35KV rail transit cable composite sheath and cable using same

Abstract

The invention discloses a 35KV rail transit cable composite sheath and a cable using the 35KV rail transit cable composite sheath, and relates to the technical field of cables, the 35KV rail transit cable composite sheath comprises an outer sheath and an inner sheath, the outer surface of the inner sheath is provided with a continuous periodic projection structure along the length direction, the outer sheath wraps the outer part of the inner sheath, and the outer surface of the inner sheath is provided with a continuous periodic projection structure along the length direction of the inner sheath. The inner surface of the inner sheath is provided with a continuous periodic concave structure matched with the convex structure on the outer surface of the inner sheath, the cable further comprises a conductor, an insulating part is arranged outside the conductor, a shielding part is arranged outside the insulating part, and the outer wall of the shielding part is fixedly connected with the inner wall of the inner sheath. Through the deep interlocking structure, the convex structure and the concave structure, the technical problem that an existing rail transit cable is poor in mechanical shock resistance and longitudinal water resistance is solved.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and in particular to a 35KV rail transit cable composite sheath and a cable using the same. Background Technology

[0002] In modern urban rail transit, power cables are a crucial component ensuring the safe and stable operation of trains, with 35kV cables widely used in some high-voltage transmission lines. Due to the limitations of the rail transit environment, cables need to possess a certain degree of resistance to external environmental influences, such as waterproofing, rodent and termite resistance, and UV protection. In environments exposed to high temperatures, humidity, underground, or outdoors, the insulation performance and durability of the cable significantly impact the system's stability and operational safety. Therefore, it is necessary to design a cable capable of withstanding these environmental challenges.

[0003] Traditional 35kV rail transit cables, as key equipment for transmitting electrical energy, operate in a complex environment, enduring severe mechanical and environmental stresses such as ballast impact, crushing by external objects, puncture by sharp objects, vibration, and changes in temperature and humidity. The outer sheath of existing 35kV rail transit cables is typically made of polyethylene or polyvinyl chloride, which, while possessing a certain mechanical strength, is still susceptible to damage such as puncture, cracking, or tearing under high-energy localized impacts. Once the sheath is damaged, external moisture can penetrate longitudinally into the cable's internal structure, especially spreading along the gaps between the filler or shielding layer and the insulation layer. Long-term moisture intrusion leads to a sharp decline in cable insulation performance, triggering partial discharge, accelerating insulation aging, and ultimately causing cable breakdown failure, seriously threatening the power supply safety and operational reliability of rail transit. Summary of the Invention

[0004] The purpose of this invention is to provide a 35KV rail transit cable composite sheath and a cable using the same, so as to solve the technical problems mentioned in the background art of poor mechanical impact resistance and poor longitudinal water blocking ability of existing rail transit cables.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a 35KV rail transit cable composite sheath, comprising an outer sheath and an inner sheath, wherein the outer surface of the inner sheath has a continuous periodic protrusion structure along its length direction, and the outer sheath covers the outside of the inner sheath, wherein its inner surface has a continuous periodic recess structure that matches the protrusion structure of the outer surface of the inner sheath. The raised structure of the inner sheath and the recessed structure of the outer sheath interlock tightly to form a mechanical interlocking interface. The mechanical interlocking interface provides mechanical buffering and stress dispersion in the radial direction of the cable, and at the same time forms a series of independent and physically sealed micro cavities in the longitudinal direction of the cable. When the outer sheath is punctured and damaged at a certain point, external moisture can only enter and remain in the local micro cavity corresponding to the damaged point, and cannot penetrate to other parts.

[0006] Preferably, the raised structure on the outer surface of the inner sheath is any one of annular corrugations, spiral ribs, toothed protrusions, or an interface interlocking effect; the recessed structure is the position that contacts the raised structure; and the micro-cavity is the position in the recessed structure that does not contact the raised structure.

[0007] Preferably, the materials of the inner and outer sheaths are selected from at least one of polyethylene, cross-linked polyethylene, polyvinyl chloride, or low-smoke halogen-free flame-retardant polymers and reach B1 rating.

[0008] Preferably, the inner sheath and the outer sheath are formed by co-extrusion or step extrusion processes.

[0009] A cable using a 35KV rail transit cable composite sheath includes a conductor, an insulation portion outside the conductor, a shielding portion outside the insulation portion, and the outer wall of the shielding portion being fixedly connected to the inner wall of the inner sheath.

[0010] Preferably, the insulating part includes an inner insulating layer, a main insulating layer, and an outer insulating layer.

