Medium-voltage fire-resistant cable structure

Abstract

The invention relates to the technical field of cables, in particular to a medium-voltage fire-resistant cable structure. The double-layer cooling liquid channel is arranged and comprises the inner-layer cooling liquid channel and the outer-layer cooling liquid channel, the outer-layer cooling liquid channel is a water inlet channel, the inner-layer cooling liquid channel is a water outlet channel, temperature monitoring is carried out in combination with the built-in temperature measuring optical fiber, and then the water flow is controlled and adjusted. The temperature of the cable can be effectively controlled, and stable operation can be ensured under a full-load condition.

Description

Technical Field

[0001] The invention relates to the technical field of cables, and in particular to a medium-voltage fire-resistant cable structure. Background Art

[0002] With the development of China's economy, the voltage of the power supply system in the city has gradually increased. If high-rise and extra-large high-rise buildings use 0.6 / 1kV low-voltage power distribution, the cable consumption and workload are huge. In order to solve the actual power supply problem, high-rise and extra-large high-rise buildings have begun to use medium-voltage power supply. The main performance required of medium-voltage power supply cables is to ensure normal power supply for a period of time under combustion conditions. Fire-resistant cables are mostly used as emergency power supply circuits and are required to work normally during fires. In large commercial buildings, high-rise buildings or data centers, fire-resistant cables are used for important power transmission. Once a fire occurs in these places, if the cable does not work properly, it will lead to serious consequences, such as power outages affecting the operation of fire-fighting equipment and data loss. The fire-resistant cable water cooling circulation system can ensure that the cable can still work normally for a period of time when a fire occurs, providing protection for personnel evacuation, fire rescue and protection of important data.

[0003] At the same time, with the emergence of an increasing number of high-rise buildings and large-scale projects, low-voltage cables can no longer meet the line voltage drop requirements in fire protection circuit systems, and because the fire-resistant structure design of traditional low-voltage cables is to add an inorganic fire-resistant layer to the conductor, this structure can be used for cables with relatively low voltage levels, but medium-voltage cables have higher voltage levels, and the insulation materials are both fire-resistant and resistant to high-voltage fields. Current material technology has not yet made a breakthrough, and the electrical insulation performance of mixed materials such as mica can only meet the insulation requirements of low-voltage cables. The currently commonly used process structure is to add high thermal resistance materials to the structure outside the insulating core to achieve the fire resistance requirements, but it is limited by factors such as material consistency and stability, and the overall fire resistance performance is not very high.

[0004] In some industrial production processes, the power supply of certain key equipment cannot be interrupted, and there may be fire risks around these equipment, such as some reaction equipment in chemical plants. Therefore, there is a need for a cable that can not only solve the problem of power supply for the entire fire protection circuit, but also meet the corresponding fire protection needs. In the event of a fire, it can maintain the normal operation of the power system for a certain period of time, thus buying more precious time for personnel evacuation and fire rescue. Summary of the invention

[0005] The object of the present invention is to provide a medium voltage fire-resistant cable structure to solve the problem that the cable cannot operate normally in a burning high temperature environment.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A medium-voltage fire-resistant cable structure, which is a multi-layer cable structure, including a cable core and an outer sheath wrapping the cable core, the structure of the outer sheath including a coolant channel, in which coolant flows; the coolant channel structure includes an aluminum sheath and a waterproof layer, and the coolant flows in the gap between the aluminum sheath and the waterproof layer; the coolant channel is a double-layer coolant channel; the double-layer coolant channel structure includes a double-layer aluminum sheath and a double-layer waterproof layer; the double-layer aluminum sheaths are respectively a first aluminum sheath and a second aluminum sheath, and the double-layer waterproof layers are respectively a first waterproof layer and a second waterproof layer; the structure of the outer sheath is, from inside to outside, a first aluminum sheath, a first waterproof layer, a second aluminum sheath, a second waterproof layer, a second wrapping tape, and an outer protective layer; the cross-sectional shape of the cable is circular.

[0008] Preferably, the double-layer coolant channel is an inner coolant channel and an outer coolant channel respectively, the inner coolant channel structure is composed of a first waterproof layer and a first aluminum sheath, and the outer coolant channel structure is composed of a second waterproof layer and a second aluminum sheath; the outer coolant channel is a water inlet channel, and the inner coolant channel is a water outlet channel; the coolant is cooling water or cooling oil.

[0009] Preferably, the structure of the cable core includes a wire core and a first tape wrapping the wire core, and the structure of the wire core is, from inside to outside, a conductor, a conductor shielding layer, an insulating layer, an insulating shielding layer, and a metal shielding layer; the number of the wire cores is greater than or equal to 1; the structure of the wire core also includes an optical fiber unit, and the optical fiber unit is arranged on the outer layer of the metal shielding layer and is wrapped and fixed by the first tape.

[0010] Preferably, the number of wire cores is 1 or 3, and the conductor is a Class 2 annealed compressed copper conductor, which is formed by twisting and compressing multiple copper wires; the conductor shielding layer is a cross-linked semi-conductive shielding layer; the insulating layer is a 35KV cross-linked polyethylene insulating layer; the insulating shielding layer is a strippable cross-linked semi-conductive outer shielding layer; the metal shielding layer is a copper tape wrapping layer; the first wrapping tape is a ceramic fire-proof and fire-resistant composite tape; the isolation sleeve is a polyethylene waterproof isolation sleeve; the first aluminum sheath and the second aluminum sheath are corrugated aluminum sheaths; the first waterproof layer and the second waterproof layer are polyethylene waterproof isolation sleeves; the second wrapping tape is a low-smoke halogen-free and highly flame-retardant tape; the outer protective layer adopts a halogen-free, low-smoke, flame-retardant thermoplastic polyolefin sheath; the conductor shielding layer, the insulating layer, and the insulating shielding layer are tightly extruded by three-layer co-extrusion technology.

