In China, where power is often located far from the city's electricity center, transmission lines need to span hundreds or even thousands of kilometers. EHV transmission technology can reduce transmission losses while maximizing transmission efficiency and achieve long-distance transmission. Sulfur hexafluoride gas insulated metal enclosed transmission line (GIL) is the ideal solution for underground power transmission and minimum transmission loss. When harsh conditions do not allow the laying of overhead lines or underground cables, the GIL is ideal for UHV transmission. The construction of Huainan-Nanjing-Shanghai 1000 kV UHVAC transmission project by State Grid Corporation is the first of the 12 key transmission channels in the national plan for air pollution prevention and control. After the completion of the project, it is estimated that the annual coal saving for power generation can reduce emissions by 960,000 tons of sulfur dioxide and 530,000 tons of nitrogen oxides. Sutong GIL integrated corridor from the bottom of the Yangtze River through the Yangtze River, is the world's first UHV cross-river tunnel. The tunnel is 5.7 kilometers long, reaching 75 meters deep at the bottom of the Yangtze River. In this project, ABB is responsible for the design, delivery and installation of the 1000 kV GIL supplied. ABB's solutions will maximize energy transmission capacity and minimize transmission losses, helping to secure the energy security of East China's UHV grid and supporting economic and social development. Zhang Jinquan, Senior Vice President of ABB Group and Head of China Division of Power Grid Division, said: "We are very pleased to participate in the world's first UHV tunnel project and provide GIL solutions .ABB is committed to enhancing customer value through innovation. Our UHV Technology will support China to achieve high-capacity power transmission, enhance grid transmission capacity and reduce environmental impact. "