In Wuyaba Village, Hongtu Township, Enshi City, Hubei Province, at the construction site of the Jinshang-to-Hubei UHV project, workers are tightening conductors and installing accessories.
In the deep mountains of the southwest, power workers "walk a tightrope" at a height of 100 meters to install spacers, keeping the conductors at a safe distance; in the central plains, machinery and equipment are busy working at a terminal converter station covering about 360 mu, with more than 1,100 kilometers of cable to be laid... Right now, nearly 10,000 builders are working together to accelerate the construction of the ±800 kV UHV DC transmission project from the upper reaches of the Jinsha River to Hubei (hereinafter referred to as "Jinshang-to-Hubei UHV").
UHV is known as the "electricity highway." Passing through four provinces—Tibet, Sichuan, Chongqing, and Hubei—the 1,901-kilometer Jinshang-to-Hubei UHV is the world's highest-altitude UHV DC transmission project. Once completed, it will gather hydropower, wind power, and solar power from the upper reaches of the Jinsha River and transmit electricity to Hubei, thousands of kilometers away, in an instant, delivering about 40 billion kWh of electricity to Central China each year.
High altitude, difficult transportation, and risky construction: the project overcomes multiple challenges
Altitude 4,797.9 meters! In October 2024, in Batang County, Garzê Tibetan Autonomous Prefecture, Sichuan, the Jinshang-to-Hubei UHV completed stringing over the Sêrongma Mountain, setting a world record for construction of a UHV project at the highest altitude. The approximately 65-meter-tall, 85-ton steel towers and the snow-capped mountains enhance each other's beauty, with silver lines stretching into the distance.
"We are the section with the highest altitude along the entire line, ranging from 3,700 to 4,800 meters above sea level, and in some areas the conductor ice coating reaches 60 millimeters thick. People are prone to hypoxia, and the performance of ordinary machinery and equipment is also affected." Shi Mingqing, project manager of the Sichuan Section 4 of the Jinshang-to-Hubei UHV, introduced that this construction all used machinery and equipment specially designed for high altitudes, and portable oxygen, medicines, and other supplies were also provided on site, effectively ensuring the smooth progress of the project.
As the first UHV DC project to enter the hinterland of the Sichuan-Tibet Plateau, the construction of the Jinshang-to-Hubei UHV has successively overcome multiple challenges.
—Difficult transportation: opening roads in uninhabited high mountains.
With cliffs on both sides, it looks like the back of a knife when viewed from the air. The task of the Sichuan Section 10 of the Jinshang-to-Hubei UHV is to build 113 steel towers on the "Knife Back Ridge," where the steepest slope reaches 65 degrees. How to transport nearly 75,000 tons of materials needed to erect the steel towers into the deep mountains and up to the "Knife Back Ridge" was the primary problem the construction team had to solve.
Zou Zhongxuan, project manager of the Sichuan Section 10, introduced that the construction team built six roads totaling 36 kilometers. To protect the ecological environment to the greatest extent possible, except for sections where temporary roads had to be built, all other points used cableway transportation, with 82 transport cableways built in total, with a cumulative length of more than 60 kilometers.
From the expressway to the temporary roads, materials are transported by large trucks; from the temporary roads to the starting points of the cableways, they are carried by mules and horses; then they are transferred from primary cableways to secondary cableways, like "ants moving an elephant." "From Luding County, Sichuan, to the construction site, one must pass through more than 100 S-shaped or U-shaped curves; a single cableway transports less than 5 tons of tower materials per day on average. Taking a 143-ton steel tower as an example, under ideal conditions it would take a month to complete, not to mention that the heaviest tower weighs nearly 400 tons," Zou Zhongxuan said.
—Risky construction: stringing conductors over a rushing great river.
In a distance of less than 900 meters, the line must cross three 110 kV transmission lines, two provincial roads, and the Dadu River, which is more than 350 meters wide. In July 2024, all conductor stringing work for the Jinshang-to-Hubei UHV crossing the Dadu River was completed.
"It rained those days, and the friction between the conductors and the pulleys decreased. If traction was too fast, the conductors could easily slip off, so less than 60 meters could only be paid out very carefully per minute," said Sheng Yuqiang, construction team leader of the Sichuan Section 10. During the crossing of the Dadu River, three 110 kV transmission lines needed to be powered off and temporarily supplied by other lines. To reduce the impact on residents' lives, they worked in "two shifts" to shorten the construction period.
In the Chongqing section, mountainous terrain accounts for more than 60%, with a cumulative total of 9 crossings over high-speed railways and expressways, 6 crossings over navigable rivers, and 30 crossings over important power lines; in the Hubei section, the line crosses the Yangtze River twice, and in the Enshi section, 60% of the tower foundations are in karst landform areas, with caves scattered throughout the tower foundation sites...
No matter how many challenges there are, it must be built! The important reason is that the Jinshang-to-Hubei UHV project has multiple significant meanings.