[0011] Preferably, the cable structure further includes a sealing device, a cable head fixing device and a water cooling circulation system connected to the coolant channel.

[0012] Preferably, the water cooling circulation system connected to the coolant channel includes a water inlet pipe, a water outlet pipe, a water pump, a water tank, a cooler, and a controller; the water inlet pipe and the water outlet pipe are both arranged at the same end of the cable; the water inlet pipe is connected to the outer coolant channel in the double-layer coolant channel to transport water to the cable, and the water outlet pipe is connected to the inner coolant channel in the double-layer coolant channel to transport the circulated water; one side of the water tank is connected to the water pump and the water inlet pipe to transport water to the cable, and the other side is connected to the water outlet pipe to receive the circulated water; the water tank is also connected to the cooler, and the cooler cools the water in the water tank; the controller is connected to the water pump, the cooler and the optical fiber unit.

[0013] Preferably, the sealing device seals the head and tail ends of the cable respectively, and the sealing position is a double-layer coolant channel; the seal of the head end of the cable is a multiple seal, including a waterproof filling rubber layer, a sealing ring reinforcement layer, and a heat shrink tube covering layer; the seal of the tail end of the cable is a double seal, including a rubber U-shaped sealing sleeve and a sealing ring.

[0014] Preferably, the sealing structure of the head end of the cable further includes an electrical flame retardant tape, and the electrical flame retardant tape is arranged on the outer layer of the heat shrink tube.

[0015] Preferably, the cable head fixing device includes a base, a disc, a tripod, and a cable head fixing piece. The bottom of the tripod is fixed to the base by bolts, the disc is fixed to the upper end of the tripod and the disc is parallel to the horizontal plane. The cable head fixing piece is welded to the upper plane of the disc and is perpendicular to the upper plane of the disc. The cable head fixing piece includes a ring and a plurality of support pieces. The ring is welded to the upper plane of the disc and is perpendicular to the upper plane of the disc. The support piece includes two telescopic fixing pieces and a self-locking plug rod. The telescopic fixing piece includes A fixing rod, a telescopic rod, a pressing block, and a pulling ring, wherein the pressing block is arranged at the bottom of the telescopic rod, and the pressing block can be brought into contact with and fixed to the cable by adjusting the telescopic rod; the self-locking plug rod passes through the upper parts of the two telescopic fixings, and when the self-locking plug rod is pressed, the telescopic rod can be pressed so that the pressing block at the bottom of the telescopic rod is pressed against the surface of the cable; the pulling ring is arranged at the upper part of the telescopic fixing, and is used to lock and fix the position of the self-locking plug rod. When the pulling ring is removed, the position of the self-locking plug rod is loosened, and then the pressing block at the bottom of the telescopic rod leaves the surface of the cable, and the position of the cable can be moved.

[0016] Preferably, the number of the water inlet pipes and the water outlet pipes is 2; the number of the supporting members is 4, and the water inlet pipes and the water outlet pipes are PE water pipes.

[0017] In summary, the medium-voltage fire-resistant cable structure of the present invention is provided with a double-layer coolant channel, which is an inner coolant channel and an outer coolant channel. The outer coolant channel is a water inlet channel, and the inner coolant channel is a water outlet channel. This setting is combined with the built-in temperature measuring optical fiber for temperature monitoring, and then controls and adjusts the water flow rate to achieve effective control of the cable temperature and ensure stable operation under full load conditions. In the cable cluster laying scenario, the collective temperature rise generated by multiple circuits may affect the current carrying capacity of the cable, but this cable structure effectively alleviates this problem with its excellent heat dissipation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the medium voltage fire-resistant cable of the present invention;

[0019] Figure 2 It is another structural schematic diagram of the medium voltage fire-resistant cable of the present invention;

[0020] Figure 3 It is a schematic diagram of the cross-sectional structure of the medium voltage fire-resistant cable of the present invention;

[0021] Figure 4 It is a schematic diagram of the three-dimensional structure of the cable head fixing device of the present invention when fixing the cable;

[0022] Figure 5 It is a schematic diagram of the three-dimensional structure of the cable head fixing member of the present invention;

[0023] Explanation of the reference numerals: 1-conductor; 2-conductor shielding layer; 3-insulating layer; 4-insulating shielding layer; 5-metal shielding layer; 6-optical fiber unit; 7-first wrapping tape; 8-isolating sleeve; 9-first aluminum sheath; 10-first waterproof layer; 11-second aluminum sheath; 12-second waterproof layer; 13-second wrapping tape; 14-outer protective layer; 101-sealing device; 201-water inlet pipe; 202-water outlet pipe; 301-ring; 302-base; 303-self-locking plug rod; 304-telescopic fixing piece; 305-disc; 306-tripod; 307-fixing rod; 308-telescopic rod; 309-pressing block; 310-pull ring; 401-water cooling circulation system; 501-controller. DETAILED DESCRIPTION

[0024] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation modes, but it does not constitute a limitation on the protection scope of the present invention.

[0025] The rated current carrying capacity of a power cable is determined by the maximum allowable operating temperature of the cable insulation, that is, the maximum allowable temperature of the outer surface of the cable core. When the cable is working, the temperature of the upper surface of its core is not only closely related to the load current carried by the cable, but also to the lateral heat transfer characteristics in the cable and the ambient temperature when the cable is running. Therefore, the present invention provides a medium-voltage fire-resistant cable structure, which is intended to effectively improve the fire resistance and current carrying capacity of the cable, while ensuring the safe and stable operation of the cable under extreme conditions, which is of great significance for improving the reliability and safety of the power system.

[0026] The present invention is applied to the power supply cables of these devices, which can improve the reliability of power supply and reduce production accidents and economic losses caused by cable failures. For example, there are a large number of cables connecting various devices in a substation, and the normal operation of the cables is crucial to the stable power supply of the substation.

