Six important indicators for quality inspection of wires and cables

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

1、 Measurement of Direct Current Resistance of Conductors
The conductive cores of wires and cables mainly transmit electrical energy or signals. The resistance of a wire is the main indicator of its electrical performance. Under the action of AC voltage, the resistance of the wire core is larger due to the skin effect and proximity effect surface than under the action of DC voltage. However, at an electrical frequency of 50Hz, the difference between the two is very small. Currently, the standard only requires testing whether the DC resistance or resistivity of the wire core exceeds the specified value in the standard. Through this inspection, certain defects in the production process can be found, such as wire breakage or partial single wire breakage; The cross-section of the wire does not meet the standard; The length of the product is incorrect, etc.

2、 Detection of insulation resistance
Insulation resistance is an important indicator reflecting the insulation characteristics of wire and cable products, which is closely related to the product's electrical strength, dielectric loss, and the gradual deterioration of insulation materials in working conditions. For communication cables, low insulation resistance between lines can increase circuit attenuation, crosstalk between circuits, and long-distance power supply leakage on conductive wire cores. Therefore, it is required that the insulation resistance should be higher than the specified value.

3、 Measurement of capacitance and loss factor
When an AC voltage is applied to a cable, a current flows through it. When the amplitude and frequency of the voltage are constant, the magnitude of the capacitive current is proportional to the capacitance (Cx) of the cable. For ultra-high voltage cables, the current of this capacitor may reach a value comparable to the rated current, becoming 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, various insulation degradation phenomena such as insulation moisture, insulation layer and shielding layer detachment can be found. Therefore, capacitance and TAN are carried out in both cable manufacturing and cable operation δ Measurement of.

4、 Insulation strength test
The insulation strength of wires and cables refers to the ability of the insulation structure and insulation materials to withstand electric fields without breakdown damage. In order to check the quality of wire and cable products and ensure their safe operation, insulation strength tests are generally required for all types of wires and cables. The insulation strength test can be divided into withstand voltage test and breakdown test. The voltage of time is generally higher than the rated working voltage of the test object. The specific voltage value and withstand time are specified in the product standard. Through withstand voltage testing, the reliability of the product operating at working voltage can be tested, serious defects in insulation can be discovered, and some shortcomings in the production process can also be discovered.

5、 Aging and stability testing
Aging test is a stability test to determine whether stable performance can be maintained under stress (mechanical, electrical, thermal). Thermal aging test: A simple thermal aging test is a test of the aging characteristics of the test object under the action of heat. The test object is placed in an environment above the rated working temperature and at a certain temperature value, so as to achieve a shorter lifespan at a higher temperature T.

6、 Thermal stability test
Thermal stability test is a method of evaluating the stability of insulation by measuring certain sensitive performance parameters of a cable that is heated by an electric current while also withstanding a certain voltage after undergoing a certain period of heating. The insulation stability test is divided into two types: long-term stability test or short-term accelerated aging test.