Medium voltage fire resistant cable construction

Abstract

The application relates to the technical field of cables, in particular to a medium-voltage fire-resistant cable structure. The application is provided with double-layer cooling liquid channels, namely an inner-layer cooling liquid channel and an outer-layer cooling liquid channel, the outer-layer cooling liquid channel is a water inlet channel, and the inner-layer cooling liquid channel is a water outlet channel. The arrangement combines the built-in temperature measuring optical fiber to monitor the temperature, and then controls and adjusts the water flow mode, effectively controls the cable temperature, and ensures stable operation under full load conditions.

Description

Technical Field

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

[0002] With China's economic development, the voltage of urban power supply systems has gradually increased. High-rise and extra-large high-rise buildings using 0.6 / 1kV low-voltage power distribution would require enormous cabling and labor. To address this practical power supply problem, high-rise and extra-large high-rise buildings have begun to adopt medium-voltage power supply. The key performance requirement for medium-voltage power supply cables is to ensure that they can maintain normal power supply for a period of time in the event of a fire. Fire-resistant cables are mostly used as emergency power supply circuits and are required to function properly in the event of a fire. In large commercial buildings, high-rise buildings, and data centers, fire-resistant cables are used for critical power transmission. In such locations, if the cables fail to function properly, the consequences could be serious, such as power outages affecting firefighting equipment and data loss. Fire-resistant cable water cooling circulation systems ensure that the cables remain functional for a period of time in the event of a fire, ensuring evacuation, fire rescue, and the 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. In addition, the fire-resistant structure design of traditional low-voltage cables is to add an inorganic fire-resistant layer to the outside of 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. 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. However, due to factors such as material consistency and stability, the overall fire resistance performance is not very high.

[0004] In some industrial production processes, the power supply to certain critical 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 not only solves the problem of power supply for the entire fire protection circuit, but also meets the corresponding fire protection requirements. In the event of a fire, it can maintain the normal operation of the power system for a certain period of time, buying more valuable 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 solutions:

[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 wrapping tape wrapping the wire core, and the structure of the wire core is, from the inside to the 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 wrapping tape.

[0010] Preferably, the number of wire cores is 1 or 3, and the conductor adopts Class 2 annealed compacted copper conductor, which is formed by twisting and compacting multiple copper wires; the conductor shielding layer is a cross-linked semi-conductive shielding layer; the insulation layer is a 35KV cross-linked polyethylene insulation layer; the insulation shielding layer is a strippable cross-linked semi-conductive outer shielding layer; the metal shielding layer is a layer of 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 insulation layer, and the insulation 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 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.

[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 several supporting pieces. The ring is welded to the upper plane of the disc and is perpendicular to the upper plane of the disc. The supporting 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 pull ring. The pressing block is arranged at the bottom of the telescopic rod, and the pressing block can be made to contact and fix the cable by adjusting the telescopic rod; the self-locking plug rod passes through the upper part of the two telescopic fixing parts, 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 pull ring is arranged at the upper part of the telescopic fixing part, and is used to lock and fix the position of the self-locking plug rod. When the pull 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 cable surface, and the cable position can be moved.

[0016] Preferably, the number of the water inlet pipes and the water outlet pipes is 2; the number of the support 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, namely 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 This is another structural schematic diagram of the medium voltage fire-resistant cable of the present invention;

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

[0021] Figure 4 This is a schematic diagram of the three-dimensional structure of the cable head fixing device of the present invention when fixing a 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 methods, but it does not constitute a limitation on the scope of protection 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's insulation, specifically the maximum allowable temperature of the cable's core's outer surface. During operation, the temperature of the cable's core's upper surface is closely related not only to the load current carried by the cable but also to the lateral heat transfer characteristics within the cable and the ambient temperature during operation. Therefore, the present invention provides a medium-voltage fire-resistant cable structure designed to effectively improve the cable's fire resistance and current carrying capacity while ensuring safe and stable operation under extreme conditions. This structure is of great significance for improving the reliability and safety of power systems.

[0026] The present invention is applied to power supply cables for these devices, which can improve power supply reliability and reduce production accidents and economic losses caused by cable failures. For example, a large number of cables are connected to various devices in a substation, and the normal operation of the cables is crucial for 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 includes a coolant channel, and coolant flows in the coolant channel; 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] In the double-layer coolant channel, the outer 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 coolant circulation.

[0030] Specifically, the structure of the cable core includes a wire core and a first wrapping tape 7 that wraps the wire core. The structure of the wire core is, from the inside to the 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 wrapping tape 7.

