aluminum strip (31) wrapped with a predetermined overlap ratio.

2. The medium-voltage fire-resistant and flame-retardant power cable according to claim 1, characterized in that, A ceramic flame-retardant layer (32) is formed on a local area of ​​one side surface of the wrinkled aluminum strip (31) through anodizing treatment, and the non-anodized area (311) on the surface of the wrinkled aluminum strip (31) is completely covered by the overlapping area.

3. The medium-voltage fire-resistant and flame-retardant power cable according to claim 1, characterized in that, The overlap rate of the wrinkled aluminum strip (31) is 35-45%.

4. The medium-voltage fire-resistant and flame-retardant power cable according to claim 1, characterized in that, The flame-retardant filler rope (2) includes a first filler rope near the core (1) and a second filler rope near the fire-resistant layer (3). The first filler rope is a ceramicized silicone rubber flame-retardant filler rope, and the second filler rope is a glass fiber flame-retardant filler rope.

5. The medium-voltage fire-resistant and flame-retardant power cable according to claim 1, characterized in that, The inner sheath layer (4) includes a low-smoke, halogen-free, flame-retardant polyolefin sheath layer.

6. The medium-voltage fire-resistant and flame-retardant power cable according to claim 1, characterized in that, The armor layer (5) includes an inner steel strip wrapping layer (51) and an outer steel strip wrapping layer (52). The inner steel strip wrapping layer (51) includes a first steel strip wrapping structure, and the outer steel strip wrapping layer (52) includes a second steel strip wrapping structure. The first steel strip wrapping structure wraps around and covers the outer wall of the inner sheath layer (4), and the second steel strip wrapping structure wraps around the outer wall of the first steel strip wrapping structure.

7. The medium-voltage fire-resistant and flame-retardant power cable according to claim 6, characterized in that, The first steel strip wrapping structure is formed by wrapping a first steel strip (511) with a first wrapping overlap ratio to form a tubular structure, and the second steel strip wrapping structure is formed by wrapping a second steel strip (521) with a second wrapping overlap ratio to form a tubular structure.

8. The medium-voltage fire-resistant and flame-retardant power cable according to claim 7, characterized in that, The width of the second steel strip (521) is 1 / 3 to 2 / 3 of the width of the first steel strip (511), the first wrapping overlap rate is 20 to 30%, and the second wrapping overlap rate is 0 to 10%.

9. The medium-voltage fire-resistant and flame-retardant power cable according to claim 7, characterized in that, The surface of the first steel strip (511) is provided with a plurality of protruding structures (512), and the second steel strip (521) is provided with a plurality of movable parts (522). When the second steel strip (521) is wound around the surface of the first steel strip (511), when the movable part (522) overlaps with the protruding structure (512), the movable part (522) can be lifted by the protruding structure (512), forming a plurality of burrs protruding from the surface of the second steel strip (521).

10. The medium-voltage fire-resistant and flame-retardant power cable according to claim 1, characterized in that, The outer sheath layer (6) includes a flame-retardant polyolefin sheath layer, and a closed foam layer is provided inside the flame-retardant polyolefin sheath layer.

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