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China's electrical industry from 1957 to 1973, has developed a aluminum row, aluminum wire, aluminum core insulated wire and cable, aluminum core electromagnetic wire, steel and aluminum tram lines, aluminum core flexible cables and aluminum clad steel wire and other products, made very With great achievements, the proportion of aluminum conductors in total conductor usage has risen to more than 60%. In the mid-1990s, under the promotion and promotion of certain organizations, the promotion of copper core cables has a monopolistic market trend. Nowadays, the use of aluminum conductors has been declining.
The supply of copper concentrate in China is less than 30%, and the proportion of more than 70% depends on imports, which is far higher than the external dependence of iron ore and petroleum in China. Driven by domestic demand, China has become the largest copper consumer in the world. In 2006, copper consumption in China totaled 4 million tons, accounting for about 22% of the total global supply. At present, most of the copper used for cable is imported from foreign countries, and foreign mineral monopoly companies are rushing to raise prices, causing high building electrical costs. On the other hand, China has ascertained that the reserves of bauxite are 3.7 billion tons. Under such a situation of mineral resources, it is hard to praise the European counterparts for their eagerness to promote importing copper without investing in the abundant aluminum resources that they own. Some French cable operators once said that France does not produce copper but aluminum has abundant resources. Therefore, more than 60% of French power cables use aluminum conductors and are recognized by the French Electric Power Company (EDF).
With the development of science and technology, aluminum materials with high quality and high-tech content have been developed. Combined with the current situation of copper-rich aluminum resources in the world, copper parts are currently more than three times aluminum prices (about 6 million yuan/ton of copper). Aluminum is about 17,000 yuan / ton), "aluminum" on behalf of copper has become a natural choice. In foreign countries in the research and application of aluminum conductors, the United States and Canada have developed AA8000 series of electrical grade aluminum alloy as a conductor material. According to NEC2008 version 310.14 of the National Electric Code of the United States, solid conductors of 8AWG, 10AWG, and 12AWG cross sections (equivalent to domestic 8.37mm2, 5.26mm2, and 3.332mm2) shall be made of AA8000 series electrical grade aluminum alloy materials; twisted conductors from 8AWG To 1000Kcmil (equivalent to domestic 506.7mm2) should also be made of AA8000 series electrical grade aluminum alloy conductor material. Shandong Wanda Cable Co., Ltd. has specially developed aluminum alloy cables adapted to the distribution of civil buildings according to the above specifications.
Definition of aluminum alloy cable
Aluminium alloy power cable is a new type of material power cable with AA-8000 series aluminum alloy material as conductor, special pressing technology and annealing treatment, and advanced technology such as interlocking armoring technology.
The difference between alloy cable and ordinary cable
The alloy cable uses the AA-8000 series aluminum alloy conductor, while the ordinary cable uses copper or pure aluminum as the cable conductor.
Why use an alloy cable?
At the same volume, the actual weight of an aluminum alloy is about one-third that of copper. According to this calculation, the same weight aluminum alloy cable is twice as long as the copper cable under the same electrical performance. Therefore, the weight of aluminum alloy cables at the same current carrying capacity is about half that of copper cables. The use of aluminum alloy cables instead of copper cables can reduce the weight of cables, reduce installation costs, and reduce equipment and cable wear, making installation easier.
The advantages of alloy cable over ordinary cable:
The conductivity of aluminum alloy is 61.5% of the most commonly used reference material, copper IACS, and the current carrying capacity is 79% of that of copper, which is superior to the pure aluminum standard.
The alloy material and annealing process of aluminum alloy conductors reduce the "creep" tendency of conductors under heat and pressure. Compared to pure aluminum, the creep resistance is improved by 300%, avoiding relaxation problems due to cold flow or creep. .
Tensile strength and elongation
Compared with pure aluminum conductors, aluminum alloy conductors have added special components and special processing techniques, which greatly increase the tensile strength, increase the elongation rate to 30%, and make them more safe and reliable.
Thermal expansion coefficient
The thermal expansion coefficient is used to calculate the dimensional change of the material when the temperature changes. Aluminum alloys have a coefficient of thermal expansion comparable to that of copper, and aluminum connectors have been reliably used for copper and aluminum conductors for many years, and most of the electrical connectors used today are made of aluminum, which is particularly suitable for aluminum alloys. Therefore, the expansion and contraction of the aluminum alloy conductor and the connector are completely the same.
