35kV polyvinyl non-crosslinking insulated power cable conductor shielding layer repairing process

Abstract

The invention relates to the technical field of cable repair, and discloses a 35kV polyvinyl non-crosslinked insulated power cable conductor shielding layer repair process which comprises the following steps: S1, processing the end parts of a first cable and a second cable to form sections, and polishing the first cable and the second cable to expose cable conductor layers; s2, welding and connecting the first cable and the second cable along the cross section, and polishing a welding spot until the diameter of the welding spot is equal to that of an original cable conductor layer; s3, arranging a semi-conductive hollow tube to wrap a cable conductor layer; s4, a heating mold is arranged to heat the semi-conductive hollow pipe so that the semi-conductive hollow pipe and the cable conductor layer can be connected into a whole; s5, after the heating mold is naturally cooled, the heating mold is dismantled; and S6, polishing the fused and molded semi-conductive hollow tube to enable the semi-conductive hollow tube to be consistent with the conductor shielding layers of the first cable and the second cable, and completing the repair of the conductor shielding layers. Compared with the prior art, according to the cable repairing process, an original conductor shielding layer and an existing conductor shielding layer are combined in a melting mode, and a gap between a semi-conductive layer of a cold shrinkage prefabricated part body and a cable body is eliminated.

Description

Technical Field

[0001] The invention relates to the technical field of cable repair, and 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 fusion joints. The wrapping type fusion joints are made of the same cross-linked material as the cross-linked polyethylene cable body. The 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-linked 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 fusion 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, polyimide tapes for shaping, heating tapes for heating and insulation cloth for insulation, 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 needs to use 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 shielding layer repair process, which is used to repair and connect a first cable and a second cable, wherein the first cable comprises a first conductor layer, a first conductor shielding layer, a first insulating layer and a first insulating shielding layer arranged in sequence from the inside to the outside, and the second cable comprises a second conductor layer, a second conductor shielding layer, a second insulating layer and a second insulating shielding layer arranged in sequence from the inside to the outside, and the cable repair process comprises the following steps:

[0006] S1. Cut the first cable and the second cable along one end to form a connection 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, as the first cable gradually moves away from the connection 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 connection 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 the axes of the first cable and the second cable 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 and the second cable together through the welding points;

[0008] S3, providing a semiconductor hollow tube with an inner diameter the same as the outer diameter of the first conductor layer and the second conductor layer, using a cutting tool to cut the semiconductor hollow tube along the axial direction to form an opening connecting the inside and the outside of the semiconductor hollow tube, sleeve the semiconductor hollow tube outside the first conductor layer and the second conductor layer through the opening, and make the semiconductor hollow tube overlap the first conductor shielding layer and the second conductor shielding layer;

[0009] S4, setting a heating mold to cover the semiconductor hollow tube, heating the semiconductor vacuum tube by the heating mold to make it melt, gradually locking 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 heating mold to cool naturally, and then remove the heating mold;

[0011] S6. The cooled 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, and the appearance of the conductor shielding repair layer is visually inspected to confirm that there are no defects such as holes, pits and scratches on the surface of the conductor shielding repair layer;

[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, and a heating rod is provided in the heating hole. Connecting bolts are passed through the connecting holes 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 each of the heating holes is sequentially arranged along the circumference of the heating groove.

[0017] In some embodiments of the present application, in step S4, a plurality of connection holes are provided.

[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 35kV polyethylene-based non-cross-linked insulated power cable conductor shielding layer repair process, which has the following beneficial effects compared with the prior art:

[0020] The semiconductive hollow tube of the present application adopts a thermoplastic semiconductive material consistent with the cable body. Compared with thermosetting cross-linked materials, it can be reused, and the repaired cable joint has the same service life as the cable body.

[0021] The repaired conductor shielding repair layer is fused with the original conductor shielding layer, eliminating the gap between the main 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 is evenly transitioned, avoiding electric field distortion at the break of the cable conductor shielding layer, and ensuring safe cable operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of repairing a first cable and a second cable according to 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 diagram of the structure of a heating mold in some embodiments of the present application;

[0027] Figure 5 This is a schematic diagram of the structure of the 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 specific implementation of the present invention is further described in detail below in conjunction with 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 the terms "front", "back", etc. to describe various information, but these information should not be limited to these terms, and these terms are only used to distinguish the same type of information from each other. For example, "front" information may also be referred to as "back" information, and "back" information may also be referred to as "front" information without departing from the scope of the present invention.

[0031] like Figures 1 to 5 As shown, the embodiment of the present invention provides a 35kV polyethylene-based non-cross-linked insulated power cable conductor shielding layer repair process, which is used to repair and connect 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, and 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 connection 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, 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 connection section, the first conductor shielding layer 12 and the first insulating layer 13 are arranged in a conical shape, and as the second cable 2 gradually moves away from the connection section, the second conductor shielding layer 22 and the second insulating layer 23 are arranged in a conical 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 the axes of the first cable 1 and the second cable 2 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, a semiconductor hollow tube 4 having an inner diameter the same as the outer diameter of the first conductor layer 11 and the second conductor layer 21 is provided, the semiconductor hollow tube 4 is made of the same material as the first conductor layer 11 and the second conductor layer 21, a cutting tool is used to cut the semiconductor hollow tube 4 along the axial direction to form an opening communicating the inside and the outside of the semiconductor hollow tube 4, the semiconductor hollow tube 4 is sleeved outside the first conductor layer 11 and the second conductor layer 21 through the opening, and 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 set 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 to be set, and the heating plate 51 is provided with a heating hole 52 and a connecting hole 53. When in use, the heating rod is set in the heating hole 52, and the connecting bolt is passed through the connecting hole 53 to fix the two heating plates 51, and 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, so that the heating mold 5 is always in contact with 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 heat-insulated;

[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. The cooled 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 there are no defects such as holes, pits and scratches on the surface of the conductor shielding repair layer 6.

