Crosslinked polyethylene insulated power cable with a fluoroplastic flame retardant layer

Abstract

This invention relates to the field of power cable technology and proposes a cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer. The cable comprises several stranded conductors, each of which is sequentially covered from the inside out with a cross-linked polyethylene insulation layer, a shielding layer, and a fluoroplastic flame-retardant layer. It also includes a filler layer, support frames, an early warning support assembly, and a flame-retardant assembly. A filler layer is disposed between the conductors, and the filler layer is sequentially covered with a wrapping layer, an armor layer, and a sheath layer. Several support frames are spaced apart at the bottom of the sheath layer, each support frame is equipped with an early warning support assembly, and flame-retardant assemblies are disposed on both sides of each support frame. The flame-retardant assemblies are installed on the sheath layer. This technical solution solves the problem in the prior art where it is difficult to detect localized temperature rise in the cable before a fire occurs and to provide early warning, leading to difficulties in effectively suppressing fires.

Description

Technical Field

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

[0002] Cross-linked polyethylene (XLPE) insulated power cables are cables composed of a conductor, an insulation layer, and an outer sheath. The insulation layer is made of XLPE material, the conductor is the main part for current transmission and is usually made of materials such as copper, the insulation layer is an important part that protects the internal electric field of the cable from external interference, and the outer sheath can resist ultraviolet radiation and external chemical corrosion. In some densely populated and fire-prone places, such as inside buildings like shopping malls and supermarkets, or in transportation areas like subway tunnels, cables in these places are prone to fire problems. To adapt to laying environments with high fire safety requirements, a fluoroplastic flame-retardant layer can be added to the cable structure to improve the flame-retardant and flame-suppressing capabilities of the cable itself. In this way, the cable as a whole has both reliable electrical transmission and basic fire protection performance, making it the mainstream choice for flame-retardant power cables.

[0003] In existing technologies, flame-retardant cross-linked polyethylene insulation and fluoroplastic flame-retardant layers are generally used to improve the cable's own flame resistance, thereby inhibiting the spread of flames along the cable body. At the same time, fire-retardant bags, fireproof putty, and flame-retardant partitions are used to seal the cable trays to block the spread of flames. However, these methods are passive protection and can only play a role after a fire starts. It is difficult to detect the local temperature rise of the cable before a fire occurs, making it difficult to provide early warning in the early stages of a fire. They have a certain lag and are not effective in suppressing the occurrence of fires. Summary of the Invention

[0004] This invention proposes a cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer, which solves the problem in the prior art that it is difficult to detect local temperature rise in the cable before a fire occurs and to provide early warning of a fire, thus making it difficult to effectively suppress the fire.

[0005] The technical solution of the present invention is as follows: A cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer includes several conductors twisted together. Each conductor is covered from the inside out with a cross-linked polyethylene insulation layer, a shielding layer, and a fluoroplastic flame-retardant layer, and further includes: A filling layer is provided between multiple conductors, and a wrapping layer, an armor layer and a sheath layer are sequentially provided on the outside of the filling layer; Support frames, with a plurality of support frames spaced apart at the bottom of the sheath layer; Early warning support components are installed on each of the support frames for installing cables and triggering an alarm when the outside temperature rises to the danger zone in the early stages of a fire. Flame-retardant components are provided on both sides of each support frame. The flame-retardant components are installed on the sheath layer to prevent the spread of fire in the event of a fire.

[0006] To provide early warning of fires before they occur or in their early stages, the early warning support components include: The snap-fit ​​bracket has fasteners on both sides, and the two fasteners are arranged symmetrically. The snap-fit ​​bracket is installed on the corresponding support bracket by means of the fasteners. Support pads are installed inside the snap-fit ​​bracket and on the top of the support bracket, and the support pads abut against the sheath layer; The warning unit is installed on the top of each of the card holders and is used to issue an alarm when the outside temperature reaches a specified temperature.

[0007] Based on the aforementioned scheme, the early warning unit includes: Warning lights are mounted on the top of each of the card holders via brackets. A triggering component is installed on each of the card holders to trigger the warning light when the ambient temperature reaches a dangerous range.

[0008] Based on the aforementioned scheme, the triggering component includes an expansion cavity, each of the snap-fit ​​brackets has an expansion cavity at its top, each expansion cavity has a push rod inside, and each push rod has a push plate fixedly installed at its bottom, with the push plate slidingly engaging with the interior of the expansion cavity.

