CN-121983891-A - Repair method of cable insulating layer

Abstract

The application relates to a repair method of a cable insulating layer, which comprises the steps of S1, winding an insulating material around a damaged area of the cable insulating layer to form a repair section, S2, sleeving a cold shrink tube on the repair section, enabling the cold shrink tube to shrink to apply pressure, S3, coating a graphene heating film outside the cold shrink tube, S4, heating the graphene heating film for a preset time to enable the insulating material to be molten, S5, removing the graphene heating film and the cold shrink tube after the insulating material is cooled and solidified, and S6, polishing the repair section until the size of the repair section is consistent with the outer diameter of the cable insulating layer in an undamaged area. The repairing method solves the problems of uneven heating, poor pressure control and the like in the existing repairing method, improves the electrical performance and long-term reliability of the repaired cable insulating layer, and meets the requirements of a nuclear power plant and the like on the power supply reliability. In addition, the cable is not required to be replaced integrally, so that the repair cost and the construction difficulty are reduced, and the operation risk is reduced.

Inventors

• ZHAO CHEN
• ZHANG XUAN
• XIANG LIANG
• Xu Longce
• XU NAIPING
• WANG YUFENG
• JIANG GUIBIN
• ZHANG WEI
• ZHANG CHUNYU
• ZHAO JUNWEN
• ZHANG HAO
• WU XIAODONG
• Niu Dongyuan
• WEI XIAO

Assignees

• 中广核核电运营有限公司

Dates

Publication Date

20260505

Application Date

20260202

Claims (10)

1. 1. A method of repairing an insulating layer of a cable, the method comprising: S1, winding an insulating material on a damaged area of a cable insulating layer to form a repair section; S2, sleeving the cold shrink tube on the repair section, and enabling the cold shrink tube to shrink so as to apply pressure; s3, coating a graphene heating film outside the cold shrink tube; S4, heating the graphene heating film for a preset time to enable the insulating material to be molten; s5, after the insulating material is cooled and solidified, the graphene heating film and the cold shrink tube are removed; and S6, polishing the repair section until the size of the repair section is consistent with the outer diameter of the cable insulating layer in the undamaged area.
2. 2. The repair method according to claim 1, wherein in step S1, the insulation material is wound around the damaged area in a half-lap manner, the half-lap manner including spirally winding at least one layer in a unidirectional direction along the cable axis and then spirally winding at least one layer in a reverse direction; the thickness of the repair section formed after winding is greater than 10% of the nominal outer diameter of the cable.
3. 3. The repairing method according to claim 1, wherein in step S2, a shrink tube having an inner diameter smaller than 30% of the outer diameter of the repairing section is selected and sleeved on the repairing section.
4. 4. The repair method of claim 1, wherein in step S2, a cold shrink tube having a support bar is selected, and the cold shrink tube is naturally contracted by drawing out the support bar of the cold shrink tube to apply a constant pressure.
5. 5. The repair method according to claim 1, further comprising step S21 of coating the heat conductive layer and the heat insulating layer in order outside the cold shrink tube after step S2.
6. 6. The repair method according to claim 5, wherein in step S21: The heat conducting layer is a metal foil; The heat insulation layer is a high-temperature-resistant film, and the high-temperature-resistant film is attached to the outer side of the heat conduction layer to fix the heat conduction layer.
7. 7. The repairing method according to claim 1, further comprising step S31 after step S3, wherein the graphene heating film is coated with an insulating layer.
8. 8. The repair method according to claim 1, wherein in step S4, the temperature of the graphene heat-generating film is raised to a temperature range of 185 ℃ to 195 ℃ and maintained for a preset time in the temperature range.
9. 9. The repair method according to claim 1, wherein in step S6, the repair segment is screw milled using a milling tool.
10. 10. The repair method according to claim 9, characterized in that in step S6, the outer diameter of the repair segment is measured in real time with a measuring tool while milling and grinding to control grinding accuracy.

