Polyethylene flame-retardant power cable

Abstract

The application relates to the technical field of cross-linked polyethylene power cables, and discloses a polyethylene flame-retardant power cable, which is characterized in that a flame-retardant structure layer is arranged between a cable core insulating layer and a cable armor layer, the structure layer is composed of equally-spaced separation ring assemblies and ceramic fillers filled between the separation ring assemblies, an outer part is uniformly wound with a ceramicized adhesive tape layer, the separation ring assemblies contain expanded fillers, the expanded fillers are driven to expand and push the inner thrust plates to slide when on fire, and the ceramic fillers are bidirectionally extruded: the ceramic fillers are dynamically filled in the gaps generated due to the collapse of the cable core insulating layer, and the internal fire passage is blocked; the ceramic fillers push the ceramicized adhesive tape layer in a softened state to embed into the armor layer pores, mechanical anchoring is formed, and interlayer peeling caused by solidification shrinkage is prevented. The application changes the cable from a passive fire resistance into an active fire prevention system with self-adaptive plugging and anchoring capacity, and significantly improves the structural integrity and flame-retardant reliability of the cable in a real fire.

Description

Technical Field

[0001] This invention relates to the field of cross-linked polyethylene power cable technology, and more particularly to a flame-retardant polyethylene power cable. Background Technology

[0002] Flame-retardant polyethylene power cables are power transmission cables that use polyethylene as the main insulation or sheath material and achieve flame-retardant performance through the addition of flame retardants, the adoption of flame-retardant structural designs, or the use of composite flame-retardant materials. They are mainly used for the transmission and distribution of electrical energy in power transmission and distribution systems and various power engineering scenarios. Their core structure typically includes a conductor, a polyethylene insulation layer, a flame-retardant layer, an armor layer, and an outer sheath. The flame-retardant properties are achieved by inhibiting the spread of combustion, reducing the release of toxic fumes, and preventing the continued combustion of open flames, meeting the fire safety requirements of different scenarios. Combining the excellent electrical insulation, chemical corrosion resistance, and flexibility of polyethylene with the fire safety of flame-retardant materials, they are suitable for high-rise buildings, rail transit, mines, chemical industrial parks, and other places with high fire safety requirements. They can effectively reduce the spread of fire and the hazards of toxic fumes caused by cable combustion in fire accidents, ensuring the stability of power system operation and the safety of personnel and property. They also feature convenient installation and a long service life, making them an important cable type in the power transmission field that balances functionality and safety.

[0003] Under high-temperature conditions during a fire, the ceramic flame-retardant layer inside the flame-retardant cable shrinks in volume as it solidifies, while other structural layers such as the sheath and filler expand due to the high temperature. Because the thermal expansion coefficients of the materials in each layer are mismatched, interlayer separation can easily occur, forming axial gaps and voids. Simultaneously, the polymer insulation material of the cable core softens or even melts and collapses at high temperatures, creating new voids between it and the outer sheath. These voids, generated at different locations within the cable, interconnect, forming axial channels for the rapid propagation of smoke and flames. This allows the fire to spread along the cable's path, accelerating the destruction of the cable's internal structure under direct exposure to high temperatures and flames, thus affecting its fire resistance integrity and safety reliability. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the existing technology has the disadvantage that, under high temperature fire conditions, the internal gaps generated by the shrinkage of the ceramic layer and the softening and collapse of the insulation layer in the flame-retardant cable provide an axial channel for the spread of flames and smoke, which easily damages its fire resistance integrity. To this end, we propose a polyethylene flame-retardant power cable.

[0005] To achieve the above objectives, this application adopts the following technical solution: a polyethylene flame-retardant power cable, comprising: a cable core conductor, the cable core conductor being wrapped with a cable core insulation layer, the cable core insulation layer being coaxially sleeved with a cable armor layer, a flame-retardant structural layer being installed in the interlayer cavity between the cable core insulation layer and the cable armor layer, the flame-retardant structural layer comprising a separator ring assembly, the separator ring assemblies being arranged at equal intervals inside the interlayer cavity, the separator ring assembly being filled with expansion filler, and the annular cavity formed by the separator ring assemblies being filled with ceramicized filler, the separator ring assembly and the ceramicized filler being spaced apart, and the separator ring assembly and the ceramicized filler being jointly wrapped with a ceramicized tape layer; the separator ring assembly comprising a rigid support ring, and two sets of push plates being slidably connected to the inner wall of the rigid support ring, when the expansion filler expands due to heat, it pushes the push plates outward, applying extrusion pressure to the ceramicized filler in the annular cavity, causing the ceramicized filler to push towards the inner and outer walls of the annular cavity.

