How to detect commonly used wires and cables? 1. Electr […]
How to detect commonly used wires and cables?
1. Electrical function detection
Wires mainly include conductor DC resistance, insulation resistance, product voltage test and voltage test between insulated cores. Each item is very important. The conductor resistance directly reflects the electrical transmission function of the cable and directly affects the temperature, life, Voltage drop and safe operation. It mainly investigates the material and cross-sectional area of the conductor. If the conductor material is not good or the cross-sectional area is severely insufficient, the conductor DC resistance will be severely overrun. This kind of cable will increase the current on the line. The loss when passing on the road causes the cable conductor itself to heat up, causing the insulation aging and cracking of the covered conductor, forming a power supply line leakage, short circuit, or even a fire, endangering the safety of people and property. The standard has strict regulations on the DC resistance values of the conductors of different standard cables, and shall not be greater than the value of the standard regulations.
Insulation resistance, product voltage test and voltage test between insulated wires all investigate the electrical insulation function of cable insulation layer and sheath layer. Insulation resistance is to detect the resistance of the insulation material between two conductors. To the effect of insulation maintenance. The product voltage test and the voltage test between the insulated wires not only require the cable to have satisfactory insulation ability, but also require that the insulation or sheath material is uniform and free of impurities, the thickness is satisfactory and uniform, and the appearance must not have invisible trachoma, pinholes, etc., otherwise it will form Partial breakdown during the pressure test.
2. Mechanical function detection
It is mainly to investigate the tensile strength and crack elongation of insulation and sheath plastic materials, including before and after aging, as well as the deflection test, bending test, load breaking core test, insulation wire core tear test, etc. Static deflection test, etc. The tensile strength before and after aging, and the crack elongation before and after aging are the most important and fundamental goals of cable insulation and jacket materials. They are required to be used as cable insulation and jacket materials. They must have satisfactory tensile strength and are not easy to pull. It must have certain flexibility. Aging refers to the ability of insulation and sheath materials to maintain their original function under high temperature conditions. Aging should not severely affect the tensile strength and elongation of the material, which will directly affect The service life of the cable, if the tensile strength and crack elongation are unqualified, it is very easy to crack the sheath or insulator during the construction of the cable, or the sheath and insulation of the cable used in light and heat environment are easy to change Brittle and cracked, which exposes the live conductor and creates the risk of electric shock.
Because other flexible cables are not fixedly laid, there are repeated dragging and twisting during use. Therefore, there are other regulations about flexible cable standards. Dynamic bending test, twist test, load core breaking test and insulated core are added to the cable of the product. Tear test, static deflection test, etc., to ensure that this cable meets the requirements in actual use. For example, the dynamic deflection test mainly checks whether the flexible conductor's stranded wire is cracked to reduce the transmission function of electricity when the flexible cable is subjected to external mechanical stretching and bending stress, or punctures the insulation to reduce the insulation electrical function; insulation The stress effect is a test method of whether the deformation or cracking affects the electrical insulation function of the cable.
3. Insulation and sheath material function test
Including thermal weight loss, thermal shock, high temperature pressure, low temperature tortuosity, low temperature stretching, low temperature impact, flame retardant function, etc. These are to investigate the function of the plastic material of the insulation and sheath. For example, the thermal weight loss test is to detect the degree of material degradation and evaporation after 7 days of 80 ℃ high temperature aging; the thermal shock test is performed after a special roll after 150 ℃ high temperature for 1h Whether the wound insulation is cracked; the high temperature pressure tests the insulation of the insulating material after high temperature and then cooling; all low temperature tests generally refer to the change of its mechanical function under the condition of -15 ℃, which is to detect the cable material. Whether it becomes brittle, easy to crack or easy to break under low temperature environment.
The flame-retardant function of other cables is very important. The test to investigate this function is the non-extended flame test, that is, the product cable according to the standard device is ignited with a special flame for a certain period of time, and the cable is checked after the flame is extinguished by itself. The burning condition, of course, the less the burned part, the better, which means that it has poor flammability, good flame retardancy and safety.
4. Logo viewing
The wire manufacturer's standard requires that the cable packaging should be accompanied by a label or mark indicating the product type, standard, standard number, factory name and place of origin, and the standard includes additional voltage, core number and nominal cross-section of the conductor, etc.; the appearance of the cable should be printed with the manufacturer's name, Continuous marking of product type and additional voltage, marking interval requirements ≤200mm (insulated appearance) or ≤500mm (sheathed appearance), the content of the mark should be thorough, clear, and scratch-resistant, this requirement is to facilitate users to understand the cable type standard and voltage To prevent faults in laying. In addition, the wire insulation core should prefer the color recommended by the standard, especially the yellow/green two-color core. This kind of wire is generally used in the power cord of electrical products. This special two-color wire is dedicated to grounding. /The green matching standard also has the following rules: that for each section of 15mm long insulated wire core, one color should cover at least 30% of the appearance of the insulated wire core, and not more than 70%, and the other color covers the insulated wire core The rest of the two, namely the yellow/green color, should be balanced at all.
5. Structural scale detection
The wire includes the thickness of the insulation and sheath, the thinnest thickness, the external dimensions, etc. The thickness of the insulation and the sheath have important effects on how strong the voltage the cable can withstand, and whether its mechanical function is good or bad, so for cables of different standards, the standards have strict regulations on the thickness, and the requirements must not be lower than the national Standard rules. If the thickness of the cable insulation is too thin, it will seriously affect the safety of the cable, and it will bring about potential safety hazards such as cable breakdown and conductor exposure. Of course, the thicker the better, the device should not be affected. Therefore, the standard sets a shape size requirement. Limit this.