Fire-resistant cable and preparation method thereof, and power transmission equipment

Abstract

The present invention relates to a fire-resistant cable and a preparation method thereof, and a power transmission device. The fire-resistant cable comprises: an insulating cable core, the insulating cable core comprises an insulating core and a semi-conductive buffer layer and a metal shielding layer sequentially coated on the surface of the insulating core; an inorganic fireproof mud layer, the inorganic fireproof mud layer is coated on the outside of the insulating cable core and is in direct contact with the metal shielding layer; a reinforcing fiber winding layer, the reinforcing fiber winding layer is coated on the surface of the inorganic fireproof mud layer, and the reinforcing fibers in the reinforcing fiber winding layer are embedded in the inorganic fireproof mud layer; and a tape layer, a metal armor layer, a flame retardant layer and a sheath sequentially coated on the surface of the reinforcing fiber winding layer. The metal shielding short-circuit current of the cable is high.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a fire-resistant cable and a preparation method thereof, and power transmission equipment. Background Art

[0002] Cable fires can easily lead to power outages in power systems. Therefore, fire-resistant cables are often used in places such as power plants and substations where there are a large number of electrical equipment and densely laid cables. The properties of fire-resistant cables are very important to ensure continuous power supply to important circuits.

[0003] With the development of science and technology and living standards, more and more high-rise, super-high-rise and super-large buildings are emerging. For example, in the fire protection circuits of large stadiums, airports, etc., it is necessary to use medium-voltage cables with a rated voltage of 3.6 / 6kV~26 / 35kV for secondary transformation to meet the power supply needs of the entire fire protection circuit. At the same time, with the continuous development of urban power grids and the extension of urban cable lines, the short-circuit capacity level of the power supply system has gradually increased. When the cable is short-circuited to the ground, the short-circuit current is also getting larger. When a system short-circuit occurs, the cable metal shielding layer is often burned or the cable insulation is damaged, resulting in the scrapping of the cable. The existing cables can withstand a small short-circuit current of the cable metal shielding, which is far from meeting the demand.

[0004] Therefore, the existing technology still needs to be improved. Summary of the invention

[0005] Based on this, the present invention provides a fire-resistant cable capable of improving the short-circuit current of the cable metal shield, a preparation method thereof, and a power transmission equipment.

[0006] One aspect of the present invention provides a fire-resistant cable, comprising:

[0007] An insulating cable core, the insulating cable core comprising an insulating core and a semi-conductive buffer layer and a metal shielding layer sequentially coated on the surface of the insulating core;

[0008] An inorganic fireproof mud layer, which is coated on the outside of the insulating cable core and is in direct contact with the metal shielding layer;

[0009] A reinforcing fiber winding layer, wherein the reinforcing fiber winding layer is coated on the surface of the inorganic fireproof mud layer, and the reinforcing fibers in the reinforcing fiber winding layer are embedded in the inorganic fireproof mud layer; and

[0010] A tape layer, a metal armor layer, a flame retardant layer and a sheath are sequentially coated on the surface of the reinforcing fiber winding layer.

[0011] In some embodiments, the embedding depth is greater than 2 mm; and / or

[0012] The material of the reinforcing fiber winding layer is aramid fiber.

[0013] In some of the embodiments, the insulating cable cores are coaxially arranged and are jointly covered by the inorganic fireproof mud layer, and the gaps formed by the insulating cable cores are filled with the inorganic fireproof mud in the inorganic fireproof mud layer.

[0014] In some of the embodiments, the melting point of the inorganic fireproof mud layer is higher than 1000°C.

[0015] In some embodiments, the semi-conductive buffer layer is made of semi-conductive polyester tape; and / or

[0016] The material of the metal shielding layer is copper or aluminum.

[0017] In some embodiments, the insulated wire core includes a conductor and a conductor shielding layer, an insulating layer and an insulating shielding layer sequentially coated on the conductor from the inside to the outside.

[0018] In some embodiments, the material of the insulating layer is selected from at least one of cross-linked polyethylene and ethylene-propylene rubber; and / or

[0019] The conductor shielding layer and / or the insulating shielding layer is made of semi-conductive shielding material.

