Clean energy generated from melted snow water on the Qinghai-Tibet Plateau can traverse 2,681 kilometers in just 9 milliseconds to illuminate thousands of homes in the Guangdong-Hong Kong-Macao Greater Bay Area—this seemingly sci-fi scenario is about to become reality through the Tibet-Guangdong DC transmission project.
"This is China's first ultra-high voltage project spanning such complex terrain," said Dong Yanle, Deputy General Manager of the Engineering Construction Department at China Southern Power Grid Co., Ltd. "We face world-class challenges including ultra-high altitude, snowy mountains and frozen soil, geological disasters, heavy equipment transportation, and environmental protection."
This 2,681-kilometer "power skyway" needs to cross three geographical tiers: the Qinghai-Tibet Plateau, Yunnan-Guizhou Plateau, and South China Hills. Nearly 90% of the route consists of mountainous terrain, with 30% being high mountains and ridges, reaching a maximum altitude of 5,300 meters. Facing such challenges, the Tibet-Guangdong DC line, currently the world's most powerful, technologically advanced, and largest investment-scale flexible DC transmission project, is creating multiple "world firsts" in power construction history. Behind this achievement lies years of intensive research battles by scientists.
On New Year's Day 2023, in Hongpo Village, Shangri-La City, Diqing Tibetan Autonomous Prefecture, Yunnan Province, at an altitude of 3,400 meters, the sound of gap breakdown discharge echoed in the air as a group of researchers held their breath while staring at discharge curves on screens. They were conducting full-scale tests of long air gap discharge at high altitude, aiming to understand the "temperament" of electric fields and master the safety distance baseline for converter station equipment operating under high-altitude ultra-high voltage DC conditions.
"When I first received this task, my immediate feeling was that it was impossible," recalled Liu Lei, leader of the Southern Power Grid Research Institute's high-altitude testing team. At that time, full-scale test data for high-altitude long air gap discharge was completely blank—their experiment was like searching for an invisible path in the snow.
High-altitude regions present unimaginable difficulties due to low oxygen content, large temperature differences between day and night, and strong ultraviolet radiation. The most challenging aspect was "capturing data"—air gap breakdown occurs in microseconds, like trying to catch lightning in a blizzard. During this months-long experiment, they conducted 23 major categories and 114 groups of tests, with over 3,000 impulse discharges, ultimately obtaining valuable high-altitude discharge test data that cleared the first obstacle for subsequent engineering construction.
If high-altitude discharge testing was "paving the road," then the instability of new energy sources represents the "dangerous rapids" blocking the path.
When 20 million kilowatts of green electricity travels 2,681 kilometers to Guangdong, any grid failure would be like a sudden traffic jam on a highway—surplus energy would instantly "overwhelm" the "heart" of the transmission system: the flexible DC converter valves.
"When short-circuit faults occur in the receiving AC grid, massive surplus energy rushes into the converter valve power modules, causing system lockout due to overvoltage and threatening grid security," explained Zhao Xiaobin, a core team member from the Southern Power Grid Research Institute. His team needed to solve the world's first fault ride-through challenge for ten-million-kilowatt-level flexible DC systems: how to prevent converter valves from "going on strike" when the receiving grid short-circuits?
The team pioneered a completely new energy self-balancing flexible DC converter valve topology structure, creating a robust "heart" for flexible DC transmission systems.
After countless attempts, the team finally conquered the key technical challenge of rapid energy balancing in ultra-high voltage long-distance and new energy-integrated flexible DC transmission systems, developing the world's first energy self-balancing flexible DC converter valve.
At the highest altitude section of 5,300 meters in Tibet, there's an even more "mysterious" challenge—cosmic rays. The atmospheric neutron flux here is 20 times that of plains, while the core components of transmission systems, IGBTs (power devices), are like delicate "electronic nerves" that may suddenly fail when affected by neutron radiation from cosmic rays. The lack of relevant data and technology undoubtedly brought enormous challenges to the design and construction of the Tibet-Guangdong DC project.
"I used to think cosmic rays were far from us, until I saw the environmental data from Tibet," said Yang Liu, a core team member from the Southern Power Grid Research Institute. To find answers, the team sent power devices to the China Spallation Neutron Source in Dongguan—this national large-scale scientific facility that can accelerate neutron beams can simulate decades of device radiation exposure at high altitude in just a few hours, quickly verifying the reliability of power devices in high-altitude environments.
Ultimately, they not only found the "safe voltage threshold" for devices but also provided measures to reduce failure rates—meaning converter valves can operate safely even at 5,300 meters altitude.
Through a series of technological breakthroughs, the Tibet-Guangdong DC project finally adopted the world-leading "ultra-high voltage multi-terminal flexible DC transmission" technology, capable of flexibly scheduling green electricity generated at different times and locations, reducing current disturbances and impacts on the grid.
Once completed, the Tibet-Guangdong DC project will annually deliver over 43 billion kilowatt-hours of clean energy to the Guangdong-Hong Kong-Macao Greater Bay Area, equivalent to half of the Three Gorges Power Station's annual generation capacity, adding 5 million kilowatts of power supply capacity each to Guangzhou and Shenzhen.