[0009] The system also includes a sensor, which is installed at the bottom of each bracket. The sensor is electrically connected to the warning light, and the trigger position of the sensor is located directly above the push rod.

[0010] The expansion cavity is filled with expanded graphite powder.

[0011] In order to prevent the fire from spreading further in the event of a fire, the flame-retardant component includes mounting rings. Each support frame has mounting rings on both the front and rear sides. Each mounting ring consists of two arc-shaped mounting frames, which are arranged symmetrically. Each arc-shaped mounting frame has an anti-slip pad at its bottom, which abuts against the sheath layer.

[0012] In addition to the aforementioned solutions, the following are also included: Each of the arc-shaped mounting brackets has a mounting slot; An intumescent flame-retardant block is installed in each of the mounting slots.

[0013] Each of the mounting rings has cable ties at both ends, and the arc-shaped mounting bracket has an arc-shaped groove at the position where it contacts the cable ties.

[0014] The working principle and beneficial effects of this invention are as follows: 1. In this invention, when a section of cable in the cable tray begins to heat up until it reaches a set temperature range, the expanded graphite powder expands. When the expanded graphite powder expands, it pushes the push plate to move, thereby pushing the push rod to move until the push plate contacts the inner top wall of the expansion chamber. At this time, the top of the push rod just contacts the trigger position of the sensor, and the sensor turns on the warning light to issue an alarm. When the staff receives the alarm signal, they can go to the corresponding location to check the condition of the cable. If it is in the early stage of a fire, fire-fighting measures can be taken in time, thereby reducing the occurrence of fire and reducing economic losses.

[0015] 2. In this invention, when a fire occurs and burns along the cable, in order to prevent the fire from spreading, when the fire approaches the arc-shaped mounting bracket, the expanding flame-retardant block comes into contact with the flame. When heated, the expanding flame-retardant block rapidly expands to form a flame-retardant layer, which plays a role in flame retardancy. Furthermore, as the volume expands, it can also form a seal inside the cable tray, further preventing the fire from spreading, buying time for firefighting operations, and reducing the losses caused by the fire. Attached Figure Description

[0016] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the cable body structure in this invention; Figure 3 This is a schematic diagram of the structure of the early warning support component and the flame retardant component in this invention. Figure 4 This is a cross-sectional structural diagram showing the cooperation of the support frame, fasteners, support pads, and early warning support components in this invention. Figure 5 This is a cross-sectional view of the early warning support component in this invention; Figure 6 This is a schematic diagram of the separation structure of the flame-retardant component in this invention.

[0018] In the diagram: 1. Conductor; 2. Cross-linked polyethylene insulation layer; 3. Shielding layer; 4. Fluoroplastic flame-retardant layer; 5. Filler layer; 6. Wrapping tape layer; 7. Armor layer; 8. Sheath layer; 9. Support frame; 10. Clip-on frame; 11. Fastener; 12. Support pad; 13. Warning light; 14. Bracket; 15. Expansion chamber; 16. Push rod; 17. Push plate; 18. Sensor; 19. Expanded graphite powder; 20. Arc-shaped mounting bracket; 21. Anti-slip pad; 22. Mounting groove; 23. Expanded flame-retardant block; 24. Cable tie; 25. Arc-shaped groove. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figures 1 to 6 As shown, this embodiment proposes a cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer 4, comprising several conductors 1 twisted together. Each conductor 1 is covered from the inside out with a cross-linked polyethylene insulation layer 2, a shielding layer 3, and a fluoroplastic flame-retardant layer 4. It also includes a filler layer 5, support frames 9, a warning support assembly, and a flame-retardant assembly. A filler layer 5 is disposed between the multiple conductors 1. The filler layer 5 is covered from the outside with a wrapping tape layer 6, an armor layer 7, and a sheath layer 8. Several support frames 9 are spaced apart at the bottom of the sheath layer 8, and each support frame 9 is equipped with a warning support. The support assembly is used to install cables and triggers an alarm when the outside temperature rises to the danger zone in the early stage of a fire. The early warning support assembly includes a snap-fit ​​bracket 10, a support pad 12, and an early warning unit. Each snap-fit ​​bracket 10 has fasteners 11 on both sides, and the two fasteners 11 are arranged symmetrically. The snap-fit ​​bracket 10 is installed on the corresponding support frame 9 by the fasteners 11. The support pad 12 is installed inside the snap-fit ​​bracket 10 and on the top of the support frame 9. The support pad 12 abuts against the sheath layer 8. An early warning unit is installed on the top of each snap-fit ​​bracket 10 to trigger an alarm when the outside temperature reaches a specified temperature.

