Insulated cable and preparation method thereof

Abstract

The invention provides an insulated cable and a preparation method, and relates to the technical field of power cables. The insulated cable comprises a cable core and an insulating layer wrapping the outer side of the cable core, the cable core comprises an invar steel core and an aluminum alloy conductor wire which are twisted together in a non-compressed circular structure, and the surface, making contact with the insulating layer, of the cable core has roughness. The preparation method comprises the following steps: arranging the invar steel cores and the aluminum alloy conductor wires in a set form, and twisting the invar steel cores and the aluminum alloy conductor wires into a non-compressed circular structure to form a cable core; polishing the outer surface of the cable core to a set roughness; and coating the outer side of the cable core with an insulating layer to obtain the insulated cable. The linear expansion coefficient of invar steel is obviously smaller than that of a common steel core; the grinding process of the outermost layer of the cable core can effectively improve the adhesive force between the cable core and the coating layer. Therefore, sag is effectively reduced, and stringing span is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of power cables, and in particular to an insulated cable and a preparation method thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Steel-core aluminum alloy overhead insulated conductors, due to their lightweight and high strength (low density and high tensile strength), are suitable for densely populated urban areas and rural power grids. However, when transmitting power over long distances and at long spans, increased sag can hinder the use of large spans. This is due to the following: the conductor reinforcement wire is made of steel wire, which has a high coefficient of expansion of 11.5 × 10⁻⁶ (1 / °C). Furthermore, the stranded conductors commonly used are typically compacted conductors with a smooth surface, resulting in poor adhesion to the insulation layer and prone to relative movement between the conductor and the insulation layer. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide an insulated cable and a preparation method, which uses Invar as a reinforcing core, adopts a non-compacted round shape and outer layer grinding process in the stranded conductor, reduces the relative movement between it and the insulation layer, prevents the occurrence of oxidation reaction corrosion without affecting other performance, and reduces the AC resistance of the conductor, thereby reducing sag at high temperatures.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions: In a first aspect, an insulated cable comprises: a cable core and an insulating layer wrapped around the outside of the cable core, the cable core comprising an Invar steel core and an aluminum alloy conductor wire twisted together in a non-compressed circular structure, and the surface roughness of the cable core in contact with the insulating layer is Ra0.4~Ra1.6.

[0006] In a second aspect, a method for preparing the above-mentioned insulated cable comprises: S1. Arrange the Invar steel core and the aluminum alloy conductor wire in a set pattern and twist them into a non-compact circular structure to form a cable core; S2. Grind the outer surface of the cable core to a set roughness; S3. Cover the outer side of the cable core with an insulating layer to obtain an insulated cable.

[0007] The beneficial effects of the present invention are as follows: The present invention uses Invar as the reinforcing core in the cable core. The linear expansion coefficient of Invar is significantly smaller than that of ordinary steel core, which can reduce sag under high temperature. The non-compressed circular structure can reduce the extrusion force of each part in the cable core, which is beneficial to the recovery of the cable length. The outermost layer polishing process of the cable core can effectively improve the adhesion between the cable core and the coating layer, and reduce the relative movement between the insulation layer and the cable core. This effectively reduces sag, increases the line spacing, reduces the tension borne by the suspension clamp, extends the service life of the clamp and the insulated cable, and reduces maintenance and laying costs. It is beneficial to the construction of cables in densely populated urban areas and rural power grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0009] Figure 1 This is the preparation flow chart in Example 1. DETAILED DESCRIPTION

[0010] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0011] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0012] One or more specific embodiments of the present invention provide an insulated cable, comprising: a cable core and an insulation layer wrapped around the outside of the cable core, the cable core comprising an Invar steel core and an aluminum alloy conductor wire twisted together in a non-compacted circular structure, and the surface roughness of the cable core in contact with the insulation layer is Ra0.4~Ra1.6.

[0013] In the above structure, the Invar material has a low expansion coefficient, which can effectively reduce the increase in sag caused by temperature; the non-compressed circular structure can reduce the degree of extrusion of each wire inside the cable core, thereby reducing the stress imbalance caused by external force or temperature; and the expansion coefficient of the insulation layer is lower than that of the metal cable core. Therefore, increasing the roughness of the outer surface of the cable core can use the insulation layer to provide resistance to the expansion process of the cable core; multiple aspects work together to reduce cable sag.

[0014] Optionally, the volume ratio of the Invar steel wire to the aluminum alloy conductor wire is 0.12-0.18.

[0015] Optionally, the diameter of the Invar steel core in the cable core is 5-8 mm.

[0016] Optionally, the diameter of the aluminum alloy conductor wire is 2~4mm.

[0017] Optionally, the Invar steel core and the aluminum alloy conductor wire are twisted in a concentric layer twisting or a special twisting method.

[0018] Optionally, the material of the aluminum alloy conductor wire includes one or more of medium-strength aluminum alloy and high-strength aluminum alloy.

[0019] Optionally, the thickness of the insulating layer is 1-3 mm.

[0020] Optionally, the roughness of the contact surface between the steel core and the aluminum alloy conductor wire is Ra1.6~Ra3.2.

[0021] One or more specific embodiments of the present invention provide a method for preparing the above-mentioned insulated cable, comprising the steps of: S1. Arrange the Invar steel core and the aluminum alloy conductor wire in a set pattern and twist them into a non-compact circular structure to form a cable core; S2. Grind the outer surface of the cable core to the set roughness.

[0022] S3. Cover the outer side of the cable core with an insulating layer to obtain an insulated cable.

[0023] Optionally, in S2, the grinding method is collision grinding, which uses abrasive particles to collide with the surface of the cable core to produce tiny pits and increase the surface roughness of the cable.