[0027] See also Figure 1-Figure 5 The present invention provides a medium-voltage fire-resistant cable structure, which is a multi-layer cable structure, including a cable core and an outer sheath wrapping the cable core, the structure of the outer sheath including a coolant channel, in which coolant flows; the coolant channel structure includes an aluminum sheath and a waterproof layer, and the coolant flows in the gap between the aluminum sheath and the waterproof layer; the coolant channel is a double-layer coolant channel; the double-layer coolant channel structure includes a double-layer aluminum sheath and a double-layer waterproof layer; the double-layer aluminum sheath is respectively a first aluminum sheath 9 and a second aluminum sheath 11, and the double-layer waterproof layer is respectively a first waterproof layer 10 and a second waterproof layer 12; the structure of the outer sheath is, from inside to outside, a first aluminum sheath 9, a first waterproof layer 10, a second aluminum sheath 11, a second waterproof layer 12, a second wrapping tape 13, and an outer protective layer 14; the cross-sectional shape of the cable is circular.

[0028] As a preferred embodiment of the present invention, the double-layer coolant channel is respectively an inner coolant channel and an outer coolant channel, the inner coolant channel structure is composed of a first waterproof layer 10 and a first aluminum sheath 9, and the outer coolant channel structure is composed of a second waterproof layer 12 and a second aluminum sheath 11; the outer coolant channel is a water inlet channel, and the inner coolant channel is a water outlet channel; the coolant is cooling water or cooling oil.

[0029] The outer coolant channel in the double-layer coolant channel is the water inlet channel (i.e., it flows between the second waterproof layer 12 and the second aluminum sheath 11), and the inner coolant channel is the water outlet channel; then the capacity of the outer coolant channel is greater than that of the inner coolant channel, and the capacity of the water inlet channel is greater than that of the water outlet channel, which is more conducive to the circulation of the coolant.

[0030] Specifically, the structure of the cable core includes a wire core and a first tape 7 that wraps the wire core. The structure of the wire core is, from inside to outside, a conductor 1, a conductor shielding layer 2, an insulating layer 3, an insulating shielding layer 4, and a metal shielding layer 5; the number of wire cores is greater than or equal to 1; the structure of the wire core also includes an optical fiber unit 6, which is arranged on the outer layer of the metal shielding layer 5 and is wrapped and fixed by the first tape 7.

[0031] The present invention is also provided with a cable optical fiber temperature sensing system, which is based on the optical time domain reflection principle of optical fiber and the backward Raman scattering temperature effect of optical fiber. When the laser pulse is transmitted in the optical fiber, scattering will occur due to the microscopic inhomogeneity of the refractive index in the optical fiber. By measuring the intensity of these scattered lights, the temperature of each part of the optical fiber can be calculated. By detecting the information of the reflected light in the optical fiber, the temperature signal generated by the conductor 1 distributed along the optical fiber during the operation of the cable can be obtained.

[0032] Fiber optic temperature measurement is a truly linear monitoring system that can monitor the real-time status of the temperature of conductor 1 when the cable is running. However, the temperature-sensing cable can only report the status of the entire area, and cannot be fixed at a fixed point or temperature, which is not conducive to timely prevention and control. Combining the water cooling circulation system 401 with the cable fiber optic temperature sensing is to use the water cooling circulation system 401 to cool the cable fiber optic temperature sensing cable to prevent its performance from being damaged or malfunctioning in a high temperature environment. During the operation of the cable, the cable conductor 1 will generate heat, and the fiber optic temperature sensing system will monitor the temperature. When the temperature of the conductor 1 is too high, the water cooling circulation system 401 will start to cool down the relevant cables to ensure the normal operation of the entire system. The fiber optic temperature sensing structure can monitor the temperature of the entire system. Through the distributed temperature measurement characteristics of the optical fiber, the temperature conditions of each location can be accurately known, so as to promptly detect overheating or local temperature abnormalities that may occur in the cooling circulation system. This cable structure monitors the return water temperature and uses the built-in temperature measuring optical fiber for temperature monitoring, and then controls and adjusts the water flow to achieve effective control of the cable temperature.

[0033] The water cooling circulation system 401 can cool the equipment in the optical fiber temperature sensing structure to ensure that the optical fiber temperature sensing structure can work normally and stably, and prevent problems such as equipment failure due to excessive temperature affecting the accuracy of temperature measurement.

[0034] Specifically, the cable structure further includes a sealing device 101, a cable head fixing device and a water cooling circulation system 401 connected to the cooling liquid channel.

[0035] Specifically, the water cooling circulation system 401 connected to the coolant channel includes an inlet pipe 201, an outlet pipe 202, a water pump, a water tank, a cooler, and a controller 501; the inlet pipe 201 and the outlet pipe 202 are both arranged at the same end of the cable; the inlet pipe 201 is connected to the outer coolant channel in the double-layer coolant channel to transport water to the cable, and the outlet pipe 202 is connected to the inner coolant channel in the double-layer coolant channel to transport the circulated water; one side of the water tank is connected to the water pump and the inlet pipe 201 to transport water to the cable, and the other side is connected to the outlet pipe 202 to receive the circulated water; the water tank is also connected to the cooler, and the cooler cools the water in the water tank; the controller 501 is connected to the water pump, the cooler and the optical fiber unit 6.

[0036] The water cooling circulation system 401 realizes cold water circulation through two water inlet pipes 201 and two water outlet pipes 202. The circulating cold water takes away the heat and keeps the cable within a suitable operating temperature range, thereby ensuring the normal operation of the medium voltage cable and reducing the risk of failure due to overheating.

[0037] The components of the entire water cooling circulation system 401 include a water inlet pipe 201 , a water outlet pipe 202 , a water pump, a water tank, a cooler, and a controller 501 .

[0038] Water inlet pipe 201 and water outlet pipe 202 are connected to the water tank to guide the flow of cooling water.