[0020] In some embodiments, the material of the tape layer is at least one of non-woven fabric, polypropylene and polyester; and / or

[0021] The flame retardant layer is made of glass fiber; and / or

[0022] The material of the metal armor layer is selected from at least one of aluminum and its alloys, copper and its alloys and steel; and / or

[0023] The material of the sheath is at least one of polyvinyl chloride, polyethylene, polyolefin plastic and rubber material.

[0024] Another aspect of the present invention provides a method for preparing a fire-resistant cable, comprising the following steps:

[0025] The surface of the insulating core is coated with a semi-conductive buffer layer and a metal shielding layer in sequence to obtain an insulating cable core;

[0026] Directly coating the surface of the metal shielding layer of the insulating cable core to form an inorganic fireproof mud layer;

[0027] Winding reinforcing fibers on the surface of the inorganic fireproof mud layer to form a reinforcing fiber winding layer, and the reinforcing fibers are embedded in the inorganic fireproof mud layer;

[0028] The surface of the reinforcing fiber winding layer is coated in sequence to form a tape layer, a metal armor layer, a flame retardant layer and a sheath to obtain a fire-resistant cable.

[0029] According to another aspect of the present invention, there is provided a power transmission device, wherein the power transmission device comprises the fire-resistant cable as described above.

[0030] In the above-mentioned fire-resistant cable, on the one hand, the inorganic fire-retardant mud layer is directly coated on the outside of the insulating cable core and is in direct contact with the metal shielding layer, that is, the inorganic fire-retardant mud layer is in direct contact with the metal shielding layer. The temperature resistance of the inorganic fire-retardant mud layer is much higher than that of other polymer materials, thereby increasing the final temperature that the layer in direct contact with the metal shielding layer can withstand when the cable catches fire, thereby increasing the short-circuit current that the metal shielding layer can withstand; at the same time, the inorganic fire-retardant mud layer has the characteristic of being difficult to burn, so that when the cable catches fire, it is difficult for the flame to penetrate the inorganic fire-retardant mud layer, so as to fully protect the internal structure of the cable. On the other hand, the reinforced fiber winding layer is coated on the surface of the inorganic fireproof mud layer, and the reinforced fibers in the reinforced fiber winding layer are embedded in the inorganic fireproof mud layer, which plays a role in supporting the inorganic fireproof mud layer to improve the strength of the inorganic fireproof mud layer and avoid the inorganic fireproof mud layer from cracking due to heat, thereby causing the short-circuit current of the metal shielding layer to decrease; at the same time, a tape layer, a metal armor layer, a flame retardant layer and a sheath are sequentially arranged on the surface of the reinforced fiber winding layer to further protect the internal structure of the cable from damage by high temperature; in this way, the various parts work together to improve the short-circuit current of the cable metal shield.

[0031] The metal shielding short-circuit current of the above-mentioned cable is high and can maintain a relatively high metal shielding short-circuit current at a rated voltage of 3.6 / 6kV~26 / 35kV.

[0032] Furthermore, the embedding depth is greater than 2 mm, and the strength of the inorganic fireproof mud layer is further enhanced by controlling the embedding depth.

[0033] Furthermore, the material of the above-mentioned semi-conductive buffer layer is semi-conductive Tetoron tape, which has the characteristic of high strength. By arranging a semi-conductive buffer layer made of semi-conductive Tetoron tape between the insulating shielding layer and the metal shielding layer, it is avoided that when the cable catches fire, the insulating core expands due to heat and directly contacts the rigid metal shielding layer, causing damage to the cable insulation layer, thereby protecting the fire-resistant cable from normal power supply when encountering high-temperature combustion.

[0034] The above-mentioned power transmission equipment includes the fire-resistant cable as described above. The cable metal shielding of the above-mentioned fire-resistant cable has a high short-circuit current, thereby improving the fire resistance of the power transmission equipment, so that it can withstand a higher short-circuit current when subjected to high-temperature combustion, thereby ensuring normal operation within a specified time range and avoiding major safety accidents caused by high-temperature combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic structural diagram of a fire-resistant cable according to an embodiment of the present invention;

[0036] Figure 2 Schematic diagram of the preparation process of a semiconductive buffer layer in one embodiment of the present invention.

