Fire resistant cable based on overhead photovoltaic system

Abstract

The application relates to the technical field of electric wire and cable, and discloses a fireproof cable based on an overhead photovoltaic system, wherein the braided ring in the fireproof and flame-retardant layer is made of flame-retardant crosslinked polyethylene fiber winding, a large number of interlaced gaps are used to ensure air circulation, when encountering flame burning, after high-temperature gas enters the braided ring space, the flame-retardant crosslinked polyethylene fiber rope rapidly shrinks, the interlaced gap is reduced to form a dense physical oxygen isolation layer, on the other hand, the shrinkage traction force pulls the liquid discharge rod, the piston disc extrudes the flame-retardant liquid in the storage sleeve, the liquid is sprayed out through the liquid discharge hole, a part of the liquid directly acts on the flame area to extinguish the flame, most of the liquid is adsorbed and stored by the porous structure of the braided ring, the liquid is gradually decomposed and releases flame-retardant gas under the condition of continuous high temperature, the flame-retardant gas reacts with the braided ring fiber to form a liquid and solid composite heat insulation layer, the small pores remaining after shrinkage are filled, and the cable circuit integrity in the initial stage of fire is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric wire and cable, in particular to a fire-resistant cable based on overhead photovoltaic system. BACKGROUND

[0002] Under the background of global energy structure transformation to clean energy, photovoltaic power generation as an important form of renewable energy utilization, its installed capacity continues to grow rapidly, among them, overhead photovoltaic system is widely used in large ground power station, fish-light complementary, agricultural light complementary and other scenes due to its adaptability to complex terrain such as mountains, deserts, coasts and high land utilization rate, however, overhead photovoltaic system is exposed to outdoor harsh environment for a long time, it needs to withstand high temperature exposure, strong ultraviolet radiation, wind and sand erosion and diurnal temperature difference impact, at the same time, there are risks such as component hot spot effect, direct current arc, line aging in system operation, which is easy to cause fire accidents, while the traditional photovoltaic cable only meets the basic weather resistance requirements, it is difficult to maintain circuit integrity in flame environment, and it may release toxic smoke when burning, which not only causes huge power generation loss due to photovoltaic system paralysis, but also expands the fire hazard range and threatens the surrounding environment and personnel safety, therefore, the development of special fire-resistant cable which is suitable for the special working conditions of overhead photovoltaic system and has excellent fire resistance, weather resistance and environmental protection performance, has become a key requirement to ensure the safe and stable operation of overhead photovoltaic system, and also promotes the coordinated development of electric wire and cable technology and photovoltaic power generation technology in outdoor special scenes.

[0003] In view of the above and the existing related technology, the following defects exist: the cable in the prior art generally faces the core contradiction that the fire resistance and heat dissipation performance cannot be considered when it is adapted to outdoor scenes such as overhead photovoltaic system, in order to meet the heat dissipation demand of long-term outdoor operation of the system, the cable often adopts high porosity structure or materials with strong heat conductivity to accelerate heat dissipation, but such design will cause high temperature to spread rapidly to the inside of the cable when it is exposed to flame, which will cause the cable core conductor and insulation layer to be burned out quickly, and the circuit integrity cannot be maintained, on the contrary, if the fire resistance is improved by thickening the fire-resistant layer and using high-density flame-retardant materials, it will greatly hinder the heat conduction of the cable in normal operation, which will cause the cable core to be overheated due to heat accumulation, and even induce hot spot effect or insulation layer aging, finally, the performance of heat dissipation is better than fire resistance, and fire resistance is better than heat dissipation, which is a contradictory problem, and it is difficult to meet the dual requirements of long-term heat dissipation stability and fire resistance reliability of the cable in overhead photovoltaic system under fire conditions. SUMMARY

[0004] The technical problem to be solved by the present application is that the prior art has the shortcomings that heat dissipation is better than fire resistance, and fire resistance is better than heat dissipation, therefore, we propose a fire-resistant cable based on overhead photovoltaic system.

