Cable copper and aluminum to replace the eight aspects of your comparison did not?

Aluminum alloy power cable is AA8030 series of aluminum alloy for the conductor, the use of special pressing process and annealing and other advanced technology to create a new type of material power cable. The copper cable is now used by the public to the copper material for the conductor of the power cable.
 
I. Introduction
 
With China's economy into the development of new normal, aluminum alloy cable in the electrical market occupies a certain share. Related media and enterprises put forward in the field of power cable to promote the "aluminum on behalf of the copper", and crown the future "development direction" to solve the shortage of copper resources, "strategic initiatives." This paper mainly on the aluminum alloy cable and copper cable in eight aspects of horizontal comparison, combined with practical application, rational and prudent view of copper and aluminum alternative.
 
Second, the actual comparison of copper and aluminum mineral resources
 
China's relative shortage of copper resources is an objective fact, but the aluminum resources are not rich. The so-called "aluminum-rich copper" is not in line with national conditions misleading publicity. As we all know, the domestic aluminum processing industry due to a serious excess capacity, has long been included in the national restrictions on the elimination of backward production sequence. Domestic bauxite aluminum and silicon ratio is low, alumina production costs are high. Over-exploitation of aluminum ore makes the domestic storage and storage ratio of only 6.6 years, much lower than the oil industry 10 years of storage and production ratio, obviously reserves can not meet the rapid economic growth needs. However, in order to maintain a huge aluminum production capacity, must be a large number of overseas procurement of aluminum resources, is expected to "thirteenth five" aluminum overseas dependence will reach more than 60%. In the long run, there is a systematic risk of the shortage of aluminum resources. In contrast, copper as 100% recyclable metal, the domestic storage and storage ratio is still 16 years, if the current foreign exchange reserves and low-cost copper advantage, a large number of foreign copper resources acquisition, "copper in the country" no doubt More prominent strategic significance.
 
Third, the performance of aluminum alloy cable and copper cable comparison
 
Aluminum alloy cable is based on ordinary aluminum to add trace elements as a conductor cable form, although the aluminum cable upgrade version, but compared with the copper cable is still a significant disadvantage.
 
1, aluminum alloy cable conductivity is poor
 
Aluminum alloy cable conductivity is only 61% of copper cable. The same cable section, the large resistance will inevitably lead to high line loss, reduce energy efficiency. Under the same current carrying capacity, the resistivity of the aluminum alloy cable is always slightly larger than that of the copper cable. To the load current 380A, the use of hours 4500h, operating life of 30 years, for example, copper cable section if the use of 150mm ², the aluminum alloy cable section to be 240mm ², the resistivity of the two were 0.148 / km and 0.150 / km, Consumption of 288495kwh / km and 292410kwh / km, the whole life cycle of the two energy consumption difference of 117450kwh / km. Obviously the life cycle of aluminum alloy cable loss is too large, away from the national "energy-saving emission reduction" direction of development.
 
2, aluminum alloy cable carrying low flow
 
City power supply reliability requirements of 99.99%, the core area to reach a higher level of 99.999%. As the city cable network using ring network structure, the case of failure within a short time to protect the action, quickly cut the load to the opposite side of the line to ensure uninterrupted user power supply. But to achieve high reliability grid, improve the network structure, excellent equipment and lines are essential. The power supply line in the power grid must have a high current carrying capacity, in addition to its own load but also bear the temporary switching load. The same section of the copper cable than the aluminum alloy cable carrying capacity higher than 30%, obviously better meet the requirements of urban power supply reliability.
 
3, aluminum alloy cable mechanical low tensile strength
 
Aluminum alloy cable tensile strength is only 46% of copper cable, allowing traction than copper cable 60% lower. The urban distribution network uses a large number of cable ring network structure, planning and design to minimize the use of cable intermediate joints. In actual use, single copper cable laying length is generally in the range of 600 ~ 800 meters. Considering that under the same current carrying capacity, the laying length of single ordinary aluminum cable is only 500 meters. Considering the impact of traction, the laying length of a single aluminum alloy cable is only 350 meters. Obviously low tensile strength will inevitably lead to a single traction cable length is limited, need to add a large number of intermediate joints, increase follow-up operation and maintenance risks.
 