[0039] Water pump: installed on the outer wall of one side of the water tank, responsible for extracting the cooling water in the water tank and transporting it to the cable cooling pipe and other places where cooling water is needed to ensure the circulation of cooling water. In the circulating cooling water system used in cable production, the water pump is one of the power sources for the entire cooling water cycle to ensure the normal operation of the system. According to the heat generated by the cable and the cooling requirements of the system, select a circulating water pump with appropriate flow and head. If the cable generates a lot of heat, a water pump with a larger flow rate is required to ensure that the cooling water can take away the heat in time.

[0040] Water tank: used to store cooling water. One side of the outer wall is connected to a water pump and a water inlet pipe 201, and the other side of the outer wall is connected to the cooler. It plays the role of buffering and storing cooling water to ensure that the system has sufficient cooling water supply. Due to the importance of medium-voltage cables, the water quality of the cooling circulation system needs to be strictly controlled. Impurities in the water may form scale in the pipes, affect the heat exchange efficiency, and may even cause electrical failures. Install water purification equipment such as filters and ion exchangers to remove impurities and ions in the water. At the same time, set up a water quality monitoring device to monitor the pH, conductivity and other parameters of the water quality in real time so that timely adjustments can be made.

[0041] Chiller: Chiller provides cooling effect to the cooling water.

[0042] Controller 501: Controller 501 is used to adjust the operation of the water pump, the cooler and the optical fiber unit 6.

[0043] Working principle:

[0044] Medium-voltage fire-resistant cables generate heat during operation. The heat in the cable is transferred to the aluminum sheath layer by layer. Since there is cooling water in the aluminum sheath, the temperature of the aluminum sheath is lower than the temperature of other parts of the cable. According to the principle of heat conduction, heat is transferred from the high temperature to the aluminum sheath, and then the aluminum sheath transfers the heat to the cooling water.

[0045] Start the water cooling circulation system 401, and the circulating water pump is started first. At this time, the cooling water in the cooling water tank is pumped into the gap between the double-layer aluminum sheath and the waterproof layer. The cooling water flows in the gap between the aluminum sheath and the waterproof layer. The temperature of the cooling water increases after absorbing the heat of the cable. At this time, the high-temperature cooling water flows out from the water channel and enters the cooling water tank or heat exchanger through the outlet pipe 202 for cooling. The outflowing cooling water can be cooled to the initial temperature in the cooling water tank by air cooling or water cooling, and then pumped into the double-layer aluminum sheath by the water pump again to form a cycle.

[0046] Specifically, the sealing device 101 seals the head and tail ends of the cable respectively, and the sealing position is the double-layer coolant channel; the sealing of the head end of the cable is a multiple seal, including a waterproof filling rubber layer, a sealing ring reinforcement layer, and a heat shrink tube covering layer; the sealing of the tail end of the cable is a double seal, including a rubber U-shaped sealing sleeve and a sealing ring. Specifically, the sealing structure of the head end of the cable also includes an electrical flame retardant tape, which is arranged on the outer layer of the heat shrink tube.

[0047] The coolant channel at the head end of the cable is sealed separately. When sealing, waterproof filling glue is first used, and a sealing ring is used to reinforce the seal. At the same time, the position of the water inlet pipe and the water outlet pipe must be reserved for sealing. After the water inlet pipe and the water outlet pipe are installed, they are covered with heat shrink tubes and heated to shrink them to further enhance the sealing effect. In order to improve the waterproof performance, a layer of electrical flame retardant tape or other types of protective layers can be added outside the heat shrink tube to ensure the sealing of the water inlet pipe and the water outlet pipe after installation.

[0048] When the coolant channel at the tail end of the cable is sealed, the double-layer aluminum sheath and the double-layer waterproof layer form an interconnected circulation channel. A rubber-type U-shaped sealing sleeve is used to seal the first aluminum sheath 9, the second aluminum sheath 11, the first waterproof layer 10 and the second waterproof layer 12. The U-shaped sealing sleeve is reinforced and sealed with a sealing ring to prevent coolant leakage.

[0049] Specifically, the cable head fixing device includes a base 302, a disc 305, a tripod 306, and a cable head fixing piece. The bottom of the tripod 306 is fixed to the base 302 by bolts, the disc 305 is fixed to the upper end of the tripod 306 and the disc 305 is parallel to the horizontal plane. The cable head fixing piece is welded to the upper plane of the disc 305 and is perpendicular to the upper plane of the disc 305; the cable head fixing piece includes a ring 301 and a plurality of support pieces. The ring 301 is welded to the upper plane of the disc 305 and is perpendicular to the upper plane of the disc 305; the support piece includes two telescopic fixing pieces 304 and a self-locking plug rod 303. The telescopic fixing piece 304 includes a fixing rod 307, a telescopic rod 308, a pressing block 309, and a pulling ring 310. The pressing block 309 is arranged at the bottom of the telescopic rod 308. The telescopic rod 308 can be adjusted to make the pressing block 309 contact and fix the cable; the self-locking plug rod 303 passes through the upper part of the two telescopic fixing members 304. When the self-locking plug rod 303 is pressed, the telescopic rod 308 can be pressed so that the pressing block 309 at the bottom of the telescopic rod 308 is pressed against the surface of the cable; the pulling ring 310 is arranged at the upper part of the telescopic fixing member 304, and is used to lock and fix the position of the self-locking plug rod 303. When the pulling ring 310 is removed, the position of the self-locking plug rod 303 is loosened, and then the pressing block 309 at the bottom of the telescopic rod 308 leaves the cable surface, and the cable position can be moved.

[0050] The cable head needs to be connected to the water cooling circulation system 401 and the water inlet pipe 201 and the water outlet pipe 202, etc. Therefore, this part of the cable needs to be fixed. The most appropriate fixing method should be selected to ensure that the cable is firmly fixed without shaking or loosening, and to ensure the durability and reliability of the fixing material. Professional cable fixing fixtures are preferred to meet higher safety requirements.