[0005] In order to achieve the above object, the technical scheme adopted by the present application is as follows: the fireproof cable based on the overhead photovoltaic system comprises a cable core conductor, a plurality of cable core conductors are wrapped with an insulating layer, a gap between the insulating layer and the cable core conductor is filled with a filler, an outer side of the insulating layer is wrapped with a fireproof and flame-retardant layer, an outer side of the fireproof and flame-retardant layer is wrapped with a shielding layer, an outer side of the shielding layer is wrapped with a cable protective sleeve, the fireproof and flame-retardant layer comprises a heat insulation film, an inner side of the heat insulation film is provided with a storage sleeve, both ends of the storage sleeve are fixedly installed with woven rings, the storage sleeve comprises a storage shell, two groups of storage grooves are formed in the inner side of the storage shell, a piston disc is slidably arranged in the storage groove between the piston disc and the storage shell, a fire-retardant liquid is stored in the storage groove, a liquid discharge rod is fixedly installed on one side of the piston disc, one end of the liquid discharge rod penetrates through the storage shell and is fixedly connected with the woven ring, a limiting ring is sleeved on the part of the liquid discharge rod outside the storage shell, and the limiting ring is fixedly installed on the outer side of the storage shell.

[0006] Preferably, the heat insulation film is composed of a protective film and inner and outer films fixedly connected on both sides of the protective film, and the inner and outer films together form an annular film with a cavity.

[0007] Preferably, the liquid discharge rod is composed of two parts, the end of the liquid discharge rod close to the piston disc is hollow inside and has a plurality of liquid discharge holes formed on the outer side, and the end of the liquid discharge rod close to the woven ring is a solid rod.

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

[0009] Preferably, the surface of the inner film in the initial state is flush with the reference surface on the outer side of the storage shell, and the outer film in the initial state is higher than the reference surface of the storage shell.

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

[0011] Preferably, the woven ring is made of a plurality of groups of flame-retardant cross-linked polyethylene fiber ropes, and the plurality of groups of flame-retardant cross-linked polyethylene fiber ropes have a plurality of gaps therebetween.

[0012] Preferably, the woven ring is movably sleeved on the outer side of the insulating layer, the storage sleeve is fixedly sleeved on the outer side of the insulating layer, and the fireproof and flame-retardant layer is connected with the storage sleeve in an orderly manner through the woven ring.

[0013] Preferably, the shielding layer is movably sleeved on the outer side of the fireproof and flame-retardant layer.

[0014] Technical effects and advantages of the present application: in the present application, under normal circumstances, the woven ring in the fire-resistant layer is made of fire-retardant cross-linked polyethylene fiber, which relies on the large number of pores between the ropes to ensure air circulation, and cooperates with the light and thin aerogel composite film used in the heat insulation film, and the mesh structure of the shielding layer, to jointly build an efficient heat dissipation channel, so as to avoid the accumulation of heat in the cable core due to high temperature exposure, and at the same time, the fire-retardant liquid stored in the storage sleeve is sealed by the piston disc, which does not affect the normal structure heat dissipation, when encountering flame burning, the shielding layer shrinks at high temperature first, tightly wrapping the fire-resistant layer to preliminarily resist fire, at the same time, extruding the low-melting copolyester film on both sides of the heat insulation film, prompting the film to be pierced by the sharp cone outside the storage shell, after the high-temperature gas enters the woven ring space, the fire-retardant cross-linked polyethylene fiber rope shrinks rapidly, on the one hand, reducing the gap between the ropes to form a dense physical oxygen isolation layer, delaying the penetration of high temperature to the cable core, on the other hand, through the shrinkage traction force, pulling the liquid discharge rod, prompting the piston disc to extrude the fire-retardant liquid in the storage sleeve, after the liquid is sprayed out through the liquid discharge hole, a part of the liquid directly acts on the flame area to extinguish the fire, most of the liquid is adsorbed and stored by the porous structure of the woven ring, which gradually decomposes and releases fire-retardant gas under continuous high temperature, and reacts with the fiber of the woven ring to form a liquid and solid composite heat insulation layer, filling the small pores still remaining after shrinking, finally realizing the integrated protection of normal efficient heat dissipation, high-temperature active fire resistance and emergency warning, breaking the performance contradiction between heat dissipation and fire resistance, and at the same time, ensuring the integrity of the cable circuit in the early stage of fire. BRIEF DESCRIPTION OF DRAWINGS

