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. Power supply lines in the power grid must have a high current carrying capacity, in addition to their own load can 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.
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.
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