State Grid built the world's highest 750 kV double-circuit line on the same tower

On December 24, 2010, the Xining-Yongdeng 750 kV transmission line project invested by Northwest Power Grid Co., Ltd. and Xining Power Transmission & Distribution (Construction) Co., Ltd. was responsible for project construction management and successfully passed the re-inspection for commissioning. This project is the world’s highest 750 kV double-circuit transmission line on the same tower.

The Xining-Yongdeng double-circuit transmission line on the same tower is located in the hinterland of the Qinghai-Tibet Plateau and connects Qinghai and Gansu provinces. It is a key power transmission and transformation project that implements the national “Western Development” strategy and the “West-to-East Electricity Transmission” strategy. The line corridor passes through the highest elevation of 3200 meters. The completion of the project will ensure the adjustment of hydropower in Qinghai Yellow River Basin and thermal power generation and wind power compensation in Xinjiang, Gansu, and Ningxia, and will also adjust the peaks for North China and East China Power Grids.

The project started at the 750-kilovolt Xining substation in Qinghai and ended at the 750-kV Yongdeng substation in Gansu Province. A new dual-circuit 750-kilovolt transmission line was built with a path length of 170.507 kilometers and a total of 341 towers. In order to meet the requirements for airport headroom flight, the line reduced the height of the tower when passing through Xining Airport and installed a warning ball between overhead lines.

Northwest Power Grid Co., Ltd. attaches great importance to the construction of the project. Combining with the geological characteristics of the line corridor, it has carried out many innovations in engineering design and construction.

According to relevant sources, in the aspect of engineering design, the project is aimed at the topographic limitations of the terminal towers of Laxiwa outlets, and adopts three discrete designs according to local conditions. Taking full account of the geological and topographical features of Gansu and Qinghai provinces, the first use of LGJ-500/45 six-split steel-cored aluminum-cored-strand conductors in the northwestern region, and the use of double-loop tensile tower transposition technology and improved cage-type jumpers, While improving the windage of the jumper, the layout of the tower head is more compact and the height of the tower is reduced.

In terms of engineering construction, the construction unit adjusted the proportion of the lime-soil in the foundation cushion in conjunction with the geological characteristics of the collapsible loess along the project, effectively solving the problem of foundation subsidence of collapsible loess. In light of the high tower heights and tower weights of high-altitude twin-circuit transmission towers on the same tower, new technologies such as the erection of towers with large-section cross-section poles and auxiliary poles have been applied.