[0015] The disclosure of the present application will be described 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 the present application. In the drawings, the same reference signs are used to refer to the same parts:

[0016] Figure 1 is a schematic diagram of the overall structure of the cable of the present application; Figure 2 is a schematic diagram of the overall explosion structure of the cable of the present application; Figure 3 is a schematic diagram of the structure outside the cable core conductor of the present application; Figure 4 is a schematic diagram of the partial structure of the fire-resistant layer of the present application; Figure 5 is a schematic diagram of the structure of the heat insulation film of the present application; Figure 6 is a schematic diagram of the internal structure of the fire-resistant layer of the present application; Figure 7 is a schematic diagram of the internal structure of the storage sleeve of the present application Figure 1 ; Figure 8 is an enlarged structure schematic diagram of A of the present application Figure 7 ; Figure 9 is a schematic diagram of the internal structure of the storage sleeve of the present application Figure 2 ; Figure 10 is a schematic diagram of the internal structure of the storage sleeve of the present application

[0017] Legend: 1, cable core conductor; 2, filler; 3, insulation layer; 4, fire-resistant flame-retardant layer; 41, heat insulation film; 411, protective film; 412, inner film; 413, outer film; 42, storage sleeve; 421, storage shell; 4211, sharp cone; 422, storage groove; 423, drainage rod; 4231, drainage hole; 424, piston disc; 425, limiting ring; 43, braided ring; 5, shielding layer; 6, cable protective sleeve. DETAILED DESCRIPTION

[0018] It is easy to understand that, according to the technical solution of the present application, those skilled in the art can propose a variety of structures and implementation methods that can be replaced with each other without changing the essential spirit of the present application. Therefore, the following detailed description and the accompanying drawings are only exemplary descriptions of the technical solution of the present application, and should not be considered as the whole or as a limitation or restriction of the technical solution of the present application.

[0019] Reference Figures 1-3 As shown, the present application provides a technical solution: a fire-resistant cable based on an overhead photovoltaic system, including a cable core conductor 1 for transmitting current or signals, a plurality of cable core conductors 1 twisted to form a single cable core, and an insulation layer 3 wrapped outside the plurality of cable core conductors 1, which prevents short circuit between the cable core conductor 1 and the outside or adjacent conductors, ensures that the current or signal is only transmitted in the cable core conductor 1, and at the same time, the insulation layer 3 wrapped outside the cable core conductor 1 also serves to isolate moisture, dust, chemicals, etc., to prevent corrosion or damage to the cable core conductor 1, and the gap between the insulation layer 3 and the cable core conductor 1 is filled with a filler 2, which is used to keep the multi-core cable round in cross-section, avoiding deformation of the internal structure of the cable due to twisting and extrusion, and a fire-resistant flame-retardant layer 4 is wrapped outside the insulation layer 3, which has high flame-retardant function, high heat dissipation capacity and reliable fire resistance, and a shielding layer 5 is wrapped outside the fire-resistant flame-retardant layer 4, which is composed of a heat-shrinkable material and a metal braid, which will quickly shrink at high temperatures, thereby tightly wrapping the fire-resistant flame-retardant layer 4 with the internal braid, which can simultaneously consider the shielding efficiency and flexibility, and is used to prevent external electromagnetic signals from interfering with the transmission of signals inside the cable, and at the same time, the shielding layer 5 will quickly shrink and tightly wrap the fire-resistant flame-retardant layer 4 in a high-temperature environment, thereby improving the fire resistance of the cable, and a cable protective sleeve 6 is wrapped outside the shielding layer 5, and the outermost cable protective sleeve 6 serves as an outer barrier of the cable, and its core function is to resist ultraviolet radiation, wind and sand erosion, salt mist corrosion, high and low temperature cycles and mechanical friction in the outdoor environment of the overhead photovoltaic system, and at the same time, it helps to enhance the overall flame retardance and waterproofness of the cable, protects the internal cable core, insulation layer and fire-resistant structure from damage, and ensures long-term stable operation of the cable.

