A 35 kV polyethylene non-crosslinked insulation power cable conductor shield repair process

Abstract

The application relates to the technical field of cable repair, and discloses a 35kV polyethylene-based non-cross-linked insulation power cable conductor shielding layer repair process, which comprises the following steps: S1, processing the end portions of first and second cables to form sections, and polishing the first and second cables to expose cable conductor layers; S2, welding and connecting the first and second cables along the sections, and polishing the welding points to be equal in diameter to the original cable conductor layers; S3, arranging a semi-conductive hollow pipe to cover the cable conductor layers; S4, arranging a heating mold to heat the semi-conductive hollow pipe so that the semi-conductive hollow pipe is integrated with the cable conductor layers; S5, waiting for the heating mold to naturally cool, and removing the heating mold; S6, polishing the fused semi-conductive hollow pipe so that the semi-conductive hollow pipe is consistent with the conductor shielding layers of the first and second cables, and the repair of the conductor shielding layers is completed. Compared with the prior art, the cable repair process adopts fusion to combine the original conductor shielding layer with the existing conductor shielding layer, and eliminates the gap between the cold-shrink preformed part main semi-conductive layer and the cable body.

Description

Technical Field

[0001] The present invention relates to the technical field of cable repair, in particular to a repair process for a 35kV polyethylene-based non-cross-linked insulated power cable conductor shielding layer. Background Art

[0002] At present, the widely used 35kV cross-linked polyethylene power cable joints are mainly wrapping type welding joints. The wrapping type welding joints are made of the same cross-linked material as the cross-linked polyethylene cable body. The above-mentioned strip is wrapped around the cable in a semi-lap manner. By using an elastic silicone rubber tube and a heating belt to apply a certain pressure and temperature, the cross-linking material is combined with the cable body to form an inseparable whole to complete the production of the cable joint.

[0003] However, the wrapping hot melt process still has many shortcomings. Specifically, the above operation relies too much on manual operation, which makes the whole process take a long time. In addition, the surface of the restored conductor shielding layer is not round due to the uneven thickness of the tape after wrapping, and it takes more time to polish. In addition to wrapping the tape with the same material as the cable body, the wrapping welding joint also needs to use a variety of tapes and accessories, such as silicone rubber tubes that provide elastic pressure, tin foil for uniform heat, shaped polyimide tapes, heating tapes and insulation cloth for heat preservation, etc., which leads to many steps in the installation process, long installation time and reduced installation efficiency. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a 35kV polyethylene-based non-cross-linked insulated power cable conductor shielding layer repair process, which solves the problem that a wrap-around fusion joint requires the use of a variety of tapes and accessories with different functions to repair the cable, resulting in a large amount of installation materials and a long installation time.

[0005] Based on this, the present invention provides a 35kV polyethylene-based non-cross-linked insulated power cable conductor shield repair process for repairing and connecting a first cable and a second cable, wherein the first cable includes a first conductor layer, a first conductor shield layer, a first insulation layer, and a first insulation shield layer arranged in sequence from the inside to the outside, and the second cable includes a second conductor layer, a second conductor shield layer, a second insulation layer, and a second insulation shield layer arranged in sequence from the inside to the outside. The cable repair process comprises the following steps:

[0006] S1. Cut the first cable and the second cable along one end to form a connecting section, grind the first insulating shielding layer, the first insulating layer, and the first conductor shielding layer of the first cable to expose the first conductor layer of the first cable, grind the second insulating shielding layer, the second insulating layer, and the second conductor shielding layer of the second cable to expose the second conductor layer of the second cable, and as the first cable gradually moves away from the connecting section, the first conductor shielding layer and the first insulating layer are arranged in a tapered shape. As the second cable gradually moves away from the connecting section, the second conductor shielding layer and the second insulating layer are arranged in a tapered shape.