[0051] Therefore, the present invention is provided with a cable head fixing device, including a quadrilateral base 302, a disc 305, a tripod 306, and a cable head fixing member; the cable head fixing member includes a ring 301 and a plurality of supporting members; the supporting member includes two telescopic fixing members 304 and a self-locking plug rod 303, and the telescopic fixing member 304 includes a fixing rod 307, a telescopic rod 308, a pressing block 309, and a pull ring 310. At the same time, the cable head fixing device of the present invention is made of metal material, which has the characteristics of elasticity and corrosion resistance.

[0052] The self-locking plug rod 303 is mainly used to fix the telescopic rod 308. After the self-locking rod is inserted into a certain position, it interacts with the teeth or grooves to fix it, that is, it is self-locking; after self-locking, the telescopic fixing part 304 is stable, and the cable will not loosen due to vibration, external force and other factors, thereby ensuring the continuity and stability of power transmission or signal transmission.

[0053] The support member is made of metal material and is fixed in position by welding with the ring 301, providing an upward or downward supporting force to prevent the cable from moving and being pulled by external forces, thereby further improving the stability of the device.

[0054] The ring 301 is fixed on the disc 305. The cable head is passed through the ring 301 and the self-locking rod 303 is pressed down. Then, the telescopic rod 308 in the support can be adjusted. A pressing block 309 is provided under the telescopic rod 308, so that the pressing block 309 contacts and fixes the cable, and is pressed and fixed on the surface of the cable. When the self-locking rod 303 is pressed down, it interacts with the card slot of the pull ring 310 on the support to stabilize the cable head and prevent the cable from moving. If the position of the cable head needs to be moved, the pull ring 310 on the support is pulled, and the self-locking rod 303 is separated from the card slot, so that the pressing block 309 at the bottom of the telescopic rod 308 leaves the cable surface, and the cable can be moved.

[0055] Specifically, the number of the water inlet pipe 201 and the water outlet pipe 202 is 2; the number of the supporting members is 4, and the water inlet pipe 201 and the water outlet pipe 202 are PE water pipes.

[0056] The water inlet pipe 201 and the water outlet pipe 202 are made of PE water pipes, which have the characteristics of high strength, corrosion resistance, and non-toxicity. It is ensured that when the cooling circulation system is running under a certain pressure, the water inlet pipe 201 and the water outlet pipe 202 have corresponding pressure without rupture and deformation. The reasonable design of the water inlet pipe 201 and the water outlet pipe 202 helps to maintain the pressure stability of the entire water cooling circulation system 401. The stable pressure can ensure that the water flows at a suitable flow rate in the system, ensure the uniformity of the cooling effect, and thus ensure the service life of the water pipe and the stability of the system.

[0057] Specifically, the cable structure with the number of cores being 1 is shown in Figure 2 , the cable structure with 3 cores is shown in Figure 3 .

[0058] The conductor 1 adopts the second type annealed compacted copper conductor, which is formed by twisting and compacting multiple copper wires; the conductor shielding layer 2 is a cross-linked semi-conductive shielding layer; the insulating layer 3 is a 35KV cross-linked polyethylene insulating layer; the insulating shielding layer 4 is a strippable cross-linked semi-conductive outer shielding layer; the metal shielding layer 5 is a copper tape wrapping layer; the first wrapping tape 7 is a ceramic fire-proof and fire-resistant composite tape; the isolation sleeve 8 is a polyethylene waterproof isolation sleeve; the first aluminum sheath 9 and the second aluminum sheath 11 are aluminum sheaths with embossing treatment; the first waterproof layer 10 and the second waterproof layer 12 are polyethylene waterproof isolation sleeves; the second wrapping tape 13 is a low-smoke halogen-free and highly flame-retardant tape; the outer protective layer 14 adopts a halogen-free, low-smoke, flame-retardant thermoplastic polyolefin sheath; the conductor shielding layer 2, the insulating layer 3, and the insulating shielding layer 4 are tightly extruded by three-layer co-extrusion technology.

[0059] The specific contents and technical effects of the inner and outer layers of the cable structure of the present invention are as follows:

[0060] 1. Conductor

[0061] The second type annealed compacted copper conductor is made of multiple strands of copper wire twisted and compacted. The compacted copper conductor has excellent conductivity, mechanical strength and production efficiency, which not only improves the efficiency and safety of power transmission, but also reduces the cost of long-term operation.

[0062] 2. Conductor shielding layer

[0063] The conductor shield uses cross-linked semi-conductive shielding material, which is tightly wrapped in the insulation layer through three-layer co-extrusion technology. It forms equipotential with the cable conductor and metal shielding layer respectively, and forms a smooth interface between the insulation and the high voltage potential and the ground potential, which plays a role in eliminating burrs or protrusions on the surface of the metal conductor, uniforming the interface electric field distribution, suppressing excessive local field strength, and preventing local discharge, so as to improve the electrical strength of the cable and improve the service life of the cable.

[0064] 3. Insulation layer

[0065] 35KV cross-linked polyethylene insulation material is used. The peroxide cross-linking method is used to change the polyethylene molecule from a linear molecular structure to a three-dimensional network structure, and from a thermoplastic material to a thermosetting material, which significantly improves the current carrying capacity of the cable. The insulation material has heat resistance, insulation performance, mechanical properties, chemical resistance, etc.

[0066] 4. Insulation shielding layer

[0067] The strippable cross-linked semi-conductive outer shield is tightly wrapped around the insulation layer through three-layer co-extrusion technology. It has good contact with the shielded insulation layer and forms an equipotential with the metal shielding layer, thus avoiding partial discharge between the insulation layer and the sheath.

[0068] 5. Metal shielding layer

[0069] A layer of copper tape is used to wrap the metal shield to prevent axial surface discharge. It has excellent lightning protection characteristics. In the event of a short circuit, the metal tape can serve as a loop for the short-circuit fault current.

[0070] 6. Fiber Optic Unit

[0071] A set of optical fiber units is used for optical signal transmission in the system to realize the intelligent functions of online monitoring and risk identification.

