Co-extrusion shielding medium-voltage power cable

Abstract

The invention discloses a co-extrusion shielding medium-voltage power cable, and relates to the technical field of cables, the outer side of an inner reinforcing rope is provided with a supporting flame-retardant assembly, the outer side of the inner reinforcing rope is sleeved with a reinforcing spiral, the outer side of the reinforcing spiral is sleeved with a heat conduction pipe, a flame-retardant bag is installed between adjacent supporting rods, and one side of a heat conduction film is bonded with a flame-retardant silica adhesive tape. According to the invention, the reinforced connecting rods embedded in the reinforced through holes can extrude the supporting rods to deform, so that bending is resisted, and excessive bending deformation is prevented; heat generated in the use process of the cable can be dispersed to other positions of the cable, local overheating of the cable is prevented, influences on other inner conductors are reduced due to various reasons such as cooling, fire extinguishing and keeping away of the inner conductors, it is guaranteed that the cable can work normally for a longer time, and the other normal inner conductors are protected.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to a co-extruded shielded medium-voltage power cable. Background Technology

[0002] Medium-voltage cables are power cables with voltages between 3kV and 35kV. They are mainly used in urban power grids, factory power distribution, photovoltaic booster stations, and other scenarios. They have a more complex structure than low-voltage cables, usually using co-extrusion technology, with thicker insulation layers. They also need to pass rigorous partial discharge tests. In order to improve their anti-interference capabilities, a shielding layer is also set inside the cable to further improve its performance.

[0003] However, during the use of medium-voltage cables on the market, the internal conductors are prone to overheating and catching fire. When a conductor catches fire, other conductors may also be damaged due to their proximity. The flame-retardant effect is poor, and the shielding layer is easily damaged due to excessive bending during installation. Summary of the Invention

[0004] This invention provides a co-extruded shielded medium-voltage power cable, which can effectively solve the problems mentioned in the background art, such as when the conductor catches fire, other normal conductors will also be damaged due to their close proximity, resulting in poor flame retardant effect, and the shielding layer is easily damaged due to excessive bending during laying.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a co-extruded shielded medium-voltage power cable, comprising an inner reinforcing rope, wherein a flame-retardant support assembly is provided on the outside of the inner reinforcing rope, and the flame-retardant support assembly comprises a reinforcing spiral; The inner reinforcing rope is sleeved with a reinforcing spiral on the outside, the reinforcing spiral is sleeved with a heat-conducting tube on the outside, and a support rod is evenly bonded to the outside of the heat-conducting tube. A flame-retardant bag is installed between adjacent support rods. A heat-conducting film is uniformly bonded to the outside of the heat-conducting pipe. A flame-retardant silicone rubber strip is bonded to one side of the heat-conducting film. An inner conductor is provided on one side of the flame-retardant silicone rubber strip. An expansion groove is formed on the side of the flame-retardant silicone rubber strip near the inner conductor. A thermal expansion sheet is uniformly bonded inside the expansion groove. The inner conductor is wrapped inside the inner insulation layer. Pressure relief holes are uniformly formed on the outside of the inner insulation layer. A heat-shrinkable tube is filled inside the inner insulation layer outside the inner conductor. A flame-retardant braided tube is sleeved on the outside of the heat-shrinkable tube.

[0006] According to the above technical solution, a fire extinguishing bag is attached to one end of the flame retardant bag near the heat conduction pipe, and a top sealing block is attached to the other end of the flame retardant bag. A reinforcing connecting rod is fixedly installed through the middle of the top sealing block. A reinforcing through hole is opened on the support rod corresponding to the reinforcing connecting rod. Spray holes are opened on both sides of the flame retardant bag, and a hot melt sheet is attached inside the spray hole.

[0007] According to the above technical solution, the inner insulation layer is wrapped with a shielding layer on the outside, the shielding layer is wrapped with a co-extruded inner layer on the outside, and the co-extruded inner layer is wrapped with a co-extruded outer layer on the outside.