[0007] S2. Keep the connecting section of the first cable and the second cable flat, align the first cable and the second cable so that their axes are on the same horizontal line, set welding points at the connecting section of the first cable and the second cable, grind and polish the welding points, and weld the first cable to the second cable through the welding points;

[0008] S3. Provide a semiconductor hollow tube having an inner diameter identical to the outer diameters of the first and second conductor layers. Use a cutting tool to cut the semiconductor hollow tube axially to form an opening connecting the inside and the outside of the semiconductor hollow tube. Slide the semiconductor hollow tube over the first and second conductor layers through the opening, and ensure that the semiconductor hollow tube overlaps the first and second conductor shielding layers.

[0009] S4. Setting a heating mold to cover the semiconductor hollow tube, heating the semiconductor vacuum tube through the heating mold to melt it, gradually tightening the heating mold as the semiconductor vacuum tube melts, so that the heating mold always fits the semiconductor hollow tube, and stopping heating when the temperature of the heating mold reaches a specified value, and performing heat preservation treatment on the heating mold;

[0010] S5. After the heat preservation is completed, wait for the heated mold to cool naturally, and then remove the heated mold;

[0011] S6. After cooling, the semiconductor hollow tube forms a conductor shielding repair layer integrated with the first conductor layer and the second conductor layer. The conductor shielding repair layer is polished according to the original size of the first conductor shielding layer. The appearance of the conductor shielding repair layer is visually inspected to confirm that the surface of the conductor shielding repair layer is free of defects such as holes, pits, and scratches.

[0012] In some embodiments of the present application, the repair process further comprises the following steps:

[0013] S7. Repeat steps S3 to S6, set an insulating hollow tube with the same size as the first insulating layer to complete the repair of the first insulating layer and the second insulating layer, and set a semiconductor hollow tube with the same size as the first insulating shielding layer to complete the repair of the first insulating shielding layer and the second insulating shielding layer.

[0014] In some embodiments of the present application, in step S3, the semiconductor hollow tube is made of the same material as the first conductor shielding layer and the second conductor shielding layer.

[0015] In some embodiments of the present application, the heating mold includes heating plates arranged in pairs, and the two heating plates cooperate to form a heating groove for the semiconductor hollow tube to be set. The heating plates are provided with heating holes and connecting holes. A heating rod is provided in the heating hole, and a connecting bolt is passed through the connecting hole to fix the two heating plates.

[0016] In some embodiments of the present application, in step S4, a plurality of heating holes are provided, and the heating holes are sequentially arranged along the circumference of the heating groove.

[0017] In some embodiments of the present application, in step S4, there are multiple connecting holes.

[0018] In some embodiments of the present application, in step S4, a layer of polytetrafluoroethylene tape is laid inside the heating plate before the heating plate is set.

[0019] The embodiment of the present invention provides a process for repairing the shield layer of a 35kV polyethylene-based non-cross-linked insulated power cable conductor. Compared with the prior art, the process has the following advantages:

[0020] The semi-conductive hollow tube of the present application adopts the same thermoplastic semi-conductive material as the cable body. Compared with the thermosetting cross-linked material, it is reusable, and the service life of the repaired cable joint is the same as that of the cable body.

[0021] The repaired conductor shielding repair layer is fused with the original conductor shielding layer, eliminating the gap between the semi-conductive layer of the cold shrink preform and the cable body, thus avoiding the influence of discharge in the gap on the quality of the cable joint.

[0022] The repaired conductor shielding repair layer has the same size as the original conductor shielding layer, so that the electric field between the two sections of the cable transitions evenly, avoiding the distortion of the electric field at the break of the cable conductor shielding layer, and ensuring the safe operation of the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of repairing the first cable and the second cable in some embodiments of the present application;

[0024] Figure 2 A cross-sectional view of a semiconductor hollow tube according to some embodiments of the present application;

[0025] Figure 3 A side view of a semiconductor hollow tube according to some embodiments of the present application;

[0026] Figure 4This is a schematic structural diagram of a heating mold in some embodiments of the present application;

[0027] Figure 5 This is a schematic structural diagram of a conductor repair shielding layer in some embodiments of the present application.

