Ultra-high-voltage transmission has brought profound changes to our production and daily life. But have you ever considered this question: although the West pioneered UHV transmission technology more than a century ago, China overtook it in just over a decade, turning it into another hallmark of national strength—on par with nuclear power and high-speed rail. What accounts for this remarkable achievement?
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Today, we take stock of the ever‑breaking records in ultra‑high‑voltage transmission and witness the remarkable leap forward in China’s power‑transmission technology.
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First, here’s a map of China’s ultra-high-voltage transmission network.
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Map of China’s UHV transmission lines in operation and under construction
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As of the end of 2020, China had successfully put into operation “ 14 to 16 straight “Thirty ultra-high-voltage projects have a cross-provincial and cross-regional transmission capacity of 140 million kilowatts, with cumulative power deliveries exceeding 2.5 trillion kilowatt-hours. In addition, two AC and three DC ultra-high-voltage projects are currently under construction. Each of these UHV projects carries extraordinary significance and boasts unique, world‑leading strengths.”
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Overview of Ultra-High Voltage – Part 01.
Long transmission distance
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The defining characteristic of ultra-high voltage transmission is its long transmission distance.
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So, which UHV project currently holds the record for the longest transmission distance in the world?
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Jun Dong–Wannan ±1100 kV Ultra-High-Voltage Direct Current Transmission Project , with a total length of 3,324 kilometers, it spans half of China, traversing the six provinces (and autonomous regions) of Xinjiang, Gansu, Ningxia, Shaanxi, Henan, and Anhui.
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. Jun Dong–Wannan ±1100 kV UHV DC Transmission Project, Guquan UHV Converter Station | Photo by Xu Ke........................................
To date, the ultra-high-voltage AC transmission and transformation project with the longest transmission distance is Yulin–Weifang 1,000 kV UHV AC Transmission and Transformation Project With a total length of 2 × 1,059 kilometers, it traverses Shaanxi, Shanxi, Hebei, and Shandong provinces from west to east. This ultra-high-voltage transmission line serves as a “coal transporter,” not only promoting the efficient utilization of coal resources in northern Shaanxi but also helping to alleviate electricity supply shortages and air pollution in the Beijing–Tianjin–Hebei–Shandong region.
Currently, the longest ultra-high-voltage transmission line in operation abroad is the 1,150-kV line built by the former Soviet Union in 1985, which spans 900 kilometers. It is now operated at a reduced voltage of 500 kV. Although Japan once constructed two ultra-high-voltage lines as well, they have since been downrated to lower voltages following the Fukushima nuclear accident.
Review of Ultra-High Voltage – Part 02.
Strong transmission capacity
When it comes to transmission capacity, Jun Dong–Wannan ±1100 kV Ultra-High-Voltage Direct Current Transmission Project Unsurpassed.
This project is a bundled transmission corridor for wind, solar, and thermal power from Northwest China, capable of delivering 66 billion kWh of electricity annually to the East China region, with a transmission capacity of 9 million kW. It is one of the 26 ultra-high-voltage projects currently in operation in China, boasting a substantial transmission capacity that ranks among the highest worldwide. It has a transmission capacity of 12 million kilowatts, enough to simultaneously meet the electricity needs of 50 million households in East China, and can deliver 100 million kilowatt-hours of power every 8 hours and 20 minutes.
Jun Dong–Wannan ±1,100 kV UHVDC Transmission Project | Source: State Grid Daily
In addition, there is another record related to Zhejiang: the Lingzhou–Shaoxing ±800 kV ultra-high-voltage direct current transmission project. In 2020, its annual UHV utilization hours reached 6,229, ranking first among all UHV DC projects nationwide, while its total outbound power delivery of 49.8 billion kWh placed it at the top of State Grid’s portfolio.
2021 Annual Maintenance of the Shaoxing Converter Station for the Lingzhou–Shaoxing ±800 kV UHVDC Transmission Project
Review of Ultra-High Voltage – Part 03.
Ultra-High-Voltage “Tower King”
The world’s “tower king” of ultra-high voltage is located at Zhangbei–Xiong’an 1,000 kV Ultra-High-Voltage Transmission and Transformation Project In the project, two steel towers—Towers 4S004 and 4S005—stand atop the mountains at Wulonggou in Baoding, Hebei Province, at an elevation exceeding 1,000 meters. With heights of 211.6 meters and 208.6 meters respectively, and weights of 730 tons and 740 tons, they truly deserve the title of “tower kings” in the heavyweight category.