[0024] Optionally, in S3, the coating method includes: one or more of extrusion and tube extrusion.

[0025] Example 1 At present, the cable length is longer than the length when it was installed due to temperature differences caused by seasonal changes and local bending during the installation process. The phenomenon of cable stretching is the result of stress imbalance between the internal parts squeezing each other and slipping between each other. When the temperature drops, this local stress imbalance is difficult to completely eliminate, resulting in the cable being difficult to shrink to its original length after being stretched even if the temperature drops. In other words, it is difficult to fully recover after the sag has increased, and additional sag margin needs to be added.

[0026] An insulated cable provided in this embodiment includes: a cable core and an insulating layer wrapped around the outside of the cable core, the cable core includes an Invar steel core and an aluminum alloy conductor wire twisted together in a non-compressed circular structure, and the surface roughness of the cable core in contact with the insulating layer is Ra0.8.

[0027] The volume ratio of the Invar steel wire to the aluminum alloy conductor wire is 0.130; the diameter of the Invar steel core in the cable core is 7.20 mm; the diameter of the aluminum alloy conductor wire is 3.60 mm; the material of the aluminum alloy conductor wire is high-strength aluminum alloy; and the thickness of the insulation layer is 2.2 mm.

[0028] The twisting method of the Invar steel core and the aluminum alloy conductor wire includes: concentric layer twisting.

[0029] The roughness of the contact surface between the steel core and the aluminum alloy conductor wire is Ra3.2.

[0030] One or more specific embodiments of the present invention provide a method for preparing the above-mentioned insulated cable, such as Figure 1 As shown, including: S1. Arrange the Invar steel core and the aluminum alloy conductor wire in a set pattern and twist them into a non-compact circular structure to form a cable core; S2. Grind the outer surface of the cable core to a set roughness of Ra0.8 by impact grinding.

[0031] S3. An insulating layer is coated on the outside of the cable core by extrusion to obtain an insulated cable.

[0032] In this embodiment, the Invar material used has a low expansion coefficient, which is 3.7×10 -6 (1 / °C) or even smaller, effectively reducing the increase in sag caused by temperature. The non-compressed circular structure reduces the degree of compression of the individual wires within the cable core, thereby reducing the stress imbalance caused by external forces or temperature and promoting recovery after sag increases. The insulation layer has a lower coefficient of expansion than the metal cable core, so increasing the roughness of the cable core's outer surface can improve the bond strength between it and the insulation layer, thereby using the insulation layer to provide resistance to the cable core's expansion process.

[0033] After measurement, the linear expansion coefficient of the insulated cable provided in this embodiment is 2.8×10 -6 / ℃. After conversion, the actual sag can be reduced by 27%.

[0034] Example 2 An insulated cable comprises a cable core and an insulating layer covering the outer side of the cable core, wherein the cable core comprises an Invar steel core and an aluminum alloy conductor wire twisted together in a non-compacted circular structure, and the surface roughness of the cable core in contact with the insulating layer is Ra0.4.

[0035] The volume ratio of the Invar steel wire to the aluminum alloy conductor wire is 0.180; the diameter of the Invar steel core in the cable core is 5.55 mm; the diameter of the aluminum alloy conductor wire is 2.38 mm; the material of the aluminum alloy conductor wire is high-strength aluminum alloy; and the thickness of the insulation layer is 1.6 mm.

[0036] The stranding method of Invar steel core and aluminum alloy conductor wire is a special stranding method.

[0037] The surface roughness of the steel core and aluminum alloy conductor wire is Ra1.6.

[0038] One or more specific embodiments of the present invention provide a method for preparing the above-mentioned insulated cable, such as Figure 1 As shown, including: S1. Arrange the Invar steel core and the aluminum alloy conductor wire in a set pattern and twist them into a non-compact circular structure to form a cable core; S2. Grind the outer surface of the cable core to a set roughness of Ra0.4 using a collision grinding method.

[0039] S3. An insulating layer is coated on the outside of the cable core by extruding a tube to obtain an insulated cable.

[0040] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. An insulated cable, characterized in that: include: The cable core and the insulation layer wrapped around the outside of the cable core, the cable core includes an Invar steel core and an aluminum alloy conductor wire twisted together in a non-compacted circular structure, and the surface roughness of the cable core in contact with the insulation layer is Ra0.4~Ra1.

6.

2. The insulated cable according to claim 1, wherein The volume ratio of Invar steel wire to aluminum alloy conductor wire is 0.12~0.

18.

3. The insulated cable according to claim 1, wherein The diameter of the Invar steel core in the cable core is 5~8mm.

4. The insulated cable according to claim 3, wherein The diameter of the aluminum alloy conductor wire is 2~4mm.

5. The insulated cable according to claim 4, wherein The stranding method of Invar steel core and aluminum alloy conductor wire is concentric layer stranding or special stranding.

6. The insulated cable according to claim 1, wherein The material of the aluminum alloy conductor wire includes one or more of medium-strength aluminum alloy and high-strength aluminum alloy.

7. The insulated cable according to claim 1, wherein The thickness of the insulation layer is 1~3mm.

8. A method for preparing an insulated cable according to any one of claims 1 to 7, characterized in that: Including steps: S1. Arrange the Invar steel core and the aluminum alloy conductor wire in a set pattern and twist them into a non-compact circular structure to form a cable core; S2. Grind the outer surface of the cable core to a set roughness; S3. Cover the outer side of the cable core with an insulating layer to obtain an insulated cable.

9. The method for preparing an insulated cable according to claim 8, wherein: In S2, the grinding method is impact grinding.

10. The method for preparing an insulated cable according to claim 8, wherein: In S3, the coating method includes: one or more of extrusion method and tube extrusion method.

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