[0028] In the figure, 1. first cable; 11. first conductor layer; 12. first conductor shielding layer; 13. first insulation layer; 14. first insulation shielding layer; 2. second cable; 21. second conductor layer; 22. second conductor shielding layer; 23. second insulation layer; 24. second insulation shielding layer; 3. welding point; 4. semiconductor hollow tube; 5. heating mold; 51. heating plate; 52. heating hole; 53. connecting hole; 6. conductor shielding repair layer. DETAILED DESCRIPTION

[0029] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0030] It should be understood that the present invention uses terms such as "front" and "back" to describe various types of information, but such information should not be limited to these terms. These terms are merely used to distinguish information of the same type from one another. For example, "front" information could also be referred to as "back" information, and "back" information could also be referred to as "front" information without departing from the scope of the present invention.

[0031] like Figures 1 to 5 As shown, an embodiment of the present invention provides a 35kV polyethylene-based non-cross-linked insulated power cable conductor shielding layer repair process for repairing and connecting a first cable 1 and a second cable 2. The first cable 1 includes a first conductor layer 11, a first conductor shielding layer 12, a first insulating layer 13, and a first insulating shielding layer 14 arranged in sequence from the inside to the outside. The second cable 2 includes a second conductor layer 21, a second conductor shielding layer 22, a second insulating layer 23, and a second insulating shielding layer 24 arranged in sequence from the inside to the outside. Specifically, the cable repair process includes the following steps:

[0032] S1. Cut the first cable 1 and the second cable 2 along one end to form a connecting section, grind the first conductor shielding layer 12, the first insulating layer 13 and the first insulating shielding layer 14 of the first cable 1 to expose the first conductor layer 11 of the first cable 1, and grind the second conductor shielding layer 22, the second insulating layer 23 and the second insulating shielding layer 24 of the second cable 2 to expose the second conductor layer 21 of the second cable 2; as the first cable 1 gradually moves away from the connecting section, the first conductor shielding layer 12 and the first insulating layer 13 are arranged in a tapered shape; as the second cable 2 gradually moves away from the connecting section, the second conductor shielding layer 22 and the second insulating layer 23 are arranged in a tapered shape;

[0033] S2. Keep the connecting section of the first cable 1 and the second cable 2 flat, align the first cable 1 and the second cable 2 so that their axes are on the same horizontal line, set a welding point 3 at the connecting section of the first cable 1 and the second cable 2, grind and polish the welding point 3, and weld the first cable 1 and the second cable 2 together through the welding point 3;

[0034] S3. Provide a semiconductor hollow tube 4 having an inner diameter identical to the outer diameters of the first conductor layer 11 and the second conductor layer 21. The semiconductor hollow tube 4 is made of the same material as the first conductor layer 11 and the second conductor layer 21. Use a cutting tool to cut the semiconductor hollow tube 4 axially to form an opening communicating the inside and the outside of the semiconductor hollow tube 4. Slide the semiconductor hollow tube 4 over the first conductor layer 11 and the second conductor layer 21 through the opening, and ensure that the semiconductor hollow tube 4 overlaps the first conductor shielding layer 12 and the second conductor shielding layer 22.

[0035] S4. A heating mold 5 is provided to cover the semiconductor hollow tube 4. The heating mold 5 includes a pair of heating plates 51. The two heating plates 51 cooperate to form a heating groove for the semiconductor hollow tube 4. The heating plates 51 are provided with heating holes 52 and connecting holes 53. When in use, a heating rod is placed in the heating hole 52, and a connecting bolt is passed through the connecting hole 53 to fix the two heating plates 51. The semiconductor vacuum tube is heated by the heating mold 5 to melt it. As the semiconductor vacuum tube melts, the heating mold 5 is gradually locked to ensure that the heating mold 5 always fits the semiconductor hollow tube 4. When the temperature of the heating mold 5 reaches a specified value, the temperature rise is stopped, and the heating mold 5 is kept warm.

[0036] S5, after the heat preservation is completed, wait for the heating mold 5 to cool naturally, and then remove the heating mold 5;

[0037] S6. After cooling, the semiconductor hollow tube 4 forms a conductor shielding repair layer 6 integrated with the first conductor layer 11 and the second conductor layer 21. The conductor shielding repair layer 6 is polished according to the original size of the first conductor shielding layer 12. The appearance of the conductor shielding repair layer 6 is visually inspected to confirm that the surface of the conductor shielding repair layer 6 is free of defects such as holes, pits, and scratches.

