Do you know about the basic knowledge of cables?

Although the wire and cable industry is only a supporting industry, it has a wide variety of products and a wide range of applications, involving electric power, construction, communications, manufacturing and other industries, and is closely related to all sectors of the national economy. Wires and cables are also known as the "arteries" and "nerves" of the national economy. They are indispensable basic equipment for transmitting electrical energy, transmitting information, and manufacturing various motors, instruments, and meters to realize electromagnetic energy conversion. Basic products necessary in a modernized society

1. In the national standard, cables starting with the letter B, such as BV, BVV, and BVR, are all wires. According to the name, fixed wiring cables can be called wires. In a broad sense, wiring wiring is just a generic term, and it does not say which type of cable is wiring. Most of them refer to fixed wiring cables inside buildings (including but not limited to power lines, network communications, cable television, optical fibers, etc.).

2. Through the model of the wire, you can roughly know the wire material, insulation or sheath material: take the BV wire as an example, the letter B is the pinyin abbreviation of the wire. The letter V is the material of the outer layer of plastic. V is the abbreviation of polyvinyl chloride PVC. The outer layer of plastic can be called insulation or sheathing. If it is BVV, it means there are two layers of sheathing. For the wire core material, the code name of copper is T, which is generally omitted and not written. If it is an aluminum wire, L is not omitted.

3. The cross-sectional area of the wire cloth: Take BV2.5 square as an example, 2.5 square is the cross-sectional area, and the unit is square millimeter. How many square lines are usually said refers to the cross-sectional area. Knowing the cross-sectional area, the diameter of the core is known. It should be noted that many people use the cross-sectional area as the criterion for judging whether the current carrying capacity is qualified or not. This is actually very unscientific. Now 70~80% of the wires on the market are non-standard wires that do not meet the standards. The copper quality of the wire is also poor. Even if the wire is enough, the resistance is still relatively large, and the current carrying capacity is not up to the standard.

4. Model specifications of low-voltage cables: With the bedding of cloth wires, the cable can be a practical example, such as VV3*50, which means copper core, PVC insulation, PVC sheath, 3 50 square power cables . Commonly used plastics, in addition to PVC, can also be added with some weather-resistant, fire-resistant, flame-retardant and other related materials. Sometimes, you will see such expressions as VV22 or VV23, 22 represents double steel tape wrapping armored PVC outer sheath, 23 represents double steel tape wrapping armored polyethylene sheath, these codes have relevant technical standards.

5. Insulation level: such as 0.6/1KV for low-voltage cables, or 8.7/15KV for high-voltage cables, it is suitable for fixed laying on transmission and distribution lines with rated voltages of 1KV and 15KV and below.

6. Other models: steel strands, used for pulling utility poles. High-voltage cables are generally contacted by installation companies. In some areas, the length from the high-voltage cable to the transformer is basically fixed. Agricultural buried line NLVV, with extremely low mechanical strength, is now gradually eliminated. Insulated high-voltage overhead lines, the steel core inside, in addition to fixing and firming, should also have a skin effect factor. Control cables, signal cables and special cables, etc., their model specifications and production processes are basically similar.

7. Bending radius: The cable has a bending radius requirement, so the diameter of the cable reel is different for the finished cables of different thicknesses. The minimum bending radius (D is the outer diameter of the cable) when the cable is laid: the single-core unarmored cable is 20D , the multi-core unarmored cable is 15D, the single-core armored cable is 15D, and the multi-core armored cable is 12D.