On the one hand, clean energy from the Sichuan-Tibet Plateau has an "outlet." After the project is put into operation, it is expected to replace more than 17 million tons of coal per year and reduce carbon dioxide emissions by about 34 million tons, greatly increasing the proportion of green electricity in Central China. On the other hand, power supply in Central China will have "support." It is estimated that by 2030, total electricity consumption in Hubei Province will increase to 405 billion kWh, while the growth rate of local conventional power units such as thermal power and hydropower is limited. The Jinshang-to-Hubei UHV will transmit about 40 billion kWh of electricity per year, providing stronger power support.
Strengthening independent innovation to improve construction safety and efficiency
Facing many construction difficulties, the Jinshang-to-Hubei UHV has strengthened independent innovation and continuously broken through the existing capabilities of high-voltage transmission technology, equipment, and construction.
Panoramic visualization makes conductor stringing safer.
"Visibility is only about 100 meters, so do not pull too fast." In Yingjing County, Ya'an City, Sichuan, a steel wire rope is connected to the traction running board, pulling two conductors with a diameter of 4.3 centimeters slowly into the air. Technicians at the traction site observe the traveling status of the running board and conductors and communicate by walkie-talkie with the tension machine operators several kilometers away.
Unlike previous conductor stringing construction, this operation applied a panoramic visualization and intelligent simulation tension stringing system, which can simulate the conductor stringing process in advance, monitor and collect in real time the working status of key equipment such as pulleys and running boards, and integrate the data into the on-site control and command center. As a result, construction efficiency increased by about 25%, and reliability was greatly improved.
How is the effect after stringing inspected, and how will operation and maintenance be carried out later? In Chongqing, the power company has innovatively developed a self-propelled conductor inspection robot, which can be quickly lifted by drone and installed on the conductor to "walk" and perform quality inspections by itself. "Through technologies such as rapid positioning and laser scanning, the robot can collect and identify data such as the appearance quality of the line, conductor sag, and obstacles in the channel. It can operate in rain, fog, nighttime, and other conditions, improving inspection efficiency," introduced Chen Jin, deputy director of the UHV Construction Division of the Construction Department of State Grid Chongqing Electric Power Company.
One station split into two stations makes hydropower, wind, and solar transmission more efficient.
Conventional UHV DC sending ends are mostly single converter stations, usually covering about 400 mu. However, the sending end of the Jinshang-to-Hubei UHV has fragmented terrain, so the project team chose to split it into two converter stations connected in series, each covering more than 200 mu: the Bangguo Converter Station is being built in the energy base dominated by hydropower in Garzê, Sichuan; and the Kamai Converter Station is being built in the mixed hydropower, wind, and solar energy base in Qamdo, Tibet.
"After being split, the converter stations still need to operate as a whole to achieve site-separated transmission of renewable energy and multi-energy complementarity. However, the connecting line in between is relatively long, and the equipment complexity and operation and maintenance requirements are higher," said Zhou Lilong, deputy director of the Tibet-aid DC Operation and Maintenance Division of the State Grid Sichuan DC Center.
At the same time, China's first independently developed 550 kV fast circuit breaker will be piloted for the first time in the converter transformer of the Bangguo Converter Station. It can shorten the opening time from 50 milliseconds to within 25 milliseconds, effectively reducing operational risks when oil-filled electrical equipment in the converter station fails.
Stabilizing investment, promoting employment, and benefiting people's livelihoods, generating multiple benefits
"This job pays well. I learned while working and also mastered skills such as concrete mixing and grounding wire laying." In July 2023, Zhao Qingxiang, a villager from Nanlin Village, Yingjing County, came to work on the UHV project, doing work such as foundation pouring and trench excavation. During the peak period of foundation construction for the Jinshang-to-Hubei UHV, more than a thousand local people joined the construction in the Sichuan section alone.
For Liu Wenlong, a villager from Xianfeng Village, Yingjing County, a road about 6 kilometers long built by the project for transporting materials has made it easier to ship mountain products such as Sichuan pepper and walnuts out of the village. "In the past, it was not easy to go up the mountain, and it took ten days to half a month to gather enough mountain products. Now with the winding mountain road, they can be transported down the mountain by tricycle the same day."
UHV projects involve large investment and play an important role in stabilizing investment, promoting employment, and benefiting people's livelihoods. It is estimated that the Jinshang-to-Hubei UHV can drive hundreds of billions of yuan in investment in upstream and downstream industries and provide more than 10,000 jobs.
In recent years, China has continued to optimize the layout of power flows, forming a cross-provincial and cross-regional power transmission pattern with three major corridors for "west-to-east power transmission": north, central, and south. By the end of 2024, China had completed and put into operation 42 UHV AC and DC projects, including 38 by State Grid and 4 by China Southern Power Grid, with cross-provincial and cross-regional power transmission capacity exceeding 300 million kilowatts. Supported by UHV projects, China's installed renewable energy capacity increased from more than 300 million kilowatts in 2012 to more than 1.5 billion kilowatts in 2023.
A relevant official from the National Energy Administration said that in 2025, China will also approve the construction of a batch of key power mutual-aid projects and actively promote the approval and commencement of transmission channels such as West Inner Mongolia to Beijing-Tianjin-Hebei, Southeast Tibet to the Guangdong-Hong Kong-Macao Greater Bay Area, the Gansu Badain Jaran Desert base to Sichuan, and Southern Xinjiang to Sichuan-Chongqing.
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