[0038] Optionally, in order to further enhance the heating effect, the heating plate 51 of the present application is provided with a plurality of heating holes 52 and connecting holes 53 .

[0039] Furthermore, in step S4 , before the heating plate 51 is used to cover the semiconductor vacuum tube, polytetrafluoroethylene tape is laid inside the heating plate 51 , thereby preventing the semiconductor vacuum tube from adhering to the heating plate 51 and facilitating normal disassembly of the heating plate 51 .

[0040] Based on the above operations, this application uses a thermoplastic semiconductor material that is consistent with the cable body. Compared with thermosetting cross-linked materials, it is reusable, and the repaired cable joint has the same life as the cable body; the repaired conductor shielding repair layer and the original conductor shielding layer are molten together, and the gap between the cold-shrink preform main semiconductor layer and the cable body is removed, avoiding the impact of discharge generated in the gap on the quality of the cable joint; the repaired conductor shielding repair layer is the same size as the original conductor shielding layer, so that the electric field between the two sections of the cable is evenly transitioned, avoiding the distortion of the electric field at the fracture of the cable conductor shielding layer, and ensuring the safe operation of the cable.

[0041] Furthermore, the semiconducting hollow tube 4 is prefabricated in the factory using the same material as the cable body. At the construction site, a cutting tool is used to cut the semiconducting hollow tube 4 in the axial direction. Since the semiconducting hollow tube 4 has a certain deformation range, the incision of the semiconducting hollow tube 4 can be enlarged, and the semiconducting hollow tube 4 is centered in the middle of the cable through the incision, so that the dimensions of the semiconducting hollow tube 4 overlapping the first conductor shielding layer 12 and the second conductor shielding layer 22 remain consistent. The tube can then be heated and used, and its surface is rounded and smooth, resulting in high surface quality after restoration. This method eliminates the need to wrap with a tape made of the same material as the cable body or to polish any uneven surfaces. Due to the high timeliness requirements for power cable construction, this method can save a certain amount of construction time and accelerate the repair of the power system.

[0042] Compared with the silicone rubber heating belt, the metal heating mold 5 has a longer lifespan, and long-term repeated heating has little effect on the mold itself and is not prone to deformation. In addition, due to its good thermal conductivity, the heating surface is round and smooth, and has good contact with the semiconductor hollow tube 4, so that the heated area during heating is large and uniform, thereby improving the quality of the cable after heating repair.

[0043] Compared with the wrap-around welding joint that uses a variety of strips and accessories to provide different functions, the metal heating mold 5 can simultaneously perform the functions of heating, heat equalization, pressurization, shaping and heat preservation. The heating mold 5 is provided with a heating tube hole for placing a heating tube for heating. The heating surface of the heating mold 5 is round and smooth, and has good contact with the semiconductor hollow tube 4, ensuring uniform heating. Because the semiconductor hollow tube 4 is designed to be surplus, the two halves of the heating mold 5 are not in contact or tightened when installing the heating mold 5, and are only initially fixed by bolts. During heating, the semiconductor hollow tube 4 gradually melts, and the bolts must be gradually tightened to ensure that the heating mold 5 is completely in contact with the semiconductor hollow tube 4 and squeeze out the excess molten semiconductor hollow tube 4. During this process, the heating mold 5 always applies a certain amount of pressure to the semiconductor hollow tube 4. During heating, the semiconductor hollow tube 4 will expand due to heat. The heating mold 5 is made of metal material, which has high rigidity and is not easily deformed, so it can shape the semiconductor hollow tube 4. The two halves of the heating mold 5 are both one-piece structures that can completely wrap the semiconductor hollow tube 4 tightly without gaps and have a certain thickness. When the temperature reaches the set value, the heat flow between the semiconductor hollow tube 4 and the heating mold 5 reaches a dynamic equilibrium, achieving a heat insulation effect on the semiconductor hollow tube 4.