[0037] Description of reference numerals:

[0038] 10: Fire-resistant cable; 11: Insulated cable core; 12: Inorganic fire-retardant mud layer; 13: Reinforced fiber winding layer; 14: Tape layer; 15: Metal armor layer; 16: Flame retardant layer; 17: Sheath; 111: Insulated core; 112: Semi-conductive buffer layer; 113: Metal shielding layer; 1111: Conductor; 1112: Conductor shielding layer; 1113: Insulating layer; 1114: Insulating shielding layer. DETAILED DESCRIPTION

[0039] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0041] The short-circuit current of the cable metal shield that the cable can withstand is closely related to the material properties and structural settings of the metal shield layer. Traditional technologies often focus on developing new metal shield layer materials or improving the structure of the metal shield layer to change its cross-sectional flux, thereby increasing the short-circuit current of the cable metal shield. However, the development of new materials or the construction of new structures to increase the short-circuit current of the cable metal shield is close to the limit of improvement, and it is difficult to make further breakthroughs.

[0042] Therefore, the technicians of the present invention break the constraints of the prior art, find another way, and creatively propose to improve the metal shielding short-circuit current of the cable by considering changing the structure of the layer adjacent to the metal shielding layer.

[0043] In order to solve this problem, technicians have done a lot of research and proposed the following fire-resistant cable and its preparation method and transmission equipment.

[0044] See also Figure 1An embodiment of the present invention provides a fire-resistant cable 10, comprising: an insulating cable core 11, an inorganic fire-retardant mud layer 12, a reinforcing fiber winding layer 13, a wrapping layer 14, a metal armor layer 15, a flame retardant layer 16 and a sheath 17.

[0045] The insulating cable core 11 includes an insulating core 111 and a semi-conductive buffer layer 112 and a metal shielding layer 113 which are sequentially coated on the surface of the insulating core 111 .

[0046] The inorganic fireproof mud layer 12 is directly coated on the outside of the insulating cable core 11 and is in direct contact with the metal shielding layer.

[0047] The reinforcing fiber winding layer 13 is coated on the surface of the inorganic fireproof mud layer 12 , and the reinforcing fibers in the reinforcing fiber winding layer 13 are embedded in the inorganic fireproof mud layer 12 .

[0048] The metal armor layer 15 , the flame retardant layer 16 and the sheath 17 are sequentially coated on the surface of the tape layer 14 .

[0049] After a large number of experiments, the technical personnel of the present application found that the magnitude of the short-circuit current that the metal shielding layer can withstand is directly related to the temperature resistance value of the material it contacts, which is explained theoretically as follows:

[0050] The metal shielding layer withstands the short-circuit current I AD The calculation formula (1) is as follows.

[0051] (1).

[0052] In formula (1), I AD is the short-circuit current calculated on an adiabatic basis; t is the short-circuit duration, in seconds; K is the constant of the current-carrying material (including the metal shielding layer and the conductor), in AS 1 / 2 / mm 2 ; S is: the geometric cross-section of the current carrier (including the metal shielding layer and the conductor), in mm 2 ; is the final temperature; is the starting temperature; β is the reciprocal of the temperature coefficient of resistance of the carrier fluid at 0°C, in K.

[0053] Among them, t, K, S, and β are clearly defined in relevant patents, such as IEC60949. Among them, some commonly used parameters of metal shielding materials and conductor materials are shown in the following table:

[0054]

[0055] is the final temperature that the carrier fluid can actually reach within the specified short circuit duration. From the above formula, we can see that at I AD ,t,K,S, After the β value is determined, The larger the metal shielding layer is, the shorter the short-circuit current I AD The bigger, It is limited by the temperature resistance of the material in direct contact with the carrier fluid.

[0056] In traditional cables, the layer in direct contact with the metal shielding layer is often a support layer, waterproof layer or oxygen barrier layer made of resin plastic or other materials with low melting or softening points. In this way, the final temperature that the carrier can actually reach within the specified short-circuit duration is The short-circuit current of the cable's metal shield is greatly limited.