[0072] 7. First packing belt

[0073] Ceramic fire-resistant composite tape is used during cabling. The ceramic fire-resistant composite tape is quickly burned into a ceramic-like hard and complete shell at a temperature of 590℃~2950℃. The hard shell armor after burning plays a good protective role for the line and ensures the smooth flow of the line in the event of fire.

[0074] 8. Isolation sleeve

[0075] A polyethylene waterproof isolation sleeve is used. The polyethylene waterproof isolation sleeve is made of polyethylene (PE) plastic and has excellent waterproof performance. It can effectively prevent water penetration. It also has isolation, puncture resistance and moisture-proof functions, and has certain chemical corrosion resistance and aging resistance.

[0076] 9. The first aluminum sheath

[0077] The aluminum strip is welded and then corrugated. The aluminum sheath adopts advanced argon arc welding technology and is equipped with online detection devices such as ultrasonic wave to ensure the sealing of the welding.

[0078] 10. The first waterproof layer

[0079] A polyethylene waterproof isolation sleeve is used. The polyethylene waterproof isolation sleeve is made of polyethylene (PE) plastic and has excellent waterproof performance. It can effectively prevent water penetration. It also has isolation, puncture resistance and moisture-proof functions, and has certain chemical corrosion resistance and aging resistance.

[0080] 11. Second aluminum sheath

[0081] The aluminum strip is welded and then corrugated. The aluminum sheath adopts advanced argon arc welding technology and is equipped with online detection devices such as ultrasonic wave to ensure the sealing of the welding.

[0082] 12. Second waterproof layer

[0083] A polyethylene waterproof isolation sleeve is used. The polyethylene waterproof isolation sleeve is made of polyethylene (PE) plastic and has excellent waterproof performance. It can effectively prevent water penetration. It also has isolation, puncture resistance and moisture-proof functions, and has certain chemical corrosion resistance and aging resistance.

[0084] 13. Second packing belt

[0085] The use of low-smoke, halogen-free and highly flame-retardant tape effectively plays a flame-retardant role.

[0086] 14. Outer protective layer

[0087] The sheath material is halogen-free, low-smoke, flame-retardant thermoplastic polyolefin. The sheath material has excellent flame retardant effect, good self-extinguishing property, low smoke release, low toxicity, and anti-rat and ant performance.

[0088] The present invention is a medium-voltage fire-resistant cable, and also a cooling system specifically used for medium-voltage fire-resistant cables. The applicable voltage range includes 3.6 / 6, 6 / 10, 8.7 / 15, 12 / 20, 18 / 30, 26 / 35, and 27.5 / 48kV. The principle is based on the circulation of water to take away the heat generated during the operation of the cable, thereby maintaining the cable within a suitable operating temperature range. The water cooling circulation system is combined with the cable optical fiber temperature sensing, and the water cooling circulation system is used to cool the cable optical fiber temperature sensing cable to prevent its performance from being damaged or malfunctioning in a high temperature environment. Heat is generated during the operation of the cable, and the optical fiber temperature sensing system monitors the temperature. When the temperature is too high, the water cooling circulation system starts to cool the relevant cables to ensure the normal operation of the entire system. The details are as follows:

[0089] 1. Real-time monitoring

[0090] A cable optical fiber temperature sensing water cooling circulation system is set up, which is an advanced temperature monitoring and control system that combines optical fiber sensing technology and a water cooling circulation system to ensure the stable operation of the power system and the safety of the cable. The main features of the system include real-time monitoring, high-precision measurement, strong anti-interference ability, multi-point measurement, high sensitivity, high stability, etc. It can obtain the temperature change of the cable in a short time and display and record the temperature data in real time.

[0091] 2. Water cooling

[0092] The temperature is monitored by a fiber optic temperature sensing system. When the temperature is too high, the water cooling circulation system starts to cool the relevant cables. The pipes with cooling water will transmit the cooling water to the cables that need cooling along the set transmission route. The cooling water absorbs the heat generated by the cables when flowing through them, and then flows back to the water tank for recirculation. This continuous cycle will continuously cool the cables and improve their service life and operating efficiency.

[0093] 3. Water cycle

[0094] The circulating water pump drives the cooling water to circulate in the cooling pipe. The cooling water is forced to flow through the pipe to the water cooling channel in the cable by the water pump pressure, and then returns to the cooling water source for cooling. The cooled water is pumped to the cooling pipe around the cable again, and the cycle is repeated to continuously remove the heat generated by the cable and ensure that the temperature of the cable remains within the appropriate range.

[0095] 4. Waterproof performance

[0096] The unique waterproof structure design, metal sheath and waterproof layer are combined through specific process design to make the cable have high waterproof performance, ensuring that the cable can maintain good electrical performance and water tightness in various environments, thereby ensuring the stable operation of the power system.

[0097] 5. Good safety and reliability

[0098] The medium voltage fire-resistant cable water cooling circulation system effectively ensures the safe operation of the medium voltage fire-resistant cable through the cooling process, circulating water system, temperature monitoring, efficient cooling capacity and other characteristics.

[0099] The present invention is tested as follows:

[0100] 1. Test equipment

[0101] 1.1 Test environment

[0102] The test should be carried out in a 3 The test shall be carried out in a suitable cabinet with facilities to remove any harmful gases produced by combustion and sufficient ventilation to maintain the flame during the test, but forced ventilation shall not be used. At the beginning of each test, the cabinet and test device shall be maintained between 10℃ and 40℃. The ventilation and barrier conditions in the cabinet shall be the same during verification and testing.

[0103] 1.2 Fire Source

[0104] 1.2.1 The fire source shall be a ribbon type propane gas blowtorch with a nozzle of nominal length 500mm and a venturi mixer. The nominal width of the nozzle shall be 15m. The nozzle shall have three rows of staggered holes with nominal diameter of 1.32m and center distance of 3.2mm. In addition, one row of small holes on each side of the nozzle is allowed as a guide hole to maintain the burning of the flame.

