Wire and cable are used for power transmission, transmission of information and electromagnetic energy conversion of a huge category of electrical products. In the process of spot check, found a large number of unqualified products. These inferior products to the normal operation of the power system buried a lot of hidden dangers.
1, mark unqualified wire and cable. Mark is the main way to use wire and cable to identify the basic information of the product. According to the standard provisions of the main content of the mark is: product model, specification, standard number, factory name, origin and so on in a certain mark space. When the mark is unqualified, it will cause construction personnel identification error, serious will cause electrical accidents.
2. Wires and cables with unqualified structure and size. The main problem of the structure size is the sheath thickness, insulation thickness, when the sheath and insulation thickness of 4mm2 solar pv cable is not up to standard, the electrical strength of wire and cable will be gravely reduced, leading to the shortened service life of wire and cable, serious can lead to wire and cable breakdown, insulation (sheath) layer can not play a normal protective role, Thus, electrical short circuit and fire occur.
3, sheath type insulation before aging tensile strength, elongation of qualified wire and cable. The tensile strength and elongation of the insulation sheath before aging considerably shorten the working life of the wire and cable, and in the construction or in a long time energized and elevated temperature environment, it is extremely easy to break the insulator, resulting in the live conductor exposed, the occurrence of electric short circuit risk. The main reason for its unqualified is the use of recycled material production, in order to reduce the cost of the product, the second is not qualified for production of tiny enterprises.
4. Wires with unqualified conductor resistance. Conductor resistance is an essential index to check whether the conductor material and section of wire and cable are in conformity. When the conductor resistance exceeds the standard, it increases the loss when the current passes through the wire and intensifies the heating of the wire and cable. The main reason for the unqualified conductor resistance is that in order to reduce the cost, enterprises shrink the copper material, which accounts for 80% of the raw material cost, either to reduce the cross-sectional area of the conductor or to use recycled copper containing too much impurities. As a result, the conductor resistance of the wire and cable exceeds the standard seriously. In the process of use, in addition to easily causing fire, it will accelerate the aging of the insulation layer covered by the wire.
In the process of buying wire and cable, consumers should pay attention to matters
First, to observe the appearance of the wire. The insulation (sheath) layer of qualified products is soft, ductile and flexible, and the surface layer is tight, smooth and without rough feeling. If the plastic that wraps the wire can easily be peeled off, there is a problem that the plastic is not strong enough.
Second, look at the section of the wire. The copper or aluminum core surface of the qualified product shall have a metallic luster. Blackened copper or white aluminum surface indicates oxidation.
Third, when buying wire, you should pay attention to checking the quality certificate. If the quality of the wire is up to standard, then the quality of the wire should have been tested and there should be no huge problem.