Fireproof cable based on overhead photovoltaic system

Abstract

The invention relates to the technical field of wires and cables, and discloses a fire-resistant cable based on an overhead photovoltaic system, a braided ring in a fire-resistant flame-retardant layer is formed by winding flame-retardant crosslinked polyethylene fibers, air circulation is guaranteed by virtue of a large number of pores among ropes, and when the fire-resistant cable is burnt by flame, high-temperature gas enters the space of the braided ring, and then the braided ring is sealed. On the other hand, the liquid drainage rod is pulled through contraction traction force, the piston disc is promoted to extrude the flame-retardant liquid in the storage sleeve, after the liquid is sprayed out through the liquid drainage holes, one part of the liquid directly acts on a flame area for fire extinguishing and flame retarding, and the flame-retardant effect is achieved. Most of the materials are adsorbed and retained by the porous structure of the braided ring, are gradually decomposed at a continuous high temperature to release flame-retardant gas, and react with braided ring fibers to form a liquid-state and solid-state composite heat-insulating layer to fill tiny pores which are still remained after shrinkage, so that the integrity of a cable circuit at the initial stage of a fire disaster is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of wire and cable technology, and more particularly to fire-resistant cables based on overhead photovoltaic systems. Background Technology

[0002] Against the backdrop of the global energy structure transitioning towards clean energy, photovoltaic (PV) power generation, as an important form of renewable energy utilization, has seen its installed capacity grow rapidly. Among them, overhead PV systems are widely used in large-scale ground-mounted power plants, fishery-solar hybrid systems, and agricultural-solar hybrid systems due to their adaptability to complex terrains such as mountains, deserts, and coastlines, and their high land utilization rate. However, overhead PV systems are exposed to harsh outdoor environments for extended periods, needing to withstand high temperatures, strong ultraviolet radiation, wind and sand erosion, and diurnal temperature fluctuations. Furthermore, the system operation is subject to risks such as component hot spot effects, DC arcing, and line aging, which can easily lead to fire accidents. Traditional PV cables mostly only meet basic weather resistance requirements and are unable to maintain circuit integrity in flame environments. Moreover, they may release toxic fumes when burning, which can not only paralyze the PV system and cause huge power generation losses but also expand the fire hazard range, threatening the surrounding environment and personnel safety. Therefore, developing specialized fire-resistant cables that are adapted to the special operating conditions of overhead PV systems and possess excellent fire resistance, weather resistance, and environmental friendliness has become a key requirement for ensuring the safe and stable operation of overhead PV systems, and is also driving the coordinated development of wire and cable technology and PV power generation technology in special outdoor scenarios.

[0003] The aforementioned and existing related technologies have the following drawbacks: When adapting to outdoor scenarios such as overhead photovoltaic systems, existing cables generally face the core contradiction of balancing fire resistance and heat dissipation performance. To meet the heat dissipation requirements of long-term outdoor operation, cables often use high-porosity structures or materials with strong thermal conductivity to accelerate heat dissipation. However, when exposed to flames, such designs cause high temperatures to spread rapidly into the cable interior, quickly burning the core conductor and insulation layer, thus failing to maintain circuit integrity. Conversely, if the fire resistance is improved by thickening the fire-resistant layer and using high-density flame-retardant materials, it will significantly hinder heat conduction during normal cable operation, causing local overheating due to heat accumulation in the core, and even inducing hot spot effects or insulation aging. Ultimately, this results in a performance contradiction where good heat dissipation leads to poor fire resistance, and strong fire resistance leads to poor heat dissipation, making it difficult to simultaneously meet the dual requirements of long-term heat dissipation stability and fire resistance reliability under fire conditions for overhead photovoltaic systems. Summary of the Invention

[0004] The technical problem to be solved by this invention is that existing technologies have the disadvantage that good heat dissipation results in poor fire resistance, and strong fire resistance results in poor heat dissipation. To address this, we propose a fire-resistant cable based on an overhead photovoltaic system.

[0005] To achieve the above objectives, this application adopts the following technical solution: a fire-resistant cable based on an overhead photovoltaic system, comprising a core conductor, multiple sets of core conductors wrapped with an insulation layer, the gap between the insulation layer and the core conductors filled with a filler, a fire-resistant and flame-retardant layer wrapped outside the insulation layer, a shielding layer wrapped outside the fire-resistant and flame-retardant layer, and a cable protective sleeve wrapped outside the shielding layer. The fire-resistant and flame-retardant layer includes a heat insulation film, and a storage sleeve is provided inside the heat insulation film. Braided rings are fixedly installed at both ends of the storage sleeve. The storage sleeve includes a storage shell, and two sets of storage tanks are opened inside the storage shell. A piston disc is slidably arranged inside each of the two sets of storage tanks. Flame-retardant liquid is stored in the storage tank between the piston disc and the storage shell. A drain rod is fixedly installed on one side of the piston disc. One end of the drain rod penetrates the storage shell and is fixedly connected to the braided ring. A limiting ring is fitted on the part of the drain rod located outside the storage shell, and the limiting ring is fixedly installed on the outside of the storage shell.