Description

Repair method of cable insulating layer Technical Field The application relates to the technical field of power equipment state maintenance, in particular to a repair method of a cable insulating layer. Background Along with the continuous improvement of the requirements of facilities such as nuclear power, hydropower and data centers on the power supply reliability, the guarantee of the long-term safe and stable operation of the internal power cable, especially the 6.6kV to 35kV medium-voltage cable, is important. The main insulating layer of the cable may have defects such as local damage, scratch and the like due to mechanical damage and the like in long-term operation. These defects may cause distortion of the electric field, induce partial discharge, and if not handled in time, may eventually lead to insulation breakdown accidents. At present, on-site repair is generally selected for local damage of cable insulation in limited spaces such as nuclear power plants. In the related art, a hot-melt repair process based on a resistance wire heating belt is often adopted, and manual polishing is assisted to restore the appearance. Specifically, the damaged area is preprocessed, then the damaged area is covered by winding the insulating material, the resistance wire heating belt is wound to heat, so that the insulating material is melted and solidified, and finally the repair area is manually polished by the experience of an operator. However, the repairing method has obvious defects that firstly, the traditional resistance wire heating belt is a linear heat source, even distribution of heat is difficult to realize when the traditional resistance wire heating belt is wound, local overheating or insufficient heating areas are easy to generate, the repairing material is unevenly melted, air gaps or internal stress are remained at a repairing interface, and the electrical strength and long-term reliability after repairing are affected. Second, the lack of constant pressure control during repair results in difficult assurance of the interfacial bond tightness of the repair material to the cable body during melting and cooling. Disclosure of Invention Accordingly, it is necessary to provide a method for repairing a cable insulation layer, which aims at solving the problems of uneven heating and poor pressure control existing in the conventional method for repairing a cable insulation layer. The application provides a repair method of a cable insulating layer, which comprises the following steps: S1, winding an insulating material on a damaged area of a cable insulating layer to form a repair section; S2, sleeving the cold shrink tube on the repair section, and enabling the cold shrink tube to shrink so as to apply pressure; s3, coating a graphene heating film outside the cold shrink tube; S4, heating the graphene heating film for a preset time to enable the insulating material to be molten; S5, after the insulating material is cooled and solidified, the heat-insulating layer, the graphene heating film, the heat-insulating layer, the heat-conducting layer and the cold shrink tube are removed; and S6, polishing the repair section until the size of the repair section is consistent with the outer diameter of the cable insulating layer in the undamaged area. In one embodiment, in step S1, the insulating material is wound around the damaged area in a half-stacked manner, where the half-stacked manner includes unidirectional spiral winding of at least one layer along the cable axis, and then spiral winding of at least one layer along the opposite direction; the thickness of the repair section formed after winding is greater than 10% of the nominal outer diameter of the cable. In one embodiment, in step S2, a cold shrink tube with an inner diameter smaller than 30% of the outer diameter of the repair section after shrinkage is selected, and is sleeved on the repair section. In one embodiment, a cold shrink tube with support strips is selected, and the cold shrink tube is naturally shrunk by drawing off the support strips of the cold shrink tube so as to apply constant pressure. In one embodiment, step S2 is followed by step S21, where the heat-conducting layer and the heat-insulating layer are sequentially coated on the outside of the cold shrink tube. In one embodiment, in step S21: The heat conducting layer is a metal foil; The heat insulation layer is a high-temperature-resistant film, and the high-temperature-resistant film is attached to the outer side of the heat conduction layer to fix the heat conduction layer. In one embodiment, step S31 is further included after step S3, and the graphene heating film is covered with an insulation layer. In one embodiment, in step S4, the temperature of the graphene heating film is raised to a temperature range of 185 ℃ to 195 ℃ and maintained for a preset time in the temperature range. In one embodiment, in step S6, the repair segment is spiral milled and polished using a polishi