[0031] The present invention also includes a cable fiber temperature sensing system based on the principles of optical time-domain reflectometry and the Raman backscattering temperature effect of optical fibers. When laser pulses are transmitted through an optical fiber, they are scattered due to microscopic inhomogeneities in the fiber's refractive index. By measuring the intensity of this scattered light, the temperature at various locations along the fiber can be calculated. By detecting the reflected light from the fiber, the temperature signal generated by the conductor 1 of the cable can be derived at various locations along the fiber.

[0032] Fiber optic temperature measurement is a truly linear monitoring system that can monitor the real-time temperature status of conductor 1 when the cable is running. However, temperature-sensing cables 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 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 at each location can be accurately known, so as to promptly detect overheating or local temperature anomalies 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, thereby controlling and adjusting 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 equipment failure caused by excessive temperature from 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, which 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 removes 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: connected to the water tank to guide the flow of cooling water.

[0039] Water pumps: Installed on the outer wall of the water tank, these pumps are responsible for pumping cooling water from the tank and delivering it to cable cooling pipes and other locations where it's needed, ensuring the cooling water's circulation. In circulating cooling water systems used in cable production, water pumps are one of the power sources for the entire cooling water cycle, ensuring proper system operation. Select a circulating water pump with the appropriate flow rate and head based on the cable's heat generation and the system's cooling requirements. If the cable generates significant heat, a higher flow rate pump will be required to ensure the cooling water can remove the heat promptly.

[0040] Water tank: Used to store cooling water. One side of the outer wall is connected to a water pump and water inlet pipe 201, and the other side of the outer wall is connected to the cooler. It serves as a buffer and storage for cooling water to ensure that the system has an adequate supply of cooling water. 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, affecting 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 water quality monitoring devices to monitor water parameters such as pH and conductivity in real time so that timely adjustments can be made.

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

[0042] Controller 501: The controller 501 is used to regulate 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 layer by layer to the aluminum sheath. Due to the presence of cooling water in the aluminum sheath, the temperature of the aluminum sheath is lower than that of other parts of the cable. According to the principle of heat conduction, heat is transferred from the high-temperature area to the aluminum sheath, and then the aluminum sheath transfers the heat to the cooling water.

[0045] Start the water cooling circulation system 401, with the circulating water pump starting first. Cooling water from the cooling water tank is then pumped into the gap between the double-layer aluminum sheath and the water barrier. The cooling water flows within this gap, absorbing heat from the cable and increasing in temperature. The high-temperature cooling water then flows out of the water channel and into the cooling water tank or heat exchanger through the outlet pipe 202 for cooling. The flowing cooling water is cooled to its initial temperature in the cooling water tank using air or water cooling, and then pumped back into the double-layer aluminum sheath by the water pump, completing the cycle.

[0046] Specifically, the sealing device 101 seals both ends of the cable, sealing the double-layer coolant channel. The cable's head end is sealed with multiple layers, including a waterproof filler layer, a sealing ring reinforcement layer, and a heat-shrink tubing covering. The tail end is sealed with a double layer, including a rubber U-shaped sealing sleeve and a sealing ring. Specifically, the cable's head end seal also includes electrical flame-retardant tape, which is applied to the outer layer of the heat-shrink tubing.

[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. After the water inlet pipe and the water outlet pipe are installed, they are covered with heat shrink tubing and heated to shrink it 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 to the outside of the heat shrink tubing to ensure the sealing of the water inlet pipe and the water outlet pipe after installation.

[0048] When sealing the coolant channel at the cable's tail end, the double aluminum sheath and double waterproof layer form a interconnected circulation channel. A rubber-based U-shaped sealing sleeve seals the first and second aluminum sheaths 9 and 11 with the first and second waterproof layers 10 and 12. A sealing ring reinforces the U-shaped sealing sleeve 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 part. 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 part 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 part includes a ring 301 and several supporting parts. 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 supporting part includes two telescopic fixing parts 304 and a self-locking plug rod 303. The telescopic fixing part 304 includes a fixing rod 307, a telescopic rod 308, pressing block 309, and pulling ring 310. The pressing block 309 is arranged at the bottom of the telescopic rod 308. The pressing block 309 can be made to contact and fix the cable by adjusting the telescopic rod 308; the self-locking plug rod 303 passes through the upper part of the two telescopic fixing parts 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 part 304, and is used to lock and fix the position of the self-locking plug rod 303. When the pull 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 headend needs to be connected to the water cooling circulation system 401, the water inlet pipe 201, and the water outlet pipe 202. 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 and will not shake or loosen. The durability and reliability of the fixing material should also be ensured. Professional cable fixing clamps are preferred to meet higher safety requirements.