[0006] Preferably, the heat insulation film consists of a protective film and an inner film and an outer film fixedly connected to both sides, the inner film and the outer film together forming an annular film with a cavity.

[0007] Preferably, the drain rod consists of two parts: the end of the drain rod near the piston disc is hollow inside and has multiple drain holes on the outside, while the end of the drain rod near the braided ring is a solid rod.

[0008] Preferably, a pointed cone is fixedly installed on the upper outer side of the storage casing, and the upper end of the pointed cone is lower than the outermost plane of the storage casing.

[0009] Preferably, the surface height of the inner film in its initial state is flush with the reference surface on the outside of the storage casing, while the outer film in its initial state is higher than the reference surface of the storage casing.

[0010] Preferably, the two sets of storage tanks are arranged symmetrically along the central axis of the storage shell.

[0011] Preferably, the braided ring is made of multiple sets of flame-retardant cross-linked polyethylene fiber ropes wound together, with multiple gaps between the multiple sets of flame-retardant cross-linked polyethylene fiber ropes.

[0012] Preferably, the braided ring is movably sleeved on the outside of the insulation layer, the storage sleeve is fixedly sleeved on the outside of the insulation layer, and the fire-resistant and flame-retardant layer is connected to the storage sleeve in an orderly manner through the braided ring.

[0013] Preferably, the shielding layer is movably sleeved on the outside of the fire-resistant and flame-retardant layer.

[0014] The technical effects and advantages of this invention are as follows: In this invention, under normal conditions, the braided rings in the fire-resistant and flame-retardant layer are made of flame-retardant cross-linked polyethylene fibers. The numerous pores between the ropes ensure air circulation. Combined with the thin aerogel composite film used in the heat insulation film and the mesh structure of the shielding layer, they jointly construct an efficient heat dissipation channel, preventing the cable core from accumulating heat due to high-temperature exposure. Simultaneously, the flame-retardant liquid pre-stored in the storage sleeve is sealed by the piston disc, without affecting the heat dissipation of the normal structure. When exposed to flames, the shielding layer first contracts at high temperature, tightly wrapping the fire-resistant and flame-retardant layer to initially extinguish the flame. At the same time, it squeezes the low-melting-point copolyester films on both sides of the heat insulation film, causing the films to be pierced by the sharp cones on the outside of the storage shell. After the high-temperature gas enters the braided ring space, the flame-retardant cross-linked polyethylene... The fiber rope rapidly contracts, reducing the gaps between ropes to form a dense physical oxygen barrier layer, delaying the penetration of high temperature into the cable core. On the other hand, the contraction pulls the drain rod, causing the piston disc to squeeze the flame-retardant liquid in the storage sleeve. After the liquid is sprayed out through the drain hole, part of it directly acts on the flame area to extinguish and retard the fire, while most of it is absorbed and retained by the porous structure of the braided ring. Under continuous high temperature, it gradually decomposes and releases flame-retardant gas, and reacts with the braided ring fibers to form a liquid and solid composite heat insulation layer, filling the tiny pores that remain after contraction. Ultimately, it achieves integrated protection of efficient heat dissipation under normal conditions, active fire retardation at high temperatures, and emergency warning, breaking the performance contradiction of good heat dissipation leading to poor fire resistance and strong fire resistance leading to poor heat dissipation, while ensuring the integrity of the cable circuit in the early stage of a fire. Attached Figure Description

[0015] 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: Figure 1 This is a schematic diagram of the overall cable structure of the present invention; Figure 2 This is a schematic diagram of the overall exploded structure of the cable of the present invention; Figure 3 This is a schematic diagram of the outer structure of the cable core conductor of the present invention; Figure 4 This is a schematic diagram of the fire-resistant and flame-retardant layer structure of the present invention; Figure 5 This is a schematic diagram of the heat insulation film structure of the present invention; Figure 6 This is a schematic diagram of the internal structure of the fire-resistant and flame-retardant layer of the present invention; Figure 7 This is a schematic diagram of the internal structure of the storage sleeve of the present invention. Figure 1 ; Figure 8 For the present invention Figure 7 A magnified structural diagram of Figure A; Figure 9 This is a schematic diagram of the internal structure of the storage sleeve of the present invention. Figure 2 ; Figure 10 This is a schematic diagram of the internal planar structure of the storage sleeve of the present invention.

