Items and purposes of common inspection cables

  1. Electrical performance testing

  The standard has strict regulations on the DC resistance value of the conductors of cables of different specifications, and it must not be greater than the value specified in the standard.There are mainly conductor DC resistance, insulation resistance, finished product voltage test and insulated wire core voltage test. Each item is very important. The conductor resistance directly reflects the electrical transmission performance of the cable, which directly affects the temperature, life, voltage drop, and operating safety of the cable during energized operation. It mainly examines the material and cross-sectional area of the conductor. If the material of the conductor is not good or the cross-sectional area is seriously insufficient, it will cause the conductor's DC resistance to seriously exceed the standard. This kind of cable is laid in the line, which will increase the loss of current when passing through the line, causing the cable conductor itself to heat up, causing the insulation of the coated conductor to age and crack, causing leakage from the power supply line. Short circuits can even cause fires, endangering the safety of people and property.

  2. Mechanical performance testing

  It is mainly to examine the tensile strength and elongation at break of insulating and sheathed plastic materials, including before and after aging, as well as the deflection test, bending test, load core breaking test, insulation core tear test, static deflection test, etc. for finished flexible cables.The tensile strength before and after aging, and the elongation at break before and after aging are the most important and basic indicators of cable insulation and sheath materials. It is required that the materials used for cable insulation and sheath must have sufficient tensile strength and not easy to break, as well as a certain degree of flexibility. Aging refers to the ability of the insulation and sheath materials to maintain their original properties under high temperature conditions. Aging should not seriously affect the tensile strength and elongation of the material, which will directly affect the service life of the cable. If the tensile strength and elongation at break are unqualified, the sheath or sheath will easily appear during the construction and installation of the cable. The insulator breaks, or the sheath and insulation of the cable used in the light and heat environment can easily become brittle and break, causing the live conductor to be exposed and the risk of electric shock occurs.

  In addition, because flexible cables are not fixed and laid, there are repeated dragging and bending in use, so the flexible cable standard additionally stipulates that dynamic deflection tests, bending tests, load core breaking tests, insulated core tearing tests, static deflection tests, etc. are added to the finished cables to ensure that this kind of cable meets the requirements in actual use.For example, the dynamic deflection test mainly assesses whether the stranded wire of the soft conductor breaks and reduces the electrical transmission performance when the flexible cable is subjected to external stresses such as mechanical stretching and bending, or whether the insulation is pierced and the electrical insulation performance is reduced; The insulation is subjected to stress. It is a test method whether deformation or cracking affects the electrical insulation properties of the cable.

  3. Insulation and sheath material performance test

  Including heat loss, thermal shock, high temperature pressure, low temperature bending, low temperature stretching, low temperature impact, flame retardant properties and so on.These are to check the performance of the insulating and sheathed plastic materials. For example, the thermal weightlessness test is to test the degree of material degradation and volatilization after 7 days of high temperature aging at 80℃; thermal shock tests whether the specially wound insulating surface cracks after 1h at a high temperature of 150℃; high temperature and pressure tests The degree to which the insulating material maintains its elasticity after high temperature and then cooling; all low temperature tests generally refer to changes in its mechanical properties under the condition of -15℃, all of which are to detect whether the cable material becomes brittle, easy to crack or easy to pull off in a low temperature environment.In addition, the flame-retardant performance of the cable is very important. The test to check the performance is a non-delayed combustion test, that is, the finished cable installed according to the standard is ignited with a special flame for a certain period of time, and the cable is burned after the flame is extinguished by itself. Of course, the less the burned part, the better, indicating that its combustion is poor, the flame-retardant is good, and the safer it is.

  4. Sign inspection

  The standard requires that the cable packaging should be accompanied by a label or logo indicating the product model, specification, standard number, factory name and place of origin. The specifications include the rated voltage, the number of cores, and the nominal cross-section of the conductor; the surface of the cable should be printed with the manufacturer's name, product model and rated voltage continuous signs, the spacing of the signs is required ≤200mm (insulating surface) or ≤500mm (sheath surface), the content of the signs should be complete, clear, and scratch-resistant. This requirement is to facilitate users to understand the model specifications and voltage levels of the cables to prevent laying errors.In addition, the color recommended by the standard should be given priority to the insulated wire core. In particular, the yellow/green two-color core should be mentioned. This kind of wire is generally used in the power cord of electrical products. This special two-color line is dedicated to grounding. The yellow/green matching standard also has the following provisions: That is, for each long and clever~ two-color insulated wire core, one color should cover at least 30% of the surface of the insulated wire core, and not more than 70%, while the other color covers the rest of the insulated wire core, that is, the yellow/green two-color should be basically evenly matched.Recommended products: communication cable

  5. Structure size inspection

  Including the thickness of the insulation and sheath, the thinnest thickness, the dimensions, etc.The thickness of the insulation and sheath plays a very important role in the strength of the voltage that the cable can withstand, as well as its mechanical properties. Therefore, for cables of different specifications, the standard has strict regulations on the thickness, and the requirements must not be lower than the specified value of the national standard.The insulation thickness of the cable is too thin, which will seriously affect the safety of the cable. It will bring safety risks such as cable breakdown and leakage caused by exposed conductors. Of course, it is not as thick as possible. It should not affect the installation. Therefore, the standard has set another size requirement to limit this.