[0011] Preferably, the inner insulating layer is made of an ultra-smooth cross-linked semi-conductive material to uniformly replace the surface electric field and eliminate the air gaps in the conductor stranding; the main insulating layer is made of a high-temperature resistant and vibration-damping material; and the outer insulating layer is made of a non-peelable semi-conductive cross-linked polymer, which is extruded synchronously with the main insulating layer.

[0012] Preferably, the shielding part is composed of a semiconductor shielding layer and a metal shielding layer on the outer wall. The semiconductor shielding layer and the metal shielding layer on the outer wall are fixed to the outside of the insulating part by spiral winding in opposite directions. The semiconductor shielding layer is fixed to the outer insulating layer.

[0013] Preferably, a flame-retardant oxygen barrier layer is fixed to the outside of the metal shielding layer.

[0014] Preferably, the outer wall of the flame-retardant oxygen barrier layer is fixedly connected to the inner wall of the inner sheath, and capsaicin, cypermethrin, and other repellents are added to the material of the outer sheath to make rodents, ants, and other pests averse to the cable.

[0015] The beneficial effects of this invention are: 1. By setting up a tight interlocking structure of protrusions and recesses to form a mechanical interlocking interface, when an external mechanical impact acts on the outer sheath, the impact force will be dispersed to a larger contact area through the tight mechanical interlocking interface. When a traditional single-layer sheath is subjected to local impact, the stress is highly concentrated, which can easily lead to direct penetration. The mechanical interlocking interface of this invention, through its raised and recessed structures, transforms radial impact force into multi-directional shear force along the interlocking interface, forcing energy dissipation and stress dispersion. This significantly improves the overall composite sheath's resistance to localized punctures and high-energy impacts, preventing or delaying further damage and ensuring the safety of the internal insulation layer. Secondly, the continuous raised structure of the inner sheath and the continuous recessed structure of the outer sheath, after tight interlocking, form a series of independent and physically sealed micro-cavities between the outer and inner sheaths. These micro-cavities can be rhomboid or annular closed units, or independent spaces separated along a spiral path. This ensures that even if the cable's outer sheath is punctured and damaged at a certain point, external moisture can only enter and remain in the corresponding local micro-cavities. Because adjacent interlocking structures form a physical barrier, moisture is effectively blocked and cannot penetrate long distances along the cable's length. This micro-cavity separation mechanism provides an inherent longitudinal water-blocking function that requires no additional absorbent material, fundamentally eliminating the risk of moisture spreading longitudinally along the cable's interior. Attached Figure Description

[0016] Figure 1 This is a schematic cross-sectional view of the present invention.

[0017] Figure 2 This is a schematic diagram of the hierarchical structure of the insulating part in this invention.

[0018] Figure 3 This is a schematic diagram of the inner shielding layer in this invention.

[0019] Figure 4 This is an exploded view of the concave and convex structures in this invention.

[0020] Figure 5 This is a schematic diagram showing the distribution of the microcavities on the recessed structure in this invention.

[0021] The attached figures are labeled as follows: 1. Outer sheath; 101. Recessed structure; 2. Inner sheath; 201. Raised structure; 202. Mechanical interlock interface; 2021. Miniature cavity; 3. Conductor; 4. Insulating part; 401. Inner insulating layer; 402. Main insulating layer; 403. Outer insulating layer; 5. Shielding part; 501. Semiconductor shielding layer; 5011. Copper wire; 5012. Wrapping layer; 502. Metal shielding layer; 6. Flame-retardant and oxygen-barrier layer. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1 In modern urban rail transit, power cables are a crucial component ensuring the safe and stable operation of trains, with 35kV cables widely used in some high-voltage transmission lines. Due to the limitations of the rail transit environment, cables need to possess a certain degree of resistance to external environmental influences, such as waterproofing, rodent and termite resistance, and UV protection. In environments exposed to high temperatures, humidity, underground, or outdoors, the insulation performance and durability of the cable significantly impact the system's stability and operational safety. Therefore, it is necessary to design a cable capable of withstanding these environmental challenges.

