Power cables are cables used to transmit or distribute high-power electrical energy in power systems. With the rapid development of the petrochemical industry worldwide, plastic-insulated power cables have become an important type of low-voltage power cable due to their simple manufacturing process and convenient construction and maintenance. However, defects such as dents, scratches, crushing damage, and breakdowns are inevitable during the extrusion process of plastic-insulated cables. In order to ensure fixed-length production, reduce waste, and ensure that the electrical performance of the finished cables meets the standard requirements, it is necessary to find suitable methods for repairing insulation damage.
1. Hot welding repair method
The hot soldering method uses a soldering iron of appropriate power to heat the insulation and fuse it together.
1.1 Low-voltage polyvinyl chloride insulated cable
Polyvinyl chloride (PVC) is a thermoplastic material, and when used to repair damaged cable insulation, it should be welded. To ensure and enhance the electrical and mechanical properties of the repaired area, insulating tape should be wrapped around the repaired area in a single layer, ensuring the wrapping is smooth.
1.2 Low-voltage cross-linked polyethylene insulated cable
Cross-linked polyethylene (XLPE) is a thermosetting material; after silane cross-linking, the insulating molecular network solidifies. Before the water-boiling cross-linking process of the insulated wire core, insulation damage is repaired using a hot welding method, followed by wrapping the repair area with transparent tape to prevent it from falling off. After the water-boiling cross-linking process, insulation damage should first be repaired using a hot welding method, followed by overlapping wrapping with 35kV high-voltage self-adhesive tape, ensuring the high-voltage tape wrapping is flat.
2. Heat shrink tubing repair method
The heat shrink tubing repair method involves placing a suitably sized heat shrink tubing over the defect, heating it to shrink it, and tightly wrapping the defect.
Regardless of whether the insulation material is thermoplastic polyvinyl chloride or thermosetting cross-linked polyethylene, insulated wire cores with a nominal cross-section of less than 10 mm2 should be repaired with heat shrink tubing. After the heat shrink tubing repair is completed, it should be wrapped with insulating tape.
3. Comparison of Repair Methods
Thermal welding repair, using tools such as soldering irons, can restore the insulation layer to the level of an intact cable. However, the repair process is relatively complex and requires operators with a high level of skill. For conductors with smaller cross-sections, thermal welding may not guarantee repair quality; in such cases, heat shrink tubing repair should be used instead.
To ensure that the electrical performance of the repaired insulated conductor meets the standard requirements, an insulation spark test and a 3.5kV/5min withstand voltage test must be performed. The above repair methods are only applicable to minor insulation damage. For severe defects such as scratches, dents, or impacts, repairs are not permitted to ensure product quality.
