Five properties of aluminum alloy cable

[China Aluminum Industry Network] aluminum alloy cable safety performance 1, history proved;

Aluminum alloy cable has been used for 43 years since it was developed and used in the United States in 1968. The use of this product has become quite common, and the market share of North American countries has reached 80%. After 43 years of practice, it has been proved that the use of aluminum alloy cables has never failed and is safe.

2, testing and certification;

Aluminum alloy cables passed UL from the United States, CUL from Canada, SAIGLOBAI from Australia, and China's national cable and wire testing center, State Grid Wuhan High Voltage Research Institute, National Fireproof Building Material Quality Supervision and Inspection Center and other authoritative organizations. The alloy conductor conforms to the requirements of the CSA Standard C22.2 Article 38 regarding the ACM alloy wire, and the GB12706.1-2008 and IEC 60502.1 newer version performance requirements, and the UL-to-AA8000 Series related standards.

3, the role of aluminum alloy components;

â—†Aluminum alloy conductor Adding rare earth and iron and other components greatly improves its conductivity and connection performance. Especially when the conductor is annealed, the addition of iron produces a high-strength creep resistance. When the current is overloaded, the iron continues to function. The role of the connection, so that the aluminum alloy conductor will not creep.

â—† Creep greatly damages the cable. If the cable is creeping, the original pressure of the contact point is not tight enough, and the contact resistance is rapidly increased due to the pressure decrease. After the current flows, the connector is overheated. If the cable is not repaired regularly, it will appear safe. Hidden danger. 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 a longer deformation that cannot be restored over time. This phenomenon is creep.

4. Flame Retardant Performance The insulation material of aluminum alloy cable adopts flame-retardant silane cross-linked polyethylene (XLPE). The process adopts self-locking armouring structure. The heat dissipation performance is far better than that of PVC material, and it can dissipate heat quickly and the flame disappears. After the flame can quickly extinguish, will not delay other materials, flame retardant performance is extremely good. Aluminum alloy cables use new materials and new processes to ensure their safer use.

Electrical properties of aluminum alloy cable 1. Cable current carrying capacity ◆ When the cross-sectional area of ​​the alloy conductor is 1.5 times that of copper, the electrical properties of the alloy conductor and copper conductor are the same, achieving the same ampacity, resistance, and pressure loss.

◆ The resistivity of aluminum alloy is between aluminum and copper, slightly higher than that of aluminum, but lower than that of copper. Under the premise of the same cutoff, the weight of aluminum alloy conductor of the same length is only half that of copper. If the conductivity of copper is calculated as 100%, the conductivity of the alloy conductor is about 61.2%, the specific gravity of the alloy is 2.7, and the specific gravity of copper is 8.9, then (8.9/2.7)×(0.612/1)=2, ie 2 The resistance per unit weight of copper is the same as the resistance of one unit mass of the alloy. Therefore, when the cross-sectional area of ​​the alloy conductor is 1.5 times that of copper, its electrical performance is the same, ie, the same cut-off, resistance, and voltage as that of copper are achieved. loss.

â—† There are many factors affecting the cut-off of the power cable, such as: line characteristics (such as working power, current type, frequency, load factor); wire and cable structure (such as the structure of the conductive core, the number of cores, the type of insulating material, shielding layer And outer and inner sheath structure and materials, 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 in the bottom of the water); high allowable working temperature of the conductive core and Ambient conditions (such as air and soil temperature, coefficient of soil thermal resistance, proximity effect of surrounding heat sources), etc.

2. Reducing the outer cable cross-section of aluminum alloy During the production process of aluminum alloy cable, Germany's more advanced compaction technology enables the fill factor of the conductor to reach 93%. And aluminum alloy cable uses silane cross-linked polyethylene, this insulation only 2/3 of the thickness of PVC can far exceed the conventional insulation properties. The fill factor of copper can only reach 80%. Commonly used insulation is polyvinyl chloride, so the outer diameter of aluminum alloy cable is only increased by 11% on the basis of copper cable, which can have the same electrical properties of copper. It can be seen that the use of aluminum alloy cables does not need to change the original pipeline design using copper cables. (General designers design the laying pipe size to be 150% of the copper cable. Considering the problem of increasing capacity more recently, the size of the laid pipe is increased to 200% of that of the copper cable, so wearing the pipe is not a problem.)

3, reduce the cable loss of non-magnetic materials, will not generate eddy currents, can reduce the loss of the line. The aluminum alloy belt tie-lock material is a non-magnetic material, and even if there is a three-phase unbalanced current, no eddy current will be generated and the loss of the circuit can be reduced.

Aluminum alloy cable mechanical properties 1, aluminum alloy cable extension performance;

Elongation is an important indicator of the mechanical performance of a conductor. It is an important indicator of the merits of a product and its ability to withstand external forces. It is also an important indicator to test the mechanical properties of cable conductors. After the aluminum alloy cable has been annealed, the elongation rate can reach 30%, while the elongation rate of the copper cable is 25%, and the elongation rate of the common aluminum rod is 15%, which is an important index that can replace the aluminum core cable and the copper cable.

2, aluminum alloy cable flexibility;

Torsion test: The main test of the toughness of metal wire, the better the toughness, the more torsion can withstand. An important drawback of ordinary aluminum wire is high brittleness. When it is installed, the conductor will crack when twisted at a certain angle and the crack will generate heat and corrosion, which is an important cause of fire. The use of aluminum alloy cables, because of its good toughness, will not produce cracks, the safety hazards that appear in the installation are reduced.

