Electrical performance testing

1. Direct current resistance of conductor

Directly reflecting the electrical transmission performance of the cable, the core examination is the conductor material and cross-sectional area. If the material is poor or the cross-sectional area is insufficient, it can lead to excessive resistance, increase current loss, cause conductor heating, insulation aging and cracking, resulting in leakage, short circuit and even fire, endangering personal and property safety. The standard sets strict upper limits on the DC resistance of conductors for cables of different specifications, and must not exceed the limit.

2. Insulation resistance/finished product voltage test/insulation wire core voltage test

Both focus on the electrical insulation performance of the insulation layer and the sheath layer. The insulation resistance needs to meet the requirement of being "sufficiently large" to ensure the insulation protection effect between conductors; The latter two tests not only require the insulation capacity of the material to meet the standard, but also ensure that the insulation/sheath material is uniform and free of impurities, with consistent thickness, and the surface is free of hidden defects such as sand holes and pinholes, otherwise local breakdown may occur during the withstand voltage test.

Mechanical performance testing

1. Basic indicators (before and after aging)

Tensile strength and elongation at break are core indicators. Require materials to have sufficient tensile strength (to avoid breakage) and good flexibility; After high temperature aging, the two indicators should not significantly decrease, otherwise it will shorten the service life of the cable - during construction and installation, it is easy for the sheath/insulator to break or become brittle and crack in the light and heat environment, resulting in exposed live conductors and the risk of electric shock.

2. Exclusive test for flexible cables

For the usage scenario of flexible cables with "non fixed laying and frequent dragging and bending", additional dynamic bending tests, bending tests, load core breakage tests, etc. are required. For example, dynamic bending test focuses on assessing whether the twisted wires of soft conductors are broken under mechanical stress (affecting conductivity), whether the insulation is deformed and cracked (affecting insulation performance), to ensure that the soft cable is suitable for actual use needs.

Performance test of insulation and sheath materials

1. High temperature related tests

Thermogravimetric test (aging at 80 ℃ for 7 days to detect the degree of material degradation and volatilization), thermal shock test (after 1 hour of high temperature at 150 ℃ to check whether the winding insulation surface cracks), and high temperature pressure test (to detect the elastic retention ability of the material after high temperature cooling) are all used to verify the stability of the material in high temperature environments.

2. Low temperature related tests

Usually conducted at -15 ℃ to assess changes in material mechanical properties and avoid becoming brittle, prone to cracking, or prone to tensile fracture in low-temperature environments.

3. Flame retardant performance test

Using a non flame retardant test, the standard installed finished cable is ignited for a specified time, and the burning situation of the cable is observed after the flame extinguishes on its own - the less burning part, the better the flame retardancy and the higher the safety of use.

sign inspection

1. Packaging and surface labeling

Cable packaging must be accompanied by labels containing product model, specifications (rated voltage, number of cores, nominal conductor cross-section), standard number, factory name, and place of origin; The surface of the cable should be printed with continuous markings (factory name, product model, rated voltage), with a spacing of less than 200mm between insulation surface markings and less than 500mm on the sheath surface. The content should be complete, clear, and scratch resistant.

2. Color of insulated wire core

Priority should be given to using standard recommended colors, with yellow/green dual color wires being dedicated grounding wires (commonly used in electrical power cords). The standard clearly requires that for every 15mm long wire core segment, one color should cover 30% -70% of the surface, and another color should cover the remaining part to ensure a balanced combination of two colors.

Structural dimension inspection

1. Thickness requirements

There are strict lower limit standards for the insulation/sheath thickness of cables of different specifications. If the thickness is too thin, it will lead to insufficient voltage resistance, causing safety hazards such as breakdown and exposed conductors.

2. Limitations on external dimensions

Thickness is not necessarily better, but installation convenience needs to be taken into account. Standards are constrained by setting upper limits on external dimensions to ensure that the product meets actual construction requirements.