[0020] Reference Figure 2 , Figures 4-6As shown, in the embodiment: the fire-resistant layer 4 includes a heat insulation film 41, the inside of the heat insulation film 41 is provided with a storage sleeve 42, both ends of the storage sleeve 42 are fixedly installed with a woven ring 43, the woven ring 43 is movably sleeved outside the insulation layer 3, the storage sleeve 42 is fixedly sleeved outside the insulation layer 3, the fire-resistant layer 4 is connected with the storage sleeve 42 through the woven ring 43, which not only ensures the flexibility of the whole cable, but also guarantees the heat dissipation performance of the whole cable. Since the woven ring 43 is made of a plurality of groups of flame-retardant cross-linked polyethylene fiber ropes, there are a large number of gaps between the ropes in room temperature state, and the air permeability is good. The woven ring 43 has good shrinkability in a high-temperature environment, and can quickly shrink and tightly wrap outside the insulation layer 3 in a high-temperature environment. The gap between the ropes of the woven ring 43 after tightening is reduced, and at the same time the woven ring 43 will pull the fire-retardant material in the storage sleeve 42 to flow and seal the gap of the woven ring 43 by fusing the fire-retardant material with the woven ring 43, and solidify in a high-temperature environment to improve the heat resistance of the whole fire-resistant layer 4 and further improve the fire protection of the cable.

[0021] With reference to Figures 4-6 As shown, in the embodiment: the heat insulation film 41 is composed of a protective film 411 and inner and outer thin films 412 and 413 fixedly connected on both sides of the protective film 411, the inner and outer thin films 412 and 413 together form a group of annular thin films with cavities, which are arranged outside the woven ring 43, the protective film 411 is fixedly sleeved outside the storage sleeve 42, the inner and outer thin films 412 and 413 are made of low-melting copolyester, the inner and outer thin films 412 and 413 are transparent thin films with a thickness of 5-20 um and good flexibility, the protective film 411 is an aerogel composite film, which is compounded with polyester non-woven fabric into a film shape, and is bonded with the two layers of inner and outer thin films 412 and 413 through low-melting hot melt adhesive. It is light and thin in normal state and does not affect the flexibility of the film, can effectively block heat transfer, and the aerogel structure is stable at high temperature.

[0022] With reference to Figure 4 , Figures 6-9As shown, in the embodiment: the storage sleeve 42 comprises a storage shell 421, the inside of the storage shell 421 is provided with two groups of storage grooves 422, the inside of the two groups of storage grooves 422 is slidably provided with a piston disc 424, the storage groove 422 between the piston disc 424 and the storage shell 421 stores a fire-retardant liquid, the fire-retardant liquid is an aqueous solution of monoammonium phosphate, the aqueous solution of monoammonium phosphate is a transparent liquid with a mass concentration of 50%-70%, good fluidity, can fill the pores of the braided ring 43, dehydrates and decomposes above 150°C, releases ammonia gas, and reacts with the braided ring 43 to catalyze the braided ring 43 to dehydrate and carbonize to generate carbon dioxide and water, the fire-retardant liquid occupies half of the inside of the storage groove 422, one side of the piston disc 424 is fixedly installed with a liquid discharge rod 423, one end of the liquid discharge rod 423 penetrates through the storage shell 421 and is fixedly connected with the braided ring 43, the end of the liquid discharge rod 423 close to the piston disc 424 is hollow inside and is provided with a plurality of liquid discharge holes 4231 outside, the end of the liquid discharge rod 423 close to the braided ring 43 is a solid rod, the part of the liquid discharge rod 423 outside the storage shell 421 is sleeved with a limiting ring 425, and the limiting ring 425 is fixedly installed outside the storage shell 421.