[0105] 1.2.2 Mass flow meters should be used because they can accurately control the rate at which gas and air flow into the burner.

[0106] For this test, the dew point of the air should not be above 0°C.

[0107] Under reference conditions of 1 bar and 20°C, the following flow rates shall be used for this test:

[0108] ——Air: (80±5)L / min;

[0109] ——Propane: (5±0.25)L / min.

[0110] 1.2.3 The blowtorch and control system should be verified according to the procedures specified in Appendix A of GB / T19216.11.

[0111] 2. Sample preparation

[0112] Take a finished cable with a length of not less than 4500mm as a sample and peel off the sheath at both ends.

[0113] At each end of the cable, the insulation shield (metal shield and semi-conductive shield) of the cable core should be stripped more than 100mm, and each conductor should be properly processed for electrical connection, and the exposed conductors should be separated to ensure a safe electrical gap when the test voltage is applied.

[0114] A rubber intercommunication U-shaped sealing sleeve is used at one end of the cable to seal the first aluminum sheath layer, the second aluminum sheath layer, the first waterproof layer and the second waterproof layer.

[0115] Separate the coolant channel at the other end of the cable and seal it. When sealing, first use waterproof filling glue and use sealing ring to reinforce the seal. At the same time, leave space for the water inlet pipe and the water outlet pipe, and connect them to the water pump. After installing the water inlet pipe and the water outlet pipe, cover them with heat shrink tube and heat them to shrink them.

[0116] 3. Leakage current detection device

[0117] The test transformer should include a leakage current detection device with sufficient range to monitor the leakage current of the cable during the test.

[0118] 4. Test transformer

[0119] During the test, the voltage waveform, allowable deviation and test voltage measurement of the test transformer that applies power frequency voltage to the sample shall meet the requirements of Article 4 of GB / T3048.8-2007.

[0120] 5. Test steps

[0121] 5.1 Install the sample on the sample holder and fix it. Adjust the blowtorch to the correct position relative to the sample so that it meets the x and y values ​​determined in the verification step of Appendix A of GB / T19216.11.

[0122] 5.2 At the end of the sample close to the transformer, each phase conductor should be connected to the transformer output terminal, and the metal shield of each insulated core should be connected to the grounding terminal of the test transformer.

[0123] 5.3 All conductors at the other end of the sample away from the transformer are left hanging.

[0124] 5.4 Turn on the water pump and circulate cooling water in the aluminum sleeve.

[0125] 5.5 Light the blowtorch and adjust the propane and air flows to the values ​​obtained in the verification step.

[0126] 5.6 Turn on the power switch and adjust the voltage to the rated voltage of the cable, that is, the test voltage between the conductor and the shield should be equal to the rated voltage U0 of the cable.

[0127] 5.7 The test should be carried out for the fire supply time given in 6.1, after which the flame should be extinguished, but the cable sample should continue to be powered for 15 minutes. That is, the total test time should be the fire supply time plus the 15-minute cooling time.

[0128] 6 Performance requirements

[0129] 6.1 Fire supply time

[0130] The fire supply time is 90 minutes.

[0131] 6.2 Qualification criteria

[0132] According to the test procedures, the cable has the characteristics of maintaining the integrity of the line, as long as during the test:

[0133] -- The sample is applied with the specified cable rated voltage U0 for the entire test duration without breakdown (any false breakdown phenomenon should be eliminated, such as flashover discharge on the test terminal surface, etc. After the false breakdown phenomenon is eliminated, the test is continued to the specified time);

[0134] ——One hour after the end of the test, check the integrity of the sample. While maintaining the original test state, apply a test voltage of 3.5U0 to the sample for 15 minutes without breakdown (any false breakdown phenomenon should be excluded, such as flashover discharge on the test terminal surface or internal discharge, etc.).

[0135] 7. Repeat the test steps

[0136] If the test fails, two more specimens shall be taken for testing according to the requirements of the relevant standards. If both specimens meet the test requirements, the test shall be considered qualified.

[0137] Test results

[0138] The test lines were subjected to combustion tests. The specific model specifications of the embodiments and comparative examples are shown in Table 1, and the specific conditions of the combustion performance indicators are shown in Table 2. The cable structure of embodiment 1 is shown in the attached figure Figure 2 , Example 2 Cable structure see attached figure Figure 1 .

[0139] Table 1 Test line model specifications

[0140]

[0141] Table 2 Specific conditions of combustion performance indicators

[0142]

[0143]

[0144] Judging from the results of this test example, the performance indicators of the medium-voltage fire-resistant cable product of the present invention are compared with the combustion performance indicators of other cables. Under the same test items, the cable of the present invention does not break down after 90 minutes of fire supply, while similar cables in the prior art use double-layer steel belt armor, fail the combustion test, and are broken down before 90 minutes of fire supply. The medium-voltage fire-resistant cable of the present invention has excellent fire resistance, excellent fire resistance, and can provide effective safety protection under high temperature conditions. In the event of a fire, its unique structural design provides better flame retardant and fire resistance. In addition, the cable further improves its performance in high temperature environments through a built-in cooling system, thereby better protecting the stable operation of the power system in a fire. This makes the medium-voltage fire-resistant cable an ideal choice for various occasions requiring a high degree of fire safety, and has broad application prospects.

[0145] At the same time, since the medium-voltage fire-resistant cable of the present invention does not break down after 90 minutes of fire supply and can still be used normally, after a long period of burning, the burned outer layer of the cable can be re-laid and can continue to be used normally.