[0006] Preferably, the push plate is symmetrically arranged about the inside of the rigid support ring, and the push plate is coaxially sleeved on the outside of the cable core insulation layer.

[0007] Preferably, the inner ring surface of the push plate is slidably connected to the outer wall of the cable core insulation layer, and the inner ring surface of the push plate is rounded.

[0008] Preferably, the rigid support ring has a partition baffle arranged in a ring array along the axial direction inside, the partition baffle being used to prevent the expansion filler filling inside the partition ring assembly from accumulating together.

[0009] Preferably, the partition baffle is fixedly connected to the rigid support ring, and the push plate is slidably connected to the partition baffle.

[0010] Preferably, two sets of limiting rings are symmetrically arranged on both sides of the rigid support ring. The limiting rings are used to restrict the sliding range of the push plate, so that the push plate can only slide inside the rigid support ring.

[0011] Preferably, the limiting ring is fixedly connected to the rigid support ring, and the top of the limiting ring is rounded. The rounded edge is used to reduce the damage to the external structure of the rigid support ring when the cable is bent.

[0012] Preferably, the outer wall of the ceramicized filler is in close contact with the inner wall of the ceramicized tape layer, and the outer wall of the ceramicized tape layer is in close contact with the inner wall of the cable armor layer.

[0013] Preferably, the cable armor layer is a steel wire braided structure, and the interior of the cable armor layer has a number of pores evenly distributed. When the ceramicized filler in the annular cavity is squeezed and pushed towards the outer wall, it can push the ceramicized tape layer, so that the ceramicized tape layer is embedded in the pores inside the cable armor layer, which is used to increase the connection strength between the ceramicized tape layer and the cable armor layer when the ceramicized tape layer is heated and cured.

[0014] Preferably, a cross-linked polyethylene protective sleeve is coaxially disposed on the outside of the cable armor layer, and the inner wall of the cross-linked polyethylene protective sleeve is tightly fitted with the outer wall of the cable armor layer.

[0015] The technical effects and advantages of this invention are as follows: This invention achieves multiple precise defenses in a fire by constructing an active and coordinated protection mechanism that integrates expansion-driven expansion of the expansion packing, bidirectional sealing, and mechanical anchoring between the ceramicized packing and the cable armor layer. The expansion packing inside the separator ring assembly, when heated, pushes the sliding baffle, simultaneously and dynamically filling the gaps formed by the collapse of the cable core, and extruding the ceramicized packing outwards, causing it to seal the gaps between the flame-retardant structural layer and the cable core again. This effectively blocks the gaps between the flame-retardant structural layer and the cable core, preventing the formation of a fire spread channel. Furthermore, the outer wall of the ceramicized packing... The external push-up ceramicized tape layer allows it to embed into the pores of the cable armor layer in a softened state, forming pilot curing anchor points. This fundamentally prevents the risk of the ceramic structure peeling off from the external armor and forming a continuous fire channel before the overall ceramic structure cures and shrinks. At the same time, the rigid support ring and zoned limiting structure ensure uniform and controllable release of expansion pressure, optimizing the sealing and anchoring effect while avoiding excessive compression damage to the outer layer. This upgrades the cable from passive fire resistance to an adaptive active fire protection system, significantly improving its structural integrity and flame-retardant reliability in real fire scenarios. Attached Figure Description

[0016] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts:

[0017] Figure 1 This is a schematic diagram of the overall cross-sectional structure of the present invention; Figure 2 This is a three-dimensional structural diagram of the entire invention; Figure 3 This is a schematic cross-sectional view of the overall structure of the present invention; Figure 4 This is a cross-sectional structural diagram of the flame-retardant structural layer portion of the present invention; Figure 5 This is a three-dimensional structural diagram of the separator ring assembly of the present invention; Figure 6 This is a three-dimensional structural diagram of the ceramicized tape layer and the cable armor layer of the present invention.

[0018] Legend: 1. Cable core conductor; 2. Cable core insulation layer; 3. Separator ring assembly; 4. Expansion filler; 5. Ceramicized filler; 6. Ceramicized tape layer; 7. Cable armor layer; 8. Cross-linked polyethylene protective sleeve; 301. Rigid support ring; 302. Limiting ring; 303. Separator baffle; 304. Push plate. Detailed Implementation

[0019] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0020] Reference Figure 1 As shown, the present invention provides a technical solution: a polyethylene flame-retardant power cable, comprising: a cable core conductor 1, a cable core insulation layer 2 wrapped around the outside of the cable core conductor 1, a cable armor layer 7 coaxially sleeved around the outside of the cable core insulation layer 2, and a flame-retardant structural layer installed in the cavity between the cable core insulation layer 2 and the cable armor layer 7.