[0024] To resolve the above technical issues, please refer to Figures 1 to 5 As shown, an embodiment of the present invention discloses a 35KV rail transit cable, comprising a conductor 3, an insulation portion 4 disposed outside the conductor 3, and a shielding portion 5 disposed outside the insulation portion 4. The outer wall of the shielding portion 5 is fixedly connected to the inner wall of the inner sheath 2. The insulation portion 4 includes an inner insulation layer 401, a main insulation layer 402, and an outer insulation layer 403. The inner insulation layer 401 is made of an ultra-smooth cross-linked semiconducting material, used to uniformly replace the surface electric field and eliminate the air gaps in the stranding of the conductor 3. The main insulation layer 402 is made of a high-temperature resistant and vibration-damping material. The outer insulation layer 403 is made of a non-peelable semiconducting cross-linked polymer, extruded synchronously with the main insulation layer 402. The shielding portion 5 consists of a semiconductor shielding layer 501 and a metal shielding layer 502 on the outer wall. The cable is composed of a semiconductor shielding layer 501 and a metal shielding layer 502 on the outer wall, which are fixed to the outside of the insulation part 4 by spiral winding in opposite directions (not shown in detail in the figure). The semiconductor shielding layer 501 is fixed to the outer insulation layer 403. A flame-retardant oxygen barrier layer 6 is fixed to the outside of the metal shielding layer 502. An inner sheath 2 and an outer sheath 1 are sequentially arranged on the outer wall of the flame-retardant oxygen barrier layer 6. The flame-retardant oxygen barrier layer 6 is fixedly connected to the inner wall of the inner sheath 2. Capsaicin, cypermethrin and other repellents are added to the material of the outer sheath 1 to make rodents and ants averse to the cable. The materials of the inner sheath 2 and the outer sheath 1 are both selected from at least one of polyethylene, cross-linked polyethylene, polyvinyl chloride or low smoke halogen-free flame-retardant polymer and reach B1 level.

[0025] When in use, when conductor 3 is conductive, the inner insulation layer 401 can uniformly distribute the electric field on the surface of conductor 3 and eliminate the air gaps caused by the stranding of conductor 3, thereby reducing the loss during transmission and preventing local discharge of conductor 3. The main insulation layer 402 is made of a material with high temperature resistance and good flexibility, which plays a certain role in vibration reduction. The outer insulation layer 403 can eliminate the electric field distortion caused by cracks on the insulation surface and prevent the insulation part 4 from discharging with the metal sheath.

[0026] The semiconductor shielding layer 501 and the metal shielding layer 502 on the outer wall are fixed to the outside of the insulation part 4 by spiral winding in opposite directions. The semiconductor shielding layer 501 is a copper wire shielding layer, which is composed of copper wire 5011 and a wrapping layer 5012. The metal shielding layer 502 can be selected as copper strip. The spiral winding directions of the two are opposite, which is not shown in detail in the figure. It can provide the cable with a certain tensile and torsional resistance.

[0027] When the flame-retardant oxygen barrier layer 6 is on the outside, it can play a role in flame retardancy and oxygen barrier. In the event of a fire, it will not allow the fire to immediately spread to the inside of the cable, and it can play a good role in flame retardancy.

[0028] Because capsaicin, cypermethrin and other repellents are added to the material of the outer sheath 1, they can abhor the cables when rodents and ants approach them, thus preventing them from actively staying away and thus preventing them from gnawing on the outer sheath 1 and causing cable damage. In addition, the materials of the inner sheath 2 and the outer sheath 1 are selected from at least one of polyethylene, cross-linked polyethylene, polyvinyl chloride or low smoke halogen-free flame retardant polymers and reach the B1 level, which can play a good flame retardant role. The above technologies are all existing technologies and will not be described in detail here.

[0029] Through the above settings, the cable can have good flame retardancy and strong anti-interference ability in rail transit, thus enabling the cable to operate stably. By adding repellents such as capsaicin and cypermethrin to the material of the outer sheath 1, rodents and ants can be kept away, thus providing a good effect of preventing rodents and ants from gnawing on the outer sheath 1.

[0030] Example 2 Traditional 35kV rail transit cables, as key equipment for transmitting electrical energy, operate in a complex environment, enduring severe mechanical and environmental stresses such as ballast impact, crushing by external objects, puncture by sharp objects, vibration, and changes in temperature and humidity. The outer sheath of existing 35kV rail transit cables is typically made of polyethylene or polyvinyl chloride, which, while possessing a certain mechanical strength, is still susceptible to damage such as puncture, cracking, or tearing under high-energy localized impacts. Once the sheath is damaged, external moisture can penetrate longitudinally into the cable's internal structure, especially spreading along the gaps between the filler or shielding layer and the insulation layer. Long-term moisture intrusion leads to a sharp decline in cable insulation performance, triggering partial discharge, accelerating insulation aging, and ultimately causing cable breakdown failure, seriously threatening the power supply safety and operational reliability of rail transit.

