There are thousands of wire and cable products, which are used in various industries. There are two general uses for them, one is to transmit current and the other is to transmit signals. The main technical performance index of the transmission current cable is the time-voltage performance of the conductor resistance; the main technical performance index of the transmission signal cable is the transmission performance-characteristic impedance, attenuation and crosstalk. Of course, the transmission signal mainly relies on electric current (electromagnetic wave) as the carrier. Now with the development of science and technology, light waves can be used as the carrier for transmission.
Main Materials of Wire and Cable:
1. The copper wire uses electrolytic copper as the raw material, and the copper wire made by the continuous casting and rolling process is called low-oxygen copper wire; the copper wire made by the up-drawing method is called oxygen-free copper wire. The oxygen content of the low-oxygen copper wire is 100-250ppm, the copper content is 99.9-9.95%, and the conductivity is 100-101%. The oxygen content of oxygen-free copper wire is 4–20p
pm, the copper content is 996-999%, and the conductivity is 102%. The specific gravity of copper is 889g/cm3.
2. The aluminum wire used as the wire must be annealed and softened. Aluminum wires used for cables generally do not need to be softened. The electrical resistivity of aluminum for wire and cable is required to reach 0.0282649mm2/m, and the specific gravity of aluminum is 2.703g/cm3.
3. Polyvinyl chloride (PVC): Polyvinyl chloride plastic is based on polyvinyl chloride resin and mixed with various compounding agents, such as antioxidants, antioxidants, fillers, brighteners, flame retardants, etc. The characteristics of PVC materials with a density of about 1.38~1.46g/m3: superior mechanical properties, chemical corrosion resistance, non-flammability, good weather resistance, good electrical insulation properties, and easy processing. The disadvantages of polyvinyl chloride materials: a large amount of toxic smoke is emitted during combustion; poor thermal aging performance, polyvinyl chloride has insulating materials and sheath materials.such as pvc insualted power cable.
4. Polyethylene (PE): Polyethylene is polymerized by refined ethylene. According to the density, it can be divided into low density polyethylene (LDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE). The density of low-density polyethylene is generally 0.91-0.925g/m3; the density of medium-density polyethylene is generally 0.925-0.94g/cm3; the density of high-density polyethylene is generally 0.94~0.97g/cm3.PE cable become a good choice because it’s more economic.
The advantages of polyethylene materials: high insulation resistance and withstand voltage strength; in a wide frequency band, the dielectric constant and the dielectric loss tangent value are small; rich in flexibility, good wear resistance; heat aging performance, low temperature Good performance and chemical resistance; good water resistance and low moisture absorption; cables made with it are light in weight and easy to use and lay. Disadvantages of polyethylene materials: easy to burn when exposed to flame; low softening temperature.
5. Cross-linked polyethylene (XLPE): There are two main types of cross-linked polyethylene currently used in the cable industry. This is a kind of silane cross-linking agent called silane cross-linking material, which is mainly used in the insulation layer of low-voltage wires and cables. The other is a cross-linked polyethylene material with dicumyl peroxide (DCP) as a cross-linking agent, which is mainly composed of polyethylene, a cross-linking agent and an antioxidant. It is mainly used on the insulation layer of medium and high voltage cables. The higher the insulation withstand voltage level, the higher the purity required. The cross-linked polyethylene material used as a cross-linking agent is mainly composed of polyethylene, a cross-linking agent and an antioxidant. It is mainly used on the insulation layer of medium and high voltage cables. The higher the insulation withstand voltage level, the higher the purity required.such as 25-400m2 PVC XLPE insulated power cable .
DCP is a kind of peroxide, th
e higher the temperature, the faster the decomposition, after its decomposition, it will catalyze the cross-linking reaction of polyethylene. DCP will also decompose at room temperature, but the decomposition rate is very slow, but it will quickly decompose when heated to a certain temperature (the temperature exceeds 125°C). The silane crosslinking agent also has the same performance, but it also needs water as an auxiliary agent to achieve a complete grafting reaction. There are currently two types of silane cross-linked polyethylene in the market, one is called the one-step method, and the other is called the two-step method (this is different from the academic silane cross-linking method). The insulating material of the one-step method is premixed with the crosslinking agent and the catalyst. It is also called the copolymer method. The two-step method is divided into material A and material B. Mix the materials A and B before production. The storage time of the one-step method is very short, and the main material of the two-step method is separated from the catalyst material, so the storage time is longer, but the mixed material must be used immediately. In addition, carbon black masterbatch can also be added to the silane cross-linking material to play a role in weather resistance and used in the insulated overhead cable series. The advantages of cross-linked polyethylene materials: electrical properties are better than polyethylene and its mechanical properties are better than polyethylene, so it is more widely used than polyethylene. The softening temperature is higher than that of PⅤC, and the normal operating temperature of the cable can reach 90℃. The disadvantage is that it is difficult to process and easy to burn.
The advantages of cross-linked polyethylene materials: electrical properties are better than polyethylene; its mechanical properties are better than polyethylene, so it is more widely used than polyethylene. The softening temperature is higher than that of PⅤC, and the normal operating temperature of the cable can reach 90℃. The disadvantage is that it is difficult to process and easy to burn.