1. Historical practice has proved that
aluminum cable has been developed and used in the United States for 43 years since 1968, and this product has been widely used, with the market share of North American countries reaching 8%. After 43 years of practice, it has been proved that aluminum cable has never had any trouble and is safe.
2. Testing and certification
aluminum cable has passed the testing and certification of UL in the United States, CUL in Canada, SAI GLOBAI in Australia, and the testing and certification of China National Cable and Wire Testing Center, State Grid Wuhan High-voltage Research Institute, National Fire-resistant Building Materials Quality Supervision and Inspection Center and other authoritative organizations. The aluminum alloy conductor meets the requirements of clause 38 of CSA standard C22.2 on ACM alloy conductor. And the latest version of GB1276.1--28 and IEC652.1, as well as UL's standards related to AA8 series.
3, the role of aluminum alloy components
◆ After adding rare earth and iron to aluminum alloy conductor components, its electrical conductivity and connection performance are greatly improved, especially when the conductor is annealed, adding iron produces high-strength creep resistance, and when the current is overloaded, iron plays a continuous connection role, so that the aluminum alloy conductor will not creep.
◆ Creep is very harmful to cables. If cables creep, the original contact pressure is not tight enough, and the contact resistance increases rapidly due to the decrease of pressure. After the current flows, the joints will be overheated. If they are not overhauled regularly, there will be potential safety hazards. It is very important to solve the problem of cable creep.
◆ Creep: Under the action of temperature, external force and self-weight, the metal will slowly produce irreversible permanent deformation over time, which is called creep.
4. Flame retardant performance
aluminum cable uses flame retardant silane crosslinked polyethylene (XLPE) as insulation material, and adopts self-locking armor structure in technology, which has far better heat dissipation performance than the sheath of PVC material, and can quickly dissipate heat. After the flame disappears, the flame can be quickly extinguished without extending to other materials, and the flame retardant performance is extremely excellent. Aluminum cable adopts new materials and new technology, which can ensure its safer use. 1. current carrying capacity of cable
◆ When the cross-sectional area of alloy conductor is 1.5 times that of copper, the electrical properties of alloy conductor and copper conductor are the same, and the same current carrying capacity, resistance and voltage loss are realized.
◆ The resistivity of aluminum alloy is between aluminum and copper, and the load is higher than that of copper, but slightly lower than that of aluminum. Under the premise of the same current carrying capacity, the weight of aluminum alloy conductor with the same length is only half that of copper. If the conductivity of copper is 1%, the conductivity of alloy conductor is about 61.2%, the specific gravity of alloy is 2.7, and the specific gravity of copper is 8.9, then (8.9/2.7)×(.612/1)=2, that is, the resistance of 2 units of copper is the same as that of 1 unit of alloy. Therefore, when the cross-sectional area of alloy conductor is 1.5 of copper,
◆ There are many factors that affect the current carrying capacity of power cables, such as line characteristics (such as operating power, current type, frequency and load factors); The structure of wire and cable (such as the structure of conductive wire core, the number of cores, the type of insulating material, the structure and material of shielding layer and inner and outer protective layer, and the total outer diameter); Laying conditions (such as laying in the air, laying in the pipeline, laying directly in the ground, laying in the underground channel, laying under the water); Maximum allowable working temperature of conductor core and surrounding environmental conditions (such as air and soil temperature, soil thermal resistance coefficient, proximity effect of surrounding heat sources), etc.
2. Reduce the external cross section of the cable
In the production process in aluminum cable, the most advanced compaction technology in Germany enables the filling factor of the conductor to reach 93%. Moreover, aluminum cable uses silane crosslinked polyethylene, which is only 2/3 of the thickness of PVC and can far exceed the conventional insulation performance. The filling coefficient of copper can only reach 8%, and PVC is commonly used for insulation. Therefore, if the outer diameter of aluminum cable is increased by less than 11% on the basis of copper cable, it will have the same electrical properties as copper. It can be seen that the use of aluminum cable does not need to change the original pipeline design using copper cables. (Generally, the size of laying pipes designed by designers is 15% of that of copper cables, so it is not a problem to wear pipes. )
3. Reduce cable line loss
Non-magnetic materials will not produce eddy current, which can reduce line loss. The locking material of aluminum alloy belt armor is non-magnetic, even if there is three-phase unbalanced current, it will not produce eddy current, which can reduce the loss of the line. 1. aluminum cable's extensibility
Elongation is an important indicator of the mechanical properties of conductors, and it is also an important symbol of the quality of products and the ability to withstand external forces. It is also an important index to test the mechanical properties of cable conductors. After aluminum cable annealing, the elongation can reach 3%, while the elongation of copper cable is 25% and that of ordinary aluminum rod is 15%, which is an important index to replace aluminum core cable and copper cable.
2. Flexibility of aluminum cable
Torsion test: It mainly tests the toughness of metal wire. The better the toughness, the more times it can withstand torsion. An important disadvantage of ordinary aluminum wire is its high brittleness. As long as it is twisted at a certain angle several times during installation, the conductor will crack, and the crack will heat up and corrode, which is an important cause of fire. The use of aluminum cable, because of its good toughness, will not produce cracks, and the potential safety hazards in installation will be reduced.