[0021] Under the intense heat of a fire, the polymer insulation material of the flame-retardant cable core, such as cross-linked polyethylene, softens and loses its structural support strength, eventually collapsing under gravity and internal stress. This process causes annular peeling between the originally tightly wrapped fire-retardant structural layer and the cable core, forming circumferential and axial gaps. These gaps become preferential channels for the longitudinal propagation of high-temperature smoke, flames, and even molten materials along the cable's interior, severely compromising the overall fire barrier function of the cable. To address these technical problems, this application proposes the following improvements:

[0022] Please see Figure 1 , Figure 2 and Figure 4As shown, the flame-retardant structural layer includes a separator ring assembly 3, which is arranged at equal intervals inside the interlayer cavity. The separator ring assembly 3 is filled with an expandable filler 4, which is made of expandable graphite material. The expandable filler 4 begins to expand when the temperature reaches approximately 200 degrees Celsius. The annular cavity formed between the separator ring assemblies 3 is filled with a ceramicized filler 5. When the temperature reaches above 200 degrees Celsius, the ceramicized filler 5 gradually softens upon heating. When the temperature gradually rises to above 500 degrees Celsius, the ceramicized filler 5 begins to solidify. The separator ring assemblies 3 and the ceramicized filler 5 are spaced apart. The equally spaced separator ring assemblies 3 can improve the mechanical strength of the cable, while the spaced ceramicized filler 5 can provide bendable points during cable laying or movement, ensuring the cable's flexibility. A ceramicized tape layer 6 is wrapped around the exterior of both the separator ring assemblies 3 and the ceramicized filler 5, forming a layer inside the cable. The continuous and complete wrapping layer undergoes a rapid ceramic transformation when exposed to fire or high temperatures, forming a continuous and dense ceramic-like inorganic protective layer. This protective layer effectively isolates the spread of flames and heat to the core of the cable, preventing the cable insulation and conductor from being ignited or burned, maintaining the cable's short-term power-carrying capacity, and improving the cable's reliability in fire scenarios. The ceramicized tape layer 6 uses the same material as the ceramicized filler 5. During the softening and subsequent ceramic curing process, it can fuse with the ceramicized filler 5 to form an integrated ceramic protective structure. The ceramicized filler 5 forms hard ceramic rings on its inner wall, which can enhance the mechanical stability of the overall structure through equally spaced rigid nodes. The ceramicized tape layer 6 ensures the protective effect of the internal cable and extends the emergency power-carrying time of the cable. The two work together to improve the overall ceramic protective structure's resistance to deformation and service life.

[0023] Please see Figure 1 and Figure 6 As shown, the outer wall of the ceramicized filler 5 is tightly bonded to the inner wall of the ceramicized tape layer 6, and the outer wall of the ceramicized tape layer 6 is tightly bonded to the inner wall of the cable armor layer 7. The cable armor layer 7 has a steel wire braided structure, and several pores are evenly distributed inside the cable armor layer 7. When the ceramicized filler 5 in the annular cavity is squeezed and pushed towards the outer wall, it can push the ceramicized tape layer 6, so that the ceramicized tape layer 6 is embedded in the pores inside the cable armor layer 7, which is used to increase the connection strength between the ceramicized tape layer 6 and the cable armor layer 7 when the ceramicized tape layer 6 is cured by heat.

[0024] Please see Figure 4 and Figure 5As shown, the separator ring assembly 3 includes a rigid support ring 301, and two sets of push plates 304 are slidably connected to the inner wall of the rigid support ring 301. When the expansion filler 4 expands due to heat, it pushes the push plates 304 outward, applying extrusion pressure to the ceramicized filler 5 in the annular cavity, causing the ceramicized filler 5 to push towards the inner and outer walls of the annular cavity. The ceramicized filler 5 pushed towards the inner wall can fill the gap formed between the cable core insulation layer 2 and the flame-retardant structural layer located in the annular cavity, and the ceramicized filler 5 pushed towards the outer wall can squeeze the ceramicized tape layer 6 from the inside out, so that the outer wall of the ceramicized tape layer 6, which is in a softened state at this time, is embedded in the pores of the inner wall of the cable armor layer 7, and the most... The outer ceramicized tape layer 6, which is embedded in the pores of the cable armor layer 7, reaches the ceramicization temperature first and begins to cure first. This effectively increases the stability of the connection between the ceramicized tape layer 6 and the cable armor layer 7. When the inner wall of the ceramicized tape layer 6 and the ceramicized filler 5 are subsequently fixed and shrunk, it can also effectively prevent interlayer delamination between the ceramicized tape layer 6 and the cable armor layer 7. This effectively prevents the formation of continuous gaps between the flame-retardant structural layer and the cable armor layer 7, blocking the path for the spread of fire or high-temperature smoke between the two, and greatly improving the overall flame-retardant reliability and structural integrity of the cable in a real fire.