[0008] According to the above technical solution, the support rod and the flame-retardant bag are alternately bonded together to form a long strip, and the ends of the support rod and the flame-retardant bag are both attached to the inner side of the inner insulation layer.

[0009] According to the above technical solution, the fire extinguishing bag is filled with aluminum hydroxide powder, and the end of the reinforced connecting rod is embedded in the reinforced through hole.

[0010] According to the above technical solution, the thermal conductive film is an aluminum foil with an insulating layer adhered to both sides, and the flame-retardant silicone strip is attached to the heat-conducting pipe and the support rod on one side and to the outer side of the inner conductor on the other side.

[0011] According to the above technical solution, a bend protection component is installed on the outer side of the co-extruded outer layer, and the bend protection component includes an annular hydraulic bag; The co-extruded outer layer is movably sleeved with an annular hydraulic bag. Support rings are glued to both sides of the inner wall of the annular hydraulic bag. Reinforcing sheets are evenly glued to both ends of the annular hydraulic bag. The ends of adjacent reinforcing sheets on the same side are respectively glued to the ends of the flexible sheet. A transmission rod is fixedly connected to the middle of the reinforcing sheet. The transmission rods on the same side are welded to one side of the outer end ring. The two outer end rings are respectively glued to the two ends inside the outer sheath. Both ends of the outer sheath are glued with internal threaded rings, and an annular glue bag is sleeved on the outside of the internal threaded ring. An external threaded retaining ring is connected to the inside of the internal threaded ring by a thread.

[0012] According to the above technical solution, a push ring is welded to one end of the external threaded retaining ring, glue holes are evenly opened near the annular glue bag of the push ring, tear pins are evenly welded to one side of the push ring, and deformation openings are opened in the middle of both the external threaded retaining ring and the push ring. The annular glue bag is filled with adhesive.

[0013] According to the above technical solution, the inner side of the annular hydraulic bag is a smooth curved surface, the annular hydraulic bag is filled with pressure oil, the support ring near the co-extruded outer layer is bonded to the inner side of the annular hydraulic bag, and the support ring near the outer sheath is on the outer side of the annular hydraulic bag. The reinforcing sheet and the flexible sheet are connected end to end and bonded in a ring shape.

[0014] According to the above technical solution, a protective film is adhered to the outer side of the outer sheath, the two ends of the protective film are aligned with the two ends of the outer sheath, and heat shrink collars are fitted onto both ends of the protective film.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. It is equipped with a flame-retardant support component. Through the internal reinforcing rope and reinforcing spiral, the overall tensile strength of the cable is improved. If the cable is bent, due to the supporting effect of the support rod and the staggered distribution, the spacing between the support rods will increase, and the reinforcing rod embedded in the reinforcing through hole will squeeze the support rod to deform, resist bending, prevent excessive bending deformation, and thus avoid damage to the metal shielding layer due to excessive bending amplitude. The heat generated during cable use is dispersed to the rest of the cable through flame-retardant silicone rubber strips, heat-conducting film, and heat-conducting tubes to prevent local overheating. If the heat continues to rise and causes the inner conductor to catch fire, the heat shrink tubing inside the flame-retardant braided tube will shrink, and the thermal expansion sheet will expand due to heat, pushing open the overheated and catching fire cable and moving it away from other cables. The aluminum hydroxide powder in the fire extinguishing bag decomposes, absorbs a large amount of heat, and the generated water vapor is ejected from the nozzle, hindering the combustion process. The gas is ejected from the pressure relief hole, passes through the shielding layer, and causes the co-extruded inner and outer layers to bulge, marking the damaged location for easy identification and repair by subsequent maintenance personnel. Due to various reasons such as cooling and fire extinguishing, as well as the distance between the inner conductors, the impact on other inner conductors is reduced, ensuring that the cable can work normally for a longer period of time, improving the cable's ability to continue normal use for a period of time after partial damage, and protecting the remaining normal inner conductors.