4, aluminum alloy cable corrosion resistance is weak
 
Cable conductor corrosion is mainly metal electrochemical corrosion, that is, the metal surface of the original battery or stray current interference caused by the role of electrolytic batteries. Aluminum alloy cable in the production process in order to improve the creep resistance by adding magnesium, copper, zinc, silicon and other elements, and increase the heat treatment process. As the cable operating conditions are complex, in the electrolyte-containing environment, the lower electrode potential of aluminum and other metal elements added to the electrode is poor, resulting in current path, pitting corrosion and crevice corrosion and other electrochemical phenomena. Aluminum alloy cable heat treatment process is also likely to cause the conductor surface physical state is not uniform, increase the possibility of electrochemical corrosion, followed by stress corrosion cracking and intergranular corrosion.
 
5, aluminum alloy cable high temperature performance is poor
 
Copper melting point of 1080, and aluminum melting point of only 660, apparently copper conductor is a better choice for fire-resistant cable. In the event of a fire, the central ambient temperature can rise above 750, and the cable must be able to maintain the basic function of the power supply to build a life support line. Obviously when the fire temperature is higher than the melting point of aluminum and aluminum, no matter what kind of insulation measures, the cable conductor will melt in a short time, loss of conductive function, which seriously affect the fire evacuation of personnel.
 
6, aluminum alloy cable connector failure risk
 
The cable operating experience shows that 80% of the faults occur at the joint. Copper has the superiority of aluminum and aluminum alloy. Copper oxide oxidation of copper oxide is a good conductor, can still protect the connector and the terminal of the electrical connection performance. Aluminum and aluminum alloy joints generated by the oxidation of alumina is insulator, hard texture, strong bonding properties make it difficult to form a good conductive contacts, easy to cause contact heat. Electrical equipment terminal is the use of copper joints, the use of aluminum alloy cable will form a copper-aluminum connection. The thermal expansion coefficient of aluminum alloy is much higher than that of copper. As the power grid operation is always peak and valley difference, when the load changes significantly, the temperature changes rapidly, the contact area appears a large lateral movement, cut off the effective connection of metal contacts, increase the contact impedance, resulting in the connection temperature rise. Cooling again when the thermal stress changes, and further the formation of interfacial shear. In the long-term hot and cold repeated effects, when the thermal stress is greater than the yield of aluminum, it will form an irreversible plastic deformation in the contact area to speed up the loss of the joints until the final connection failure. Aluminum alloy conductor in the thermal expansion and contraction is more likely to produce poor contact phenomenon, the contact area of ​​the vicious cycle and the safety of the joint operation to form a huge test.
 
7, aluminum alloy cable occupied channel resources and more
 
Under similar energy consumption conditions, aluminum alloy cable cross-section is greater than the copper cable two specifications or more, in order to achieve similar carrying capacity. However, the increased conductor cross-section has a serious impact on cable laying and cable channel construction dimensions. Cable channel resources are an important part of urban cable network construction. Most of the cables are laid by piping and piping, depending on the size of the city road and the traffic organization. The use of aluminum alloy cable laying within the laying, the row of pipe diameter must be enlarged to lay the copper cable diameter of 1.6 times or more, obviously increased the cost of cable construction costs. At the same time to expand the scale of the civil scale increased the area, in the city underground resources increasingly tense conditions, obviously not feasible.
 
8, aluminum alloy conductor installation process requires high
 
Installation of aluminum alloy cable need to use special tools, different manufacturers or even need to configure different tools, no doubt increase the construction and installation costs. Aluminum alloy cable installation process is complex, generally divided into stripping insulation layer, remove the conductor oxide layer, coated with antioxidants, insert the terminal, crimping, erase the excess antioxidant six main steps. Incorrect installation can lead to excessive contact resistance, abnormal temperature rise until a cable fault occurs. The current domestic cable construction strength uneven, on-site management level also lagged behind the developed countries. In contrast, copper cable applications are experienced, with better mechanical properties and installation of fault tolerance, the construction process is relatively simple, more suitable for the actual situation at this stage and the level of development.
 
Fourth, the conclusion
 
In summary, the aluminum alloy cable is a kind of investment risk, the market space is limited, the user safety and reliability of low security products, relative to the aluminum cable is only in the creep resistance of local improvement, but not on the aluminum cable Of the other deficiencies to provide an effective solution. Through the above analysis, aluminum alloy cable is not suitable for medium voltage system and urban distribution network to promote the use.