[0025] Please see Figure 5 As shown, the push plate 304 is symmetrically arranged about the inside of the rigid support ring 301. The push plate 304 is coaxially sleeved on the outside of the cable core insulation layer 2. The inner ring surface of the push plate 304 is slidably connected to the outer wall of the cable core insulation layer 2. The inner ring surface of the push plate 304 is rounded to reduce the mechanical damage to the outer wall of the cable core insulation layer 2 when the cable is bent.

[0026] Please see Figure 1 and Figure 4As shown, the ceramicized filler 5 fills the cavity formed by the two sets of push plates 304 and the rigid support ring 301. Supported by the rigid support ring 301, the cavity containing the expansion filler 4 does not deform when the cable bends, thus reducing the impact of cable bending on the uniformity of the distribution of the expansion filler 4. Simultaneously, the rigid support ring 301 has a ring-shaped array of partition baffles 303 arranged axially inside. The partition baffles 303 are fixedly connected to the rigid support ring 301, while the push plates 304 are slidably connected to the partition baffles 303. The partition baffles 303 divide the interior of the partition ring assembly 3 into several small cavities at equal intervals. 303 blocks and limits the expansion packing 4 in these small cavities to prevent the expansion packing 4 inside the partition ring assembly 3 from piling up due to gravity and other factors, ensuring the uniformity of the distribution of the expansion packing 4 inside the partition ring assembly 3. Thus, when it expands due to heat, it can generate a balanced and continuous expansion pressure throughout the partition ring assembly 3. This can effectively drive the push plates 304 on both sides to move outward smoothly, achieving uniform extrusion of the ceramicized packing 5, avoiding weak links in the sealing due to uneven local pressure or insufficient expansion, ensuring that the preset dynamic filling and embedded anchoring can be executed accurately and reliably, and ultimately maximizing and stabilizing the performance of the fire barrier.

[0027] Please see Figure 5 As shown, two sets of limiting rings 302 are symmetrically arranged on both sides of the rigid support ring 301. The limiting rings 302 are fixedly connected to the rigid support ring 301, and the top of the limiting rings 302 is rounded. The rounded edges are used to reduce the damage to the external structure of the rigid support ring 301 when the cable is bent. The limiting rings 302 are used to limit the sliding range of the push plate 304, so that the push plate 304 can only slide inside the rigid support ring 301. By limiting the distance of the push plate 304 sliding outward, the extrusion force it generates on the ceramicized filler 5 can be limited. Thus, the limit displacement of the ceramicized filler 5 pushing outward can be controlled, which can effectively prevent excessive radial stretching and extrusion of the outer ceramicized tape layer 6, which is also in a plastic state, during the high-temperature softening stage. This avoids the risk of bulging, thinning, or even cracking of the tape due to excessive local deformation. This ensures that the ceramicized tape layer 6 can smoothly and completely undergo the entire process of softening, embedding into the armor pores, and finally curing, forming a continuous and defect-free final ceramic barrier, fundamentally eliminating early failure caused by mechanical damage to the protective layer itself.

[0028] Please see Figure 3 As shown, a cross-linked polyethylene protective sleeve 8 is coaxially disposed on the outside of the cable armor layer 7. The inner wall of the cross-linked polyethylene protective sleeve 8 is tightly fitted with the outer wall of the cable armor layer 7. The cross-linked polyethylene protective sleeve 8 is placed on the outermost part of the cable to provide the cable with the first physical defense against external mechanical damage and environmental erosion.

[0029] Working principle: In the event of a fire, when the temperature at the cable reaches above 200 degrees Celsius, the expansion filler 4 expands due to heat. Simultaneously, the organic matter in the ceramicized filler 5 and the ceramicized tape layer 6 decomposes. Under the expansion of the expansion filler 4, the material expanding inwards gradually penetrates the gaps formed by the softening of the cable core insulation layer 2, filling and sealing the gaps between the cable core insulation layer 2 and the flame-retardant structural layer inside the separator ring assembly 3. Simultaneously, the material expanding to both sides pushes the push plates 304 on both sides outwards, i.e., towards the ceramicized filler 5, thus separating the adjacent sets of separator ring assemblies 3. The push plates 304 move towards the ceramicized filler 5, reducing the volume of the annular cavity between the two adjacent sets of separating ring assemblies 3, and squeezing the ceramicized filler 5 inside. The inner wall of the squeezed ceramicized filler 5 extends towards the cable core insulation layer 2, filling the gap between the cable core insulation layer 2 and the flame-retardant structural layer in the annular cavity; and the outer wall of the squeezed ceramicized filler 5 pushes outward, compressing the ceramicized tape layer 6 in the annular cavity, so that the outer wall of the softened ceramicized tape layer 6 is embedded in the pores of the cable armor layer 7, strengthening the connection between the ceramicized tape layer 6 and the cable armor layer 7.