[0021] It should be noted that cross-linked polyethylene (XLPE) is prepared by radiation cross-linking or chemical cross-linking, which forms a three-dimensional network structure of polyethylene linear molecular chains, thereby improving the material's heat resistance and mechanical strength, meeting the insulation requirements of cables, and significantly improving the material's heat resistance, mechanical strength, and chemical resistance. XLPE cables are widely used in power transmission and distribution. XLPE will not decompose due to high temperatures, and its heat resistance temperature can reach above 90 degrees Celsius, meeting the normal operating temperature requirements of cables (≤90 degrees Celsius). Its service life can be extended to more than 10 years. It has excellent electrical properties, heat resistance, and chemical stability. The XLPE insulation layer 2 in this invention is made of the above-mentioned XLPE material, ensuring the insulation performance of the cable.

[0022] It should be added that the main components of cross-linked polyethylene materials include polyethylene, cross-linking agent, antioxidant, stabilizer, and filler. Under normal circumstances, polyethylene, as the main matrix material, accounts for 80% to 95% of the total, providing mechanical strength and chemical corrosion resistance. Cross-linking agents (such as organic peroxides, thiols, etc.) account for 1% to 5% and are used to react with polyethylene segments to form a cross-linked structure. Antioxidants account for 0.1% to 1% and are used to prevent aging and oxidative degradation of cross-linked polyethylene. Stabilizers account for 0.1% to 1% and are used to improve the thermal stability and weather resistance of cross-linked polyethylene. Fillers account for less than 10% and are used to improve the mechanical properties, electrical conductivity, and flame retardant properties of cross-linked polyethylene.

[0023] Taking the laying of cables in a cable tray as an example, when laying cables in a cable tray, first complete the acceptance and internal cleaning of the cable tray, and lay the cables along the pre-set weak current separation channel of the cable tray using low-speed traction. According to the installation interval requirements (e.g., equidistant requirements of 0.8 to 1.0m for horizontal sections and 0.5 to 0.7m for vertical sections), install the support frame 9 in sequence, then lay the cable on the support frame 9, and then place the clamping bracket 10 on the support frame 9 in the corresponding position. Thus, the position of the cable is fixed by the setting of the internal support pad 12, and then the flame retardant components are installed.

[0024] After the cable is laid, connect the warning light 13 to the external power supply and test the warning unit to ensure that it can work reliably, accurately and stably according to the external temperature.

[0025] When a section of cable in the cable tray begins to heat up until it reaches a set temperature range, the warning unit is triggered and starts to alarm. Once the alarm signal is received, staff can go to the corresponding location to check the condition of the cable. If it is in the early stage of a fire, fire-fighting measures can be taken in time. If a fire has already started, the flame-retardant components can inhibit the spread of the fire, buying valuable time for firefighting and reducing the losses and damage caused by the fire.

[0026] The aforementioned warning unit includes a warning light 13 and a triggering component. Each mounting bracket 10 has a warning light 13 mounted on its top via a bracket 14, and each mounting bracket 10 has a triggering component mounted on it for triggering the warning light 13 when the external temperature reaches the danger zone.

[0027] When the outside temperature reaches a dangerous level, the triggering component is passively activated, which then triggers the warning light 13. The warning light 13 emits an alarm, and at the same time, the buzzer built into the warning light 13 is activated. In addition to the strong light signal, it can also alert the staff through continuous or intermittent sound.

[0028] The triggering component mentioned above includes an expansion cavity 15. Each snap-fit ​​bracket 10 has an expansion cavity 15 at its top. Each expansion cavity 15 has a push rod 16 inside. Each push rod 16 has a push plate 17 fixedly installed at its bottom. The push plate 17 slides in conjunction with the inside of the expansion cavity 15. The expansion cavity 15 is filled with expanded graphite powder 19. It also includes a sensor 18. Each bracket 14 has a sensor 18 installed at its bottom. The sensor 18 is electrically connected to the warning light 13. The trigger position of the sensor 18 is located directly above the push rod 16.