[0057] After a lot of experimental research, the technicians of the present application creatively coated the inorganic fireproof mud layer 12 directly on the surface of the metal shielding layer 113 in the insulating cable core 11, that is, the inorganic fireproof mud layer 12 is directly in contact with the metal shielding layer 113. The heat resistance of the inorganic fireproof mud layer 12 is much higher than that of other polymer materials, thereby increasing the final temperature that the layer in direct contact with the metal shielding layer 113 can withstand, thereby increasing the short-circuit current that the metal shielding layer 113 can withstand; at the same time, the inorganic fireproof mud layer 12 has the characteristic of being difficult to burn, so that when the cable catches fire, it is difficult for the flame to penetrate the inorganic fireproof mud layer 12, so as to fully protect the internal structure of the cable. On the other hand, the reinforced fiber winding layer 13 is coated on the surface of the inorganic fireproof mud layer 12, and the reinforced fibers in the reinforced fiber winding layer 13 are embedded in the inorganic fireproof mud layer 12, so as to support the inorganic fireproof mud layer 12, so as to improve the strength of the inorganic fireproof mud layer 12 and avoid the inorganic fireproof mud layer 12 from cracking due to heat, thereby causing the short-circuit current of the metal shielding layer 113 to decrease; at the same time, a wrapping layer 14, a metal armor layer 15, a flame retardant layer 16 and a sheath 17 are sequentially arranged on the surface of the reinforced fiber winding layer 13 to further protect the internal structure of the cable from damage by high temperature; in this way, the various parts work together to improve the short-circuit current of the cable metal shield.

[0058] In some embodiments, the embedding depth is greater than 2 mm.

[0059] By further controlling the embedding depth, the strength of the inorganic fireproof mud layer 12 is further enhanced to prevent the inorganic fireproof mud layer 12 from cracking due to heat.

[0060] Preferably, the material of the reinforcing fiber winding layer 13 is aramid fiber.

[0061] Aramid fiber is the full name of "aromatic polyamide fiber". It is a synthetic fiber with ultra-high strength, high modulus, high temperature resistance, acid and alkali resistance, corrosion resistance, non-conductivity, dynamic load resistance, impact resistance and other excellent properties. Its strength is 5 to 6 times that of steel wire, its modulus is 2 to 3 times that of steel wire or glass fiber, and its toughness is 2 times that of steel wire. It is mainly divided into two types, para-aramid fiber (PPTA) and meta-aramid fiber (PMIA), for example, Kevlar fiber is para-aramid fiber.

[0062] Since the aramid fiber of the present application has the characteristic of high temperature resistance, it is compatible with the high temperature resistance of the inorganic fireproof mud layer 12, and can further synergistically improve the fire resistance of the fire-resistant cable.

[0063] In some of the implementation examples, the insulating cable cores 11 are coaxially arranged and are jointly covered by the inorganic fireproof mud layer 12 , and the gaps formed by the insulating cable cores 11 are filled with the inorganic fireproof mud in the inorganic fireproof mud layer 12 .

[0064] In other words, there are multiple insulating cable cores 11 , which are coaxially arranged and commonly covered by the inorganic fireproof mud layer 12 , and the gaps formed by the multiple insulating cable cores 11 are filled with the inorganic fireproof mud in the inorganic fireproof mud layer 12 .

[0065] It is understandable that when multiple insulating cable cores are formed into a cable 11, there will be gaps between the insulating cable cores 11, and the gaps are also filled with inorganic fireproof mud, so that the inorganic fireproof mud fills all the gaps, so that the surfaces of the insulating cable cores 11 are covered to form an inorganic fireproof mud layer 12.

[0066] Please continue to refer to Figure 1 There are three insulating cable cores 11, and the inorganic fireproof mud fills the gaps formed between the insulating cable cores, so that the surfaces of the insulating cable cores 11 are covered to form an inorganic fireproof mud layer 12.

[0067] In some embodiments, the melting point of the inorganic fireproof mud layer 12 is higher than 1000°C.

[0068] The higher the melting point of the inorganic fireproof mud layer 12, that is, the higher the temperature resistance of the layer in direct contact with the metal shielding layer 113, the higher the final temperature that the carrier can actually reach within the specified short-circuit duration. The higher the value, the further the short-circuit current of the cable metal shield will be increased.

