Five main properties of the hottest aluminum alloy

2022-10-02
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Five main performances of aluminum alloy cable

safety performance of aluminum alloy cable

1, historical practice has proved

aluminum alloy cable has been developed and used in the United States for 43 years since 1968. This product has been widely used, and the market share of North American countries has reached 80%. After 43 years of practice, it has been proved that the aluminum alloy cable has never experienced any failure and is safe

2. Detection and certification

aluminum alloy cables have passed the testing and certification of UL in the United States, cul in Canada, Sai global in Australia, and the testing and certification of China national cable and wire testing center, Wuhan High Voltage Research Institute, national fireproof building materials quality supervision and inspection center and other authoritative institutions. Aluminum alloy conductors comply with the requirements of clause 38 of CSA Standard c22.2 on ACM alloy conductors, and the performance requirements of the latest versions of gb12706.1--2008 and iec60502.1, And UL's relevant standards for aa8000 series

3. Effect of aluminum alloy composition

◆ after adding rare earth, iron and other components to the aluminum alloy conductor, its conductivity and connection performance are greatly improved. Especially when the conductor is annealed, the addition of iron produces high-strength creep resistance. When the current is overloaded, iron plays a continuous connection role, so that the aluminum alloy conductor will not creep

◆ creep does great harm to the cable. If the cable creeps, its contact point is not pressed tightly enough, and the pressure decreases, which makes the contact resistance increase rapidly. After the current flows, it causes overheating at the joint. If it is not repaired 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 with the passage of time. This phenomenon is creep

4. Flame retardant performance

the insulating material of aluminum alloy cable is flame retardant silane cross-linked polyethylene (XLPE). We have developed a new experimental machine for change - microcomputer controlled bolt tension and torsion experimental machine. The self-locking armor structure is used on the machine, and the heat dissipation performance is far better than the sheath of PVC material. It can dissipate heat quickly. After the flame disappears, the flame can be extinguished quickly without delaying other materials. The flame retardant performance is extremely excellent. Aluminum alloy cable adopts new materials and new processes, which can ensure its safer use

electrical performance of aluminum alloy cable

1, cable ampacity

◆ when the sectional area of alloy conductor is 1.5 times that of copper, the electrical performance of alloy conductor and copper conductor are the same, realizing the same ampacity, resistance, and voltage loss

◆ the resistivity of aluminum alloy is between aluminum and copper, slightly higher than aluminum, but lower than copper. Under the premise of the same intercepting flow, the weight of aluminum alloy conductor with the same length is only half of copper. If the conductivity of copper is 100%, 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) × (0.612/1) =2, that is, the resistance of copper per unit weight is the same as that of alloy per unit mass. Therefore, when the cross-sectional area of the alloy conductor is 1.5 times that of copper, its electrical performance is the same, that is, it realizes the same cross-sectional flow, resistance, and voltage loss as copper

◆ there are many factors affecting the cut-off flow of power cables, such as; Line characteristics (such as working power, current type, frequency, load factor); The structure of wires and cables (such as the structure of conductor cores, the number of cores, the type of insulating materials, the structure and materials of shielding layers and inner and outer protective layers, and the total outer diameter); Laying conditions (such as laying in air, laying in pipeline, directly buried laying, laying in underground channel, and laying under water); The maximum allowable working temperature of conductive 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 outer section of the cable

in the production process of aluminum alloy cable, Germany's most advanced compression technology enables the filling coefficient of its conductor to reach 93%. And the aluminum alloy cable adopts silane crosslinked polyethylene, which can far exceed the conventional insulation performance with only 2/3 of the thickness of PVC. The filling coefficient of copper can only reach 80% generally, and PVC is commonly used for insulation, so the outer diameter of aluminum alloy cable can only be increased by less than 11% on the basis of copper cable, so it can have the same electrical performance as copper. It can be seen that using aluminum alloy cables does not need to change the original pipeline design using copper cables. (generally, the laying pipe size designed by the designer is 150% of the copper cable. Recently, considering the problem of capacity expansion, the laying pipe size has increased to 200% of the copper cable, so it is not a problem to pass through the pipe.)

3. Reduce cable line loss

non magnetic materials will not produce eddy current and can reduce line loss. Aluminum alloy belt armor lock material is non-magnetic material, even if there is three-phase unbalanced current, it will not produce eddy current, which can reduce the loss of the line

aluminum alloy cable A. select the mechanical performance of the main fixture according to the maximum experimental force of the host

1, the extension performance of aluminum alloy cable

elongation is an important indicator of the mechanical properties of conductors and an important symbol of the quality of products and the size of external forces that they can withstand. It is also an important index for testing the mechanical properties of cable conductors. The elongation of aluminum alloy cable after annealing can reach 30%, while the elongation of copper cable is 25%, and the elongation of ordinary aluminum rod is 15%, which is an important index to replace aluminum core cable and copper cable

2. Flexibility of aluminum alloy cable

torsion test: it mainly tests the toughness of metal wires. The better the toughness, the more torsion times it can withstand. An important disadvantage of ordinary aluminum wire is its high brittleness. As long as it is twisted at a certain angle for several times during installation, the conductor will produce cracks, and the cracks will be heated and corroded, which is an important cause of fire. Using aluminum alloy cable, because of its good toughness, it will not produce cracks, and the potential safety hazards in installation will be reduced