[0029] It should be noted that the normal operating temperature of cables generally does not exceed 90 degrees Celsius, and the short-term overload temperature is about 130 degrees Celsius. Therefore, warnings are only required when the cable is under overload for an extended period of time. The expansion temperature of the expanded graphite powder 19 is selected according to the normal operating temperature of the cable. Generally, the initial expansion temperature can be precisely controlled by adjusting the formulation of some components and the preparation process. For example, the minimum initial expansion temperature of commercial products is about 80 degrees Celsius.

[0030] Considering that the normal operating temperature of the cable is 90 degrees Celsius and the short-term overload temperature is 130 degrees Celsius, the expanded graphite powder 19 with an initial expansion temperature of 150 degrees Celsius can be selected. Effective expansion will occur only when this temperature is exceeded, thus achieving effective propulsion. When the expansion temperature is reached, the expanded graphite powder 19 expands. Since the expanded graphite powder 19 does not completely fill the expansion cavity 15 (the filling amount of the expanded graphite powder 19 is determined according to its expansion coefficient, and the expanded graphite powder 19 must not completely fill the expansion cavity 15, and sufficient expansion space needs to be reserved to ensure the expansion thrust), when the expanded graphite powder 19 expands, it can push the push plate 17 to move, thereby pushing the push rod 16 to move until the push plate 17 contacts the inner top wall of the expansion cavity 15. At this time, the top of the push rod 16 just contacts the trigger position of the sensor 18, and then the warning light 13 is turned on by the sensor 18.

[0031] The push rod 16 is made of a flexible material (such as rubber) to avoid damaging the sensor 18.

[0032] Each support frame 9 has flame-retardant components on both sides. The flame-retardant components are installed on the sheath layer 8 to prevent the spread of fire in the event of a fire. The flame-retardant components include mounting rings. Each support frame 9 has mounting rings on both the front and rear sides. The mounting rings are composed of two arc-shaped mounting brackets 20, which are symmetrically arranged. Each arc-shaped mounting bracket 20 has an anti-slip pad 21 at its bottom, which abuts against the sheath layer 8. It also includes mounting grooves 22 and expanding flame-retardant blocks 23. Each arc-shaped mounting bracket 20 has a mounting groove 22, and each mounting groove 22 has an expanding flame-retardant block 23 installed in it. Each mounting ring has cable ties 24 at both ends. The arc-shaped mounting bracket 20 has an arc-shaped groove 25 at the contact point with the cable ties 24.

[0033] When installing the mounting ring, first place two matching arc-shaped mounting brackets 20 in the installation position, and then set the two arc-shaped mounting brackets 20 on the cable sheath layer 8 respectively. The arc-shaped grooves 25 at both ends of the two arc-shaped mounting brackets 20 are matched. Then, by setting the cable tie 24, the two arc-shaped mounting brackets 20 that are joined together can be installed together. The anti-slip pad 21 is set to prevent the arc-shaped mounting brackets 20 from slipping.

[0034] It should be added that both the cable ties 24 and the curved mounting bracket 20 are made of fire-resistant materials.

[0035] When a fire occurs and spreads along the cable, in order to prevent the fire from spreading, when the fire approaches the arc-shaped mounting bracket 20, the expanding flame retardant block 23 comes into contact with the flame. The expanding flame retardant block 23 is made of expandable graphite flame retardant, and its main components are natural graphite or artificial graphite. When heated, the compounds between the graphite flakes decompose to produce a large amount of gas, causing the graphite volume to expand rapidly and form a dense carbon layer, which has good heat insulation and oxygen barrier properties. Furthermore, as the volume expands, it can also form a seal inside the cable tray, further preventing the fire from spreading and buying time for firefighting operations.

[0036] The working principle or usage process of this invention is as follows: When the heat in a section of the cable in the cable tray begins to rise until it reaches the set temperature range, the expanded graphite powder 19 expands. When the expanded graphite powder 19 expands, it can push the push plate 17 to move, thereby pushing the push rod 16 to move until the push plate 17 contacts the inner top wall of the expansion cavity 15. At this time, the top of the push rod 16 just contacts the trigger position of the sensor 18.