[0031] Based on the above embodiments, in order to solve the above technical problems, please refer to... Figures 1 to 5 As shown, this invention provides a composite sheath for a 35KV rail transit cable, comprising an outer sheath 1 and an inner sheath 2. The outer wall of a flame-retardant oxygen barrier layer 6 is fixedly connected to the inner wall of the inner sheath 2. The outer surface of the inner sheath 2 has a continuous periodic protrusion structure 201 along its length. The outer sheath 1 covers the outside of the inner sheath 2, and its inner surface has a continuous periodic recess structure 101 that matches the protrusion structure 201 on the outer surface of the inner sheath 2. The protrusion structure 201 of the inner sheath 2 and the recess structure 101 of the outer sheath 1 tightly interlock with each other to form a mechanical interlocking interface 202. The mechanical interlocking interface 202 provides mechanical buffering and stress dispersion functions in the radial direction of the cable, and simultaneously forms a series of independent and physically sealed microcavities 2021 in the longitudinal direction of the cable. When the outer sheath 1 is punctured and damaged at a certain point, external moisture can only enter and remain in the local micro-cavity 2021 corresponding to the damaged point, and cannot penetrate to other parts. The raised structure 201 on the outer surface of the inner sheath 2 can be any of the following: annular corrugations, spiral ribs, toothed protrusions, or interlocking structures. The recessed structure 101 is the position that contacts the raised structure 201, and the micro-cavity 2021 is the position in the recessed structure 101 that does not contact the raised structure 201. The inner sheath 2 and the outer sheath 1 are formed by co-extrusion or step extrusion process. This technology uses existing technology and will not be described in detail here. The raised structure 201 and the recessed structure 101 are intermittently set between the inner sheath 2 and the outer sheath 1, which can be quickly repaired and replaced after damage.

[0032] Based on the above embodiments, during use, when the cable outer sheath 1 is subjected to external mechanical impact (such as ballast impact, crushing by heavy objects, or puncture by sharp objects), the impact force is first transmitted to the outer sheath 1, and then transmitted to the recessed structure 101 and the raised structure 201 through the mechanical interlock interface 202. Subsequently, the recessed structure 101 and the raised structure 201 interact and transmit the impact force to the surrounding recessed structure 101 and raised structure 201, thereby diffusing the impact force to the surrounding outer sheath 1 and inner sheath 2 through the recessed structure 101 and the raised structure 201. This reduces the impact force of external mechanical impact on a single point or location, thereby achieving the effect of stress relief. It reduces the impact of external mechanical stress on the cable, preventing direct damage to the cable outer sheath 1 caused by the impact. This significantly improves the overall composite sheath's resistance to local punctures and high-energy impacts, preventing or delaying further damage and ensuring the safety of the internal insulation layer.

[0033] Furthermore, when there is a strong external mechanical impact, and the impact force on a certain part or point of the outer sheath 1 is large, causing damage to the outer sheath 1, the rail transit is in a relatively humid environment or in a relatively harsh environment, which will allow water vapor and dust to seep into the inside of the cable through the damaged part of the outer sheath 1. When water vapor or dust enters the cable through the hole, due to the setting of the recessed structure 101 and the tight connection between the raised structure 201 and the recessed structure 101, the water vapor or dust is stored in the position where the raised structure 201 and the recessed structure 101 do not contact.

[0034] Because a mechanical interlocking interface 202 is formed between the protruding structure 201 and the recessed structure 101, and a micro-cavity 2021 is formed, a series of independent and physically sealed micro-cavities 2021 are formed between the outer sheath 1 and the inner sheath 2. The micro-cavity 2021 can be a rhomboid or annular closed unit, or an independent space separated along a spiral path. In this invention, a rhomboid closed unit is used, so that even if the outer sheath 1 of the cable is punctured and damaged at a certain point, external moisture or dust can only enter and remain in the local micro-cavity 2021 corresponding to the damaged point. This allows water or dust to be stored in the micro-cavity 2021 and will not continue to penetrate along the length of the cable, thereby achieving a longitudinal water blocking effect. The separation mechanism of the micro-cavity 2021 provides an inherent longitudinal water blocking function that does not require additional water-absorbing materials, fundamentally eliminating the risk of moisture spreading longitudinally along the inside of the cable.

