8-legged power transmission "pillar"! my country completed the assembly of the "eight-legged" portal tower for the first time on the natural barrier in the southwest

On the 12th, the first portal tower assembly task of the Sichuan-Chongqing 1000 kV UHV AC project from Ganzi to Tianfu South was successfully completed. The Erlangshan section of the project starts from Ganhaizi West, Luding County, Ganzi Prefecture, Sichuan Province, and ends at Baichaping, Tianquan County, Ya'an City.

01

Various power towers

In power transmission projects, we often see tower-shaped buildings, namely transmission line towers, also known as power towers. Circuit towers, overhead lines, cables, distribution transformers, etc. form a power grid system that can convert the electricity generated by power plants into the light of your desk lamp and the heat of your electric blanket. In the transmission line, the power tower plays an important supporting and fixing role.

According to the shape of the power tower, the common power towers are elephant-shaped towers and Chinese-shaped towers . The elephant-shaped tower can be divided into wine glass-shaped towers, cat head-shaped towers, sheep horn towers, drum-shaped towers, etc.; the Chinese-shaped tower can be divided into dry-shaped towers, upper-shaped towers, gate-shaped towers, V-shaped towers, T-shaped towers, etc. As the name suggests, the gate-shaped tower looks like a "door".

02

Extra heavy ice area! Breaking through the traditional "eight-legged" portal tower!

However, the portal tower designed this time does not have the traditional four legs, but an innovative design with eight legs. Why did the designers want to "add legs" to the portal tower?

According to the enterprise standard "Technical Regulations for the Design of Overhead Transmission Lines in Medium and Heavy Ice Areas" issued by the State Grid Corporation of China: areas where the designed ice thickness of wires is between 10 mm and 20 mm (ice density 0.9 g/cm³) are called "medium ice areas"; areas where the designed ice thickness of wires is 20 mm (ice density 0.9 g/cm³) and above are called "heavy ice areas". It turns out that the line crossing Erlang Mountain is the first time that my country's UHV line has crossed the "extra-heavy ice area" of 60 mm.

Under such conditions, the traditional design with four tower legs as the supporting structure (distributed in a square shape) cannot meet the load requirements after ice covering. Therefore, this project adopts the innovative portal tower structure with eight legs for the first time, which can double the bearing capacity of the tower body. This is also the first time that an "eight-legged" portal tower has been assembled in my country.

Image source: Video screenshot

Source: Video screenshot

03

It is not easy to add legs to power towers

Although the innovative “8-legged” portal tower structure is more stable, it is a huge challenge in the actual engineering work of assembling the tower.

First of all, it is difficult to accurately control the root distance (the distance between adjacent or diagonal main steel reference lines) and height difference of the eight "tower legs". Only by accurately controlling these data can the tower be "erected" when it is assembled. To this end, the construction workers sent experienced personnel to the construction site from the excavation and pouring stages to strictly control various key data to ensure compliance with the design.

In addition, when two pairs of holding poles are used for assembly, there are mutual interference and potential safety hazards caused by high-altitude operations. For this reason, when assembling the portal tower at the construction site, the " T2D96 ground-mounted double rocker holding pole " is used . After the two sub-towers are assembled in sequence, the "hoisting cross arm" is used when closing them . These methods can effectively avoid the above-mentioned potential safety hazards.

04

The complex environment of Erlang Mountain increases the difficulty of construction

The Erlangshan section of the Ganzi to Tianfu South 1,000 kV line project is located between Tianquan County, Ya'an City, Sichuan Province and Luding County, Ganzi Tibetan Autonomous Prefecture. Erlangshan is known as "the first natural barrier from the Sichuan Basin to the Qinghai-Tibet Plateau". The altitude along the line of the project is 1,800 to 3,100 meters. The project has also become the world's highest altitude UHV AC ring network project.

The Erlangshan area has complex terrain, dangerous topography, and changeable climate, which undoubtedly increases the difficulty of construction. Faced with the harsh environment, State Grid Sichuan Construction Company and the construction unit adopted front-end control and full-process control to avoid cold, snowy weather and winter breaks, and orderly deployed materials several months in advance to ensure the supply of materials in the Erlangshan section and the stability and safety of the work and life of construction personnel in the unmanned area, thus laying a solid foundation for on-site safety production and smooth assembly of portal towers. It is reported that after the completion of the project, the clean electricity that can be transmitted each year will exceed 35 billion kilowatt-hours.

Image source: Video screenshot

Comprehensive sources: Xinhua News Agency, Science and Technology Daily, State Grid Enterprise Standards, State Grid Wuxi Power Supply Company, etc.