[0016] Legend: 1. Cable core conductor; 2. Filler; 3. Insulation layer; 4. Fire-resistant and flame-retardant layer; 41. Heat insulation film; 411. Protective film; 412. Inner film; 413. Outer film; 42. Storage sleeve; 421. Storage shell; 4211. Cone; 422. Storage tank; 423. Drain rod; 4231. Drain hole; 424. Piston disc; 425. Restriction ring; 43. Braided ring; 5. Shielding layer; 6. Cable protective sleeve. Detailed Implementation

[0017] 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.

[0018] Reference Figure 1-3 As shown, this invention provides a technical solution: a fire-resistant cable based on an overhead photovoltaic system, comprising a core conductor 1 for transmitting current or signals. Multiple sets of core conductors 1 are twisted together to form a single-strand cable core. An insulation layer 3 is wrapped around the core conductors 1 to prevent short circuits between the core conductors 1 and the outside environment or adjacent conductors, ensuring that current or signals are transmitted only within the core conductors 1. Simultaneously, the insulation layer also isolates the core conductors 1 from moisture, dust, chemicals, etc., preventing corrosion or damage. A filler 2 fills the gap between the insulation layer 3 and the core conductors 1, maintaining a circular cross-section and preventing internal structural deformation due to twisting or compression. A fire-resistant and flame-retardant layer 4 is wrapped around the outside of the insulation layer 3, possessing efficient flame-retardant properties, high heat dissipation capacity, and reliable fire resistance. The fire-retardant layer 4 is wrapped with a shielding layer 5. The shielding layer 5 is a composite of heat-shrinkable material and metal braided mesh. It shrinks rapidly at high temperatures, causing the internal braided mesh to tightly wrap around the fire-retardant layer 4. This achieves both shielding efficiency and flexibility, preventing external electromagnetic signals from interfering with the signals transmitted within the cable. At the same time, the shielding layer 5 shrinks rapidly under high temperatures to tightly wrap around the fire-retardant layer 4, thereby improving the fire-retardant performance of the cable. The outermost cable protective sleeve 6 is wrapped around the shielding layer 5. As the outermost barrier of the cable, the core function of the cable protective sleeve 6 is to resist external damage such as ultraviolet radiation, wind and sand erosion, salt spray corrosion, high and low temperature cycles, and mechanical friction in the outdoor environment of the overhead photovoltaic system. It also helps to enhance the overall flame retardancy and water resistance of the cable, protect the internal cable core, insulation layer, and fire-resistant structure from damage, and ensure the long-term stable operation of the cable.

[0019] Reference Figure 2 , Figure 4-6As shown in this embodiment: the fire-resistant and flame-retardant layer 4 includes a heat insulation film 41, and a storage sleeve 42 is provided inside the heat insulation film 41. Braided rings 43 are fixedly installed at both ends of the storage sleeve 42. The braided rings 43 are movably sleeved on the outside of the insulation layer 3, and the storage sleeve 42 is fixedly sleeved on the outside of the insulation layer 3. The fire-resistant and flame-retardant layer 4, through the orderly connection between the braided rings 43 and the storage sleeve 42, ensures both the overall flexibility of the cable and the overall heat dissipation performance of the cable. Since the braided rings 43 are made of multiple sets of flame-retardant cross-linked polyethylene fiber ropes wound together... At room temperature, there are many gaps between the ropes, which allows for good air permeability. The braided ring 43 has good shrinkage properties at high temperatures. It can quickly shrink and tightly wrap around the outside of the insulation layer 3. After tightening, the gaps between the ropes of the braided ring 43 are reduced. At the same time, the braided ring 43 will pull the fire retardant fuel inside the storage sleeve 42 into the flow and seal the gaps of the braided ring 43 by fusing with the fire retardant fuel. It will also cure at high temperatures to improve the overall heat resistance of the fire-resistant and flame-retardant layer 4, further improving the fire resistance of the cable.

[0020] Reference Figure 4-6 As shown in this embodiment: the heat insulation film 41 is composed of a protective film 411 and an inner film 412 and an outer film 413 fixedly connected to both sides. The inner film 412 and the outer film 413 together form a set of annular films with cavities. The annular film is correspondingly arranged on the outside of the braided ring 43. The protective film 411 is fixedly sleeved on the outside of the storage sleeve 42. The inner film 412 and the outer film 413 are made of low melting point copolyester. The inner film 412 and the outer film 413 are transparent films with a thickness of 5um-20um and good flexibility. The protective film 411 is an aerogel composite film, which is composited with polyester nonwoven fabric to form a film. It is bonded to the two layers of inner film 412 and outer film 413 by low melting point hot melt adhesive. Under normal conditions, it is thin and does not affect the flexibility of the film. It can effectively block heat transfer. The aerogel structure is stable at high temperatures.

