Sutong project, China

In a bid to decrease coal consumption and move towards clean energy, China is introducing technologies that reduce carbon footprint. Due to China’s large geographic size, power sources are mostly located away from cities. Consequently, electricity must travel several hundreds, or even thousands, of kilometers to reach consumption points. For this purpose, ultra high-voltage (UHV) transmission technologies are used to deliver large amounts of power across long distances and with lower energy losses.

Hitachi Energy partnered with State Grid Corporation of China (SGCC) to build the first of its kind 1,000-kilovolt (kV) gas-insulated lines (GIL) laid in the Sutong tunnel to transmit clean energy from West to East China. The engineering challenge involved laying the lines under the estuary of the Yangtze River, spanning a section of water which is 5.4 kilometers wide and 75 meters deep. The Sutong project is the first in the world that adopts UHV GIL technology in a transmission tunnel. When overhead lines and underground cables are not possible, GIL is the ideal solution for transmitting power underground with minimum transmission losses.

With a significantly reduced environmental impact, our technology is helping China to integrate more renewables into the electrical grid. Our UHV gas-insulated lines are essential in connecting remote areas with heavily populated areas, efficiently transmitting large amounts of electricity, helping to ensure energy security, as well as economic and social development.

The Sutong tunnel is helping to ease power shortages and strengthen grid reliability in the Yangtze River Delta region. It is also part of the Huainan-Nanjing-Shanghai UHV AC transmission link, bringing 6 gigawatts (GW) of clean power to the dense metropolitan area of Shanghai in the east, sufficient for 6 million people. Furthermore, it is contributing to China’s three-year Air Pollution Prevention and Control Action Plan to reduce sulfur dioxide and nitrogen oxide emissions. It will help to decrease carbon dioxide (CO₂) emissions by 310 million tons annually, equivalent to nearly 68 million passenger cars being taken off the road.