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Five performance advantages of aluminum alloy cables

2020-09-14

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一、Safety performance


1. Proof of historical practice

Aluminum alloy cables have been developed and used in the United States in 1968 for 52 years. The product has been widely used, and the market share of North American countries has reached 80%. After 52 years of practice, it is safe to use aluminum alloy cables without any failure.


2. Testing and certification

The aluminum alloy 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 the National Cable and Wire Testing Center of China, Wuhan High Voltage Research Institute of State Grid, and the National Fireproof Building Material Quality Supervision and Inspection Center. Aluminum alloy conductors meet the requirements of CSA standard C22.2 clause 38 on ACM alloy wires, and the performance requirements of the latest edition of GB/T31840-2015 and IEC60502.1, as well as UL's related standards for the AA8000 series.


3. The effect of aluminum alloy composition

◆ The addition of rare earth and iron to the aluminum alloy conductor greatly improves its electrical conductivity and connection performance. Especially when the conductor is annealed, the addition of iron produces high-strength creep resistance. When the current is overloaded, the iron continues to play The connection effect of the aluminum alloy conductor will not cause creep.

◆ Creep is very harmful to the cable. If the cable creeps, its contact point is not tight enough, and the pressure decreases, which makes the contact resistance increase rapidly. After the current flows, the joint will be overheated. If the cable is not regularly inspected, it will be safe. Hidden dangers. It is very important to solve the problem of cable creep.

◆ Creep: Under the action of temperature, external force and dead weight, metal will slowly produce permanent deformation that cannot be restored with the passage of time. This phenomenon is called creep.


4. Flame retardant performance

The insulation material of the aluminum alloy cable is flame-retardant silane cross-linked polyethylene (XLPE), and the self-locking armored structure is adopted in the process. The heat dissipation performance is far better than that of the PVC sheath. It can quickly dissipate heat, and the flame can be quickly extinguished after the flame disappears. , Will not extend to other materials, excellent flame retardant performance. The aluminum alloy cable adopts new materials and new technology to ensure its safer use.


二、Electrical performance


1. Cable 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 the copper conductor are the same, and the same current carrying capacity, resistance, and pressure loss are achieved.

◆ The resistivity of aluminum alloy is between aluminum and copper, and the load is higher than copper, but slightly lower than aluminum. Under the premise of the same current carrying capacity, the weight of the same length of aluminum alloy conductor is only half of copper. If the conductivity of copper is calculated at 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, which is 2 The resistance per unit weight of copper is the same as the resistance of 1 unit mass of alloy. Therefore, when the cross-sectional area of the alloy conductor is 1.5 times that of copper, its electrical properties are the same, that is, the same current carrying capacity, resistance, and voltage as copper are achieved. loss.

◆ There are many factors that affect the current carrying capacity of power cables, such as line characteristics (such as working power, current type, frequency, load factor); wire and cable structure (such as conductive core structure, number of cores, type of insulation material, shielding layer and The structure and material of the inner and outer sheaths, total outer diameter); laying conditions (such as laying in the air, laying in pipes, laying directly in the ground, laying in underground trenches, laying in water); the maximum allowable working temperature of the conductive core and the surrounding environment 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 of aluminum alloy cable, Germany's most advanced compression technology enables its conductor fill factor to reach 93%. In addition, the aluminum alloy cable uses silane cross-linked polyethylene, which can far exceed the conventional insulation performance with only 2/3 of the thickness of polyvinyl chloride. The filling factor of copper generally can only reach 80%, and the commonly used insulation is polyvinyl chloride, so the outer diameter of the aluminum alloy cable can only be increased by less than 11% on the basis of the copper cable to have the same electrical properties as copper. It can be seen that the use of aluminum alloy cables does not need to change the pipe design of the original copper cables. (Generally, the size of the laying pipe designed by the designer is 150% of the copper cable, so it is not a problem to wear the pipe.)


3. Reduce cable loss

Non-magnetic materials, will not produce eddy current, can reduce the loss of the line. The aluminum alloy belt and armored lock material is a non-magnetic material, even if there is a three-phase unbalanced current, it will not generate eddy current, which can reduce the loss of the line.


三、Mechanical behavior


1. The extension performance of aluminum alloy cable

Elongation is an important indicator of the mechanical properties of a conductor, and an important indicator of the product's quality and ability to withstand external forces. It is also an important index for testing the mechanical properties of cable conductors. The elongation of aluminum alloy cable after annealing treatment can reach 30%, while the elongation of copper cable is 25%, and the elongation of ordinary aluminum rod is 15%, which is an important indicator that can replace aluminum core cables and copper cables.