3. Bending performance of aluminum alloy cable

bending test: mainly tests the bending resistance of metal. Uneven or brittle materials have poor bending resistance

according to the provisions of gb/t12706 on the bending radius of copper cable during installation, the bending radius of copper cable is times the cable diameter, and the minimum bending radius of aluminum alloy cable is 7 times the cable diameter. The use of aluminum alloy cable can reduce the layout space, make it easier to lay and reduce the installation cost

4. Rebound performance of aluminum alloy cable

practice has proved that when the copper cable and aluminum alloy cable are bent 90 degrees at room temperature, the rebound angle of aluminum alloy cable is 60% of that of copper cable after stress release. Because the aluminum alloy cable has no memory, its rebound performance is better than that of copper core cable. During the installation process, the terminal connection joint is easy to compress, which increases its tightness and improves the stability of the connection

service life of aluminum alloy cable

1 there are two main types of conductor corrosion: chemical corrosion and electrochemical corrosion

◆ chemical corrosion: refers to the corrosion of metals in the atmosphere with oxygen, chlorine, sulfur dioxide, hydrogen sulfide and other gases

different metal oxides are formed after the metal surface reacts with oxygen

aluminum oxide can form a dense surface protective film with a certain hardness

the oxide structure of iron is loose and easy to fall off, and continues to penetrate and diffuse into the metal, damaging the material

copper oxide, commonly known as copper green, is between the above two and is a toxic substance

◆ electrochemical corrosion: refers to the corrosion process of metal after the primary cell is composed of metal and medium. When two metals with different electrode potentials are connected, and there is water or other electrolytes between them, current will be generated between the two metals to form a primary cell, one of which is at a positive potential and the other is at a negative potential, The metal at negative potential continuously accumulates to the metal at positive potential through electrolyte in ionic state. Make the metal at negative potential gradually lose and destroy, 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 commonly used metals is; Metal Ag (silver) Cu (copper) Pb (lead) Sn (TIN) Fe (iron) Zn (zinc) A1 (aluminum). Potential +0.8+0 33 the greater the negative value of electrode potential, the stronger the trend of metal transferring into electrolyte to become ions, that is, the more vulnerable it is to corrosion. The negative value of the electrode potential of aluminum is large, but its surface often has an oxide film protective layer, which can improve its corrosion resistance

rare earth aluminum alloy material is to add rare earth elements to aluminum, which can purify, improve purity, fill surface defects and refine grains. Reduce segregation, eliminate the effect of local corrosion caused by micro unevenness, and also bring negative shift of electrode potential of aluminum, which has the anode effect and excellent conductivity, thus greatly improving the corrosion resistance of aluminum. This material has a unique anti-corrosion mechanism for the corrosion problems of c1- in marine environment and s, h2s+c02 in petroleum and chemical environment. The strong reducibility of rare earth metals can effectively combine and interact with the strong oxidation of S, H2S, c1- to form stable compounds (c1- and rare earth aluminum alloys form stable coordination compounds), organically unify the oxidation and reduction processes in chemical reactions, interact, and fundamentally cut off the corrosion damage caused by the oxidation activities of corrosive media such as s, H2S, c1-, Thus, the problems that cannot be solved well in developed countries including the United States around the world have been completely solved. The detection and engineering case data analysis of national testing departments such as Beijing Nonferrous Metals Research Institute 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 (alternating wet and dry), saturated HZS, sulfur, high temperature and high pressure environment

2. Insulation part

◆ the current carrying capacity of power cable refers to the maximum current that the cable conductor is allowed to pass under the maximum 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 temperature of the cable. The maximum allowable temperature of the cable mainly depends on the thermal aging performance of the insulation material used, because the cable working temperature is too high, the aging of the insulation material will accelerate, and the cable life will be greatly shortened. If the cable operates above the maximum allowable temperature, the cable will work safely for 30 years

◆ XLPE is the abbreviation of the English name of cross-linked polyethylene. Polyethylene is a linear molecular structure, which is easily deformed at high temperature. The process of crosslinking polyethylene makes it become a kind of like structure. This structure has strong deformation resistance even at high temperature

◆ the excellent aging resistance and super heat-resistant deformation of XLPE determine that large current can be allowed to pass under the conditions of normal operating temperature (90C), short-term fault (130c) and short circuit (250C). Because its operating temperature is 20c higher than that of PVC, it has excellent heat resistance, increases the anti-aging so-called subtraction performance of insulation, and greatly increases its service life

aluminum alloy electricity enlightenment 3: the economic performance of "tall and tall" cables by salespeople

◆ direct purchase cost

price comparison between aluminum alloy cables and copper core cables: on the premise that aluminum alloy cables have superior safety performance, electrical performance, mechanical performance and longer service life, the price of aluminum alloy cables is only about 75% of that of copper cables

◆ lower installation cost

save installation cost: due to the bending of aluminum alloy cable

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