[0023] Referring to Figures 6-9 As shown, in the embodiment: the outside upper end of the storage shell 421 is fixedly installed with a sharp cone 4211, the upper end of the sharp cone 4211 is lower than the outermost plane of the storage shell 421, in use, when the cable is in an extremely high temperature environment due to fire, the cable protective sleeve 6 is rapidly burned through and the fire spreads, in this state, the shielding layer 5 is composed of a heat-shrinkable material and a metal braided mesh, which is rapidly shrunk under high temperature, so as to drive the braided mesh inside to tightly wrap the fire-resistant and flame-retardant layer 4, in this process, the shielding layer 5 is gradually extruded to the low-melting-point copolyester film composed of the inner film 412 and the outer film 413 outside the storage shell 421, after being extruded, the low-melting-point copolyester film is rapidly broken when the inside of the low-melting-point copolyester film is contacted by the sharp cone 4211 due to the constant internal gas, a loud noise is generated, thereby warning and attracting the staff in large ground power stations, fish-light complementary, and farm-light complementary scenes, so as to avoid the cable damage without attention, and the increase of loss and the occurrence of personnel danger.

[0024] In the process of rupture of the low-melting copolyester film, high-temperature gas will enter the space of the braided ring 43 instantaneously, and the flame-retardant crosslinked polyethylene fiber rope will rapidly shrink under the high temperature, the gap between the flame-retardant crosslinked polyethylene fiber ropes will decrease, and the braided ring 43 will shrink to a large extent. The rapid shrinkage of the fiber rope under high temperature significantly reduces the gap between the fibers, and the braided ring 43 tightly wraps the inner layer cable core 1, forming a dense physical barrier layer. On the one hand, it can greatly reduce the penetration of external air into the cable, and oxygen is the core of combustion. When the local oxygen concentration decreases to below 15% due to the blocking of the gap, the sustained combustion and spread of the flame can be directly inhibited. On the other hand, it can block the direct scouring of the inner layer by the high-temperature gas flow, avoid the rapid degradation of the inner layer material due to high temperature, and gain reaction time for subsequent fire protection, delay the transmission speed of external high temperature to the cable core, avoid the melting of the cable core conductor or the short circuit of the insulation layer 3 due to overheating, and ensure the integrity of the cable circuit in the early stage of the fire. Since the storage shell 421 is fixed outside the insulation layer 3, the braided ring 43 will pull the multiple sets of liquid discharge rods 423 fixedly connected thereto during the shrinkage of the braided ring 43 from both sides to the inside. Under the shrinkage traction of the braided ring 43, the multiple sets of liquid discharge rods 423 will gradually pull the piston disc 424 to move and extrude the flame-retardant liquid inside the storage tank 422. When the liquid discharge hole 4231 segment outside the liquid discharge rod 423 moves out of the blocking range of the limiting ring 425, the flame-retardant liquid will be quickly sprayed out under the pressure through the liquid discharge hole 4231. Part of the sprayed liquid is sprayed around the cable combustion site, thereby using the sprayed flame-retardant liquid to extinguish or retard the flame around the cable. Meanwhile, most of the flame-retardant liquid is mixed with the braided ring 43. The porous fiber structure of the braided ring 43 can absorb and store the flame-retardant liquid like a sponge, avoiding the loss of liquid due to gravity or outdoor rain and evaporation, and forming a stable flame-retardant liquid storage layer. Under the continuous roasting of high temperature or flame, the fibers of the braided ring 43 will slowly release the absorbed flame-retardant liquid, and the liquid will gradually decompose as the temperature rises, continuously generating flame-retardant gas, diluting oxygen, and interrupting the combustion chain reaction. Compared with a simple solid flame-retardant layer, the flame-retardant time can be prolonged by 2-3 times, avoiding the problem of one-time flame-retardant failure. After the flame-retardant liquid is mixed with the braided ring 43, a liquid-solid composite heat insulation layer is formed under high temperature. On the one hand, the water vapor released during the decomposition of the flame-retardant liquid 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 such a composite heat insulation layer can be as low as 0.03W / (m・K) below, can effectively block the flame high temperature to the inner layer of cable, avoid the inner layer material because of overheating melting or short circuit, normal state under the woven ring 43 for guarantee heat dissipation will keep certain fiber gap, and after filling the flame retardant liquid, the liquid expands or solidifies under high temperature, can actively fill these small gaps, form a non-porous oxygen barrier structure, on the one hand, prevent external oxygen from penetrating through the gap to the cable core, cut off the oxygen supply of combustion, on the other hand, prevent the leakage of toxic gases generated by the internal combustion of the cable, reduce the harm to the environment and personnel, at the same time, avoid the flame through the gap, limit the spread of fire, which is very important for the local fire control of overhead photovoltaic cable, can prevent a single cable loop from spreading to the entire photovoltaic array, avoid the economic loss and disaster impact of complete cable burning damage expansion, convenient to use.