2. The flexibility of aluminum alloy cables

Torsion test: mainly to test the toughness of the metal wire, the better the toughness, the more torsion times it can withstand. An important shortcoming 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 and corrode, which is an important cause of fire. The use of aluminum alloy cable, due to its good toughness, will not produce cracks, and reduce the potential safety hazards during installation.


3. Bending performance of aluminum alloy cable

Bending test: mainly to test the bending resistance of metal. Materials with uneven or brittle materials have poor bending resistance.

According to GB/T12706 on the bending radius of copper cable installation, the bending radius of copper cable is 10-20 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 , It is easier to lay and reduce installation cost.


4. Rebound performance of aluminum alloy cable

Practice has proved that the copper cable and aluminum alloy cable are bent 90 degrees at room temperature. After the stress is released, the rebound angle of the aluminum alloy cable is 60% of the copper cable. Because the aluminum alloy cable has no memory, the rebound performance is better than that of the copper core cable. The terminal connection joint is easy to be compressed during the installation process, which increases its tightness and improves the stability of the connection.


四、Service life


1、There are two main types of partial corrosion of conductors: 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.

After the metal surface interacts with oxygen, different metal oxides are formed.

Aluminum oxide can form a dense surface protective film with a certain hardness.

The iron oxide structure is loose, easy to fall off, and continue to penetrate and diffuse into the metal, destroying the material.

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

◆ Electrochemical corrosion: refers to the formation of metal corrosion process after the primary battery is composed of metal and medium. When two metals with different electrode potentials are connected with water or other electrolytes in between, there will be formation between the two metals 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 the negative potential is continuously accumulated in the ion state through the electrolyte to the metal at the positive potential. The metal at 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 electrode potential sequence 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 value of the electrode potential, the stronger the tendency to become ions in the electrolyte, that is, the more likely it is to be corroded. The negative value of the electrode potential of aluminum is relatively large, but because its surface often has a protective layer of oxide film, it can improve its corrosion resistance.

Rare earth aluminum alloy materials add rare earth elements to aluminum, which can purify, improve purity, fill surface defects, and refine grains. It reduces segregation, eliminates the effect of microscopic unevenness and causes local corrosion, and also brings about the negative shift of the electrode potential of aluminum, which has the anode effect and excellent electrical conductivity, thereby greatly improving the corrosion resistance of aluminum. This material has a unique anti-corrosion mechanism for the corrosion problems of C1- and petroleum in the marine environment, S, H2S+C02 in the chemical environment. The strong reducibility of rare earth metals can effectively combine with the strong oxidizing properties of S, H2S, and C1-, and interact to form stable compounds (C1- and rare earth aluminum alloys form stable coordination compounds), which will oxidize and reduce chemical reactions. The process is organically unified and interacts. It fundamentally cuts off the corrosion damage caused by the oxidation activities of corrosive media such as S, H2S, and C1-, thus thoroughly solving the problems that have not been well resolved in developed countries including the United States. , The testing and engineering case data analysis by Beijing Nonferrous Metals Research Institute and other national testing departments show that in chloride ion, sea water, marine atmosphere, salt spray environment (dry and wet alternate), saturated HzS, sulfur, and high temperature and high pressure environmental conditions Below, the annual corrosion rate of rare earth aluminum alloy is zero or almost zero.


2. Insulation part

◆ The current carrying capacity of a power cable refers to the maximum current allowed by the cable conductor under the maximum allowable temperature. When designing and selecting a cable, 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 depends mainly on Due to the thermal aging performance of the insulating material used, because the working temperature of the cable is too high, the aging of the insulating material will accelerate and the cable life will be greatly shortened. If the cable runs 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 that is easily deformed at high temperatures. The process of crosslinking polyethylene makes it into a network structure. This structure has strong resistance to deformation even at high temperatures.

◆ The excellent anti-aging characteristics 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-term failure (130C) and short circuit (250C). Because its operating temperature is 20C higher than that of PVC, it has excellent thermal resistance, increases the anti-aging performance of the insulation, and greatly increases the life.


五、Economic performance


◆ Direct purchase cost

Price comparison of aluminum alloy cable and copper core cable: Under the premise that 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 cable.

◆ Reduce installation cost

Save installation cost: due to the good bending performance and light weight of the aluminum alloy cable, it is easy to install.



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