1. The raw material of the cable is damp           ABC cable

The raw materials used for cable insulation and sheath are mainly plastic and rubber materials, and many kinds of materials with special functions are derived from this modification. When the material manufacturing plant manufactures materials, through the process of compounding agent mixing, kneading, granulation, cooling and drying, as well as during the transportation and storage of materials, it often suffers from moisture to varying degrees, so that the materials contain varying degrees of moisture. Therefore, before the cable manufacturer extrudes the material on the cable conductor, the material must be dried and managed. The extruder unit is equipped with a material drying device to prevent the extruded insulating layer and sheath from occurring. Bubbles and trachoma, no bubbles on the surface and other defects. This is a rigid process regulation of the cable manufacturer, otherwise the finished cable will not pass the factory withstand voltage test.

2. The cable manufacturing process is damp

During the insulation extrusion process, the insulation layer is scratched, causing the insulation layer to be broken or degummed, and the insulated wire core enters water in the cooling water tank, resulting in a decrease in insulation resistance. Or when the sheath is squeezed, the sheath is damaged and water enters, making the insulation layer damp and the insulation resistance reduced. When manufacturing multi-core cables, even if the insulation layer is extruded and intact, damage may occur when the insulated cores are twisted into a cable, and when the sheath is extruded, water will get wet, so the finished cable will not pass the factory withstand voltage test. 

3. The cable construction process is damp

During the construction of direct-buried cables, if the excavation of cable trenches, cable burying operations, and non-standard production of cable intermediate joints and terminal joints, etc., the cable sheath and insulation layer are likely to be damaged. If the soil is wet or the cable trench is flooded, the cable will be flooded. After the insulation is damp, the surface resistance of the cable insulation decreases, the surface leakage current increases, the insulation resistance decreases, and the electric field distortion between the conductor and the insulation layer is caused. The uneven distribution of the electric field in the insulation will cause free discharge inside the insulation, and even cause cable breakdown. The after-sales service practice has proved that more than 95% of the direct buried cable insulation resistance drop accidents are caused by improper construction.