The state has explicitly ordered the use of copper wires in newly built houses. But the same copper wire, there are also inferior copper wires. The copper core is made of recycled copper, which contains many impurities. Some inferior copper wires are not as conductive as iron wires, which can easily cause electrical accidents. There are many varieties, specifications, and prices of wires on the market, making it very difficult for consumers to choose. Just in terms of the price of two copper core wires of 2.5 square millimeters and 4 square millimeters commonly used in home decoration, a coil of the same specification can have a price difference of 20% to 30% because of different manufacturers. As for the quality and length, it is even more difficult for consumers to judge.
According to industry sources, the huge price difference of wires is due to the different raw materials used in the production process. The main raw materials for the production of wires are electrolytic copper, insulating materials and sheathing materials. The electrolytic copper in the raw material market is about 50,000 yuan per ton, while the recycled miscellaneous copper is only about 40,000 yuan per ton; the price of high-quality products of insulating materials and sheathing materials is between 8,000 yuan and 10,000 yuan per ton, while defective products The price is only 4,000 yuan to 5,000 yuan per ton, and the price difference is even greater. In addition, insufficient length and insufficient glue content in insulators are also important reasons for price differences. The length of each reel is 100 meters for high-quality products, while only 90 meters for inferior products. The insulators contain 35%-40% of the glue, while the defective products are only 15%. By comparison, it is not difficult for consumers to see that the difference in the sales price of finished wires is caused by the presence of tricky materials.
Aging and failure
Causes of aging
1. External force damage. Judging from the operational analysis in recent years, especially in Pudong, Shanghai, where the economy is developing rapidly, a considerable number of cable failures are caused by mechanical damage.
2. The insulation is damp. This situation is also very common, and generally occurs at the cable joints in direct burial or piping. For example: unqualified cable joints and joints made in humid weather conditions will cause the joints to enter water or water vapor. For a long time, water branches will be formed under the action of the electric field, which will gradually damage the insulation strength of the cable and cause failure.
3. Chemical corrosion. The cable is directly buried in the area with acid and alkali, which will often cause the cable armor, lead skin or outer sheath to be corroded. The protective layer suffers from chemical corrosion or electrolytic corrosion for a long time, resulting in the failure of the protective layer and the reduction of insulation. The cable is faulty. Chemical: the unit’s cable corrosion situation is quite serious
4. Long-term overload operation. Overload operation, due to the thermal effect of the current, the conductor heating will inevitably be caused when the load current passes through the cable. At the same time, the skin effect of the charge, the eddy current loss of the steel armor, and the insulation loss will also generate additional heat, which will increase the temperature of the cable.
5. The cable connector is faulty. Cable joints are the weakest link in the cable line, and cable joint failures caused by direct faults (poor construction) by personnel often occur. In the process of making cable joints, if there are reasons such as insufficient joint crimping, insufficient heating, etc., the insulation of the cable head will be reduced, which will cause an accident.
6. Environment and temperature. The external environment and heat source of the cable can also cause the cable to overheat, insulation breakdown, and even explosion and fire.
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