[0069] Specifically, the inorganic fireproof mud used in the inorganic fireproof mud layer 12 is inorganic mineral fireproof mud, including but not limited to: magnesium hydroxide slurry mud.

[0070] In some embodiments, the semi-conductive buffer layer 112 is made of semi-conductive polyester tape.

[0071] The semi-conductive Tetoron tape has the characteristic of high strength. By arranging a semi-conductive buffer layer made of the semi-conductive Tetoron tape material between the insulating core 111 and the metal shielding layer 113, it is avoided that when the cable catches fire, the insulating core 111 expands due to heat and directly contacts the rigid metal shielding layer 113, causing damage to the insulating layer 113, thereby protecting the fire-resistant cable from normal power supply when encountering high-temperature combustion.

[0072] The metal shielding layer 113 is made of copper or aluminum.

[0073] Please continue to refer to Figure 1 In some embodiments, the insulated wire core 111 includes a conductor 1111 and a conductor shielding layer 1112, an insulating layer 1113 and an insulating shielding layer 1114 sequentially coated on the conductor 1111 from the inside to the outside.

[0074] In some embodiments, the conductor shielding layer 1112 is made of semi-conductive shielding material.

[0075] In some embodiments, the insulating shielding layer 1114 is made of a semi-conductive shielding material.

[0076] The conductor shielding layer 1112 serves as the insulating inner shielding layer of the insulating core 111, so that the insulating layer 1113 and the cable conductor 1111 have a better contact surface, preventing the increase of the conductor surface electric field strength caused by the roughness of the conductor surface; the insulating shielding layer 1114 serves as the insulating outer shielding layer of the insulating core 111, preventing the increase of the surface electric field strength caused by the roughness of the insulating layer 1113, preventing discharge to the insulation under high voltage, and then destroying the insulation, so as to achieve the purpose of ensuring the service life of the cable.

[0077] The above-mentioned semi-conductive shielding material may be a semi-conductive shielding material commonly used in the art.

[0078] Specifically, the semi-conductive shielding material includes a resin base material and a conductive medium; the resin base material includes various polyolefins and copolymers thereof, and the conductive medium includes conductive carbon black.

[0079] In some embodiments, the material of the insulating layer 1113 is selected from at least one of cross-linked polyethylene and ethylene-propylene rubber.

[0080] In some embodiments, the material of the wrapping layer 14 is at least one of non-woven fabric, polypropylene and polyester.

[0081] In some embodiments, the flame retardant layer 16 is made of glass fiber.

[0082] In some embodiments, the material of the metal armor layer 15 is selected from at least one of aluminum and its alloys, copper and its alloys, and steel. During preparation, any processed form of the above materials can be used as the preparation raw material, such as steel strip, aluminum (aluminum alloy) strip, steel wire, aluminum (alloy) wire, copper (alloy) strip, copper (alloy) wire, etc.

[0083] The function of the metal armor layer 15 is to protect the cable insulation core from being damaged when the cable is squeezed or stretched by external force.

[0084] In some embodiments, the material of the sheath 17 is at least one of polyvinyl chloride, polyethylene, polyolefin plastic and rubber material.

[0085] The rubber material includes but is not limited to silicone rubber, ethylene propylene rubber, and other rubber elastomer materials.

[0086] In some embodiments, the conductor is made of copper, aluminum or aluminum alloy. Any processed material of the above materials can be used as raw materials, such as copper wire, copper wire, aluminum wire, etc.

[0087] It should be noted that when the material of the conductor is copper, the copper wire used may be a copper wire with a metal coating on the surface, or may not be coated with metal.

[0088] One embodiment of the present invention provides a method for preparing a fire-resistant cable 10, comprising the following steps S10-S40.

[0089] Step S10 , a semi-conductive buffer layer 112 and a metal shielding layer 113 are sequentially coated on the surface of the insulating core 111 to obtain an insulating cable core 11 .

[0090] In some embodiments, the step of coating the surface of the insulating core 111 with the semiconductive buffer layer 112 includes the following steps:

[0091] Preheating the semi-conductive buffer tape and coating it with silicone oil to obtain a pre-treated semi-conductive buffer tape;

[0092] The pre-treated semi-conductive buffer tape is coated on the surface of the insulating core 111 to form a semi-conductive buffer layer 112 .

