China Debuts 2-Ton Tethered Balloon for Grid Work

China’s first 2-ton-class payload tethered balloon completed a successful trial operation in the Tibet section of a major ultra-high-voltage (UHV) transmission project on September 21, marking a leap in the country’s ability to move heavy construction materials through terrain where roads and cableways cannot go. According to Xinhua News, the balloon, dubbed an “aerial porter,” lifted 2 tons of transmission tower materials to a mountain ridge at an altitude above 4,000 meters — without building roads or installing cableways.

A Large Balloon With a Precise Job

The system, developed by State Grid Corporation of China, uses a balloon measuring 25 meters in diameter with a volume of 8,000 cubic meters — roughly the height of an eight-story building. Helium buoyancy bears the main load, while a ground tether system controls the balloon’s movement.

Multiple tethers are reeled in and out in a coordinated way to precisely control the balloon’s height and horizontal position, allowing point-to-point transfer of materials. The Science and Technology Daily reported that the balloon was deployed on the Tibet segment of the Tibet-Southeast to the Guangdong-Hong Kong-Macao Greater Bay Area ±800 kV UHV Direct Current transmission project, known as the Zang-Yue DC project.

“Our innovatively developed tethered balloon transport equipment uses helium buoyancy to bear the main material load and controls the balloon’s movement via a ground tether system,” said Tu Dejun, director of the Institute of Power Transmission and Transformation Engineering Technology at the State Grid Electric Power Engineering Research Institute. “Compared with traditional transport methods, it offers advantages including large payload, long endurance in the air, low energy consumption, and small ground disturbance.”

A Leap From 500 Kilograms to 2 Tons

The trial represented a step up from China’s previous 500-kilogram-class tethered balloon capability to the 2-ton class — described as a leapfrog advancement. According to IT之家, the trial raised the transport technology’s payload capacity from the 500-kg class to the 2-ton class.

Making such a large system “lift, control, and land accurately” is not easy. Qin Jian, a researcher on the institute’s low-altitude transport technology team, said the team achieved several technical breakthroughs in the airbag, the multi-cable coordinated control system, and the hoisting equipment to address high-altitude transmission line conditions.

Among them, a high-strength composite skin material combined with an integral anchored net prevents tether cables from tearing the balloon skin in strong winds. A multi-cable tension adaptive algorithm overcomes attitude imbalance and trajectory deviation under windy conditions. For hoisting tower materials, the system uses four two-directional magnetic grippers with 800 kilograms of holding force — electromagnets that are de-energized to release — enabling automatic grasping and release of tower materials, improving loading efficiency and lowering risk.

The team had previously accumulated experience with 500-kg-class tethered balloon transport, achieving horizontal positioning accuracy within 0.2 meters and vertical lift error of no more than 0.1 meters, Science and Technology Daily reported.

Why the Terrain Demands a New Approach

The test line sits entirely above 4,000 meters in deep-mountain unmanned zones, with tower foundations mostly built on steep ridges that have no road access — the highest-altitude and worst-transport section of the whole line. Traditionally, building roads in such conditions is costly and environmentally damaging, while cableways are difficult to install and heavily constrained.

“Compared with traditional cableways, the tethered balloon is more flexible to deploy, less dependent on terrain, and faster to reposition; compared with drones, it has a larger payload and longer endurance,” said Feng Tao, project manager at State Grid Henan Power Transmission and Transformation Construction Co., the section’s construction unit. “It is especially suitable for mountainous areas with large elevation differences, dense vegetation, or conditions unsuitable for cableway installation, and it can effectively reduce temporary facilities and consumable inputs, lowering disturbance to the environment along the line.”

The Zang-Yue Project: A Record-Setting Backbone

The tethered balloon is one piece of a much larger undertaking. The Zang-Yue DC project is a key cross-provincial power transmission project under China’s 14th Five-Year Plan. The People’s Daily reported that the line runs about 2,681 kilometers across Tibet, Yunnan, Guangxi, and Guangdong, with a rated transmission capacity of 10 million kilowatts.

When fully operational in 2029, it is expected to deliver more than 43 billion kilowatt-hours of clean energy annually from a clean energy base in southeast Tibet to the Greater Bay Area — about half the annual output of the Three Gorges hydropower station — and to be 100% clean energy, replacing roughly 12 million tons of standard coal and cutting about 33 million tons of carbon dioxide emissions.

The project carries a total investment of about 53.2 billion yuan, with supporting clean energy bases drawing over 150 billion yuan. It is described as the world’s most powerful, most technologically advanced, and largest-investment flexible DC transmission project. Nearly 90% of the route is mountainous and 30% is high mountains, with 197 kilometers of line above 4,000 meters and a maximum altitude of 5,300 meters.

Low-Altitude Logistics as a System

The balloon effort reflects a broader strategy. The State Grid Electric Power Engineering Research Institute has built a power engineering low-altitude transport system centered on heavy-lift drones, transport airships, and tethered balloons — part of a push to move grid construction toward mechanization, intelligence, and unmanned operation.

For the Zang-Yue project, the practical payoff is a “green aerial corridor” for power construction in complex mountainous areas, where conventional logistics struggle most. As the project advances toward its planned 2029 commissioning, the tethered balloon system’s role — and whether it scales to routine deployment — will be a measure of how far China’s low-altitude construction logistics have come.