What are the reasons for the aging of special cables?
The aging of wires and cables will directly endanger personal safety and cause dangerous accidents. The direct cause of the aging problem of special cables for wires and cables is the breakdown caused by insulation drop. There are many factors that cause the external insulation of the cable conductor to age and the protection performance to decline. Based on 20 years of experience in production and operation, Zhengzhou Jinshui Cable has summed up several main reasons.
一、Main cause of aging：
1. External damage: According to the operation analysis in recent years, many cable faults are caused by mechanical damage. For example, the control cable laying device is not a standard construction, which is likely to cause mechanical hazards; the direct buried cable civil construction is likely to endanger the operation of the cable. Sometimes, if the damage is not severe, it takes months or even years to completely destroy the affected area. Sometimes, if the hazard is serious, a short circuit may occur, which will directly affect the electricity users and their safety in production.
2. Insulation damp: This kind of situation is also very common, and usually occurs on cable joints in direct burial or exhaust pipes. For example, if a cable joint is improperly manufactured and manufactured in a humid climate, the joint will be filled with water or mixed with water vapor. Under the action of the electric field, water branches are formed for a long time, which gradually endangers the insulation strength of the cable and causes problems. This situation often occurs in the operation of power cables.
3. Chemical corrosion: The cable is directly buried in an area with an acid-base effect, which will corrode the armor, lead skin or outer protective layer of the cable. The protective layer has been subjected to chemical corrosion or electrolytic corrosion for a long time, resulting in failure of the protective layer and reduced insulation, resulting in cable damage. malfunction occurs.
4. Long-term overload operation: During overload operation, due to the heating effect of the current, when the load current passes through the cable, it will definitely cause the conductor to heat up and the skin shrinkage effect of the charge. The eddy current losses and dielectric losses of the steel armor also generate additional heat, increasing the cable temperature. If it is overloaded for a long time, the temperature will be too high to accelerate the aging of the insulation, and even the insulation will be broken. Especially in the hot summer, the temperature rise of the cable often causes the rupture of the thin cable insulation, so the cable has many failures in summer.
5. Cable joint failure: The cable joint is a very thin link in the cable line, and the cable joint failure is usually caused by the poor construction behavior of personnel. In the process of manufacturing cable joints, some original wires such as too loose joint pressure and insufficient heating heat can cause the insulation of the cable head to drop, causing existing safety accidents.
6. Environment and temperature: The external environment and heat source where the cable is located will also cause the cable to overheat, break the insulation, and even explode and fire.
二、Measures to prevent wire aging:
1. Fully consider the current carrying capacity of the wire, select the appropriate wire, and do not make it work for a long time at close to full load;
2. Keep the surrounding environment as dry as possible to prevent the wires from getting damp;
3. A wire protection sleeve can be added to isolate it from water and air;
4. Pay attention to the wire joints of different materials (commonly the connection between copper wires and aluminum wires), which is the most prone to problems.
5. Use a thicker power cord. The safe current of the power cord must be approximately the total operating current of the electrical appliance. Try to use copper core wires. Try to use steel pipes for laying the power cord. Try not to expose the power cord to avoid sunlight or wind. rain.
三、How to check wires and cables regularly:
"Accurate method to measure insulation, the megohm is not as low as two rooms. The humidity value in rainy days can be small, and the value can be reduced by half." It means that to judge the insulation condition of the line more accurately, the insulation resistance meter can be used to measure the insulation of the electrical line.