[0016] 2. A bending protection component is installed. When the cable is bent, the spring steel transmission rod will also bend and deform. The annular hydraulic bag on the inside of the cable bend is squeezed by the transmission rod, and the annular hydraulic bag on the outside of the bend is pulled and expanded. This causes the internal liquid on the inside of the annular hydraulic bag to flow to the annular hydraulic bag on the outside of the bend. The liquid pressure in the annular hydraulic bag at the cable bend increases. Because there is more liquid on the outside of the cable bend, it will push up the outside of the cable bend, further preventing the bending process, thereby avoiding damage caused by excessive bending. In summary, the flame-retardant support component not only provides flame retardancy but also supports the cable during bending, thus preventing damage to the metal shielding layer due to excessive bending. The bending protection component further enhances the bending resistance of the flame-retardant support component, improving its bending resistance. The two components work together to provide better protection at locations with large bending amplitudes, thus better protecting the internal structure of the cable. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0018] In the attached diagram: Figure 1 This is a three-dimensional structural schematic diagram of the present invention; Figure 2 This is a schematic diagram of the structure supporting the flame-retardant component of the present invention; Figure 3 This is the present invention. Figure 2 A schematic diagram of the structure of region A; Figure 4 This is a schematic diagram of the installation structure of the flame-retardant silicone rubber strip of the present invention; Figure 5 This is a schematic diagram of the installation structure of the thermal expansion sheet of the present invention; Figure 6 This is a schematic diagram of the installation structure of the top sealing block of the present invention; Figure 7 This is a schematic diagram of the bending protection component of the present invention; Figure 8 This is a schematic diagram of the installation structure of the annular hydraulic bag of the present invention; Figure 9 This is the present invention. Figure 8 A schematic diagram of the structure of region B; Numbered in the diagram: 1. Inner reinforcing rope; 2. Supporting flame-retardant components; 201. Reinforced spiral; 202. Heat-conducting pipe; 203. Support rod; 204. Flame-retardant bag; 205. Fire extinguishing bag; 206. Top sealing block; 207. Reinforced connecting rod; 208. Reinforced through hole; 209. Spray hole; 210. Hot melt sheet; 211. Heat-conducting film; 212. Flame-retardant silicone rubber strip; 213. Inner conductor; 214. Expansion groove; 215. Thermal expansion sheet; 216. Inner insulation layer; 217. Pressure relief hole; 218. Heat shrink tubing; 219. Flame-retardant braided tubing; 220. Shielding layer; 221. Co-extruded inner layer; 222. Co-extruded outer layer; 3. Bending protection assembly; 301. Annular hydraulic bag; 302. Support ring; 303. Reinforcing sheet; 304. Flexible sheet; 305. Transmission rod; 306. Outer end ring; 307. Outer sheath; 308. Internal threaded ring; 309. Annular glue bag; 310. External threaded retaining ring; 311. Actuating ring; 312. Glue hole; 313. Tear nail; 314. Deformation opening; 315. Protective film; 316. Heat shrink collar. Detailed Implementation

