Analysis of the causes of wire and cable insulation breakdown, breakdown means that the original insulation function of the cable's insulation layer is damaged due to external force damage, (extrusion, lightning strike, etc.), aging of insulation materials, etc., and the original insulation function is lost. During the operation of the cable, the core wire to the core wire, the core wire to the outer protective steel strip of the cable and the discharge to the ground will form a fault of grounding short circuit.
There are several reasons for wire and cable insulation breakdown.
1. Mechanical damage
Due to the heavy object hitting the cable, the excavator accidentally injured the cable. When the cable is laid, the cable is bent too much, which will damage the insulation. During the shipment, the cable is severely squeezed and the insulation and protective layer are damaged. , which will damage the insulation and even break the cable.
To prevent the mechanical damage of cables, overhead cables can be used. If the cables are laid along the wall, they should be covered. The burial should be marked with obvious signs, and soil borrowing near the cable lines should be prevented in time.
2. Improper construction
Due to the poor construction method and the poor quality of the materials used, the weak links of the cable head and the center fail, resulting in the breakdown of the insulating layer.
To prevent this phenomenon, the installation quality of the cable head should be improved. During the manufacture and installation of the cable head, the insulating bag should be tight and no open space should be present. Before epoxy resin and quartz powder, it should be strictly dried to prevent air bubbles and moisture from entering the cable head, and the insulation treatment of the edge of the lead sheath should be strengthened.
3. Insulation damp
Due to the poor construction process of the cable head, moisture penetrates into the inside of the cable, or the inner sheath of the cable is damaged and moisture enters. The lead-clad cable was laid near the source of the earthquake, and it was fatigued and cracked due to long-term vibration. The cable sheath is corroded and voids occur. There are small holes or cracks in the lead pack due to poor manufacturing quality.
In view of these situations, the protection of the outer layer of the cable should be strengthened, and a layer of asphalt should be painted on the outer sheath regularly.
4. Overvoltage
The insulating layer is broken down due to atmospheric overvoltage or internal overvoltage, especially the internal overvoltage of the system will cause multiple cables to be broken down at the same time.
In this regard, lightning arresters should be installed to improve the technological level of automatic protection of the system.
5. Insulation aging
In the long-term operation of the cable, due to poor heat dissipation or overload, the electrical and mechanical properties of the insulating material are deteriorated, and the insulating layer becomes brittle or cracked.
If so, the preventive withstand voltage test of the incoming cable should be carried out periodically, and it is found that the cable insulation decline cannot meet the requirements of safe operation, and a new cable should be replaced.
Skype: verdecable