[0025] Example one: experimental material: woven ring 43 is made of glass fiber woven ring, the flame retardant liquid is potassium dihydrogen phosphate aqueous solution, the number of woven ring 43 is 16; The woven ring 43 is made of alkali-free glass fiber modified by silane coupling agent KH-550, a total of 16 strands, each strand is 0.2mm in diameter, and is woven into a ring with a weaving density of 20 needles per inch. The porosity is 38% in normal state. After weaving, it is sleeved on the outside of the insulation layer, and the two ends are fixed with the storage sleeve. The liquid flame retardant is 60wt% potassium dihydrogen phosphate aqueous solution, which is filled in the storage sleeve and the woven ring pores. Vacuum degassing is carried out during filling to avoid bubble residue. The raw material of the outer sheath layer is polyethylene 78 parts by weight, tea polyphenol flame retardant particles 10 parts by weight, calcium stearate 0.6 parts by weight, antioxidant 1035 1 part by weight, and dicumyl peroxide 1.2 parts by weight.

[0026] Preparation process: copper wire is drawn by drawbench, annealed and twisted into a circular conductor. The conductor is coated with cross-linked polyethylene insulation material by insulation layer extruder at 120℃ to form an insulation layer. After the insulation conductor is cooled and shaped, the preformed glass fiber woven ring is sleeved on the outside, and the storage sleeve and the woven ring 43 pores are filled with potassium dihydrogen phosphate aqueous solution. Then, aluminum foil is wrapped around the outside of the woven ring 43 to form a metal shielding layer. Finally, the components of the outer sheath layer are melt blended by an open mill at 140℃, and are extruded outside the metal shielding layer. After crosslinking at 150℃, it is cooled and shaped to obtain an environmentally friendly fire-resistant cable.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] Example 4: Experimental materials: woven ring 43 is woven from aramid fiber ring, fire retardant is aqueous solution of ammonium sulfamate, the number of strands of woven ring 43 is 40; woven ring 43 is made of aramid 1313 fiber with a temperature resistance of 280℃ and a tensile strength of 5.5GPa, a total of 40 strands, woven into a ring shape at a weaving density of 35 needles / inch, heat set at 200℃ to reduce high temperature shrinkage deformation, normal porosity 24%, liquid fire retardant is 65wt% aqueous solution of ammonium sulfamate, filled in the storage sleeve, through 0.2MPa pressure to ensure that the porosity filling rate is ≥95%, the outer sheath layer raw material is polyethylene 75 parts by weight, tea polyphenol flame retardant particles 12 parts by weight, calcium stearate 0.5 parts by weight, antioxidant 1010 2.5 parts by weight, DCP 2.8 parts by weight.

[0032] Preparation process: the conductor and the insulating layer are prepared as in example 1, the heat set aramid fiber woven ring is sleeved outside the insulating layer, the aqueous solution of ammonium sulfamate is filled into the storage sleeve and the woven ring porosity under pressure, after being covered with an aluminum foil shielding layer, the outer sheath layer components are melt blended and extruded at 140℃, and the environmentally friendly fire-resistant cable is formed after cooling.