Self-weight bearing capacity
Aluminum alloy improves the tensile strength of pure aluminum. Aluminum alloy cables can support 4000 meters in length and copper cables can only support 2750 meters. This advantage is particularly prominent in the wiring of large-span buildings (such as stadiums).
The inherent corrosion resistance of aluminum stems from the formation of a thin and strong oxide layer when the aluminum surface is in contact with air, and this oxide layer is particularly resistant to various forms of corrosion. The addition of rare earth elements in the alloy can further improve the corrosion resistance of the aluminum alloy, especially electrochemical corrosion. Aluminum's ability to withstand harsh environments has made it widely used in cable tray conductors, as well as many industrial components and containers. Corrosion is usually related to the connection of different metals in a wet environment. Corresponding protective measures can be used to prevent corrosion, such as the use of lubricating oils, antioxidants, and protective coatings. Alkaline soils and some types of acidic soils are more corrosive to aluminum. Therefore, aluminum conductors laid directly on the ground should be protected against corrosion by using insulating layers or molded sheaths. In sulfur-containing environments, such as railway tunnels and other similar places, aluminum alloys have much better corrosion resistance than copper.
Aluminum alloys have very good bending properties, and their unique alloy formulas and processing techniques greatly increase flexibility. Aluminum alloy is 30% more flexible than copper and 40% lower in resilience than copper. Generally, the bending radius of the copper cable is 10 to 20 times the outer diameter, while the bending radius of the aluminum alloy cable is only 7 times the outer diameter, and the terminal connection is easier.
The armored cables commonly used in China are mostly steel tape armored and have a low level of safety. When subjected to external destructive forces, they have poor resistance, are prone to breakdown, and are heavy, have high installation costs, and are poor in corrosion resistance. The service life is not long. The metal chained armored cable developed by us according to the US standard adopts aluminum alloy chain interlocking equipment, and its interlocking structure between layers ensures that the cable can withstand the powerful destructive force of the outside world, even if the cable is under great pressure. When impact force is applied, the cable is not easily broken down, improving the safety performance. At the same time, the armored structure isolates the cable from the outside. Even in the event of a fire, the armored layer enhances the fire-retardant and fire-resistant rating of the cable and reduces the risk of fire. The aluminum alloy armored armored structure is lighter than the steel armored armor and is easy to lay. It can be installed without a bridge and can reduce installation costs by 20%-40%. According to the different places of use, different outer jacket layers can be selected to make the use of armored cable more extensive.
In terms of volume conductivity alone, aluminum alloys are not as good as copper, but the conductors we developed not only improve the material properties, but also make major breakthroughs in the process. We use ultra-conventional compression technology to make the compaction coefficient It reaches 0.93, and the coefficient of compression of the profile line can reach 0.95, which is the first in the country. Through the maximum limit of the compaction, can make up for the lack of volumetric conductivity of aluminum alloy, so that the stranded conductor core as a solid conductor, significantly reduce the outer diameter of the core, improve the conductivity, under the same current conditions outside the conductor The diameter is only 10% larger than the copper cable.
In the event of a building fire, smoke and halogen-containing toxins (halogen-containing flame retardants in cables, etc.) are deadly killers. "Civil Building Electrical Design Code" (JGJ16-2008) Clause 2 of Article 7.4.1 stipulates: "For buildings with high fire protection requirements for a type of high-rise buildings and important public places, flame-retardant low-smoke halogen-free cross-linking should be used. Ethylene insulated power cable."
The insulated aluminum alloy cable produced by Shandong Wanda Cable Co., Ltd. uses low-smoke and halogen-free XLPE (cross-linked polyethylene) materials, combined with its unique self-locking armored structure, to achieve low smoke and no halogen resistance. In the IA class, this type of cable has a light transmission rate of 99% (class IA light transmittance ≥80%). It produces only a very small amount of smoke and reduces secondary damage to the human body in the event of a fire. It is conducive to timely evacuation and rescue.
Aluminum alloy belts with self-locking armored cable have good heat dissipation and can take away heat quickly. The flame retardant properties are excellent. They can be quickly extinguished after the flame is removed, and will not be delayed by other materials. According to the comparison of the burning test, the carbonization height for a 40-minute fire is only 0.15m, which is far lower than the national standard “Combustion test for cables and optical cables under flame conditions. Part 33: Vertically-directed flame propagation test for bunched wires and cables of category A” (GB / T 18380.33-2008) Flame retardant cable carbonization height ≤ 2.50m.