[0093] By preheating and coating with silicone oil, the flexibility of the semi-conductive buffer tape can be improved, wrinkling of the semi-conductive buffer tape can be prevented, and leakage of the buffer tape can be avoided. The obtained semi-conductive buffer layer 112 is flat and fits well, ensuring protection of the insulated core.

[0094] Specifically, the steps of preheating the semi-conductive buffer tape and coating the semi-conductive buffer tape with silicone oil include: preheating, coating the semi-conductive buffer tape with silicone oil, and then preheating to avoid leaking and wrinkling when the semi-conductive buffer tape is wrapped.

[0095] In some embodiments, the preheating temperature is 30°C to 40°C.

[0096] In some embodiments, in the step of coating silicone oil, the surface of the semiconductive buffer tape is soaked with silicone oil.

[0097] In a specific example, the preparation process of the semiconductive buffer layer 112 is shown in Figure 2 , place the semi-conductive buffer tape in the buffer tape wrapping device, wrap the semi-conductive buffer tape around the surface of the insulated core 111 through the buffer tape wrapping device, and the semi-conductive buffer tape passed through the buffer tape wrapping device passes through the first preheating unit, the silicone oil coating unit and the second preheating unit in sequence before wrapping, and is preheated, coated with silicone oil and then preheated again to avoid leakage and wrinkles when the semi-conductive buffer tape is wrapped.

[0098] Step S20: directly coating the surface of the metal shielding layer 113 of the insulating cable core 11 to form an inorganic fireproof mud layer 12.

[0099] Step S30, winding reinforcing fibers on the surface of the inorganic fireproof mud layer 12 to form a reinforcing fiber winding layer 13, and the reinforcing fibers are embedded in the inorganic fireproof mud layer 12.

[0100] Step S40 , forming a tape layer 14 , a metal armor layer 15 , a flame retardant layer 16 and a sheath 17 in sequence on the surface of the reinforcing fiber winding layer 13 to obtain a fire-resistant cable 10 .

[0101] In step S30, the winding step is performed when the inorganic fireproof mud in the inorganic fireproof mud layer 12 is not hardened, so as to facilitate embedding the reinforcing fibers into the inorganic fireproof mud layer 12. Further, in the winding step, the pitch between two adjacent reinforcing fibers in the formed reinforcing fiber winding layer 13 is 50-100 mm.

[0102] In some embodiments, step S10 includes a step S11 of preparing an insulated wire core.

[0103] Step S11: using a three-layer co-extrusion method to simultaneously extrude a conductor shielding layer 1112, an insulating layer 1113 and an insulating shielding layer 1114 on the surface of the conductor.

[0104] Specifically, the three-layer co-extrusion method refers to simultaneously extruding conductor shielding material, insulating material, and insulating shielding material on the three-layer co-extrusion chemical cross-linked catenary production line to form a conductor shielding layer 1112, an insulating layer 1113 and an insulating shielding layer 1114 on the surface of the conductor 1111 in sequence, and directly obtaining the insulated wire core 111.

[0105] Furthermore, the preparation steps of the conductor 1111 are: annealing the electrical round conductor wire formed after the wire drawing process, and then twisting it.

[0106] If there are multiple insulating cable cores 11, after step S10 and before step S20, the step of cabling the multiple insulating cable cores 11 is further included, which is specifically as follows:

[0107] A plurality of insulating cable cores 11 are cabled in the same cabling direction and with a pitch diameter ratio of 10 to 60 times.

[0108] In some embodiments, in step S40, the metal armor layer is formed by wrapping a metal tape or spirally winding a metal wire.

[0109] One embodiment of the present invention provides a power transmission device, which includes the fire-resistant cable 10 as described above.

[0110] The above-mentioned power transmission equipment includes the fire-resistant cable as described above. The cable metal shielding of the above-mentioned fire-resistant cable has a high short-circuit current, thereby improving the fire resistance of the power transmission equipment, so that it can withstand a higher short-circuit current when subjected to high-temperature combustion, thereby ensuring normal operation within a specified time range and avoiding major safety accidents caused by high-temperature combustion.

