China's ultra-high voltage transmission lines now breaking all records.

ELI5/TLDR

If you build wind farms in a desert and the cities that need the power are 3,000 km away, your problem isn’t generation — it’s plumbing. China solved this by inventing the world’s longest extension cord, running at a voltage so high it bends the rules of normal electrical engineering. Five years after the first one switched on, it’s still hauling roughly an Ireland’s worth of power down a single wire. A second one, even longer, is on the way from Tibet. Europe and the US can’t really copy this — partly because the kit is hard, mostly because the politics is harder.

The Full Story

Why voltage, not current

When electricity has to travel a long way, the engineer’s first lever is voltage. Imagine pushing the same amount of water through a pipe. You can use a wide pipe with gentle flow, or a narrow pipe with violent pressure. Wires work the inverse way — high current (the violent flow) heats them up, and heat is your useful energy turning into warm air. Crank the voltage instead, and the current can stay polite. Wires stay cool. Losses stay small.

Over short distances, alternating current (AC) is convenient because transformers can step the voltage up and down easily. But AC has a quiet tax: the electrons slosh back and forth at 50 or 60 times a second, leaking energy as electromagnetic radiation. Over thousands of kilometres, that tax becomes ruinous. Direct current (DC) — electrons flowing politely in one direction — doesn’t pay it. The penalty for using DC is that you need expensive converter stations at both ends to turn AC into DC and back again. Past a certain distance, the cost of those stations is less than the cost of the losses you’d otherwise eat. That break-even is where the monsters live.

The Changji–Guquan line, five years on

The original ultra-high-voltage DC (UHVDC) line that this channel covered in 2020 is still the world’s biggest. It runs at 1.1 million volts (1,100 kV — roughly twice the voltage of standard “high voltage” lines in Europe and the US) over 3,000 km, and can move 12 gigawatts. To put that in context, 12 GW is roughly the entire generation capacity of Ireland — flowing down one wire.

During a peak load period in 2024, the line sustained a high load of 10.8 GW for over twelve hours while delivering daily power transmission exceeding 250 million kilowatt-hours.

Since switch-on, the line has cumulatively delivered over 300 billion kWh from wind and solar farms in the northwest to industrial clusters in Anhui — equivalent to about 120 million tonnes of coal not burnt.

The next one: Tibet to the coast

A second mega-line is under construction. It runs 2,681 km from the Tibetan plateau to the Guangdong–Hong Kong–Macao region, costs around $7.5 billion, and will carry 10 GW. The Tibetan plateau is already studded with solar panels covering an area four times the size of Paris, wind turbines across the horizon, and hydro plants exploiting the rivers that drop off the plateau’s edge. When this line comes online in 2029 — and the presenter notes drily that Chinese projects tend to come online on schedule — it will displace about 33 million tonnes of CO2 per year. By 2050, ten such corridors are planned out of Tibet, exporting more than 500 billion kWh annually.

Why the West can’t easily copy this

The hardware is mostly buyable. ABB and Siemens already make the 40-metre, hundreds-of-tonnes converter transformers these lines need. The terrain problem is bigger. China has thousands of kilometres of sparsely populated land between its renewables-rich west and its industrial east. Europe and the US don’t. Every overhead corridor in a dense country becomes a planning fight.

Then there’s the political problem, which the presenter names plainly. China has an authoritarian government that can set 25-year infrastructure goals and ignore the inconvenience of elections. The US and Europe have fragmented regulators, multiple system operators, and cross-border legal regimes that need to align on standards, pricing, and maintenance. The non-technical barriers are bigger than the technical ones.

And these projects only pencil out if there’s reliable surplus generation at one end and reliable demand at the other for decades. If either assumption wobbles, the economics evaporate.

Key Takeaways

The voltage-vs-current trade-off: double the voltage, halve the current, quarter the resistive losses. This is why long-distance transmission is always a hunt for higher voltage.
AC vs DC break-even: AC wins short distances (easy transformers); DC wins long distances (no electromagnetic losses, no reactive power penalty). The crossover is roughly 600–800 km for overhead lines.
UHVDC threshold: above ~1,000 kV. The Changji–Guquan line runs at 1,100 kV — currently the world record.
One line, one country’s worth of power: 12 GW down a single wire is comparable to the entire grid of Ireland.
Equipment scale: converter transformers are ~40 metres long, weigh hundreds of tonnes. Built in Europe (ABB, Siemens), shipped to China.
Cumulative output: the original line has delivered over 300 billion kWh since 2020 — equivalent to ~120 million tonnes of coal avoided.
Tibet corridor: 2,681 km, 10 GW, $7.5 billion, online 2029. Ten such corridors planned by 2050.
The bottleneck is political, not technical: fragmented regulation in Europe/US makes multi-gigawatt overhead corridors harder to approve than to engineer.
UK relevance: renewable operators are currently paid to NOT generate when transmission can’t carry their output. Same problem, smaller scale.

Claude’s Take

A useful five-year check-in. The original Just Have a Think video on this line was the kind of thing where you wondered whether it was a one-off stunt. The answer is no — it works, it’s been running near rated capacity, and China is treating it as a template rather than a trophy. The pivot point in this video is the honest bit at the end: the technology is exportable, the geography mostly isn’t, and the politics definitely isn’t. The presenter’s “would we trade democracy for technological progress?” framing is a bit cute, but the underlying observation is sharp — coordinated long-term infrastructure planning is the actual moat here, not the kit.

What’s missing: any real discussion of HVDC failure modes (these lines, when they trip, dump enormous amounts of power instantaneously and need very fast load-shedding on the receiving grid), and any mention of the offshore HVDC build-out happening in Europe right now (the North Sea wind hub, the SuedLink corridor in Germany). The video frames China as uniquely capable, when really the West is doing the same thing in fits and starts, just less photogenically. An 8 — solid explainer, mildly under-curious about the alternatives.