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

[0039] Furthermore, in step S4 , polytetrafluoroethylene tape is laid inside the heating plate 51 before the heating plate 51 is used to cover the semiconducting vacuum tube, so as to avoid adhesion between the semiconducting vacuum tube and the heating plate 51 , which is helpful for normal disassembly of the heating plate 51 .

[0040] Based on the above operations, the present application adopts a thermoplastic semiconductor material consistent with the cable body. Compared with thermosetting cross-linked materials, the thermoplastic semiconductor material is reusable, and the life of the repaired cable joint is consistent with that of the cable body; the repaired conductor shielding repair layer and the original conductor shielding layer are molten bonded to remove the gap between the main semiconductor layer of the shrink preform and the cable body, thereby avoiding the influence of the 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 electric field distortion 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, and the semiconducting hollow tube 4 is cut in the axial direction using a cutting tool at the construction site. 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 size of the semiconducting hollow tube 4 overlapping the first conductor shielding layer 12 and the second conductor shielding layer 22 is consistent, and it can be heated for use, and its surface is round and smooth, and the surface quality of the restored cable is high. This method does not require wrapping with the same tape as the cable body material and polishing the uneven surface. Due to the high timeliness requirements of power cable construction, a certain amount of construction time can be saved and the repair of the power system can be accelerated.

[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 easy to deform. 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 have the functions of heating, equalizing heat, pressurizing, shaping and keeping warm. A heating tube hole is provided in the heating mold 5, and a heating tube can be placed therein for heating; the heating surface of the heating mold 5 is round and smooth, and has good contact with the semiconductor hollow tube 4, so that the heating is uniform; because the semiconductor hollow tube 4 is a surplus design, when the heating mold 5 is installed, the two halves of the mold are not in contact and tightened, and are only initially fixed by bolts. During heating, the semiconductor hollow tube 4 gradually melts, and at this time, the bolts must be tightened step by step to make the heating mold 5 completely fit and squeeze out the excess molten semiconductor hollow tube 4. During this process, the heating mold 5 always applies a certain pressure to the semiconductor hollow tube 4; during heating, the semiconductor hollow tube 4 will expand due to heat, and the heating mold 5 uses a metal material, which has high rigidity and is not easy to deform, and can shape the semiconductor hollow tube 4; the two halves of the heating mold 5 are both one-piece structures, which 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 balance, and the heat preservation effect on the semiconductor hollow tube 4 is achieved.

[0044] In addition, for the 35kV cross-linked polyethylene power cable in the present application, it can also repeat steps S3 to S6, set an insulating hollow tube with the same size as the first insulating layer 13, so as to complete the repair of the first insulating layer 13 and the second insulating layer 23, or set a semiconductor hollow tube with the same size as the first insulating shielding layer 14, so as to complete 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 shielding layer 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 shielding layer, a first insulating layer and a first insulating shielding layer arranged in sequence from the inside to the outside, and the second cable comprises a second conductor layer, a second conductor shielding layer, a second insulating layer and a second insulating shielding layer arranged in sequence from the inside to the outside, characterized in that: The steps include: S1. 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, and 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. As the first cable gradually moves away from the connection 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 connection section, the second conductor shielding layer and the second insulating layer are arranged in a tapered shape. S2. Keep the connecting section of the first cable and the second cable flat, align the first cable and the second cable so that the axes of the first cable and the second cable 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 and the second cable together through the welding points; S3, providing a semiconductor hollow tube with an inner diameter the same as the outer diameter of the first conductor layer and the second conductor layer, using a cutting tool to cut the semiconductor hollow tube along the axial direction to form an opening connecting the inside and the outside of the semiconductor hollow tube, sleeve the semiconductor hollow tube outside the first conductor layer and the second conductor layer through the opening, and make the semiconductor hollow tube overlap the first conductor shielding layer and the second conductor shielding layer; S4, setting a heating mold to cover the semiconductor hollow tube, heating the semiconductor vacuum tube by the heating mold to make it melt, gradually locking 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; S5, after the heat preservation is completed, wait for the heating mold to cool naturally, and then remove the heating 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 defects such as holes, pits and scratches on the surface of the conductor shielding repair 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 following steps are also included: 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.

3. 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 S3, the semiconductor hollow tube is made of the same material as the first conductor shielding layer and the second conductor shielding layer.

4. 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 arranged in the heating hole. Connecting bolts are passed through the connecting holes to fix the two heating plates.

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 plurality of heating holes are provided, and each of the heating holes is sequentially arranged along the circumference of the heating groove.

6. 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 plurality of connection holes are provided.

7. 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.

Images