Aluminum can play a big role in the transmission tower

At present, most of China's transmission poles and towers are made of steel, with about 200 years, but the shortcomings of iron poles and towers are dense, heavy and inconvenient transportation, especially in mountainous areas, plateau areas, transportation, installation, maintenance are very laborious, but also must be regularly maintained, otherwise it will rust, or even damage. But it's not the same if the steel it uses is replaced with aluminum. In the past, the strength of aluminum was not high, and now it is not a problem to manufacture ultra-high strength aluminum alloy. This alloy has a high enough strength for the manufacture of transmission and distribution towers, and is fully competent.

China Electric Power Research Institute (hereinafter referred to as the Institute) led by the State Grid Corporation headquarters management technology project "high-strength aluminum alloy transmission tower design processing technology and standardization research" passed acceptance. Conventional transmission towers are made of steel and must be hot-dip galvanized to prevent corrosion, but galvanized is bad for the environment, and the use of a long time, the galvanized layer will fall off, and the tower is erected in rugged mountainous areas, and it is not easy to carry materials.

Therefore, the project team explored the use of high-strength aluminum alloy materials instead of traditional steel, carried out the technology research and development of the application of high-strength aluminum alloy materials in the transmission tower, formed the high-strength aluminum alloy tower raw materials, and realized the tower material processing without galvanized, and the quality was reduced by nearly 45%.

The project results have been accepted in December 2022, and can be used for material selection, structural design and product processing of aluminum alloy transmission towers.

Using the research results of the project, the Institute of Transmission and Distribution Engineering of the Chinese Academy of Sciences has carried out the true form test of China's first self-supporting aluminum alloy tower. The test tower uses 7A21 and 7A41 high-strength aluminum alloy materials, and adopts the new YT cross-section newly developed by the Institute of Electrical Science and Technology. The test tower is equipped with 60 strain measurement points and 12 displacement observation points, and the strain measurement and displacement observation are carried out on the important components, nodes and the whole deformation of the aluminum alloy tower. There are 6 operating conditions in the test, and the overload test under 90° wind condition is carried out. The design method and processing technology of high strength aluminum alloy tower are verified successfully.

Project research groups such as the Chinese Academy of Sciences have explored a new route for the application of high-strength aluminum alloy materials in power transmission self-supporting towers, and proposed new solutions to solve the problems of tower material transportation, galvanized pollution and anti-corrosion maintenance in mountainous areas, which has promoted the technical progress of the tower industry in the development, design, scientific research, processing and construction of new materials.

7A21 and 7A41 alloys are Chinese grade alloys, and their original alloys are 7021 and 7041, which means that the composition and performance of 7A21 and 7021 alloy are equivalent, and the composition and performance of 7A41 alloy are equivalent to that of 7041 alloy. 7021 is Al-Zn-Mg alloy, 7041 is al-Zn-Mg-Cu alloy, according to the habits of the aluminum industry, they should be called super-strength alloy, rather than high strength aluminum alloy. 7021 alloy is an American alloy, registered in 1976 with the American Aluminum Association, Inc., whose calibrated composition (mass %) : Si0.25, Fe0.40, Cu0.25, Mn0.10, Mg (1.2 ~ 1.8), Cr0.05, Zn (5.0 ~ 6.0), Ti0.10, Zr (0.08 ~ 0.18), other impurities single 0.05, alloy 0.15, the rest Al. 7041 alloy is a French alloy, registered with the American Aluminum Association in 2008, its calibrated composition (mass %) : Si0.15, Fe0.25, Cu (0.40 ~ 0.9), Mn0.04, Mg (1.5 ~ 2.3), Cr 0.04, Zn (5.7 ~ 6.7), Ti0.06, Zr (0.05 ~ 0.12), other impurities single 0.05, total 0.15, the rest Al. This is a very clean alloy with very low content of impurities Si and Fe.

On January 12 this year, the world's highest transmission tower with a height of 385 meters was successfully capped in Jiangsu Province. The tower is an important part of the 500 kV transmission line project from Fengcheng in Taizhou to Meile in Wuxi, and after completion of the project, about 28.9 billion KWH of clean electric energy can be sent from the north bank of the Yangtze River to the south bank of the Yangtze River every year, meeting the daily electricity demand of about 8 million households.