[0019] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0020] Example: Figure 1-9As shown, the present invention provides a co-extruded shielded medium-voltage power cable technical solution, including an inner reinforcing rope 1, and a supporting flame-retardant component 2 provided on the outside of the inner reinforcing rope 1. The supporting flame-retardant component 2 includes a reinforcing spiral 201, a heat-conducting pipe 202, a support rod 203, a flame-retardant bag 204, a fire extinguishing bag 205, a top sealing block 206, a reinforcing connecting rod 207, a reinforcing through hole 208, a spray hole 209, a hot melt sheet 210, a heat-conducting film 211, a flame-retardant silicone rubber strip 212, an inner conductor 213, an expansion groove 214, a thermal expansion sheet 215, an inner insulation layer 216, a pressure relief hole 217, a heat shrink tube 218, a flame-retardant braided tube 219, a shielding layer 220, a co-extruded inner layer 221, and a co-extruded outer layer 222. A reinforcing spiral 201 is sleeved on the outside of the inner reinforcing rope 1. A heat-conducting pipe 202 is sleeved on the outside of the reinforcing spiral 201. A support rod 203 is evenly bonded to the outside of the heat-conducting pipe 202. A flame-retardant bag 204 is installed between adjacent support rods 203. A fire extinguishing bag 205 is bonded to one end of the flame-retardant bag 204 near the heat-conducting pipe 202. A top sealing block 206 is bonded to the other end of the flame-retardant bag 204. A reinforcing connecting rod 207 is fixedly installed through the middle of the top sealing block 206. A reinforcing through hole 208 is opened on the support rod 203 corresponding to the reinforcing connecting rod 207. The fire extinguishing bag 205 is filled with aluminum hydroxide powder. The end of the reinforcing connecting rod 207 is embedded in the reinforcing through hole 208 to facilitate the connection between the reinforcing connecting rod 207 and the reinforcing through hole 208 and improve its bending resistance. Spray holes 209 are opened on both sides of the flame-retardant bag 204. A hot melt sheet 210 is bonded inside the spray hole 209. A heat-conducting film 211 is uniformly adhered to the outer side of the heat-conducting pipe 202. The heat-conducting film 211 is aluminum foil with insulating layers adhered to both sides. A flame-retardant silicone rubber strip 212 is attached to the heat-conducting pipe 202 and the support rod 203 on one side and to the outer side of the inner conductor 213 on the other side, improving the heat conduction effect inside the cable and preventing local overheating. A flame-retardant silicone rubber strip 212 is adhered to one side of the heat-conducting film 211, and an inner conductor 213 is set on one side of the flame-retardant silicone rubber strip 212. An expansion groove 214 is opened on the side of the flame-retardant silicone rubber strip 212 near the inner conductor 213. A thermal expansion sheet 215 is uniformly adhered inside the expansion groove 214. The inner conductor 213 is completely wrapped in the inner insulation layer. Inside the inner insulation layer 216, pressure relief holes 217 are evenly distributed on the outer side of the inner insulation layer 216. The inner insulation layer 216 is filled with heat shrink tubing 218 outside the inner conductor 213. Flame-retardant braided tubing 219 is sleeved on the outside of the heat shrink tubing 218. Support rods 203 and flame-retardant bags 204 are alternately bonded together to form a long strip. The ends of support rods 203 and flame-retardant bags 204 are attached to the inner side of the inner insulation layer 216 to improve the internal support capacity of the cable and improve its pressure resistance. The outer side of the inner insulation layer 216 is wrapped with a shielding layer 220. The outer side of the shielding layer 220 is wrapped with a co-extruded inner layer 221. The outer side of the co-extruded inner layer 221 is wrapped with a co-extruded outer layer 222.

[0021] A bend protection assembly 3 is installed on the outer side of the co-extruded outer layer 222. The bend protection assembly 3 includes an annular hydraulic bag 301, a support ring 302, a reinforcing sheet 303, a flexible sheet 304, a transmission rod 305, an outer end ring 306, an outer sheath 307, an internal threaded ring 308, an annular glue bag 309, an external threaded retaining ring 310, a moving ring 311, a glue hole 312, a tear pin 313, a deformation port 314, a protective film 315, and a heat shrink collar 316. An annular hydraulic bag 301 is movably sleeved on the outer side of the co-extruded outer layer 222. Support rings 302 are bonded to both sides of the inner wall of the annular hydraulic bag 301. Reinforcing sheets 303 are evenly bonded to both ends of the annular hydraulic bag 301. The ends of adjacent reinforcing sheets 303 on the same side are respectively bonded to the ends of flexible sheets 304. The inner side of the annular hydraulic bag 301 is a smooth curved surface. The annular hydraulic bag 301 is filled with pressurized oil. The support rings 302 near the co-extruded outer layer 222 are bonded to the inner side of the annular hydraulic bag 301. The support rings 302 near the outer sheath 307 are inside the annular hydraulic bag 301. On the outside, the reinforcing sheet 303 and the flexible sheet 304 are connected end to end in a ring to prevent the annular hydraulic bag 301 from breaking due to uneven force when squeezed. A transmission rod 305 is fixedly connected to the middle of the reinforcing sheet 303. The transmission rods 305 on the same side are welded to one side of the outer end ring 306. The two outer end rings 306 are respectively bonded to the two ends inside the outer sheath 307. A protective film 315 is bonded to the outside of the outer sheath 307. The two ends of the protective film 315 are aligned with the two ends of the outer sheath 307. Heat shrink collars 316 are fitted to both ends of the protective film 315 to seal the gap at the connection. Both ends of the outer sheath 307 are bonded with internal threaded rings 308. An annular glue bag 309 is sleeved on the outside of the internal threaded ring 308. The annular glue bag 309 is filled with adhesive. An external threaded retaining ring 310 is threadedly connected inside the internal threaded ring 308. A toggle ring 311 is welded to one end of the external threaded retaining ring 310. Glue holes 312 are evenly opened near the annular glue bag 309 on the toggle ring 311. Tear nails 313 are evenly welded to one side of the toggle ring 311. Deformation holes 314 are opened in the middle of both the external threaded retaining ring 310 and the toggle ring 311.