[0030] When the temperature continues to rise above 500 degrees Celsius, the ceramicized tape layer 6 begins to gradually undergo ceramic curing to form a hard protective shell. During the ceramic curing process, since the ceramicized tape layer 6 located in the annular cavity has already been embedded with the cable armor layer 7 and the external temperature is high, it is first fixed. The connection between the ceramicized tape layer 6 and the cable armor layer 7 is cured first to ensure the stability of the connection between the ceramicized tape layer 6 and the cable armor layer 7. The inner side of the ceramicized tape layer 6 and the ceramicized filler 5 are then shrunk and cured, which can effectively prevent gaps from appearing between the ceramicized filler 5 and the ceramicized tape layer 6 and the cable armor layer 7 after shrinkage and curing, providing a channel for the spread of fire.

[0031] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A polyethylene flame-retardant power cable, characterized in that, The cable includes a core conductor, which is wrapped with a core insulation layer. A cable armor layer is coaxially sleeved on the outside of the core insulation layer. A flame-retardant structural layer is installed in the cavity between the core insulation layer and the cable armor layer. The flame-retardant structural layer includes separator ring assemblies, which are evenly spaced within the cavity. Each separator ring assembly is filled with expansion filler, and the annular cavity formed by the separator ring assemblies is filled with ceramicized filler. The separator ring assemblies and the ceramicized filler are spaced apart, and both are wrapped with a ceramicized tape layer. The component includes a rigid support ring, and two sets of push plates are slidably connected to the inner wall of the rigid support ring. When the expansion filler expands due to heat, it pushes the push plates outward, applying extrusion pressure to the ceramicized filler in the annular cavity, causing the ceramicized filler to push against the inner and outer walls of the annular cavity. The cable armor layer is a steel wire braided structure, and several pores are evenly distributed inside the cable armor layer. When the ceramicized filler in the annular cavity is compressed and pushed against the outer wall, it can push the ceramicized tape layer, causing the ceramicized tape layer to embed into the pores inside the cable armor layer, thereby increasing the connection strength between the ceramicized tape layer and the cable armor layer when the ceramicized tape layer is cured by heat.

2. The polyethylene flame-retardant power cable according to claim 1, characterized in that: The push plate is symmetrically arranged about the inside of the rigid support ring, and the push plate is coaxially sleeved on the outside of the cable core insulation layer.

3. The polyethylene flame-retardant power cable according to claim 2, characterized in that: The inner ring surface of the push plate is slidably connected to the outer wall of the cable core insulation layer, and the inner ring surface of the push plate is rounded.

4. The polyethylene flame-retardant power cable according to claim 2, characterized in that: The rigid support ring has a ring-shaped array of partition baffles arranged along the axial direction inside. The partition baffles are used to prevent the expansion filler filling inside the partition ring assembly from accumulating together.

5. The polyethylene flame-retardant power cable according to claim 4, characterized in that: The partition baffle is fixedly connected to the rigid support ring, and the push plate is slidably connected to the partition baffle.

6. The polyethylene flame-retardant power cable according to claim 1, characterized in that: Two sets of limiting rings are symmetrically arranged on both sides of the rigid support ring. The limiting rings are used to restrict the sliding range of the push plate, so that the push plate can only slide inside the rigid support ring.

7. The polyethylene flame-retardant power cable according to claim 6, characterized in that: The limiting ring is fixedly connected to the rigid support ring, and the top of the limiting ring is rounded. The rounded edge is used to reduce the damage to the external structure of the rigid support ring when the cable is bent.

8. The polyethylene flame-retardant power cable according to claim 1, characterized in that: The outer wall of the ceramicized filler is tightly bonded to the inner wall of the ceramicized tape layer, and the outer wall of the ceramicized tape layer is tightly bonded to the inner wall of the cable armor layer.

9. The polyethylene flame-retardant power cable according to claim 1, characterized in that: A cross-linked polyethylene protective sleeve is coaxially disposed on the outside of the cable armor layer, and the inner wall of the cross-linked polyethylene protective sleeve is tightly fitted to the outer wall of the cable armor layer.

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