[0037] The alarm is triggered by the sensor 18, which activates the warning light 13. At the same time, the built-in buzzer of the warning light 13 is activated. In addition to the strong light signal, the alarm can also be triggered by the continuous or intermittent sound. When the staff receives the alarm signal, they can go to the corresponding location to check the condition of the cable. If the fire is in its early stage, fire-fighting measures can be taken in time to reduce the occurrence of fire and reduce economic losses.

[0038] If a fire has already occurred and is burning along the cable, in order to prevent the fire from spreading, when the fire approaches the arc-shaped mounting bracket 20, the expanding flame-retardant block 23 comes into contact with the flame. When heated, the compounds between the graphite flakes in the expanding flame-retardant block 23 decompose, producing a large amount of gas that causes the graphite volume to expand rapidly, forming a dense carbon layer, which plays a role in flame retardancy. Furthermore, as the volume expands, it can also form a seal within the cable tray, further preventing the fire from spreading, buying time for firefighting operations, and reducing the losses and hazards caused by the fire.

[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer (4), comprising a plurality of conductors (1) twisted together, each conductor (1) being sequentially covered from the inside out with a cross-linked polyethylene insulation layer (2), a shielding layer (3), and a fluoroplastic flame-retardant layer (4), characterized in that, Also includes: A filling layer (5) is provided between multiple conductors (1), and a wrapping layer (6), an armor layer (7) and a sheath layer (8) are sequentially provided on the outside of the filling layer (5). Support frame (9), and several support frames (9) are spaced apart at the bottom of the sheath layer (8); Early warning support assembly, each of the support frames (9) is equipped with an early warning support assembly for installing cables and triggering an alarm when the outside temperature rises to the danger zone in the early stage of a fire; Flame-retardant components are provided on both sides of each of the support frames (9). The flame-retardant components are installed on the sheath layer (8) to prevent the spread of fire in the event of a fire.

2. The cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer (4) according to claim 1, characterized in that, The early warning support components include: The snap-fit ​​bracket (10) has fasteners (11) on both sides of each snap-fit ​​bracket (10), and the two fasteners (11) are arranged symmetrically. The snap-fit ​​bracket (10) is installed on the corresponding support bracket (9) by means of the fasteners (11). Support pad (12) is installed inside the snap-fit ​​bracket (10) and on the top of the support bracket (9). The support pad (12) abuts against the sheath layer (8). The warning unit is installed on the top of each of the card holders (10) for triggering an alarm when the outside temperature reaches a specified temperature.

3. A cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer (4) according to claim 2, characterized in that, The early warning unit includes: Warning light (13), each of the card holders (10) is equipped with a warning light (13) on its top via a bracket (14); A triggering component is installed on each of the card holders (10) for triggering the warning light (13) when the ambient temperature reaches the danger zone.

4. A cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer (4) according to claim 3, characterized in that, The triggering component includes an expansion cavity (15). Each of the card holders (10) has an expansion cavity (15) on its top. Each expansion cavity (15) has a push rod (16) inside it. Each push rod (16) has a push plate (17) fixedly installed at its bottom. The push plate (17) slides in cooperation with the expansion cavity (15).

5. A cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer (4) according to claim 4, characterized in that, It also includes a sensor (18), which is installed at the bottom of each bracket (14). The sensor (18) is electrically connected to the warning light (13), and the trigger position of the sensor (18) is located directly above the push rod (16).

6. A cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer (4) according to claim 5, characterized in that, The expansion cavity (15) is filled with expanded graphite powder (19).

7. A cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer (4) according to claim 1, characterized in that, The flame-retardant component includes mounting rings. Each support frame (9) has mounting rings on both the front and rear sides. Each mounting ring consists of two arc-shaped mounting frames (20) arranged symmetrically. Each arc-shaped mounting frame (20) has an anti-slip pad (21) at its bottom, and the anti-slip pad (21) abuts against the sheath layer (8).

8. A cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer (4) according to claim 7, characterized in that, Also includes: Mounting slot (22), each of the arc-shaped mounting brackets (20) is provided with mounting slot (22); An inflatable flame retardant block (23) is installed in each of the mounting slots (22).

9. A cross-linked polyethylene insulated power cable with a fluoroplastic flame-retardant layer (4) according to claim 8, characterized in that, Each of the mounting rings is provided with cable ties (24) at both ends, and the arc-shaped mounting bracket (20) is provided with an arc-shaped groove (25) at the position where it contacts the cable ties (24).

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