[0022] The working principle and usage process of this invention are as follows: A reinforcing spiral 201 is wound around the outside of an inner reinforcing rope 1 woven from steel wire. Then, a heat-conducting tube 202 is bonded and wrapped around the outside of the inner reinforcing rope 1. The heat-conducting tube 202 is made of heat-conducting carbon fiber cloth. The support rod 203 is made of flame-retardant rubber. The flame-retardant bag 204 and the support rod 203 are bonded together to form a long strip. The long strip structure is evenly bonded to the outside of the heat-conducting tube 202. Then, a thermal expansion sheet 215 is embedded in the expansion groove 214 on one side of the flame-retardant silicone rubber strip 212. The thermal expansion sheet 215 is a rubber sheet mixed with thermally expanded graphite. A heat-conducting film 211 is bonded to the other side of the flame-retardant silicone rubber strip 212. The heat-conducting film 211 is then bonded to the heat-conducting tube 202. Next, a flame-retardant silicone rubber strip 212 is bonded and fixed to the outside of the heat-conducting pipe 202. An inner conductor 213 is installed on one side of the expansion groove 214 of the flame-retardant silicone rubber strip 212. A heat shrink tube 218 wrapped with a flame-retardant braided tube 219 is filled in the gap outside the inner conductor 213. Then, an inner insulation layer 216 is wrapped on its outside by an extruder. Before the inner insulation layer 216 is completely cooled, a pressure relief hole 217 is opened on its outside. A shielding layer 220 is wrapped by a wrapping machine. Finally, the co-extruded inner layer 221 and co-extruded outer layer 222 are completed by a co-extrusion process to complete the manufacturing of the cable. During cable use, the inner reinforcing rope 1 and the reinforcing spiral 201 improve the overall tensile strength of the cable. If the cable bends, the spacing between the support rods 203 will increase due to the supporting effect and staggered distribution of the support rods 203. The reinforcing connecting rods 207 embedded in the reinforcing through hole 208 will squeeze the support rods 203 to deform, resist bending, and prevent excessive bending deformation. During cable laying, if the bending radius at the laying location is large and the internal anti-bending and support structure mentioned above is insufficient to meet the requirements, an outer sheath 307 and an external threaded retainer 310 are fitted onto the outside of the cable. The presence of the deformation port 314 makes it easy for the external threaded retainer 310 to be pulled to expand its diameter, thereby facilitating the installation of the external threaded retainer 310. The annular hydraulic bag 301 is fitted onto the center of the bend. Then, the actuating ring 311 is rotated to connect the external threaded retainer 310 to the internal threaded ring 308 through the thread until the external threaded retainer 310 is bent and embedded into the internal threaded ring 308. During this process, the tear pin 313 of the actuating ring 311 rotates and approaches the annular glue bag 309 until the annular glue bag 309 is torn, and the internal adhesive flows out through the glue hole 312. The heat shrink sleeve 316 is quickly heated, and the heat shrink sleeve 316 shrinks and squeezes the glue, so that the glue fills the gap at the joint, completing the bonding combination operation of the outer sheath 307 and the co-extruded outer layer 222. When the cable is bent, the spring steel transmission rod 305 will also bend and deform. The annular hydraulic bag 301 on the inner side of the cable bend is squeezed by the transmission rod 305, and the annular hydraulic bag 301 on the outer side of the bend is pulled and expanded. This causes the internal liquid on the inner side of the annular hydraulic bag 301 to flow to the annular hydraulic bag 301 on the outer side of the bend. The liquid pressure in the annular hydraulic bag 301 at the cable bend increases. Because there is more liquid on the outer side of the cable bend, it will push up the outer side of the cable bend, further preventing the bending process. This avoids damage caused by excessive bending. The bending protection component 3 is an optional structure that is only installed when needed to improve its bending resistance locally. If the inner conductor 213 of the cable heats up during use, the heat will be dispersed to the rest of the cable through the flame-retardant silicone rubber strip 212, the heat-conducting film 211 and the heat-conducting pipe 202 to prevent local overheating of the cable. If the heat continues to rise, causing the inner conductor 213 to catch fire, the temperature at that location will rise rapidly. The heat-shrink tubing 218 inside the flame-retardant braided tube 219 will shrink, its diameter decreasing, creating a gap. The thermal expansion sheet 215 will expand due to the heat, pushing open the overheated cable. The inner conductor 213 and the flame-retardant silicone rubber strip 212 will separate, moving them away from other cables. Simultaneously, under high temperature, the heat-fused sheet 210 will soften, and the aluminum hydroxide powder inside the fire extinguishing bag 205 will decompose, absorbing a large amount of heat. The resulting water vapor will push open the heat-fused sheet 210 and spray out from the nozzle 209, thus preventing the fire. To prevent combustion, the high-pressure internal gas will be ejected from the pressure relief hole 217, passing through the shielding layer 220, causing the co-extruded inner layer 221 and co-extruded outer layer 222 to bulge, marking the damaged location. The location of each inner conductor 213 is separated by a structure composed of heat-conducting pipe 202, support rod 203 and flame-retardant bag 204 to prevent mutual interference in the event of a fire. Due to various reasons such as cooling and fire extinguishing and the distance between the inner conductors 213 and other inner conductors, the impact on other inner conductors 213 is reduced, ensuring that the cable can work normally for a longer period of time until the operator reaches the bulging damaged location for repair.

