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Several important indicators of wire and cable quality inspection

Oct 30, 2019

The selection of qualified wire and cable products is related to the safety of people's production and life. For ordinary consumers, in addition to knowing how to select qualified wire and cable products, it is necessary to understand the general monitoring knowledge of wire and cable. In the quality inspection of wire and cable, there are mainly the following important indicators.

1. Measurement of wire DC resistance:

The conductive core of the wire and cable mainly transmits electrical energy or electrical signals. The resistance of the wire is the main indicator of its electrical performance. When the AC voltage is applied, the wire core resistance is larger due to the skin effect and the adjacent effect surface is stronger than the DC voltage. However, when the electric eye frequency is 50 Hz, the difference between the two is small. That can only require the DC resistance or resistivity of the test core to exceed the value specified in the standard. Through this inspection, some defects in the production process can be found. DC resistance measuring meter is often used at this time

2. Test of insulation resistance:

Insulation resistance reflects the important characteristics of the insulation properties of wire and cable products, and has a close relationship with the product's electrical strength, dielectric loss, and the gradual deterioration of the insulation under working conditions. For the communication cable, the insulation resistance between the lines is too low, which also increases the loop attenuation, the crosstalk between the circuits, and the long-distance power supply leakage on the conductive core. You can use our insulation resistance tester.

Insulation Resistance Tester

Insulation Resistance Tester

3. Measurement of capacitance and loss factor:

When the cable is connected to the AC voltage, current flows. When the amplitude and frequency of the voltage are constant, the magnitude of the capacitor current is proportional to the capacitance of the cable (Cx). For ultra-high voltage cables, the current of such capacitors may reach a value comparable to the rated current, which is 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 various insulation degradation phenomena such as insulation moisture, insulation layer and shielding layer fall off, so capacitance and TAN δ measurement are performed in cable manufacturing or cable operation.

4. Insulation strength test:

The insulation strength of wire and cable refers to the ability of insulation structure and insulation material to withstand electric field without breakdown damage. In order to check the quality of wire and cable products and ensure the safe operation of products, all insulation type wires and cables are generally tested for insulation strength. The dielectric strength test can be divided into a withstand voltage test and a breakdown test.

5. Aging and stability test:

The aging test is a stability test that maintains stable performance under the action of stress (mechanical, electrical, and thermal). Heat aging test chamber: A simple heat aging test is a test of the aging characteristics of a test product under the action of heat. The test sample is placed in an environment above a rated temperature of the rated working temperature, so that at a higher temperature T, Shorter life.

6. Thermal stability test:

The thermal stability test is that the cable is heated by the current while still receiving a certain voltage. After a certain period of heating, some sensitive performance parameters are measured to evaluate the stability of the insulation. The insulation stability test is divided into two types: long-term stability test or short-term accelerated aging test.

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