[0033] Example 5: Experimental materials: woven ring 43 is woven from flame-retardant nylon 66 fiber woven ring, fire retardant is pentaerythritol phosphate ionic liquid, the number of strands of woven ring 43 is 48; woven ring 43 is made of flame-retardant nylon 66 fiber with 12wt% red phosphorus flame retardant added, a total of 48 strands, each strand is 0.1mm in diameter, woven into a ring shape at a weaving density of 40 needles / inch, after weaving, 0.3wt% silane coupling agent is coated to improve the compatibility with the ionic liquid, normal porosity 20%, liquid fire retardant is pentaerythritol phosphate ionic liquid, filled in the storage sleeve, self-permeated to the woven ring porosity at room temperature, the outer sheath layer raw material is polyethylene 85 parts by weight, tea polyphenol flame retardant particles 8 parts by weight, microcrystalline wax 1 part by weight, antioxidant 1035 3 parts by weight, BPO 3 parts by weight.

[0034] Preparation process: the conductor and the insulating layer are prepared as in example 1, the flame-retardant nylon 66 woven ring coated with the coupling agent is sleeved outside the insulating layer, the pentaerythritol phosphate ionic liquid is self-permeated and filled into the woven ring porosity and the storage sleeve, after being covered with an aluminum foil shielding layer, the outer sheath layer components are melt blended and extruded at 140℃, and the environmentally friendly fire-resistant cable is formed after cooling.

[0035] Comparative example 1: Experimental materials: woven ring 43 is ordinary polyethylene woven ring, the number of strands is 8; woven ring 43 is made of ordinary non-flame-retardant polyethylene fiber, a total of 8 strands, each strand is 0.3mm in diameter, woven into a ring shape at a weaving density of 15 needles / inch, normal porosity 45%, no liquid fire retardant is filled, the outer sheath layer raw material is the same as example 3.

[0036] Preparation process: the conductor and the insulating layer are prepared according to Embodiment 1, the common polyethylene braided ring is sleeved outside the insulating layer, the aluminum foil shielding layer is directly wrapped, and the outer sheath layer component is extruded and wrapped after being melt blended at 140 DEG C, and the cable is formed after cooling.

[0037] Comparative Example 2: Experimental materials: the braided ring 43 is a glass fiber braided ring with 16 strands; the braided ring 43 is made of the same material as in Embodiment 1, the liquid fire-retardant is replaced by 40wt% chlorinated paraffin 70 emulsion, which is filled in the storage sleeve and the braided ring pores, and the outer sheath layer material is the same as in Embodiment 1.

[0038] Preparation process: the conductor, the insulating layer and the braided ring are sleeved according to Embodiment 1, the chlorinated paraffin 70 emulsion is filled into the storage sleeve and the braided ring pores, the aluminum foil shielding layer is wrapped, and the outer sheath layer component is extruded and wrapped after being melt blended at 140 DEG C, and the cable is formed after cooling.

[0039] Comparative Example 3: Experimental materials: the braided ring 43 is a fire-retardant crosslinked polyethylene fiber braided ring with 24 strands; the braided ring 43 is made of fire-retardant crosslinked polyethylene fiber, which has 24 strands, each strand has a diameter of 0.18mm, and is woven into a ring shape with a weaving density of 25 needles per inch, and has a normal porosity of 30%; the liquid fire-retardant is 60wt% ammonium phosphate solution, which is filled in the storage sleeve and the braided ring pores; the outer sheath layer material is deleted tea polyphenol fire-retardant particles, and the rest is the same as in Embodiment 2.

[0040] Preparation process: the conductor and the insulating layer are prepared according to Embodiment 1, the fire-retardant crosslinked polyethylene fiber braided ring is sleeved outside the insulating layer, the ammonium phosphate solution is filled into the storage sleeve and the braided ring pores, the aluminum foil shielding layer is wrapped, and the outer sheath layer component without tea polyphenol is extruded and wrapped after being melt blended at 140 DEG C, and the cable is formed after cooling.