[0021] Reference Figure 4 , Figure 6-9As shown in this embodiment: the storage sleeve 42 includes a storage shell 421, and two sets of storage tanks 422 are provided inside the storage shell 421. A piston disc 424 is slidably arranged inside each of the two sets of storage tanks 422. The storage tank 422 between the piston disc 424 and the storage shell 421 contains a flame-retardant liquid. The flame-retardant liquid is a monoammonium phosphate aqueous solution. The monoammonium phosphate aqueous solution is a transparent liquid with a mass concentration of 50% to 70%. It has good fluidity and can fill the pores of the braided ring 43. It dehydrates and decomposes at temperatures above 150°C, releasing ammonia gas, which reacts with the braided ring 43 and can catalyze the dehydration of the braided ring 43. Carbonization produces carbon dioxide and water. The flame-retardant liquid occupies half of the space inside the storage tank 422. A drain rod 423 is fixedly installed on one side of the piston disc 424. One end of the drain rod 423 penetrates the storage shell 421 and is fixedly connected to the braided ring 43. The end of the drain rod 423 near the piston disc 424 is hollow inside and has multiple drain holes 4231 on the outside. The end of the drain rod 423 near the braided ring 43 is a solid rod. The part of the drain rod 423 located outside the storage shell 421 is fitted with a limiting ring 425. The limiting ring 425 is fixedly installed on the outside of the storage shell 421.

[0022] Reference Figure 6-9 As shown in this embodiment: A pointed cone 4211 is fixedly installed on the upper outer side of the storage shell 421. The upper end of the pointed cone 4211 is lower than the outermost plane of the storage shell 421. In use, when the cable is exposed to extreme high temperature due to a fire, the cable protective sleeve 6 is quickly burned through and the fire spreads. In this state, the shielding layer 5 is made of heat-shrinkable material and metal braided mesh interwoven into a mesh. It will shrink rapidly at high temperature, thereby causing the internal braided mesh to tightly wrap the fire-resistant and flame-retardant layer 4. During this process, the shielding layer 5 shrinks and gradually squeezes the low-melting-point copolyester film composed of inner film 412 and outer film 413 on the outside of the storage shell 421. After being squeezed, the low-melting-point copolyester film will quickly rupture when the inner side of the low-melting-point copolyester film is contacted by the pointed cone 4211 due to the constant internal gas. This produces a loud sound, thereby warning and attracting the staff of large ground power stations, fishery-solar complementary, and agricultural-solar complementary scenarios, so as to avoid the situation where the cable is damaged but no one notices, resulting in increased losses and personnel danger.

