Electric wire and cable is a kind of electrical product which is used to transmit power, transmit information and realize electromagnetic energy conversion. 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 many hidden dangers. 

1. Mark unqualified wires and cables. Mark is the main way to identify the basic information of the product used for electric wires and cables. According to the standard, the main content of the mark is: product model, specification, standard number, factory name, origin, etc., within a certain mark spacing. 

2. Wires and cables with unqualified structure and size. Structure size of the main problem is the thickness of sheath and insulation thickness, when the thickness of sheath and insulation of the cable is not up to standard, the electric wire electric cable electric resistance strength can severely reduce, lead to the service life of wire and cable, serious when can be led to the breakdown, wire and cable insulation (sheath) less than normal protective layer, thus the phenomenon such as electrical short circuit and fire. 

3, sheath insulation before aging tensile strength, elongation of qualified wire and cable. Insulation sheath aging before the tensile strength, elongation is not qualified directly greatly shorten the working life of the wire and cable, and in the construction or in a long time power and high temperature environment, it is very easy to appear insulator fracture, resulting in live conductor exposed, can shock type short circuit risk. The main reason for its unqualified is the use of recycled materials production, to reduce product costs, two is not qualified for the production of small enterprises. 

4, conductor resistance unqualified wire. Conductor resistance is an important index to evaluate whether the conductor material and cross section of wires and cables conform. When the conductor resistance exceeds the limit, it will increase the loss of current through the line, aggravating the heat of the wire and cable. Conductor resistance is unqualified, basically into the enterprise to reduce costs, will account for 80% of the cost of raw materials of copper shrink, or reduce the cross-sectional area of conductors, or use renewable copper containing impurity is too high, so the electric wire electric cable conductor resistance exceeds bid badly, in use process in addition to the fire, will also accelerate coated outside the wire insulation aging. 

In the process of purchasing wires and cables, consumers should pay attention to the following matters: 

First, observe the appearance of the wires. The insulation (sheath) layer of the qualified products is soft, flexible and flexible, and the surface layer is compact, smooth and free from roughness. If the plastic covering the wires is easily removed, the problem is that the plastic is not strong enough. 

Second, to see the section of the wire. The surface of the copper or aluminum core of the qualified product shall have a metallic luster, and the black copper or white aluminum indicates that it has been oxidized. 

Third, in the purchase of power lines should pay attention to check the quality certificate. If the wire quality is good, then the wire quality should also be inspected, there will be no major problems.