State Grid completed two world-class power grid innovation projects

On September 26, Kou Wei, Chairman and Secretary of the Party Committee of State Grid Corporation of China, announced the completion and operation of the Zhundong-Southern Anhui ±1100 kV UHV DC transmission project and the Sutong 1000 kV AC UHV GIL integrated pipeline project, marking the official operation of these two world-class power grid innovation projects.

The commissioning of the Zhundong-South Anhui and Sutong GIL integrated pipeline project is a vivid practice of State Grid Corporation of China in implementing General Secretary Xi Jinping's new energy security strategy of "four revolutions and one cooperation". In June 2014, General Secretary Xi Jinping proposed the new energy security strategy of "four revolutions and one cooperation" at the sixth meeting of the Central Financial and Economic Leading Group, leading the development of my country's energy industry into a new era. The 19th National Congress of the Communist Party of China made major arrangements for my country's energy transformation and green development, emphasizing the strengthening of infrastructure network construction such as power grids, promoting the revolution in energy production and consumption, building a clean, low-carbon, safe and efficient energy system, and continuously implementing air pollution prevention and control actions to win the battle to protect blue skies. UHV power grids are major infrastructure, energy networks and ecological and environmental protection projects. As a large-scale state-owned key backbone enterprise related to the lifeline of the national economy and national energy security, State Grid is accelerating the construction of a world-class energy Internet enterprise with "three types and two networks" to further expand the scale of "west-to-east power transmission" and "north-to-south power supply". The commissioning of the Zhundong-South Anhui and Sutong GIL integrated pipeline projects is an important innovative achievement of the State Grid in promoting the construction of a world-class energy Internet enterprise with "three types and two networks", and is a milestone in the development history of my country's power industry. Both projects occupy the commanding heights of their respective fields of power transmission technology in the world today, promoting a new leap in my country's electrical equipment manufacturing capabilities and significantly improving my country's ability to optimize energy allocation on a large scale.

The Zhundong-Annan project is the world's highest voltage level, largest transmission capacity, longest transmission distance, and most advanced technology DC transmission project, which has set a new height for the world's power grid technology. The Zhundong-Annan project starts in Changji Autonomous Prefecture, Xinjiang, and ends in Xuancheng City, Anhui. It passes through six provinces (regions) including Xinjiang, Gansu, Ningxia, Shaanxi, Henan, and Anhui. Two new converter stations, Changji and Guquan, are built with a conversion capacity of 24 million kilowatts and a total line length of 3,324 kilometers. The project has an investment of 40.7 billion yuan and was approved by the National Development and Reform Commission in December 2015. On the basis of successfully breaking through the ±800 kV DC transmission technology, the State Grid organized joint research at home and abroad, and overcame world-class problems such as ±1100 kV DC transmission system scheme demonstration, ultra-long air gap insulation, overvoltage depth control, and electromagnetic environment control, achieving a comprehensive improvement in DC voltage, transmission capacity, and AC grid voltage. The DC voltage level increased from ±800 kV to ±1100 kV, the transmission capacity increased from 6.4 million kilowatts to 12 million kilowatts, and the economic transmission distance increased to 3000~5000 kilometers. The transmission loss per thousand kilometers was reduced to about 1.5%, further improving the transmission efficiency and saving precious land and corridor resources. The line sending end is connected to the 750 kV AC grid, and the receiving end is connected to the 500 kV and 1000 kV AC grids in high and low layers. It has a high level of safety and stability, strong flexibility and adaptability, and has effectively enhanced my country's core competitiveness in the field of electrical equipment manufacturing.

The Sutong GIL integrated pipeline corridor project is the first in the world to use UHV GIL technology in an important power transmission channel. It is currently the world's highest voltage level, largest transmission capacity, and highest technical level ultra-long distance GIL innovation project, achieving a new leap in the world's power grid technology. The Sutong GIL integrated pipeline corridor project is one of the components of the Huainan-Nanjing-Shanghai 1000 kV UHV AC project. The project uses two (6-phase) 1000 kV GIL (gas-insulated metal-enclosed transmission lines) laid in the pipeline corridor (tunnel). The total length of the GIL pipeline is about 35 kilometers, which is equivalent to the total length of GIS busbars of 20 UHV substations. The project was approved in July 2016, the tunnel was fully connected in August 2018, and all GIL equipment was installed in August 2019. The project crosses the Yangtze River 1 km upstream of the Sutong Bridge. Two 500 kV cables and municipal general pipelines such as communications and cable TV are reserved in the tunnel. The project starts from the north bank (Nantong) access station and ends at the south bank (Suzhou) access station. The tunnel is 5468.5 meters long and the shield diameter is 12.07 meters. It is currently the largest underwater tunnel in China with the largest burial depth and the highest water pressure. Focusing on the goal of "successful commissioning at one time and long-term safe operation", the State Grid organized a large-scale joint research and tackled technical difficulties such as the development of high-performance insulation components, the suppression of metal particle motion characteristics under high field strength, the flexible design of the GIL full pipe system, high-reliability sealing, and accurate fault positioning. It was the first in the world to master the full set of UHV GIL transmission technology, which has driven the comprehensive upgrade of my country's GIL transmission technology and equipment level, and reserved technology for advanced compact transmission across rivers, across seas and densely populated areas.

准东—皖南、苏通GIL综合管廊工程投运之后，清洁电力将实现更加可靠、高效、灵活地汇入华东特高压交流环网，对于优化能源配置、保障电力供应、防治大气污染、拉动经济增长、引领技术创新等具有显著的综合效益和长远的战略意义。