[0023] During the rupture of the low-melting-point copolyester film, high-temperature gas instantly enters the space of the braided ring 43. Under intense high temperatures, the flame-retardant cross-linked polyethylene fiber ropes rapidly contract, reducing the gaps between them. The braided ring 43 as a whole undergoes significant contraction. This rapid contraction at high temperatures significantly reduces the gaps between fibers, allowing the braided ring 43 to tightly wrap around the inner cable core 1, forming a dense physical barrier layer. This significantly reduces the penetration of external air into the cable. Since oxygen is the core of combustion, when the local oxygen concentration drops below 15% due to gap sealing, it directly inhibits the continued combustion and spread of the flame. On the one hand, it can block the high-temperature airflow of flames from directly scouring the inner layer, preventing the inner layer material from deteriorating rapidly due to high temperature, thus buying time for subsequent fire protection, slowing down the transmission speed of external high temperature to the cable core, preventing the cable core conductor from melting due to overheating or short circuit due to the melting of the insulation layer 3, and ensuring the integrity of the cable circuit in the early stage of a fire. Since the storage shell 421 is fixed on the outside of the insulation layer 3, as the braided ring 43 gradually contracts from both sides to the inside, the braided ring 43 will pull the multiple sets of drain rods 423 fixedly connected to it. Under the contraction traction force of the braided ring 43, the multiple sets of drain rods 423 will gradually pull the piston disc 424 to move and squeeze the flame-retardant liquid inside the storage tank 422. When the liquid is drained... When the drain hole 4231 on the outer side of rod 423 moves out into the blocking range of limiting ring 425, the flame retardant liquid will be rapidly sprayed out through the drain hole 4231 under pressure. Part of the sprayed liquid is sprayed around the burning part of the cable, thereby using the sprayed flame retardant liquid to extinguish or extinguish the flames around the cable. At the same time, most of the flame retardant liquid mixes with braided ring 43. The porous fiber structure of braided ring 43 can absorb and retain the flame retardant liquid like a sponge, preventing the liquid from being lost due to gravity or evaporating due to outdoor rain, forming a stable flame retardant liquid reserve layer. Under high temperature or continuous scorching of flames, the fibers of braided ring 43 will slowly release the absorbed flame retardant liquid. The liquid is flammable and gradually decomposes as the temperature rises, continuously producing flammable gases that dilute oxygen and interrupt the combustion chain reaction. Compared to a simple solid flame retardant layer, the flame retardant effect can be extended by 2-3 times, avoiding the problem of one-time flame retardant failure. When the flame retardant liquid is mixed with the braided ring 43, a liquid-solid composite heat insulation layer is formed at high temperature. On the one hand, the water vapor released when the flame retardant liquid decomposes can absorb heat and reduce the surface temperature of the braided ring 43. On the other hand, the inorganic components in the liquid will react with the fibers of the braided ring 43 to form a dense inorganic heat insulation film on the surface of the braided ring 43, or catalyze the carbonization of the braided ring 43 to form an expanded carbon layer. The thermal conductivity of this type of composite heat insulation layer can be as low as 0.With a heat resistance of 0.3 W / (m·K) or less, it can effectively block the transmission of high flame temperature to the inner layer of the cable, preventing the inner layer material from melting or short-circuiting due to overheating. Under normal conditions, the braided rings 43 retain certain fiber gaps to ensure heat dissipation. However, after being filled with flame-retardant liquid, the liquid expands or solidifies upon heating at high temperatures, actively filling these tiny gaps and forming a non-porous oxygen-barrier structure. This prevents external oxygen from penetrating into the cable core through the gaps, cutting off the oxygen supply for combustion. It also prevents the leakage of toxic gases generated during internal combustion, reducing harm to the environment and personnel. Simultaneously, it prevents flames from spreading through the gaps, limiting the spread of fire. This is crucial for localized fire control in overhead photovoltaic cables, preventing a single cable circuit fire from spreading to the entire photovoltaic array, avoiding the economic losses and disaster impacts caused by complete cable combustion, and is easy to use.

[0024] Example 1: Experimental materials: Braided ring 43 is made of glass fiber braided ring, the flame retardant is potassium dihydrogen phosphate aqueous solution, and the braided ring 43 has 16 strands; Braided ring 43 is made of alkali-free glass fiber modified with silane coupling agent KH-550, with a total of 16 strands, each strand having a diameter of 0.2 mm, braided into a ring at a braiding density of 20 needles / inch, with a normal porosity of 38%. After braiding, it is sleeved on the outside of the insulation layer, and the two ends are fixed to the storage sleeve. The liquid flame retardant is 60wt% potassium dihydrogen phosphate aqueous solution, which fills the storage sleeve and the pores of the braided ring. Vacuum degassing is performed during the filling process to avoid residual air bubbles. The outer sheath material is 78 parts by weight of polyethylene, 10 parts by weight of tea polyphenol flame retardant particles, 0.6 parts by weight of calcium stearate, 10351 parts by weight of antioxidant, and 1.2 parts by weight of dicumyl peroxide.

[0025] Preparation process: Copper wire is drawn and annealed by a wire drawing machine and then stranded into a round conductor. Cross-linked polyethylene insulation material is used to cover the conductor at 120°C using an insulation extrusion machine to form an insulation layer. After the insulated conductor cools and sets, a pre-made glass fiber braided ring is placed on its outside. At the same time, potassium dihydrogen phosphate aqueous solution is filled into the storage sleeve and the pores of the braided ring 43. Then, aluminum foil is wrapped around the outside of the braided ring 43 to form a metal shielding layer. Finally, the components of the outer sheath layer are melt-blended at 140°C using an open mill and extruded onto the outside of the metal shielding layer. After cross-linking is completed at 150°C, the material is cooled and solidified to obtain an environmentally friendly fire-resistant cable.

[0026] Example 2: Experimental materials: Braided ring 43 is a basalt fiber braided ring, the flame retardant is zinc borate suspension, and the braided ring 43 has 24 strands; the braided ring 43 is made of alkali-free basalt fiber with a temperature resistance of over 600℃, a total of 24 strands, each strand with a diameter of 0.18mm, twisted into a ring at a braiding density of 25 needles / inch, and preheated at 180℃ to enhance the adhesion with the flame retardant. The normal porosity is 32%. The liquid flame retardant is a 55wt% zinc borate suspension with 0.5wt% Tween 80 emulsifier added, which is filled in the storage sleeve and filled into the pores of the braided ring by negative pressure permeation. The outer sheath material is 80 parts by weight of polyethylene, 11 parts by weight of tea polyphenol flame retardant particles, 0.7 parts by weight of stearic acid, 1.5 parts by weight of antioxidant 1010, and 1.8 parts by weight of benzoyl peroxide.

