Wire and cable aging reasons and analysis of bad points
What are the general reasons for cable aging? The most direct cause of wire cable aging failure is the breakdown of insulation and breakdown. There are many factors that reduce the conductivity of the conductive insulation. According to the actual operating experience, it can be summarized in the following cases.
1) Cable aging causes: external force damage. From the operational analysis in recent years, especially in Shanghai Pudong, where the economy is developing at a high speed, quite a number of cable faults are now caused by mechanical damage. For example, when the cable is laid and installed, the construction is not standardized, which is easy to cause mechanical damage. It is also very easy to damage the cable during operation by conducting civil construction on the directly buried cable. Sometimes if the damage is not serious, it will take months or even years to cause the damage to break down completely, and sometimes the damage may occur, and the short-circuit fault may occur, which directly affects the safe production of electricity and electricity.
2) Cable aging reasons: insulation is damp. This is also common and occurs generally at cable joints in direct buried or drained pipes. For example, if the cable joint is unqualified and the joint is made under humid climatic conditions, the joint will be filled with water or mixed with water vapor. After a long time, the water branch will form under the action of the electric field, which will gradually damage the insulation strength of the cable and cause malfunction.
3) Causes of cable aging: chemical corrosion. The cable is directly buried in an acid-base area, which often causes the cable armor, lead or outer sheath to be 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. Cable failure. Chemical: The corrosion of the cable in the unit is quite serious.
4) Cable aging reasons: long-term overload operation. Overload operation, due to the thermal effect of the current, the load current will inevitably lead to the heating of the conductor when passing through the cable. At the same time, the skin effect of the charge and the eddy current loss of the steel crucible and the loss of the insulating medium will also generate additional heat, thereby increasing the cable temperature. In the case of long-term overload operation, too high a temperature will accelerate the aging of the insulation, and the insulation will be broken down. Especially in the hot summer months, the temperature rise of the cable often leads to the breakdown of the cable insulation first, so in the summer, the cable is particularly faulty.
5) Cable aging reasons: cable connector failure. Cable joints are the weakest link in cable lines, and cable joint failures caused by direct personnel failure (poor construction) often occur. During the process of making the cable joints, the construction personnel may cause the cable head insulation to be lowered if there is a joint such as a tight crimping or insufficient heating, which may cause an accident.
6) Cable aging reasons: environment and temperature. The external environment and heat source where the cable is located can also cause excessive cable temperature, insulation breakdown, and even an explosion.