[0051] Therefore, the present invention provides a cable head fixing device, comprising a quadrilateral base 302, a disc 305, a tripod 306, and a cable head fixing member. The cable head fixing member comprises a ring 301 and several supporting members. The supporting member comprises two telescopic fixing members 304 and a self-locking plug rod 303. The telescopic fixing member 304 comprises a fixing rod 307, a telescopic rod 308, a pressing block 309, and a pull ring 310. Furthermore, the cable head fixing device of the present invention is made of metal material, which has elastic and corrosion-resistant properties.

[0052] The main function of the self-locking rod 303 is 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 pulling 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 upward or downward support force to prevent the cable from moving and being pulled by external forces, thereby further improving the stability of the device.

[0054] Ring 301 is fixed to disk 305. Pass the cable head through ring 301 and press down on self-locking rod 303. This adjusts the telescopic rod 308 in the support. A pressing block 309 is placed beneath telescopic rod 308, allowing pressing block 309 to contact and secure the cable, pressing it against the cable surface. When self-locking rod 303 is pressed down, it interacts with the slot in pull ring 310 on the support, securing the cable head and preventing it from moving. To move the cable head, pull ring 310 on the support, separating self-locking rod 303 from the slot. This allows the pressing block 309 at the bottom of telescopic rod 308 to leave the cable surface, allowing the cable to move.

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

[0056] The inlet and outlet pipes 201 and 202 are constructed of PE pipes, which are characterized by high strength, corrosion resistance, and non-toxicity. This ensures that when the cooling system operates under a certain pressure, the inlet and outlet pipes 201 and 202 maintain the corresponding pressure without rupturing or deforming. The rational design of the inlet and outlet pipes 201 and 202 helps maintain stable pressure throughout the water cooling system 401. Stable pressure ensures that water flows at an appropriate rate throughout the system, ensuring uniform cooling, thereby extending the pipe's service life and ensuring system stability.

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

[0058] The conductor 1 is a Class 2 annealed compacted copper conductor, which is made of multiple copper wires twisted and compacted; the conductor shielding layer 2 is a cross-linked semi-conductive shielding layer; the insulation layer 3 is a 35KV cross-linked polyethylene insulation layer; the insulation 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 embossed aluminum sheaths; 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 insulation layer 3, and the insulation shielding layer 4 are tightly extruded through 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-class 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 a cross-linked semi-conductive shielding material, tightly wrapped within the insulation layer through three-layer co-extrusion technology. It forms an equipotential with the cable conductor and metal shield layer, creating a smooth interface between the insulation, high voltage potential, and ground potential. This eliminates burrs or protrusions on the metal conductor surface, evens out the interfacial electric field distribution, suppresses localized excessive field strength, and prevents partial discharge, thereby improving the cable's electrical strength and extending its service life.

[0064] 3. Insulation layer

[0065] The cable uses 35KV cross-linked polyethylene insulation material, which is cross-linked by peroxide. This transforms the polyethylene molecules from a linear molecular structure to a three-dimensional network structure, and from a thermoplastic material to a thermosetting material, significantly improving the cable's current carrying capacity. The insulation material has excellent heat resistance, insulation properties, mechanical properties, and chemical resistance.

[0066] 4. Insulation shielding layer

[0067] The strippable, cross-linked, semi-conductive outer shield is tightly wrapped around the insulation layer using a three-layer co-extrusion process. It maintains good contact with the shielded insulation layer and forms an equipotential with the metal shield, thus preventing partial discharge between the insulation layer and the sheath.

[0068] 5. Metal shielding layer

[0069] A layer of copper tape is wrapped around the metal shield to prevent axial surface discharge and 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 tape

[0073] Ceramic fire-proof and fire-resistant composite tape is used during cabling. The ceramic fire-proof and 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. 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 ultrasonic and other online detection devices 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 ultrasonic and other online detection devices 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 strap

[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 emission, 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. Its 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. During the operation of the cable, heat will be generated, 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 fiber-optic cable temperature sensing and water cooling circulation system has been installed. This advanced temperature monitoring and control system combines fiber-optic sensing technology with a water cooling circulation system to ensure stable power system operation and cable safety. Key features of the system include real-time monitoring, high-precision measurement, strong anti-interference capabilities, multi-point measurement, high sensitivity, and high stability. It can quickly detect cable temperature changes and display and record 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 to circulate again. This continuous cycle works to continuously cool the cables and improve the service life and operating efficiency of the cables.

[0093] 3. Water cycle

[0094] The circulating water pump drives the cooling water to circulate in the cooling pipes. The water is forced through the pipes to the water cooling channels in the cables by the pump pressure, and then returns to the cooling water source for cooling. The cooled water is then pumped back into the cooling pipes surrounding the cables. This cycle repeats, continuously removing heat generated by the cables and ensuring that the cable temperature remains within the appropriate range.