[0023] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A co-extruded shielded medium-voltage power cable, comprising an inner reinforcing rope (1), characterized in that: The inner reinforcing rope (1) is provided with a flame-retardant support component (2) on the outside, and the flame-retardant support component (2) includes a reinforcing spiral (201). The inner reinforcing rope (1) is sleeved with a reinforcing spiral (201) on the outside, and a heat-conducting tube (202) is sleeved on the outside of the reinforcing spiral (201). A support rod (203) is evenly bonded to the outside of the heat-conducting tube (202), and a flame-retardant bag (204) is installed between adjacent support rods (203). A heat-conducting film (211) is uniformly bonded to the outside of the heat-conducting pipe (202). A flame-retardant silicone rubber strip (212) is bonded to one side of the heat-conducting film (211). An inner conductor (213) is provided on one side of the flame-retardant silicone rubber strip (212). An expansion groove (214) is opened on the side of the flame-retardant silicone rubber strip (212) near the inner conductor (213). A thermal expansion sheet (215) is uniformly bonded inside the expansion groove (214). The inner conductor (213) is wrapped inside the inner insulation layer (216). A pressure relief hole (217) is uniformly opened on the outside of the inner insulation layer (216). A heat shrink tube (218) is filled inside the inner insulation layer (216) at the outside of the inner conductor (213). A flame-retardant braided tube (219) is sleeved on the outside of the heat shrink tube (218).