[0111] The metal shielding short-circuit current of the above-mentioned cable is high, and it can maintain a relatively high metal shielding short-circuit current at a rated voltage of 3.6 / 6kV~26 / 35kV. Therefore, the above-mentioned power transmission equipment is very suitable for places such as airports, hospitals, schools, subways, power stations, large venues and industrial bases that require continuous high and medium-high voltage power supply. When a fire occurs, even if the fire-resistant cable in the power transmission equipment catches fire, it can still supply power to the power system within the specified time range, which is helpful for personnel escape and fire rescue, and avoids major accidents that cause casualties or property losses.

[0112] The above-mentioned power transmission equipment includes but is not limited to: motors, lighting appliances, fire alarms, fans and electric pumps, etc.

[0113] The present invention will be described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present invention. Under the guidance of the concept of the present invention, those skilled in the art should realize that certain changes made to the various embodiments of the present invention will be covered by the spirit and scope of the claims of the present invention.

[0114] The following are specific embodiments. Specific embodiments Example 1

[0116] (1) Please refer to Figure 1, the copper wire is subjected to a wire drawing process to form an electrical round conductor wire, which is then annealed and twisted to obtain a conductor 1111; then a conductor shielding material, an insulating material and an insulating shielding material are simultaneously extruded by a three-layer co-extrusion method to form a conductor shielding layer 1112, an insulating layer 1113 and an insulating shielding layer 1114 on the surface of the conductor 1111 to obtain an insulated wire core 111. Among them, the conductor shielding material is a semi-conductive cross-linked polyethylene shielding material, the insulating material is cross-linked polyethylene, and the insulating shielding material is a strippable semi-conductive cross-linked polyethylene shielding material.

[0117] A semi-conductive polyester tape is wrapped around the surface of the insulating core 111 to form a semi-conductive buffer layer 112. The preparation process of the semi-conductive buffer layer 112 can be found in Figure 2 , place the semi-conductive buffer tape in the buffer tape wrapping device, and wrap the semi-conductive buffer tape around the surface of the insulating core 111 through the buffer tape wrapping device. Before wrapping, the semi-conductive buffer tape passed through the buffer tape wrapping device first passes through the first preheating unit, the silicone oil coating unit and the second preheating unit in sequence for preheating and coating with silicone oil in sequence to avoid leakage or wrinkles when the semi-conductive buffer tape is wrapped.

[0118] The temperature in the first preheating unit and the second preheating unit is set to 35° C., and in the step of coating silicone oil, the surface of the semiconductive buffer tape is soaked with silicone oil.

[0119] Then, a copper tape is used to wrap to form a metal shielding layer 113 to obtain an insulated cable core 11.

[0120] (2) Please continue to refer to Figure 1 , three insulated cable cores 11 are cabled in the same cabling direction with a pitch diameter ratio of 40 times, and then inorganic fireproof mud is extruded in the gaps and around to form an inorganic fireproof mud layer 12, and when the inorganic fireproof mud is in a soft state, aramid fiber filaments are wound on the surface of the inorganic fireproof mud layer 12, and the aramid fiber is embedded in the inorganic fireproof mud layer 12 with an embedding depth of not less than 2 mm to form a reinforced fiber winding layer 13; wherein the inorganic fireproof mud is an inorganic mineral material made of a mixture of magnesium hydroxide and sodium silicate, and has a melting point higher than 1000°C.

[0121] (3) Please continue to refer to Figure 1 A non-woven fabric is used to wrap the reinforcing fiber winding layer 13 to form a tape layer 14, and then a steel wire is used to wrap the metal armor layer 15, and then a glass fiber is used to wrap the flame retardant layer 16, and finally a polyolefin sheath 17 is covered to obtain a fire-resistant cable 10.

