Smooth aluminum sheath cable

Abstract

The utility model discloses a smooth aluminum sheath cable, which comprises a wire core and a sheath, and is characterized in that the wire core structurally comprises a conductor and a first shielding layer wrapped outside the conductor; the sheath is sequentially provided with a second shielding layer, an insulating layer, a third shielding layer, a water-blocking tape and a smooth aluminum sheath from inside to outside. The conductor is composed of a central conductor and a split conductor composed of a plurality of fan-shaped strand blocks surrounding the central conductor. The cable is reasonable in structural design, and has the following beneficial effects: the conductor is formed by stranding strand block structures, so that the mechanical strength and the stability of the cable are improved, the heat loss of the cable can be reduced, and the transmission efficiency of the cable is improved; multiple shielding layers are arranged, burrs or protrusions on the surface of the metal conductor can be eliminated, interface electric field distribution is uniform, local field intensity is restrained from being too high, and partial discharge is prevented; the arrangement of the smooth aluminum sheath improves the metal shielding electrical connection of the cable, reduces the ablation phenomenon of the semi-conductive buffer strip, and improves the safety of the cable line.

Description

Technical Field

[0001] The utility model relates to the technical field of cables, in particular to a smooth aluminum sheathed cable. Background Art

[0002] In recent years, frequent buffer layer ablation failures of corrugated aluminum sheathed cables have attracted widespread attention from the domestic power industry to smooth aluminum sheathed high-voltage cross-linked polyethylene cables, whose bending performance is a technical difficulty that limits engineering applications. Liu Ying, Chen Jiawei, Zhao Mingwei, Jin Jinyuan, and Yue Zhenguo, researchers from the School of Electrical Engineering of Xi'an Jiaotong University and Zhejiang Chenguang Cable Co., Ltd., wrote an article in the 23rd issue of "Transactions of the Chinese Society of Electrotechnical Engineering" in 2021, building a four-point bending three-dimensional simulation model of smooth aluminum sheathed XLPE cables, simulating the mechanical behavior of the adhesive layer with a cohesive force model, and studying the effects of hot melt adhesive bonding, buffer layer thickness, non-metallic outer sheath thickness and material, and cable radial dimensions on the bending performance of smooth aluminum sheathed composite structures.

[0003] The research results show that if the aluminum sheath is not bonded to the outer sheath, its resistance to bending deformation is poor, and it is easy to wrinkle and squeeze the internal insulation; after bonding, an overall composite sheath is formed, and its bending resistance is related to the total thickness. Among them, the thickness of the aluminum sheath can be determined according to the short-circuit capacity requirements, and the outer sheath makes up for the total thickness required for bending strength, and the elastic modulus of the outer sheath material should not be lower than 800MPa; the thickness of the buffer layer has little effect on the bending performance of the aluminum sheath, and is mainly designed from the perspective of absorbing the thermal expansion of the insulation.

[0004] European and American countries widely use smooth aluminum sheaths and aluminum-plastic composite sheaths; in China, almost all high-voltage cross-linked polyethylene cables use corrugated aluminum sheath structures, mainly using their excellent bending properties to reduce the risk of mechanical damage to the cables. In recent years, domestic corrugated aluminum sheathed XLPE cables have frequently experienced buffer layer ablation failures, posing a serious threat to line reliability and grid security. Such failures have also occurred in Singapore, Japan and other countries. Although relevant research on buffer layer ablation has not yet been concluded, poor electrical contact between the metal sheath and the insulation shield is undoubtedly one of the important causes of the failure. Utility Model Content

[0005] The utility model aims to provide a smooth aluminum sheathed cable, which can avoid poor electrical contact, improve radial heat dissipation of the cable, increase interlayer friction, and is suitable for use of ultra-high voltage large-section cables in high-drop environments.

[0006] In order to achieve the above-mentioned purpose, the technical solution of the utility model provides a smooth aluminum sheathed cable, including a wire core and a sheath for wrapping the wire core, the structure of the wire core includes a conductor and a first shielding layer wrapped around the conductor; the sheath is provided with a second shielding layer, an insulating layer, a third shielding layer, a water-blocking tape and a smooth aluminum sheath in sequence from the inside to the outside; the conductor is composed of a central conductor and a divided conductor composed of a plurality of fan-shaped strands surrounding the central conductor.

[0007] Furthermore, the conductor is an oxygen-free copper conductor.

[0008] Furthermore, each sector-shaped strand constituting the segmented conductor is wrapped with a layer of crepe paper tape.