3, the bending performance of aluminum alloy cable bending test: The main test of the metal's resistance to bending. Materials with uneven or brittle materials have poor bending resistance.

According to the provisions of GB/T 12706 for the bending radius of copper cable installation, the bending radius of copper cable is 10-20 times the cable diameter, the smaller the bending radius of aluminum alloy cable is 7 times the cable diameter, the use of aluminum alloy cable can reduce the layout Space, easier to install and reduce installation costs.

4, aluminum alloy cable rebound performance;

Practice has proved that: In the room temperature conditions, the copper cable and aluminum alloy cable bending 90 degrees, the stress release, the aluminum alloy cable rebound angle of 60% of the copper cable. Because the aluminum alloy cable has no memory, the rebound performance is better than the copper core cable. In the installation process, the terminal connection joint is easy to compress, increase its tightness, and improve the stability of the connection.

The service life of aluminum alloy cable 1 There are two main types of conductor corrosion: chemical corrosion and electrochemical corrosion;

â—†Chemical corrosion: The metal is corroded with oxygen, chlorine, sulphur dioxide, hydrogen sulfide and other gases in the atmosphere.

After metal surfaces react with oxygen, different metal oxides are generated.

Aluminum oxide can form a dense, hard surface protective film.

The iron oxide structure is loose, easy to fall off, and continues to infiltrate, diffuse into the metal, and damage the material.

Copper oxide, commonly known as patina, is a toxic substance between the above two.

â—†Electrochemical corrosion: refers to the formation of the metal corrosion process after the primary battery is composed of metal and dielectric. When two different electrode potentials are connected to each other and there is water or other electrolyte, the two metals will be generated. The current forms a galvanic cell in which one metal is at a positive potential and the other is at a negative potential. The metal at a negative potential is constantly being accumulated in the ion state through the electrolyte to the metal at a positive potential. The metal at a 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 severe the corrosion of the metal.

Different metals have different electrode potentials. The order of the electrode potentials of several commonly used metals is: Metal Ag (silver) Cu (copper) Pb (lead) Sn (tin) Fe (iron) Zn (zinc) A1 (aluminum). Potential +0.8+0.334-0.122-0.16-0.44-0.76-1.33 The greater the negative electrode potential, the stronger the tendency of the metal to become an ion in the electrolyte, ie, the more susceptible it is to corrosion. The negative electrode potential of aluminum is relatively large, but its surface is often covered with an oxide film, which can improve its corrosion resistance.

Rare-earth aluminum alloy material is added with rare earth elements in aluminum, which can play a role in purification, increase purity, fill surface defects, and refine grains. Reducing segregation, eliminating microscopic unevenness and leading to localized corrosion, it also brings about a negative shift in the electrode potential of aluminum, which has an anode effect and excellent electrical conductivity, thus greatly improving the corrosion resistance of aluminum. For corrosion problems in the marine environment such as C1- and S, H2S+C02 in the oil and chemical environment, this material has a unique anti-corrosion mechanism. The strong reducibility of rare earth metals can be effectively combined with the strong oxidizing properties of S, H2S, and C1— to interact with each other to produce stable compounds (C1—a rare earth aluminum alloy with stable coordination compounds) that oxidizes and reduces chemical reactions. The process is organically unified and interacts, fundamentally cutting off the corrosion damage caused by the oxidation activities of corrosive media such as S, H2S, and C1, and thus completely solving the problems that developed countries including the United States in the world have not been able to solve well. Analysis and engineering data analysis by major testing departments such as the Beijing Nonferrous Metals Research Institute show that chloride ions, seawater, marine atmosphere, salt fog environment (wet and dry alternation), saturation HzS, sulfur and high temperature and high pressure environment The annual corrosion rate of rare earth aluminum alloys is zero or almost zero.

2. Insulation Part â—† The ampacity of the power cable refers to the larger current allowed by the cable conductor at higher allowable temperatures. When designing the cable, the heat generated by the loss of each part of the cable shall not exceed the allowable temperature of the cable. In most cases, the transmission capacity of the cable is determined by the higher temperature limit of the cable, and the higher allowable temperature of the cable. Depending on the thermal aging properties of the insulation materials used, because the operating temperature of the cable is too high, the aging of the insulation material will accelerate, and the cable life will be greatly shortened. If the cable runs above the allowable temperature, the cable will work safely for 30 years.

â—† XLPE is the abbreviation of English name for cross-linked polyethylene. Polyethylene is a kind of linear molecular structure and it is easily deformed under high temperature. The crosslinked polyethylene process turns it into a network structure. This structure also has a strong resistance to deformation even at high temperatures.

â—†Excellent anti-aging property and super heat-resistant deformation of cross-linked polyethylene determine that high current can be allowed to pass under the conditions of normal operating temperature (90C) short-time failure (130C) and short-circuit (250C). Because its operating temperature is 20C higher than that of polyvinyl chloride, it has excellent thermal resistance, increases the anti-aging properties of insulation, and greatly increases its life.

Economic performance of aluminum alloy cable â—† Direct purchase cost Comparison of aluminum alloy cable and copper core cable: Aluminum alloy cable has superior safety performance, electrical performance, mechanical performance and longer service life. The price of aluminum alloy cable is only About 75% of copper cables.

â—† Lower installation costs Save installation costs: As the aluminum alloy cable has good bending performance and light weight, it is easy to install.

Aluminum alloy cable installation and installation without bridge, do not wear pipe, can save a lot of installation materials, installation costs can be reduced by 20% - 50%.

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