[0122] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0123] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A fire-resistant cable, characterized in that: It is composed of: An insulated cable core, the insulated cable core comprising an insulated wire core and a semi-conductive buffer layer and a metal shielding layer sequentially coated on the surface of the insulated wire core; the insulated wire core comprising a conductor and a conductor shielding layer, an insulating layer and an insulating shielding layer sequentially coated on the conductor from the inside to the outside; the semi-conductive buffer layer is made of a semi-conductive terylene tape; An inorganic fireproof mud layer, which is coated on the outside of the insulating cable core and is in direct contact with the metal shielding layer; A reinforcing fiber winding layer, wherein the reinforcing fiber winding layer is coated on the surface of the inorganic fireproof mud layer, the reinforcing fibers in the reinforcing fiber winding layer are embedded in the inorganic fireproof mud layer, and the pitch between two adjacent reinforcing fibers in the reinforcing fiber winding layer is 50-100 mm; the embedding depth is greater than 2 mm; and The tape layer, metal armor layer, flame retardant layer and sheath are sequentially coated on the surface of the reinforcing fiber winding layer; the material of the metal shielding layer is copper or aluminum; the material of the metal armor layer is selected from at least one of aluminum and its alloys, copper and its alloys and steel; the material of the flame retardant layer is glass fiber; The step of coating the surface of the insulating core to form the semiconductive buffer layer comprises: Preheating the semiconductive buffer tape in sequence and coating it with silicone oil to obtain a pretreated semiconductive buffer tape; Covering the pretreated semi-conductive buffer tape on the surface of the insulating wire core to form the semi-conductive buffer layer; The preheating temperature is 30°C to 40°C.

2. The fire-resistant cable according to claim 1, characterized in that The material of the reinforcing fiber winding layer is aramid fiber.

3. The fire-resistant cable according to claim 1, characterized in that The insulating cable cores are coaxially arranged and are commonly covered by the inorganic fireproof mud layer, and the gaps formed by the plurality of insulating cable cores are filled with the inorganic fireproof mud in the inorganic fireproof mud layer.

4. The fire-resistant cable according to any one of claims 1 to 3, characterized in that: The melting point of the inorganic fireproof mud layer is higher than 1000°C.

5. The fire-resistant cable according to any one of claims 1 to 3, characterized in that: The material of the insulating layer is selected from at least one of cross-linked polyethylene and ethylene-propylene rubber.

6. The fire-resistant cable according to any one of claims 1 to 3, characterized in that: The conductor shielding layer and / or the insulating shielding layer is made of semi-conductive shielding material.

7. The fire-resistant cable according to any one of claims 1 to 3, characterized in that: The material of the wrapping layer is at least one of non-woven fabric, polypropylene and polyester.

8. The fire-resistant cable according to any one of claims 1 to 3, characterized in that: The material of the sheath is at least one of polyolefin plastic and rubber material.

9. The fire-resistant cable according to any one of claims 1 to 3, characterized in that: The material of the sheath is at least one of polyvinyl chloride plastic and polyethylene plastic.

10. A method for preparing a fire-resistant cable, characterized in that: The steps include: The surface of the insulating core is coated with a semi-conductive buffer layer and a metal shielding layer in sequence to obtain an insulating cable core; the insulating core comprises a conductor and a conductor shielding layer, an insulating layer and an insulating shielding layer sequentially coated on the conductor from the inside to the outside; the semi-conductive buffer layer is made of a semi-conductive terylene tape; Directly coating the surface of the metal shielding layer of the insulating cable core to form an inorganic fireproof mud layer; Reinforcing fibers are wound on the surface of the inorganic fireproof mud layer to form a reinforcing fiber winding layer, and the reinforcing fibers are embedded in the inorganic fireproof mud layer, and the pitch between two adjacent reinforcing fibers in the reinforcing fiber winding layer is 50-100 mm; the embedding depth is greater than 2 mm; The surface of the reinforcing fiber winding layer is coated in sequence to form a tape layer, a metal armor layer, a flame retardant layer and a sheath to obtain a fire-resistant cable; the material of the flame retardant layer is glass fiber; The step of coating the surface of the insulating core to form the semiconductive buffer layer comprises the following steps: Preheating the semiconductive buffer tape in sequence and coating it with silicone oil to obtain a pretreated semiconductive buffer tape; Covering the pretreated semi-conductive buffer tape on the surface of the insulating wire core to form the semi-conductive buffer layer; The preheating temperature is 30°C to 40°C.

11. A power transmission device, characterized in that: The power transmission equipment includes the fire-resistant cable as described in any one of claims 1 to 9.

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