[0035] By tightly interlocking the raised structure 201 and the recessed structure 101 to form a mechanical interlocking interface 202, when an external mechanical impact acts on the outer sheath 1, the impact force is dispersed to a larger contact area through the tight mechanical interlocking interface 202. This avoids the situation where, in traditional cables, moisture directly extends along the cable's extension direction after the outer sheath 1 is penetrated. The mechanical interlocking interface 202 of this invention, through the raised structure 201 and the recessed structure 101, can convert radial impact force into multi-directional shear force along the interlocking interface, forcing energy dissipation and stress dispersion. This significantly improves the overall composite sheath's resistance to localized punctures and high-energy impacts, preventing or delaying further damage and ensuring the safety of the inner insulation layer. Furthermore, due to the inner sheath... After the continuous protruding structure 201 of the outer sheath 2 and the continuous recessed structure 101 of the inner sheath 1 are tightly interlocked, a series of independent and physically sealed micro-cavities 2021 are formed between the outer sheath 1 and the inner sheath 2. The micro-cavities 2021 are diamond-shaped closed units, so that even if the outer sheath 1 of the cable is punctured and damaged at a certain point, external moisture can only enter and remain in the local micro-cavities 2021 corresponding to the damaged point. Since the adjacent interlocking structures form a physical barrier, the moisture is effectively blocked and cannot penetrate long distances along the length of the cable. This micro-cavity 2021 separation mechanism provides an inherent longitudinal water-blocking function that does not require additional water-absorbing materials, fundamentally eliminating the risk of moisture spreading longitudinally along the inside of the cable.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A composite sheath for a 35KV rail transit cable, comprising an outer sheath and an inner sheath, characterized in that, The outer surface of the inner sheath has a continuous periodic protrusion structure along its length direction, and the outer sheath covers the outside of the inner sheath, and its inner surface has a continuous periodic concave structure that matches the protrusion structure of the outer surface of the inner sheath. The raised structure of the inner sheath and the recessed structure of the outer sheath interlock tightly to form a mechanical interlocking interface. The mechanical interlocking interface provides mechanical buffering and stress dispersion in the radial direction of the cable, and at the same time forms a series of independent and physically sealed micro cavities in the longitudinal direction of the cable. When the outer sheath is punctured and damaged at a certain point, external moisture can only enter and remain in the local micro cavity corresponding to the damaged point, and cannot penetrate to other parts.

2. The composite sheath for a 35KV rail transit cable according to claim 1, characterized in that, The raised structure on the outer surface of the inner sheath is any one of annular corrugations, spiral ribs, toothed protrusions, or capable of achieving interface interlocking. The recessed structure is the position that contacts the raised structure, and the micro cavity is the position in the recessed structure that does not contact the raised structure.

3. The composite sheath for a 35KV rail transit cable according to claim 1, characterized in that, The materials of both the inner and outer sheaths are selected from at least one of polyethylene, cross-linked polyethylene, polyvinyl chloride, or low-smoke halogen-free flame-retardant polymers and meet the B1 rating.

4. The composite sheath for a 35KV rail transit cable according to claim 1, characterized in that, The inner and outer sheaths are formed by co-extrusion or step extrusion processes.

5. A cable with a composite sheath for 35KV rail transit cables as described in claims 1-4, comprising a conductor, characterized in that, An insulating part is provided on the outside of the conductor, and a shielding part is provided on the outside of the insulating part. The outer wall of the shielding part is fixedly connected to the inner wall of the inner sheath.

6. The cable according to claim 5, characterized in that, The insulating part includes an inner insulating layer, a main insulating layer, and an outer insulating layer.

7. The cable according to claim 6, characterized in that, The inner insulation layer is made of an ultra-smooth cross-linked semi-conductive material to uniformly replace the surface electric field and eliminate the air gaps in the conductor stranding. The main insulation layer is made of a high-temperature resistant and vibration-damping material. The outer insulation layer is made of a non-peelable semi-conductive cross-linked polymer and is extruded synchronously with the main insulation layer.

8. The cable according to claim 7, characterized in that, The shielding part consists of a semiconductor shielding layer and a metal shielding layer on the outer wall, and the semiconductor shielding layer is fixed to the outer insulating layer.

9. The cable according to claim 8, characterized in that, A flame-retardant and oxygen-barrier layer is fixed to the outside of the metal shielding layer.

10. The cable according to claim 9, characterized in that, The outer wall of the flame-retardant oxygen barrier layer is fixedly connected to the inner wall of the inner sheath. Capsaicin, cypermethrin and other repellents are added to the material of the outer sheath to make rodents and ants averse to the cable.

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