[0027] Preparation process: The conductor and insulation layer are prepared in the same way as in Example 1; the preheated basalt fiber braided ring is placed on the outside of the insulation layer, and the zinc borate suspension is penetrated into the pores of the braided ring and filled into the storage sleeve through a negative pressure device. After covering the aluminum foil metal shielding layer, the components of the outer sheath layer are melted and blended at 140°C, extruded onto the outside of the shielding layer, and cooled and shaped to obtain an environmentally friendly fire-resistant cable.

[0028] Example 3: Experimental materials: Braided ring 43 is made of flame-retardant polyester fiber, the flame retardant is ammonium polyphosphate aqueous solution, and the number of braided ring 43 strands is 32. Braided ring 43 uses flame-retardant polyester fiber modified with 15wt% magnesium hydroxide, a total of 32 strands, each strand with a diameter of 0.15mm, braided into a ring at a braiding density of 30 stitches / inch. After braiding, it is pretreated by soaking in 5% APP aqueous solution to improve flame retardant synergy. The normal porosity is 28%. The liquid flame retardant is 50wt% ammonium polyphosphate aqueous solution, which is filled into the storage sleeve and left to stand at room temperature for 2 hours to ensure that the braided ring fully adsorbs the flame retardant. The outer sheath material is 82 parts by weight of polyethylene, 9 parts by weight of tea polyphenol flame retardant particles, 0.8 parts by weight of calcium stearate and oxidized polyethylene wax, 2 parts by weight of antioxidants 1035 and 10102, and 2.2 parts by weight of di-tert-butyl peroxide.

[0029] Preparation process: The conductor and insulation layer are prepared in the same way as in Example 1. The pretreated flame-retardant polyester fiber braided ring is placed on the outside of the insulation layer, and the APP aqueous solution is filled into the storage sleeve and allowed to stand for adsorption. After covering the aluminum foil shielding layer, the outer sheath layer components are melt-blended and extruded at 140°C, and the environmentally friendly fire-resistant cable is obtained after cooling.

[0030] Example 4: Experimental materials: Braided ring 43 is a aramid fiber braided ring, the flame retardant is an ammonium aminosulfonate aqueous solution, and the braided ring 43 has 40 strands; Braided ring 43 uses aramid 1313 fiber with a temperature resistance of 280℃ and a tensile strength of 5.5GPa, a total of 40 strands, braided into a ring at a braiding density of 35 needles / inch, and heat-set at 200℃ to reduce high-temperature shrinkage and deformation, with a normal porosity of 24%, the liquid flame retardant is 65wt% ammonium aminosulfonate aqueous solution, filled in the storage sleeve, and the pore filling rate is ensured to be ≥95% by applying pressure of 0.2MPa; the outer sheath material is 75 parts by weight of polyethylene, 12 parts by weight of tea polyphenol flame retardant particles, 0.5 parts by weight of calcium stearate, 2.5 parts by weight of antioxidant 1010, and 2.8 parts by weight of DCP.

[0031] Preparation process: The conductor and insulation layer are prepared in the same way as in Example 1. The heat-set aramid fiber braided ring is placed on the outside of the insulation layer. Ammonium aminosulfonate aqueous solution is filled under pressure into the storage sleeve and the pores of the braided ring. After covering with aluminum foil shielding layer, the outer sheath layer components are melt-blended and extruded at 140°C and cooled to form an environmentally friendly fire-resistant cable.

[0032] Example 5: Experimental materials: Braided ring 43 is a braided ring made of flame-retardant nylon 66 fiber, the flame retardant is pentaerythritol phosphate ionic liquid, and the braided ring 43 has 48 strands; Braided ring 43 uses flame-retardant nylon 66 fiber with 12wt% red phosphorus flame retardant, a total of 48 strands, each strand with a diameter of 0.1mm, braided into a ring at a braiding density of 40 stitches / inch, and coated with 0.3wt% silane coupling agent after braiding to improve compatibility with ionic liquid, with a normal porosity of 20%, the liquid flame retardant is pentaerythritol phosphate ionic liquid, which is filled in the storage sleeve, and self-permeates into the pores of the braided ring at room temperature, the outer sheath material is 85 parts by weight of polyethylene, 8 parts by weight of tea polyphenol flame retardant particles, 1 part by weight of microcrystalline wax, 10353 parts by weight of antioxidant, and 3 parts by weight of BPO.