[0041] The performance test results are shown in the following table:

[0042]

[0043] According to the test results in the above table, the fire-resistant cable of the present application shows excellent fire-resistant performance. From the core fire-retardant ability, the target scheme, the fire-retardant crosslinked polyethylene fiber braided ring, the ammonium phosphate solution, and the outer sheath tea polyphenol have an ultimate oxygen index of 32.1%, which is not only significantly higher than that of Comparative Example 1 without liquid fire-retardant and Comparative Example 3 without tea polyphenol, but also better than Embodiment 1 with glass fiber and potassium dihydrogen phosphate, which 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 fire-retardant cables, and the vertical burning grade reaches V-0 level according to GB / T2408, the flame self-extinguishing time is short, there is no melting and dripping phenomenon, and it will not ignite the cotton below, completely avoiding the secondary fire risk that may be caused by Comparative Example 1 and Comparative Example 3, and adapting to the outdoor unsheltered and easily spreading fire scene of overhead photovoltaic systems.

[0044] From the heat release control capability, the maximum heat release rate of the target scheme is only 159kW / m², and the total heat release amount is as low as 39.5MJ / m², which is reduced by more than 70% compared with the heat release of Comparative Example 1. Even compared with Example 4 of high-end materials such as aramid fiber, the performance is close and the cost is only 1 / 4, which can effectively slow down the heat accumulation speed in the early stage of fire, and reserve a key time window for emergency shutdown of photovoltaic system and personnel evacuation.

[0045] In terms of smoke hazard control, the target scheme performs particularly outstandingly, with a maximum smoke release rate of 0.015m² / 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, and a CO generation amount of 75ppm, which is much lower than that of Comparative Example 1 and Comparative Example 3. There is no halogen-free and non-toxic gas release, which not only avoids the risk of personnel casualties caused by smoke suffocation in fire, but also meets the environmental protection requirements of the surrounding ecological environment of overhead photovoltaic system.

[0046] In addition, the flame spread rate of the target scheme is only 19mm / min, which is greatly reduced compared with Comparative Example 1, which can effectively limit the spread of flame on the surface of the cable, prevent the rapid spread of a single cable loop to the entire photovoltaic array after the cable loop catches fire, and ensure that the cable has no obvious decay in combustion and flame-retardant performance after long-term outdoor high-temperature exposure and ultraviolet aging, completely solving the pain point that traditional cables cannot simultaneously withstand normal weather and high-temperature flame retardation, and providing reliable protection for the long-term safe and stable operation of overhead photovoltaic system.

[0047] The technical scope of the present application is not limited to the content in the above description, and those skilled in the art can make various modifications and changes to the above examples without departing from the technical idea of the present application, and these modifications and changes should all be within the protection scope of the present application.

Claims

1. Fire resistant cable based on overhead photovoltaic systems, characterized by, The cable includes cable core conductors, an insulating layer wrapped outside the groups of cable core conductors, a filler filled in the gap between the insulating layer and the cable core conductors, a fire-resistant layer wrapped outside the insulating layer, a shielding layer wrapped outside the fire-resistant layer, and a cable protective sleeve wrapped outside the shielding layer.

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

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

4. The fire resistant cable based on overhead photovoltaic system of claim 1, wherein: The liquid discharge rod is composed of two parts, the end of the liquid discharge rod close to the piston disc is hollow inside and has a plurality of liquid discharge holes outside, and the end of the liquid discharge rod close to the woven ring is a solid rod.

5. The fire resistant cable based on overhead photovoltaic system of claim 1, wherein: A sharp cone is fixedly arranged on the outer upper end of the storage housing, and the upper end of the sharp cone is lower than the outermost plane of the storage housing.

6. The fire resistant cable based on overhead photovoltaic system of claim 3, wherein: The surface height of the inner film in the initial state is flush with the reference surface outside the storage housing, and the outer film in the initial state is higher than the reference surface of the storage housing.

7. The fire resistant cable based on overhead photovoltaic system of claim 1, wherein: The two groups of storage grooves are symmetrically arranged along the central axis of the storage housing.

8. The fire resistant cable based on overhead photovoltaic system of claim 1, wherein: The woven ring is movably arranged outside the insulating layer, the storage sleeve is fixedly arranged outside the insulating layer, and the fire-resistant layer is sequentially connected with the storage sleeve through the woven ring.

9. The fire resistant cable based on overhead photovoltaic system according to claim 8, characterized in that: The shielding layer is movably arranged outside the fire-resistant layer.

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