2. The co-extruded shielded medium-voltage power cable according to claim 1, characterized in that, A fire extinguishing bag (205) is attached to one end of the flame retardant bag (204) near the heat conduction pipe (202), and a top sealing block (206) is attached to the other end of the flame retardant bag (204). A reinforcing connecting rod (207) is fixedly installed through the middle of the top sealing block (206). A reinforcing through hole (208) is opened on the support rod (203) corresponding to the reinforcing connecting rod (207). Spray holes (209) are opened on both sides of the flame retardant bag (204), and a hot melt sheet (210) is attached inside the spray hole (209).

3. The co-extruded shielded medium-voltage power cable according to claim 1, characterized in that, The inner insulation layer (216) is wrapped with a shielding layer (220) on the outside, the shielding layer (220) is wrapped with a co-extruded inner layer (221) on the outside, and the co-extruded inner layer (221) is wrapped with a co-extruded outer layer (222) on the outside.

4. The co-extruded shielded medium-voltage power cable according to claim 1, characterized in that, The support rod (203) and the flame-retardant bag (204) are alternately bonded together in a long strip shape, and the ends of the support rod (203) and the flame-retardant bag (204) are attached to the inner side of the inner insulation layer (216).

5. A co-extruded shielded medium-voltage power cable according to claim 1, characterized in that, The fire extinguishing bag (205) is filled with aluminum hydroxide powder, and the end of the reinforcing rod (207) is embedded in the reinforcing through hole (208).

6. The co-extruded shielded medium-voltage power cable according to claim 1, characterized in that, The thermal conductive film (211) is an aluminum foil with an insulating layer adhered to both sides. The flame-retardant silicone strip (212) is attached to the heat-conducting pipe (202) and the support rod (203) on one side and to the outside of the inner conductor (213) on the other side.

7. A co-extruded shielded medium-voltage power cable according to claim 3, characterized in that, A bend protection assembly (3) is installed on the outer side of the co-extruded outer layer (222), the bend protection assembly (3) including an annular hydraulic bag (301). An annular hydraulic bag (301) is movably sleeved on the outer side of the co-extruded outer layer (222). Support rings (302) are bonded to both sides of the inner wall of the annular hydraulic bag (301). Reinforcing sheets (303) are evenly bonded to both ends of the annular hydraulic bag (301). The ends of adjacent reinforcing sheets (303) on the same side are respectively bonded to both ends of the flexible sheet (304). A transmission rod (305) is fixedly connected to the middle of the reinforcing sheet (303). The transmission rods (305) on the same side are welded to one side of the outer end ring (306). The two outer end rings (306) are respectively bonded to the two ends inside the outer sheath (307). Both ends of the outer sheath (307) are bonded with internal threaded rings (308), and an annular glue bag (309) is sleeved on the outside of the internal threaded ring (308). An external threaded retaining ring (310) is threadedly connected inside the internal threaded ring (308).

8. A co-extruded shielded medium-voltage power cable according to claim 7, characterized in that, One end of the external threaded retainer (310) is welded with a push ring (311). The push ring (311) has glue holes (312) evenly opened near the annular glue bag (309). Tear nails (313) are evenly welded on one side of the push ring (311). Deformation holes (314) are opened in the middle of both the external threaded retainer (310) and the push ring (311). The annular glue bag (309) is filled with adhesive.

9. A co-extruded shielded medium-voltage power cable according to claim 7, characterized in that, The inner side of the annular hydraulic bag (301) is a smooth curved surface. The annular hydraulic bag (301) is filled with pressure oil. The support ring (302) near the co-extruded outer layer (222) is bonded to the inner side of the annular hydraulic bag (301), and the support ring (302) near the outer sheath (307) is on the outer side of the annular hydraulic bag (301). The reinforcing sheet (303) and the flexible sheet (304) are connected end to end and bonded in a ring shape.

10. A co-extruded shielded medium-voltage power cable according to claim 7, characterized in that, A protective film (315) is adhered to the outside of the outer sheath (307). The two ends of the protective film (315) are aligned with the two ends of the outer sheath (307). Heat shrink collars (316) are fitted onto both ends of the protective film (315).

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