[0033] Preparation process: The conductor and insulation layer are prepared in the same way as in Example 1. Flame-retardant nylon 66 braided rings coated with coupling agent are placed on the outside of the insulation layer. Pentaerythritol phosphate ionic liquid is self-permeable to fill the pores of the braided rings and the storage sleeve. After covering with aluminum foil shielding layer, the outer sheath layer components are melt-blended and extruded at 140°C. After cooling, an environmentally friendly fire-resistant cable is obtained.

[0034] Comparative Example 1: Experimental materials: Braided ring 43 is a common polyethylene braided ring with 8 strands; Braided ring 43 is made of common non-flame-retardant polyethylene fiber, with a total of 8 strands, each strand having a diameter of 0.3 mm, and is braided into a ring at a braiding density of 15 needles / inch, with a normal porosity of 45%, without liquid flame retardant filling, and the outer sheath material is the same as in Example 3.

[0035] Preparation process: The conductor and insulation layer are prepared in the same way as in Example 1. Ordinary polyethylene braided rings are placed on the outside of the insulation layer, and aluminum foil shielding layer is directly wrapped. The outer sheath layer components are melt-blended and extruded at 140°C, and then cooled and molded to obtain the cable.

[0036] Comparative Example 2: Experimental materials: Braided ring 43 is a glass fiber braided ring with 16 strands; the material of braided ring 43 is the same as in Example 1, the liquid flame retardant is replaced with 40wt% chlorinated paraffin 70 emulsion, which fills the storage sleeve and the pores of the braided ring, and the material of the outer sheath is the same as in Example 1.

[0037] Preparation process: The conductor, insulation layer and braided ring are arranged as in Example 1. Chlorinated paraffin 70 emulsion is filled into the storage sleeve and braided ring pores. After covering with aluminum foil shielding layer, the outer sheath layer components are melt-blended and extruded at 140°C and cooled to form the cable.

[0038] Comparative Example 3: Experimental Materials: Braided ring 43 is a flame-retardant cross-linked polyethylene fiber braided ring with 24 strands; Braided ring 43 is made of flame-retardant cross-linked polyethylene fiber, with a total of 24 strands, each strand having a diameter of 0.18 mm, and is braided into a ring at a braiding density of 25 needles / inch, with a normal porosity of 30%. The liquid flame retardant is a 60 wt% monoammonium phosphate aqueous solution, which fills the storage sleeve and the pores of the braided ring. The outer sheath material removes the tea polyphenol flame retardant particles, and the rest is the same as in Example 2.

[0039] Preparation process: The conductor and insulation layer are prepared in the same way as in Example 1. Flame-retardant cross-linked polyethylene fiber braided rings are placed on the outside of the insulation layer. Monoammonium phosphate aqueous solution is filled into the storage sleeve and the pores of the braided ring. After covering with aluminum foil shielding layer, the outer sheath layer components without tea polyphenols are melt-blended and extruded at 140°C and cooled to form the cable.

[0040] The performance test results are shown in the table below:

[0041] According to the test results in the table above, the fire-resistant cable of the present invention exhibits excellent fire resistance. In terms of core flame retardant capability, the target solution, with flame-retardant cross-linked polyethylene fiber braided rings, monoammonium phosphate aqueous solution, and outer sheath tea polyphenols, has a limiting oxygen index of 32.1%, which is not only significantly higher than Comparative Example 1 without liquid flame retardant and Comparative Example 3 without tea polyphenols, but also superior to Example 1 with glass fiber and potassium dihydrogen phosphate. This means that the cable can still effectively suppress combustion in an environment with low oxygen concentration, far exceeding the conventional LOI standard of 26% for general flame-retardant cables. The vertical combustion rating reaches the V-0 level specified in GB / T2408. During combustion, the flame self-extinguishing time is short, there is no melting and dripping phenomenon, and it will not ignite the cotton lint below, completely avoiding the secondary fire risk that may be caused by Comparative Example 1 and Comparative Example 3. It is suitable for outdoor unshaded and easily spread fire scenarios of overhead photovoltaic systems.

[0042] In terms of heat release control capability, the target scheme has a maximum heat release rate of only 159kW / m² and a total heat release of only 39.5MJ / m², which is more than 70% less than the heat release of Comparative Example 1. Even compared with Example 4, which uses high-end materials such as aramid fiber, the performance is similar and the cost is only 1 / 4 of it. It can effectively slow down the heat accumulation rate in the early stage of a fire and reserve a critical time window for emergency shutdown of the photovoltaic system and evacuation of personnel.