[0009] Furthermore, the first shielding layer is a layer of semi-conductive nylon tape.

[0010] Furthermore, the second shielding layer, the insulating layer and the third shielding layer are three layers co-extruded and wrapped around the wire core; the second shielding layer and the third shielding layer are ultra-smooth cross-linked semi-conductive shielding layers, and the insulating layer is an ultra-clean cross-linked polyethylene insulating layer.

[0011] Furthermore, the water-blocking tape is a semi-conductive buffer water-blocking tape.

[0012] Furthermore, the smooth aluminum sheath is provided with an anti-corrosion layer and an outer protective layer.

[0013] Furthermore, the anti-corrosion layer is a hot melt adhesive layer.

[0014] Furthermore, the outer protective layer is a cold-resistant and flame-retardant high-density polyethylene sheath layer.

[0015] In summary, the device structure of the utility model is reasonably designed, and the use of the technical scheme of the utility model has the following beneficial effects: the conductor of the utility model is composed of a split conductor and a central conductor twisted in a strand block structure. The strand block structure can improve the mechanical strength and stability of the cable and prevent the cable from breaking when subjected to external force. At the same time, the strand block structure can reduce the heat loss of the cable and improve the transmission efficiency of the cable; at the same time, the utility model is provided with a multi-layer shielding layer, which can eliminate burrs or protrusions on the surface of the metal conductor, evenly distribute the interface electric field, suppress excessive local field strength, and prevent local discharge; the setting of the smooth aluminum sheath improves the effectiveness of the electrical connection of the cable metal shield, reduces the occurrence of the "ablation" phenomenon of the semi-conductive buffer zone, and improves the safety and reliability of the cable line. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the cross-sectional structure of the utility model smooth aluminum sheathed cable;

[0017] Figure 2This is a schematic diagram of the cross-sectional structure of the conductor of the utility model smooth aluminum sheathed cable:

[0018] Explanation of the reference numerals: 1-conductor, 101-center conductor, 102-divided conductor; 2-corrugated paper tape; 3-first shielding layer; 4-second shielding layer; 5-insulating layer; 6-third shielding layer; 7-water-blocking tape; 8-smooth aluminum sheath; 9-anti-corrosion layer; 10-outer protective layer. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention, but this does not constitute a limitation on the protection scope of the present invention.

[0020] In the present invention, for a clearer description, the following explanation is made: the terms "front end", "rear end", "left side", "right side", "middle", "upper", "lower", etc. in the text indicate directions or positional relationships based on the directions or positional relationships set in the drawings, and are only for the convenience of clearly describing the present invention, and do not indicate or imply that the structures or components referred to must have a specific direction or be constructed in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", and "fourth" are only used for the purpose of clarifying or simplifying the description, and cannot be understood as indicating or implying relative importance or quantity.

[0021] Based on the research conclusions of the 23rd issue of the Journal of China Electrotechnical Society in 2021 in the background technology, the utility model sets up a 110kV smooth aluminum sheathed XLPE cable and verifies it through type tests. In view of the ablation of the buffer layer, it is analyzed that poor electrical contact between the metal sheath and the insulation shield is one of the important causes of the fault.

[0022] Smooth aluminum sheathed cables avoid the problem of poor electrical contact, improve radial heat dissipation of cables, and increase interlayer friction because there is no gap between the aluminum sheath and the buffer layer. They are especially suitable for the use of ultra-high voltage large-section cables in high-drop environments. Compared with corrugated aluminum sheathed cables, smooth aluminum sheathed cables have a small outer diameter, light weight, and increased reel length, which can reduce the number of joints in the line and reduce the structural dimensions of the cable corridor, with significant economic benefits. With the development of the industry and technological progress, the laying environment and construction conditions of domestic cable lines continue to improve, creating conditions for the engineering application of smooth aluminum sheathed cables and stimulating the demand for product research and development.

[0023] See also Figure 1-Figure 2The utility model provides a smooth aluminum sheathed cable, comprising a wire core and a sheath for wrapping the wire core, wherein the structure of the wire core comprises a conductor 1 and a first shielding layer 3 wrapped outside the conductor 1; the sheath is provided with a second shielding layer 4, an insulating layer 5, a third shielding layer 6, a water blocking tape 7 and a smooth aluminum sheath 8 in sequence from the inside to the outside; the conductor 1 consists of a central conductor 101 and a divided conductor 102 consisting of a plurality of fan-shaped stock blocks surrounding the central conductor 101.