[0146] The above 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 those of ordinary skill in the art, 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 medium voltage fire-resistant cable structure, which is a multi-layer cable structure, comprising a cable core and an outer sheath wrapping the cable core, characterized in that: The structure of the outer sheath includes a coolant channel, in which coolant flows; The coolant channel structure comprises an aluminum jacket and a water-insulating layer, and the coolant flows in the gap between the aluminum jacket and the water-insulating layer; The coolant channel is a double-layer coolant channel; the double-layer coolant channel structure includes a double-layer aluminum jacket and a double-layer water-proof layer; The double-layer aluminum sheaths are respectively the first aluminum sheath and the second aluminum sheath, and the double-layer waterproof layers are respectively the first waterproof layer and the second waterproof layer; The structure of the outer sheath from inside to outside is the first aluminum sheath, the first waterproof layer, the second aluminum sheath, the second waterproof layer, the second wrapping tape, and the outer protective layer; The cross-sectional shape of the cable is circular.

2. A medium voltage fire-resistant cable structure according to claim 1, characterized in that: The double-layer coolant channel is respectively an inner coolant channel and an outer coolant channel, the inner coolant channel structure is composed of a first waterproof layer and a first aluminum jacket, and the outer coolant channel structure is composed of a second waterproof layer and a second aluminum jacket; the outer coolant channel is a water inlet channel, and the inner coolant channel is a water outlet channel; the coolant is cooling water or cooling oil.

3. A medium voltage fire-resistant cable structure according to claim 2, characterized in that: The structure of the cable core includes a wire core and a first tape wrapping the wire core, and the structure of the wire core is, from inside to outside, a conductor, a conductor shielding layer, an insulating layer, an insulating shielding layer, and a metal shielding layer; the number of the wire cores is greater than or equal to 1; the structure of the wire core also includes an optical fiber unit, and the optical fiber unit is arranged on the outer layer of the metal shielding layer and is wrapped and fixed by the first tape.

4. A medium voltage fire-resistant cable structure according to claim 3, characterized in that: The number of wire cores is 1 or 3, and the conductor is a Class 2 annealed compressed copper conductor, which is formed by twisting and compressing multiple copper wires; the conductor shielding layer is a cross-linked semi-conductive shielding layer; the insulating layer is a 35KV cross-linked polyethylene insulating layer; the insulating shielding layer is a strippable cross-linked semi-conductive outer shielding layer; the metal shielding layer is a copper tape wrapping layer; the first wrapping tape is a ceramic fire-proof and fire-resistant composite tape; the isolation sleeve is a polyethylene waterproof isolation sleeve; the first aluminum sheath and the second aluminum sheath are corrugated aluminum sheaths; the first waterproof layer and the second waterproof layer are polyethylene waterproof isolation sleeves; the second wrapping tape is a low-smoke halogen-free and highly flame-retardant tape; the outer protective layer adopts a halogen-free, low-smoke, flame-retardant thermoplastic polyolefin sheath; the conductor shielding layer, the insulating layer, and the insulating shielding layer are tightly extruded by three-layer co-extrusion technology.

5. A medium voltage fire-resistant cable structure according to any one of claims 1 to 4, characterized in that: The cable structure also includes a sealing device, a cable head fixing device and a water cooling circulation system connected to the cooling liquid channel.

6. A medium voltage fire-resistant cable structure according to claim 5, characterized in that: The water cooling circulation system connected to the coolant channel includes a water inlet pipe, a water outlet pipe, a water pump, a water tank, a cooler, and a controller; the water inlet pipe and the water outlet pipe are both arranged at the same end of the cable; the water inlet pipe is connected to the outer coolant channel in the double-layer coolant channel to transport water to the cable, and the water outlet pipe is connected to the inner coolant channel in the double-layer coolant channel to transport the circulated water; one side of the water tank is connected to the water pump and the water inlet pipe to transport water to the cable, and the other side is connected to the water outlet pipe to receive the circulated water; the water tank is also connected to the cooler, and the cooler cools the water in the water tank; the controller is connected to the water pump, the cooler and the optical fiber unit.

7. A medium voltage fire-resistant cable structure according to claim 5, characterized in that: The sealing device seals the head and tail ends of the cable respectively, and the sealing position is a double-layer coolant channel; the sealing of the head end of the cable is a multiple seal, including a waterproof filling rubber layer, a sealing ring reinforcement layer, and a heat shrink tube covering layer; the sealing of the tail end of the cable is a double seal, including a rubber U-shaped sealing sleeve and a sealing ring.

8. A medium voltage fire-resistant cable structure according to claim 7, characterized in that: The sealing structure of the head end of the cable also includes an electrical flame retardant tape, and the electrical flame retardant tape is arranged on the outer layer of the heat shrink tube.

9. A medium voltage fire-resistant cable structure according to claim 6, characterized in that: The cable head fixing device includes a base, a disc, a tripod, and a cable head fixing piece. The bottom of the tripod is fixed to the base by bolts, the disc is fixed to the upper end of the tripod and the disc is parallel to the horizontal plane. The cable head fixing piece is welded to the upper plane of the disc and is perpendicular to the upper plane of the disc. The cable head fixing piece includes a ring and a plurality of support pieces. The ring is welded to the upper plane of the disc and is perpendicular to the upper plane of the disc. The support piece includes two telescopic fixing pieces and a self-locking plug rod. The telescopic fixing piece includes a fixing The invention relates to a rod, a telescopic rod, a pressing block and a pulling ring, wherein the pressing block is arranged at the bottom of the telescopic rod, and the pressing block can be contacted and fixed to the cable by adjusting the telescopic rod; the self-locking plug rod passes through the upper part of two telescopic fixings, and when the self-locking plug rod is pressed, the telescopic rod can be pressed so that the pressing block at the bottom of the telescopic rod is pressed against the surface of the cable; the pulling ring is arranged at the upper part of the telescopic fixing, and is used to lock and fix the position of the self-locking plug rod. When the pulling ring is removed, the position of the self-locking plug rod is loosened, and then the pressing block at the bottom of the telescopic rod leaves the surface of the cable, and the position of the cable can be moved.

10. A medium voltage fire-resistant cable structure according to claim 9, characterized in that: The number of the water inlet pipes and the water outlet pipes is 2; the number of the supporting members is 4, and the water inlet pipes and the water outlet pipes are PE water pipes.

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