Purchasing must read: how to judge the quality of wire and cable

Release time: 2024-10-10

Wire and cable are wire products used to transmit electric energy, information and realize electromagnetic energy conversion, and their quality and performance are very important for the stable operation of power system. The following is an in-depth analysis of the most important indicators of wire and cable, and a detailed explanation of how to judge its quality:

The most important indicators of 1. wire and cable

1. Insulation resistance

Definition:Insulation resistance is an important indicator to reflect the insulation characteristics of wire and cable products, and the product's electrical strength, media loss and insulation materials in the working state of the gradual deterioration of all have a close relationship.
Importance:For communication cables, low line-to-line insulation resistance will increase loop attenuation, crosstalk between loops, and leakage during long-distance power supply on the conductive core.
Judgment Method:Insulation resistance is usually required to be higher than the specified value, and measured by ohmmeter (shaking table), galvanometer comparison method or high resistance meter method.

2. Capacitance and loss factor

Definition:Capacitance represents the ability of the cable to store charge in the AC electric field, and the loss factor (TAN) represents the dielectric loss of the insulator in the cable due to the leakage current and the presence of various polarizations.
Importance:The current of the capacitor may reach a value compared with the rated current, which becomes an important factor limiting the cable capacity and transmission distance. The loss factor not only wastes electric energy, but also heats the medium (insulator) and accelerates the aging of the insulation.
Judgment Method:Through the measurement of capacitance and loss factor, various insulation deterioration phenomena such as insulation moisture, insulation layer and shielding layer falling off can be found.

3. Partial discharge

Definition:Partial discharge refers to the discharge phenomenon that occurs in a local area of an insulator under the action of an electric field.
Importance:Partial discharge damage to plastic, rubber and other insulating materials is more serious, with the increase of voltage level, the increase of working field strength, this problem is more serious.
Judgment Method:For high-voltage extruded cables, partial discharge measurement shall be carried out in the factory test.

How to judge the quality of wire and cable

1. Observe copper core color and eccentricity

COPPER CORE COLOR:The copper core of high-quality wire and cable should be bright purple (red copper mark), if the dark black may contain impurities, the quality of general.
eccentricity:The copper core of the wire and cable should be in the center of the insulation layer. If the copper core is found to be offset, the eccentricity may be too large. Such wires and cables are easily broken down by current during use.

2. Check flexibility and strength

Flexibility:The high-quality wire and cable are extremely flexible, and even if they are bent repeatedly, the insulation layer will not leave traces. Poor quality wire and cable may turn white or even break the skin at the bend.
Strength:The wire and cable should have a certain strength and elasticity to withstand the tension and pressure that may be applied during use.

3. Test flame retardancy and combustion

Flame resistance:Ignite a small length of wire and cable with a lighter and observe its burning. Good quality wire and cable insulation should have a certain degree of flame retardancy, leaving the flame will be extinguished within 5-8 seconds, and no heavy black smoke and pungent smell.

4. Check the packaging and marking

Packing:The packaging of wires and cables should be intact and marked with clear production information.
Identification:The wire and cable shall be printed with trademark, specification, voltage and other information, and shall be accompanied by certificate and seal. At the same time, should check whether the China Electrical Products Certification Committee logo and production license number.

5. Weighing and comparison

Weighing:The high-quality wires and cables have certain weight requirements, and only qualified products can meet the national standards.
Comparison:You can make a choice by comparing the differences in price and quality of wires and cables of different brands and models. But it should be noted that the price of low wire and cable may be discounted.

To sum up, judging the quality of wire and cable needs to be considered comprehensively from many aspects. When purchasing and using wires and cables, relevant standards and regulations should be strictly followed to ensure the stable operation of the power system and personal safety.

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