[0024] The conductor 1 of the utility model is composed of a split conductor 102 twisted in a strand block structure and a central conductor 101. The strand block structure can improve the mechanical strength and stability of the cable, prevent the cable from breaking when subjected to external force, and at the same time, the strand block structure can reduce the heat loss of the cable and improve the transmission efficiency of the cable.

[0025] The smooth aluminum sheath 8 adopts double-gun welding of the aluminum sheath welding seam, and the smooth aluminum sheath 8 improves the effectiveness of the cable metal shield electrical connection, reduces the occurrence of "ablation" of the semi-conductive buffer zone, and improves the safety and reliability of the cable line.

[0026] Specifically, the conductor 1 is an oxygen-free copper conductor 1 , and each sector-shaped strand constituting the segmented conductor 102 is wrapped with a layer of crepe paper tape 2 .

[0027] When the conductor 1 strands are twisted, each segmented strand needs to be wrapped with a layer of crepe paper tape 2 to prevent arc discharge and spark discharge between the conductors 1, avoid direct contact between the conductors 1, reduce the electric field strength, and improve the insulation performance of the cable.

[0028] Specifically, the first shielding layer 3 is a layer of semi-conductive nylon tape. A layer of semi-conductive nylon tape is wrapped around the surface of the conductor 1 as a shielding layer, which is equipotential with the shielded conductor 1 and in good contact with the insulating layer 5, thereby avoiding partial discharge between the conductor 1 and the insulating layer 5.

[0029] As a preferred embodiment of the utility model, the second shielding layer 4, the insulating layer 5, and the third shielding layer 6 are three layers co-extruded and wrapped around the wire core. The second shielding layer 4 and the third shielding layer 6 are ultra-smooth cross-linked semi-conductive shielding layers, and the insulating layer 5 is an ultra-clean cross-linked polyethylene insulating layer 5.

[0030] The insulating layer 5 adopts an ultra-clean cross-linked polyethylene layer. The ultra-clean cross-linked polyethylene insulating layer 5 is mainly made of high-quality low-density polyethylene resin as raw material, with antioxidants, cross-linking agents and other auxiliary materials added, and is prepared by a closed mixing device. It has excellent purity, uniformity, insulation performance, machining performance, anti-aging performance, heat resistance, corrosion resistance, etc.

[0031] The second shielding layer 4 and the third shielding layer 6 are ultra-smooth cross-linked semi-conductive shielding layers, which are tightly wrapped inside and outside the insulating layer 5 through three-layer co-extrusion technology. The inner and outer semi-conductive shielding layers form equipotentials with the cable conductor 1 and the metal shielding layer, respectively, and form a smooth interface between the insulation and the high voltage potential and the ground potential, which plays a role in eliminating burrs or protrusions on the surface of the metal conductor 1, uniforming the interface electric field distribution, suppressing excessive local field strength, and preventing local discharge.

[0032] Specifically, the water blocking tape 7 is a semi-conductive buffer water blocking tape 7. The water blocking tape 7 is applied between the three-layer co-extruded insulating shielding layer and the aluminum sheath armor layer of the high-voltage cable to play the role of electrical connection, reduce the enrichment of the surface charge of the insulation, and reduce the possibility of local discharge. It has good electrical conductivity and optical properties, and its main chemical properties include reactivity such as oxidation, grafting and sulfonation, as well as catalytic action, free radical elimination action and anti-aging action.

[0033] As a preferred embodiment of the utility model, the smooth aluminum sheath 8 is provided with an anti-corrosion layer 9 and an outer protective layer 10, the anti-corrosion layer 9 is a hot melt adhesive layer, and the outer protective layer 10 is a cold-resistant and flame-retardant high-density polyethylene sheath layer.

[0034] The anti-corrosion layer 9 of the metal sheath adopts hot melt adhesive as the anti-corrosion layer 9. It can improve the anti-corrosion performance of the cable, extend the service life of the cable, improve the bending performance of the cable, and reduce the construction difficulty of the cable. The outer protective layer 10 adopts a cold-resistant flame-retardant high-density polyethylene sheath layer, which has good flame retardant performance, heat resistance and mechanical properties, and also has excellent anti-cracking performance.