[0043] In terms of controlling the hazards of smoke and toxicity, the target solution performs particularly well, with a maximum smoke release rate of 0.015 m² / s and a smoke density level of 16.1%, which is only about 50% of that of the halogenated flame retardant liquid comparative example 2. The CO generation is 75 ppm, which is far lower than that of comparative examples 1 and 3. There is no release of halogen or toxic gases, which not only avoids the risk of casualties from asphyxiation due to toxic smoke in fires, but also meets the environmental protection requirements of the surrounding ecological environment of the overhead photovoltaic system.

[0044] Furthermore, the flame spread rate of the target solution is only 19 mm / min, which is significantly lower than that of Comparative Example 1. This effectively limits the spread of the flame on the cable surface and prevents the fire in a single cable circuit from spreading rapidly to the entire photovoltaic array. The synergistic effect of its braided ring and liquid flame retardant also ensures that the flame retardant performance of the cable does not significantly decrease after long-term exposure to outdoor high temperatures and ultraviolet aging. This completely solves the problem that traditional cables cannot achieve both normal weather resistance and high-temperature flame retardancy, and provides a reliable guarantee for the long-term safe and stable operation of overhead photovoltaic systems.

[0045] 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 fire-resistant cable based on an overhead photovoltaic system, characterized in that, The cable includes a core conductor, multiple sets of which are wrapped with an insulation layer. The gap between the insulation layer and the core conductor is filled with a filler. A fire-resistant and flame-retardant layer is wrapped outside the insulation layer. A shielding layer is wrapped outside the fire-resistant and flame-retardant layer. A cable protective sheath is wrapped outside the shielding layer. The fire-resistant and flame-retardant layer includes a heat insulation film. A storage sleeve is provided inside the heat insulation film. Braided rings are fixedly installed at both ends of the storage sleeve. The storage sleeve includes a storage shell. Two sets of storage slots are opened inside the storage shell. A piston disc is slidably installed inside each of the two sets of storage slots. Flame-retardant liquid is stored in the storage slot between the piston disc and the storage shell. A drain rod is fixedly installed on one side of the piston disc. One end of the drain rod passes through the storage shell and is fixedly connected to the braided ring. A limiting ring is fitted on the part of the drain rod located outside the storage shell. The limiting ring is fixedly installed on the outside of the storage shell.

2. The fire-resistant cable based on an overhead photovoltaic system according to claim 1, characterized in that: The heat insulation film consists of a protective film and an inner film and an outer film fixedly connected to both sides. The inner film and the outer film together form an annular film with a cavity.

3. The fire-resistant cable based on an overhead photovoltaic system according to claim 2, characterized in that: The inner and outer films are fixedly disposed between the two sets of storage shells, and the heat insulation film is fixedly disposed on the outside of the storage shell.

4. The fire-resistant cable based on an overhead photovoltaic system according to claim 1, characterized in that: The drain rod consists of two parts: the end of the drain rod near the piston plate is hollow inside and has multiple drain holes on the outside, while the end of the drain rod near the braided ring is a solid rod.

5. The fire-resistant cable based on an overhead photovoltaic system according to claim 1, characterized in that: A pointed cone is fixedly installed on the upper outer side of the storage casing, and the upper end of the pointed cone is lower than the outermost plane of the storage casing.

6. The fire-resistant cable based on an overhead photovoltaic system according to claim 3, characterized in that: The surface height of the inner film in its initial state is flush with the reference surface on the outside of the storage casing, while the outer film in its initial state is higher than the reference surface of the storage casing.

7. The fire-resistant cable based on an overhead photovoltaic system according to claim 1, characterized in that: The two sets of storage tanks are symmetrically arranged along the central axis of the storage shell.

8. The fire-resistant cable based on an overhead photovoltaic system according to claim 1, characterized in that: The braided ring is made of multiple sets of flame-retardant cross-linked polyethylene fiber ropes wound together, with multiple gaps between the multiple sets of flame-retardant cross-linked polyethylene fiber ropes.

9. The fire-resistant cable based on an overhead photovoltaic system according to claim 8, characterized in that: The braided ring is movably sleeved on the outside of the insulation layer, the storage sleeve is fixedly sleeved on the outside of the insulation layer, and the fire-resistant and flame-retardant layer is connected to the storage sleeve in an orderly manner through the braided ring.

10. The fire-resistant cable based on an overhead photovoltaic system according to claim 1, characterized in that: The shielding layer is movably sleeved on the outside of the fire-resistant and flame-retardant layer.

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