Factors that cause insulation degradation
1> Insulation is damp. This condition is also common and generally occurs at cable joints in direct buried or drained pipes. For example, if the cable joint is not qualified and the joint is made under humid climatic conditions, the joint will be filled with water or mixed with water vapor. For a long time, the water branch will form under the electric field effect, which will gradually damage the insulation strength of the cable and cause problems.
2> Chemical corrosion. The cable is directly buried in the acid-base effect area, and the cable sheathing, lead skin or outer sheath is often corroded. The protective layer is chemically corroded or electrolytically corroded for a long time, causing the protective layer to fail and the insulation to be lowered. Causes cable problems. The corrosion of the cable in the unit is quite serious.
3> Long-term overload operation. Overloading, because of the thermal effect of the current, the load current will cause the conductor to heat up when passing through the cable. The skin effect of the charge together with the eddy current loss of the steel stern and the loss of the insulating medium will also generate additional heat, and then increase the cable temperature. Excessive temperature during the long-term overload operation will accelerate the aging of the insulation, so that the insulation is broken down. Especially on hot summer days, the temperature rise of the cable often leads to the breakdown of the insulation of the cable, so in the summer, the cable is particularly problematic.
4> Cable connector problems. The cable connector is the thinnest link in the cable line, and the fault caused by the direct fault of the person (poor construction) often occurs. During the process of manufacturing the cable joints, if the original network is not tightly crimped or insufficiently heated, the insulation of the cable head will be reduced, and then the incident will be triggered.
5> Environment and temperature. The external environment and heat source where the cable is located may also cause excessive cable temperature, insulation breakdown, and even an explosion. In order to be safe, we must pay attention to the above points.