[0044] In addition, for the 35kV cross-linked polyethylene power cable in this application, steps S3 to S6 can be repeated to set an insulating hollow tube with the same size as the first insulating layer 13, thereby completing the repair of the first insulating layer 13 and the second insulating layer 23, or setting a semiconductor hollow tube with the same size as the first insulating shielding layer 14, thereby completing the repair of the first insulating shielding layer 14 and the second insulating shielding layer 24.

[0045] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A 35kV polyethylene-based non-cross-linked insulated power cable conductor shield repair process, used for repairing and connecting a first cable and a second cable, wherein the first cable comprises a first conductor layer, a first conductor shield layer, a first insulation layer, and a first insulation shield layer arranged in sequence from the inside to the outside, and the second cable comprises a second conductor layer, a second conductor shield layer, a second insulation layer, and a second insulation shield layer arranged in sequence from the inside to the outside, characterized in that: The steps include: S1. Polish the first insulating shielding layer, the first insulating layer, and the first conductor shielding layer of the first cable to expose the first conductor layer of the first cable; polish the second insulating shielding layer, the second insulating layer, and the second conductor shielding layer of the second cable to expose the second conductor layer of the second cable; as the first cable gradually moves away from the connection section, the first conductor shielding layer and the first insulating layer are tapered; as the second cable gradually moves away from the connection section, the second conductor shielding layer and the second insulating layer are tapered; S2. Keep the connecting section of the first cable and the second cable flat, align the first cable and the second cable so that their axes are on the same horizontal line, set welding points at the connecting section of the first cable and the second cable, grind and polish the welding points, and weld the first cable to the second cable through the welding points; S3. Provide a semiconducting hollow tube having an inner diameter identical to the outer diameters of the first and second conductor layers, the semiconducting hollow tube being made of the same material as the first and second conductor shielding layers. Use a cutting tool to cut the semiconducting hollow tube axially to form an opening communicating the inside and outside of the semiconducting hollow tube. Slide the semiconducting hollow tube over the first and second conductor layers through the opening, overlapping the first and second conductor shielding layers. S4. Setting a heating mold to cover the semiconductor hollow tube, heating the semiconductor hollow tube through the heating mold to melt it, gradually tightening the heating mold as the semiconductor hollow tube melts, so that the heating mold always fits the semiconductor hollow tube, and stopping heating when the temperature of the heating mold reaches a specified value, and performing heat preservation treatment on the heating mold; S5. After the heat preservation is completed, wait for the heated mold to cool naturally, and then remove the heated mold; S6. After cooling, the semiconductor hollow tube forms a conductor shielding repair layer integrated with the first conductor layer and the second conductor layer. The conductor shielding repair layer is polished according to the original size of the first conductor shielding layer. The appearance of the conductor shielding repair layer is visually inspected to confirm that there are no holes, pits, or scratches on the surface of the conductor shielding repair layer. S7. Repeat steps S3 to S6, set an insulating hollow tube with the same size as the first insulating layer to complete the repair of the first insulating layer and the second insulating layer, and set a semiconductor hollow tube with the same size as the first insulating shielding layer to complete the repair of the first insulating shielding layer and the second insulating shielding layer.

2. The 35kV polyethylene-based non-cross-linked insulated power cable conductor shielding layer repair process according to claim 1 is characterized in that: The heating mold includes heating plates arranged in pairs, and the two heating plates cooperate to form a heating groove for the semiconductor hollow tube to be set. The heating plates are provided with heating holes and connecting holes. A heating rod is provided in the heating hole, and a connecting bolt is passed through the connecting hole to fix the two heating plates.

3. The 35kV polyethylene-based non-cross-linked insulated power cable conductor shielding layer repair process according to claim 2 is characterized in that: In the step S4, a plurality of heating holes are provided, and the heating holes are sequentially arranged along the circumference of the heating tank.

4. The 35kV polyethylene-based non-cross-linked insulated power cable conductor shielding layer repair process according to claim 2 is characterized in that: In step S4, a plurality of connection holes are provided.

5. The 35kV polyethylene-based non-cross-linked insulated power cable conductor shielding layer repair process according to claim 1 is characterized in that: In the step S4, a layer of polytetrafluoroethylene tape is laid inside the heating plate before the heating plate is set.

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