[0035] Compared with corrugated aluminum sheath, the use of smooth aluminum sheath in cables has the following beneficial effects:

[0036] 1. Use smooth aluminum sheath to reduce the thickness of the aluminum sheath and reduce the eddy current loss in the aluminum sheath;

[0037] 2. There is no air gap between the buffer layer and the smooth aluminum sheath. Under the same conditions, the current carrying capacity of the smooth aluminum sheath structure is about 15% higher than that of the corrugated aluminum sheath;

[0038] 3. Smooth aluminum sheath has no corrugation defects, and the cable has excellent repeated bending performance;

[0039] 4. The smooth aluminum sheath and the buffer layer can reach the level of surface contact, so that the current can flow evenly through the buffer layer;

[0040] 5. The smooth aluminum sheath reduces the outer diameter of the cable by 5-8%, making the cable lighter and less expensive;

[0041] 6. The average cable drum length of smooth aluminum sheath can be increased by about 10%.

[0042] The utility model is a high-voltage cable improved on the basis of the drawbacks of high-voltage corrugated aluminum sheathed cables. The corrugated aluminum sheath has a spiral air gap space, and the trough position of the corrugated aluminum sheath structure is close to the buffer layer, which makes the electric field inside the aluminum sheath unevenly distributed, easily causing the semi-conductive buffer layer to burn, and even causing the insulation shield to burn. The utility model is provided with a unique cable structure and adopts a smooth aluminum sheath. The smooth aluminum sheath is in close surface contact with the semi-conductive buffer layer and has a uniform spacing with the insulation shield, which can make the buffer layer more effectively transmit the cable charging current, insulation layer leakage current, neutral point current, unbalanced current, fault current and surge current, thereby improving the electrical connection effectiveness of the cable metal sheath. The water-blocking powder in the buffer layer of the corrugated aluminum sheathed cable electrochemically corrodes with the metal aluminum sheath in the presence of current when it meets water, forming an insulating material. The moisture or water immersion inside the cable increases the resistance of the semi-conductive layer. The smooth aluminum sheath has a compact structure. When the water-blocking expansion tape of the same material is used, the longitudinal water-blocking performance of the aluminum sheath is better than that of the corrugated aluminum sheath.

[0043] The smooth aluminum sheath of this utility model adopts two welding processes, and the weld quality is more reliable and the uninterrupted welding time is longer. The smooth aluminum sheath structure completely improves the effectiveness of the cable metal shield electrical connection, reduces the occurrence of semi-conductive buffer zone ablation, and improves the safety and reliability of the cable line; hot melt adhesive is used instead of asphalt anti-corrosion to make the non-metallic outer sheath and aluminum sheath form a whole, so that the smooth aluminum sheath cable and the corrugated aluminum sheath cable have the same level of bending performance, while ensuring low smoke, non-toxic, flame retardant, and improved fireproof level; the smooth aluminum sheath cable has a compact structure, improved longitudinal water-blocking performance, reduced total cable mass, and increased reel volume by about 15%. It is convenient for transportation and construction, and the occupation of laying channel resources is effectively reduced.

[0044] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the protection scope of the present invention.

Claims

1. A smooth aluminum sheathed cable, comprising a core and a sheath for wrapping the core, characterized in that: The structure of the wire core includes a conductor and a first shielding layer wrapped around the conductor; the sheath is provided with a second shielding layer, an insulating layer, a third shielding layer, a water-blocking tape and a smooth aluminum sheath in sequence from the inside to the outside; the conductor is composed of a central conductor and a divided conductor consisting of a plurality of fan-shaped strands surrounding the central conductor; the second shielding layer, the insulating layer and the third shielding layer are three-layer co-extruded and wrapped around the wire core, the second shielding layer and the third shielding layer are ultra-smooth cross-linked semi-conductive shielding layers, and the insulating layer is an ultra-clean cross-linked polyethylene insulating layer.

2. A smooth aluminum sheathed cable according to claim 1, characterized in that: The conductor is an oxygen-free copper conductor.

3. A smooth aluminum sheathed cable according to claim 1 or 2, characterized in that: Each sector-shaped stock block constituting the split conductor is wrapped with a layer of crepe paper tape.

4. A smooth aluminum sheathed cable according to claim 3, characterized in that: The first shielding layer is a layer of semi-conductive nylon tape.

5. A smooth aluminum sheathed cable according to claim 4, characterized in that: The water blocking tape is a semi-conductive buffer water blocking tape.

6. A smooth aluminum sheathed cable according to claim 1 or 5, characterized in that: An anti-corrosion layer and an outer protective layer are arranged outside the smooth aluminum sheath.

7. A smooth aluminum sheathed cable according to claim 6, characterized in that: The anti-corrosion layer is a hot melt adhesive layer.

8. A smooth aluminum sheathed cable according to claim 7, characterized in that: The outer protective layer is a cold-resistant and flame-retardant high-density polyethylene sheath layer.

Images