3. Bending performance of aluminum cable
Bending test: it mainly tests the bending performance of metal. Uneven or brittle materials have poor bending resistance.
according to GB/T1276, the bending radius of copper cable is 1-2 times the cable diameter, and the minimum bending radius of aluminum cable is 7 times the cable diameter. Using aluminum cable can reduce the layout space, make it easier to lay and reduce the installation cost.
4. Rebound performance of aluminum cable
Practice has proved that when the copper cable and aluminum cable are bent at 9 degrees at room temperature, the rebound angle of aluminum cable is 6% of that of copper cable after the stress is released. Because aluminum cable has no memory, its rebound performance is better than that of copper-core cable. In the installation process, the terminal connection joint is easy to be pressed, which increases its tightness and improves the connection stability. 1. there are two main types of conductor partial corrosion: chemical corrosion and electrochemical corrosion
◆ chemical corrosion: refers to the corrosion of metals when exposed to oxygen, chlorine, sulfur dioxide, hydrogen sulfide and other gases in the atmosphere.
after the metal surface reacts with oxygen, different metal oxides are generated.
The oxide of aluminum can form a compact surface protective film with a certain hardness.
The oxide of iron is loose in structure and easy to fall off, and it continues to infiltrate and diffuse into the metal, destroying the material.
copper oxide, commonly known as patina, is a toxic substance between the above two.
◆ electrochemical corrosion: refers to the corrosion process of metal after the primary battery is composed of metal and medium. When two metals with different electrode potentials are connected and there is water or other electrolyte between them, an electric current will be generated between the two metals to form a primary battery, in which one metal is at a positive potential and the other is at a negative potential, and the metal at a negative potential will continuously accumulate to the metal at a positive potential in ionic state through the electrolyte. The metal in negative potential is gradually lost and destroyed, forming electrochemical corrosion. The greater the difference between the electrode potentials of the two metals, the stronger the electrochemical corrosion. The higher the temperature, the more serious the corrosion of metal.
different metals have different electrode potentials. The order of electrode potentials of several metals in common use is: Metal Ag (silver) Cu (copper) Pb (lead) Sn (tin) Fe (iron) Zn (zinc) A1 (aluminum). Potential+.8+.334-.122-.16-.44-.76-1.33 The greater the negative electrode potential, the stronger the tendency of the metal to become ions in the electrolyte, that is, the more susceptible to corrosion. The electrode potential of aluminum has a large negative value, but its corrosion resistance can be improved because there is often a protective layer of oxide film on its surface.
Rare earth aluminum alloy material is added with rare earth elements, which can purify, improve purity, fill surface defects and refine grains. It can reduce segregation and eliminate local corrosion caused by microscopic unevenness, and at the same time, it also brings negative shift of electrode potential of aluminum, which has anode effect and excellent conductivity, thus greatly improving the corrosion resistance of aluminum. For C1- in marine environment and S, H2S+C2 in petroleum and chemical environment, this material has a unique anticorrosion mechanism. The strong reducibility of rare earth metals can effectively combine with the strong oxidizability of S, H2S and C1- and interact with each other to generate stable compounds (C1- and rare earth aluminum alloy generate stable coordination compounds), which organically unifies and interacts with the oxidation and reduction processes in chemical reactions, and fundamentally stops the corrosion damage caused by the oxidation activities of S, H2S, C1- and other corrosive media. Thus, the problems that have not been well solved in developed countries including the United States around the world have been thoroughly solved. The data analysis of national testing departments such as Beijing Nonferrous Metals Research Institute and other engineering examples show that the annual corrosion rate of rare earth aluminum alloy is zero or almost zero under the conditions of chloride ion, seawater, marine atmosphere, salt spray environment (dry-wet alternation), saturated HzS, sulfur and high temperature and high pressure environment.
2. Insulated part
◆ The current carrying capacity of power cable refers to the maximum current allowed by the cable conductor at the highest allowable temperature. When designing and selecting cables, the heat generated by the loss of each part of the cable should not exceed the maximum allowable temperature of the cable. In most cases, the transmission capacity of the cable is determined by the maximum allowable temperature of the cable. The maximum allowable temperature of the cable mainly depends on the thermal aging performance of the insulating materials used, because the working temperature of the cable is too high, the aging of the insulating materials will be accelerated and the service life of the cable will be greatly shortened. If the cable runs above the maximum allowable temperature, it will work safely for 3 years.
◆XLPE is the abbreviation of the English name of crosslinked polyethylene, which is a linear molecular structure and easily deformed at high temperature. The process of crosslinking polyethylene makes it become a network structure. This structure has strong deformation resistance even at high temperature.
◆ The excellent anti-aging characteristics and super thermal deformation of crosslinked polyethylene determine that large current can be allowed to pass under the conditions of short-term fault (13C) and short circuit (25C) at normal operating temperature (9C). It is precisely because its operating temperature is 2C higher than that of PVC that it has excellent thermal resistance, increases the aging resistance of insulation and greatly prolongs its service life. ◆ Direct procurement cost
Price comparison between aluminum cable and copper core cable: On the premise that aluminum cable has superior safety performance, electrical performance, mechanical performance and longer service life, the price of aluminum cable is only about 75% of that of copper cable.
◆ Lower installation cost
Save installation cost: aluminum cable is easy to install due to its good bending performance and light weight.