By Ding Yiting, Hou Linliang, Wang Jintao, People’s Daily
China’s first “wind-solar-thermal-storage integration” ultra-high voltage (UHV) project, the Longdong-Shandong ±800 kilovolt direct current (DC) transmission project, was put into operation on May 8.
Developed by the State Grid Corporation of China (SGCC), the project stretches 915 kilometers from Qingyang in the wind-swept province of Gansu to Tai’an, east China’s Shandong province. Designed to deliver 36 billion kilowatt-hours of electricity annually — enough to power over 10 million households — the line will transmit a blend of renewable and conventional energy, with half of that electricity coming from clean sources.
The project functions like a high-speed expressway for power: direct, high-capacity, low-loss, and highly efficient. Backed by an investment of 20.2 billion yuan ($2.8 billion), it can deliver electricity generated in Gansu to Shandong in just three milliseconds, faster than the blink of an eye.
Gansu, long known for its wealth of wind and solar resources, now sees renewables accounting for over 60 percent of its total installed capacity — second only to one other province in China. With the rapid growth of clean energy production,the need for a strong and flexible grid has become urgent. The new UHV line will enable the stable transmission of over 10 million kilowatts of renewable power, facilitating the coordinated flow of energy across regions.
At the heart of the project is a vast energy base run by China Huaneng Group, a major state-owned power company.According to Chairman Wen Shugang, the project demonstrates how different forms of energy can work in tandem to maximizeefficiency.Even the thermal power component is also transitioning to cleaner and more efficient generation. One standout effort is the construction of the world’s largest carbon capture demonstration facilityat a coal-fired plant, with aprojected annual capture capacity of 1.5 million tons.
Much of the project’s success hinges on advances in grid technology. Yang Pengcheng, deputy director of the converter station department of SGCC’sUHV Division, noted that the line is the first in China to deploy a range of homegrown switchgear, control systems, and protection equipment — each developed with independent intellectual property rights. These systems have endured intensive tests under high voltage and large currents, helping fortify China’s foothold in advanced transmission equipment manufacturing.
Among the most significant innovations is the use of domestically produced on-load tap changers for converter transformers — critical devices that modulate voltage much like a car’s gear shifter. During periods of peak demand, they can rapidly boost voltage to stabilize the grid; when renewable energy generation spikes, they can lower voltage to prevent overloads, ensuring steady, efficient power flow along the “expressway.”
“Each tap changer contains over 1,000 components and performs eight precise actionsper switch,” said Li Shiwei, general manager of the grid construction division of China’s State Grid Gansu Electric Power Co., Ltd. “More than 400 components must work together with millisecond precision for every operation. Until now, only a few foreign firms had the capacity to supply such reliable systems. Now we can do it ourselves.”
Other breakthroughs includeself-developed DC control and protection systems built with Chinese chips. According to Han Qi, head of the construction department at China’s State Grid Shandong Electric Power Company, these systems act as the “safety commanders” of the transmission network, monitoring transmission lines in real time and automatically cutting off dangerous current flows when abnormalities arise. The domestically developed chip used in these systems is no bigger than a fingernail but completes two billion calculations per second — twice as fast as comparable imported chips — reducing system response time down to milliseconds.
The Longdong-Shandong project also marks the debut of China’s standardized technology for UHVDC transmission at ±800 kilovolts and 8 million kilowatts. Several similar projects are now underway across China.
According to Yang, the project developed over 550 sets of standardized technical documents, more than 5,500 design drawings, and contributed to the drafting or revision of one international standard, nine industry standards, and 100 corporate standards.
“With standardized parameters, future UHV projects can be assembled like LEGO blocks,” Yang said. “Modular, plug-and-play solutions will streamline design, equipment installation, and construction — cutting construction time by around 30 percent and maintenance costs by about 25 percent.”
To date, SGCC has completed 39 UHV transmission projects — 22 AC and 17 DC — establishing the largest UHV power transmission network in the world. Capable of transmitting more than 340 million kilowatts of electricity across provinces and regions, the system provides robust support for energy supply and China’s transition to green, low-carbon development.