[0095] 4. Waterproof performance

[0096] The unique waterproof structure design, the combination of metal sheath and waterproof layer and the specific process design 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 features.

[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 enclosure with facilities for removing any harmful gases produced by combustion and with sufficient ventilation to maintain the flame during the test, but forced ventilation shall not be used. At the beginning of each test, the enclosure and test apparatus shall be maintained between 10°C and 40°C. The ventilation and barrier conditions within the enclosure shall be the same during verification and testing.

[0103] 1.2 Fire Source

[0104] 1.2.1 The ignition source shall be a ribbon-type propane gas burner with a nozzle of nominal length 500 mm and a Venturi mixer. The nozzle shall have a nominal width of 15 mm. The nozzle shall have three staggered rows of drilled holes with a nominal diameter of 1.32 mm and a center spacing of 3.2 mm. In addition, one row of small holes on each side of the nozzle shall serve as pilot holes to maintain 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 should 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 interconnected 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 and seal the coolant channel at the other end of the cable. Use waterproof filling glue first and reinforce the seal with a sealing ring. Leave space for the water inlet and outlet pipes and connect them to the water pump. After installing the water inlet and outlet pipes, cover them with heat shrink tubing and heat it 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 standard.

[0120] 5. Test steps

[0121] 5.1 Install the specimen on the specimen holder and secure it. Adjust the blowtorch to the correct position relative to the specimen so that the x and y values ​​determined in the verification step in Appendix A of GB / T 19216.11 are met.

[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 ground terminal of the test transformer.

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

[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 that, the flame should be extinguished, but the power supply to the cable sample should continue 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 does not break down when the specified cable rated voltage U0 is applied to it during the entire test duration (any false breakdown phenomenon should be eliminated, such as flashover discharge on the test terminal surface. After the false breakdown phenomenon is eliminated, the test should be continued for 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 should 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 tested for combustion. The specific specifications of the examples 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 Example 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 Combustion performance index details

[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 and 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-resistant performance. 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 during 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, it can still be used normally. Therefore, after a long period of burning, the burned outer layer of the cable can be re-laid and the cable can continue to be used normally.

[0146] The above embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. 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, characterized in that: The structure of the outer sheath includes a coolant channel, and coolant flows through the coolant channel; The coolant channel structure includes 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 sheath and a double-layer water-insulating 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; The cable structure also includes a sealing device, a cable head fixing device and a water cooling circulation system connected to the coolant channel; The sealing device seals the head and tail ends of the cable separately, and the sealing position is the double-layer coolant channel; the coolant channel at the head end of the cable is sealed separately, and 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; 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; 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 several supporting pieces. The ring is welded to the upper plane of the disc and is perpendicular to the upper plane of the disc. The supporting piece includes two telescopic fixing pieces and a self-locking plug rod. The telescopic fixing piece includes a fixed The invention relates to a rod, a telescopic rod, a pressing block and a pull ring. The pressing block is arranged at the bottom of the telescopic rod, and the pressing block can be made to contact and fix the cable by adjusting the telescopic rod; the self-locking plug rod passes through the upper part of the two telescopic fixing parts, 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 pull ring is arranged at the upper part of the telescopic fixing part, and is used to lock and fix the position of the self-locking plug rod. When the pull 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 cable surface, and the cable position can be moved.

2. A medium voltage fire-resistant cable structure according to claim 1, characterized in that: 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.

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 wrapping tape wrapping the wire core. The structure of the wire core is, from the inside to the 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, which is arranged on the outer layer of the metal shielding layer and is wrapped and fixed by the first wrapping 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 compacted copper conductor, which is formed by twisting and compacting multiple copper wires; the conductor shielding layer is a cross-linked semi-conductive shielding layer; the insulation layer is a 35KV cross-linked polyethylene insulation layer; the insulation 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 first aluminum sheath and the second aluminum sheath are embossed 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, insulation layer, and insulation shielding layer are tightly extruded by three-layer co-extrusion technology.

5. A medium voltage fire-resistant cable structure according to claim 4, 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 the coolant 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 coolant; one side of the water tank is connected to the water pump and the water inlet pipe to transport the coolant to the cable, and the other side is connected to the water outlet pipe to receive the circulated coolant; 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.

6. A medium voltage fire-resistant cable structure according to claim 5, characterized in that: The sealing structure of the head end of the cable further comprises an electrical flame retardant tape, and the electrical flame retardant tape is arranged on the outer layer of the heat shrink tube.

7. A medium voltage fire-resistant cable structure according to claim 6, characterized in that: The number of the water inlet pipe and the water outlet pipe is 2; the number of the supporting members is 4, and the water inlet pipe and the water outlet pipe are PE water pipes.

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