The inspection of wire and cable has always been an important part of national standard wire and cable. The higher the quality inspection department of a wire and cable enterprise is, the better the quality of the wire and cable produced by the enterprise is and the more trustworthy it is. And the more stringent the third-party quality inspection department is, the more conducive to the development of the industry.
1.Measurement of dc resistance of wire
The conductor cores of electric wires and cables mainly transmit electric energy or electrical signals. Conductor resistance is the main index, its electric performance of the ac voltage effect when the wire core resistance due to the surface of skin effect and proximity effect than dc voltage function, but when the electric frequency of 50 hz and small lines of standard specifies requirements that are only now the core of dc resistance or the resistivity is more than standard value, through the inspection can be found in the process of production of certain defects, such as broken wire or part of the single fracture; Traverse section does not meet the standard; Incorrect length of product, etc.
2. Test insulation resistance
The insulation resistance is an important index to reflect the insulation characteristics of wire and cable products, which is closely related to the electrical resistance, dielectric loss, and the gradual deterioration of insulation materials in the working state. For communication cables, if the insulation resistance between wires is too low, it will also increase circuit attenuation, cross-talk between circuits and long-distance power supply leakage on the conducting wire core, etc., so the insulation resistance shall be higher than the specified value.
3. Measurement of capacitance and loss factor
When the cable is applied with an AC voltage, a current flows through it. When the amplitude and frequency of the voltage are constant, the capacitive current is proportional to the capacitance of the cable (Cx). For ultra high voltage cables, the current of the capacitance may be comparable to the rated current, which becomes an important factor limiting the cable capacity and transmission distance. Therefore, the capacitance of the cable is also one of the main electrical performance parameters. By measuring the capacitance and the loss factor, it can be found that the insulation is affected by moisture, the insulation layer and the shielding layer fall off and other kinds of insulation deterioration phenomenon. Therefore, the measurement of capacitance and TAN delta is always carried out in the cable manufacture or operation.
4. Insulation strength test
The insulation strength of wire and cable refers to the ability of the insulation structure and material to withstand the action of electric field without breaking down. In order to check the quality of wire and cable products and ensure the safe operation of the products, all types of insulation wires and cables generally need to conduct insulation strength tests. The insulation strength test can be divided into pressure test and breakdown test. The voltage of time is generally higher than the rated working voltage of the test product. The specific voltage value and withstand voltage time are stipulated in the product standard. Through the withstand voltage test, the reliability of the product operation under the working voltage can be tested and serious defects in insulation can be found, as well as some shortcomings of the production process can be found
5. Aging and stability test
The aging test is a stability test that can maintain stable performance under the action of stress (mechanical, electrical, thermal). Thermal aging test: The simple thermal aging test is to test the characteristics of the test product under the action of heat aging. The test product is placed in an environment with a certain value above the rated working temperature, so as to obtain a shorter life at a higher temperature.
6. Thermal stability test
The thermal stability test is to evaluate the insulation stability by measuring some sensitive performance parameters after the cable is heated by current and subjected to a certain voltage during a certain period of heating. Insulation stability test can be divided into long-term stability test or short-term accelerated aging test.