Six Important Indicators Of Wire And Cable Quality Inspection

The detection of wires and cables has always been an important part of the national standard wires and cables. The higher the quality inspection department in a wire and cable enterprise, the better the quality of wires and cables produced by the enterprise and the more trustworthy they are. The more strict the third-party quality inspection department, the more conducive to the development of this industry.

1、 Measurement of DC resistance of conductor

The conductive core of wires and cables mainly transmits electric energy or electrical signals. The resistance of the wire is the main indicator of its electrical performance. The resistance of the wire core under the action of AC voltage is larger than that under the action of DC voltage due to skin effect and proximity effect surface, but the difference between them is very small when the electrical frequency is 50Hz. Now the standard stipulates that only the DC resistance or resistivity of the wire core can be detected to see whether it exceeds the value specified in the standard. Through this inspection, some defects in the production process can be found, For example, the conductor breaks or some single wires break; The cross-section of the conductor does not conform to the standard; The length of the product is incorrect.

2、 Detection of insulation resistance

The insulation resistance is an important indicator reflecting the insulation characteristics of wire and cable products, which is closely related to the electrical strength of the product, dielectric loss, and the gradual deterioration of insulation materials under working conditions. For communication cables, if the insulation resistance between lines is too low, it will also increase circuit attenuation, crosstalk between circuits, and long-distance power supply leakage on conductive wire cores. Therefore, the insulation resistance is required to be higher than the specified value.

3、 Measurement of capacitance and loss factor

When AC voltage is applied to the cable, there will be current flow. When the amplitude and frequency of the voltage are fixed, the capacitance current is proportional to the capacitance (Cx) of the cable. For ultra-high voltage cables, the current of such capacitors may reach a value comparable to the rated current, which becomes an important factor limiting cable capacity and transmission distance. Therefore, the capacitance of the cable is also one of the main electrical performance parameters of the cable. Through the measurement of capacitance and loss factor, it can be found that insulation is affected with moisture, insulation layer and shielding layer fall off and other insulation deterioration phenomena. Therefore, capacitance and TAN are carried out no matter in cable manufacturing or cable operation δ Measurement of.

4、 Insulation strength test

The insulation strength of wires and cables refers to the ability of insulating structures and insulating materials to withstand electric field without breakdown damage. In order to check the quality of wire and cable products and ensure safe operation of products, insulation strength tests are generally required for all insulated types of wires and cables. The insulation strength test can be divided into voltage withstand test and breakdown test. The time voltage is generally higher than the rated working voltage of the test object. The specific voltage value and withstand voltage time are specified in the product standard. The withstand voltage test can test the reliability of the product under the working voltage, find serious defects in the insulation, and also find some defects in the production process.

5、 Aging and stability test

The aging test is the stability test of whether the performance can be stable under the action of stress (mechanical, electrical, thermal). Thermal aging test: a simple thermal aging test is to test the aging characteristics of the test object under the action of heat. Put the test object in an environment higher than the rated working temperature and at a certain temperature, so that a shorter life can be obtained at a higher temperature T.

6、 Thermal stability test

The thermal stability test is to measure some sensitive performance parameters to evaluate the stability of insulation after the cable is heated by current and also bears a certain voltage. Insulation stability test is divided into long-term stability test or short-term accelerated aging test.