Zhangbei–Xiong’an 1,000 kV Ultra-High-Voltage Transmission and Transformation Project | Source: Official Website of State Grid Corporation of China
The Zhangbei–Xiong’an 1,000-kV UHV AC transmission and transformation project also features the world’s highest‑voltage, largest‑capacity 1,000-kV, 200-Mvar AC stepped‑controlled shunt reactor. Previously, reactors developed in Western countries all weighed around a thousand tons; because these devices cannot be disassembled or subjected to impact, issues related to transportation and lifting had plagued Western nations for many years. China has reduced the size of this massive apparatus to just over 200 tons, and by developing compression springs, using screw‑type clamping for the iron core, and incorporating vibration‑damping pads and springs, it has brought reactor noise levels down to world‑class standards.
Review of Ultra-High Voltage – Part 04.
Nanchang–Changsha 1,000 kV UHV AC Transmission Line Project The 1,000-kV transformer used in the project weighs 490 tons and is the world’s highest‑voltage, largest‑capacity AC transformer. But that is not all: the route traverses complex terrain, with mountainous areas accounting for 74% of the corridor, requiring cableways to transport materials to most foundation locations. The line also passes through severe ice‑prone zones—posing the greatest construction challenges among existing UHV AC projects in China—and there is no prior experience to draw upon for constructing angle‑steel towers in 40‑mm ice‑covered regions.
High-altitude location with a high seismic design category.
Northwest Yunnan–Guangdong ±800 kV Ultra-High-Voltage Direct Current Transmission Project Stretching approximately 1,953 kilometers from Jianchuan County in Dali Prefecture, Yunnan Province, the project traverses four provinces and autonomous regions—Yunnan, Guizhou, Guangxi, and Guangdong—and represents the first ultra-high-voltage direct-current transmission line under the West-to-East Power Transmission initiative to terminate in Shenzhen. Technically, the project has overcome numerous world‑leading challenges: for instance, the Xinsong Converter Station is situated at an elevation of 2,350 meters, the highest in the world; its electrical equipment is designed to withstand seismic activity up to magnitude 9, also a global record; and its DC transmission lines cross terrain with elevations as high as 3,600 meters, again setting a world‑class benchmark.
Power System Simulation Platform
The China Academy of Electrical Sciences has completed Power System Simulation Platform It conducted comprehensive simulation analyses of an ultra-large-scale UHV AC/DC hybrid power system comprising a 220–1,000 kV grid, 2,258 generators, 35,932 transmission lines, and 11,547 nodes, modeling over 100,000 fault scenarios and operating conditions. This next-generation simulation system, characterized by robust simulation capabilities, high computational efficiency, and precise modeling accuracy, has developed key technologies underlying the “three‑line defense” framework and established an internationally recognized security‑defense architecture for large‑scale power grids.
Zhejiang’s ultra-high-voltage transmission project has also yielded world‑class innovative achievements.
The Xiluodu Left Bank–Jinhua, Zhejiang ±800 kV ultra-high-voltage direct current transmission project represents a world‑class innovation in China’s energy sector and stands as one of the flagship achievements of contemporary UHVDC technology. Building on the foundations of the Xiangshang and Jin‑Su UHVDC projects, this undertaking further elevates transmission capacity by addressing critical technical challenges across system research and integrated design, electromagnetic environment control, engineering design, equipment development, construction, and operation and maintenance—thus marking a pinnacle of global UHVDC technology. Key 5,000‑A DC equipment, including converter transformers, converter valves, and wall bushings, were all developed in‑house.
Xiluodu Left Bank–Jinhua ±800 kV UHV DC Transmission Project, Jinhua Converter Station
Over the years, State Grid Zhejiang Electric Power has achieved a series of innovative breakthroughs in key technologies for ultra-high-voltage transmission projects, including research and development on the mechanisms of lightning flashover and corresponding protection techniques for UHV transmission lines, the study and application of critical technologies for the Anhui–East China UHV AC transmission demonstration project, and the extensive R&D of advanced technologies and devices for induced‑overvoltage protection on extra‑UHV transmission lines. These achievements have placed its technical capabilities among the world’s leading.
China has successfully carried out live-line work on a 1,000-kV double-circuit UHV transmission line erected on the same tower.
