GRID · HVDC
The Grid’s Long-Distance Super-Links
Most of the grid is alternating current— a meshed web of lines tying a whole region together, the network the transmission layer draws. HVDC is the opposite: long, point-to-point direct-currentexpress lines that shoot enormous amounts of power in a single straight haul — across deserts, over mountains, and crucially beneath seas — far more efficiently than AC can manage over those distances, and the only practical way to tie two separate grids together. This layer maps every HVDC link OpenStreetMap holds: 275 named links, roughly 111,208 km of conductor in all — enough to wrap the Earth about 2.8 times — reaching up to ±1100 kV. They’re drawn as glowing magenta lines, brighter and heavier the higher the voltage, so the ultra-high-voltage super-grids read first — and split by build type: overhead lines draw solid, while cables — the buried city links and the famous subsea interconnectors — draw dashed. Tap one for its name, voltage and build type.
From ±80 kV to ±1100 kV
HVDC climbs a voltage ladder, and the higher you go the further and the more power you can push. At the top sit the ultra-high-voltage (UHVDC)giants — ±800 and ±1100 kV — almost all of them in China, hauling power thousands of kilometres from inland dams and solar fields to the coastal megacities (283mapped segments reach this tier). The middle rungs, ±320 to ±660 kV, are the modern interconnectortier — the converter-based links stitching national grids together, including most of the subsea cables under the North Sea and the Baltic. The lowest rungs are older or smaller back-to-back ties. The bar shows how the mapped network splits across the four classes.
Overhead lines and cables
Almost all of an HVDC link’s length is ordinary overhead line— towers and conductors marching across land, just like AC pylons but carrying direct current. 758 of the mapped segments (68% by count, about 94,887 km) are overhead. The rest are cables: 353 segments, roughly 16,321km. Most cable runs are short buried stretches threading converter stations into dense cities — but a handful are the long subsea interconnectors that let power cross water no tower could span: NorNed, NordLink, North Sea Link, Viking Link, Basslink, IFA and the Baltic links. They are few but long: subsea cable accounts for about 72% of all cable-kilometres here, the longest single mapped crossing being North Sea Link at 707 km. On the map overhead lines draw solid and every cable draws dashed, so you can read at a glance where the grid takes to the air and where it goes underground or to sea.
The longest links
The giants of the DC network run for thousands of kilometres in a single haul. Changji–Guquan is the world’s highest-voltage line at ±1100 kV, carrying power right across China; Belo Monte brings Amazon hydro to Rio and São Paulo; Rio Madeira and Cahora Bassa move bulk power across Brazil and southern Africa. Lengths are great-circle sums of the longest single mapped run for each link.
Where HVDC runs
HVDC leans hard towards China, which has built more long-distance DC than the rest of the world combined to carry renewable power from its interior to the coast. Europe is the other centre of gravity, but for a different reason — the subsea interconnectors knitting national grids across the North Sea and the Baltic. As with the other mapped layers, read this as a guide to what OpenStreetMap has charted rather than a definitive league table.
About this data
Every link comes from OpenStreetMap (power=line and power=cable carrying frequency=0, via the Overpass API, ODbL). Voltage is recorded on about 95% of these ways, so voltageis what sets the colour and weight — an honest axis the data actually supports. Two kinds of line are deliberately left out: HVDC electrode lines(the grounding conductors tagged at 0 kV, which aren’t the power-carrying poles) and low-voltage DC traction and industrial lines below 80 kV, neither of which is the long-distance HVDC this layer is about. Link lengths are great-circle sums of the longest single mapped run, so two parallel bipoles sharing a name never inflate into one impossible distance, while the network total is the true sum of every conductor. Operators are never shown. Coverage follows where OSM mapping is densest — genuinely strongest in China for HVDC — so this is the publicly mapped network, not a complete census. Snapshot taken 2026-06-27.
On overhead-vs-cable: the solid/dashed split comes straight from each way’s OSM tag — power=line draws solid (overhead), power=cable draws dashed. That tag is reliable enough to render, but it is the mapper’s tag, not a resurvey, and a few older Nordic subsea interconnectors — Baltic Cable, Konti-Skan, Skagerrak and SwePol— are tagged as lines in OpenStreetMap, so they read as overhead here even though they run under the sea. We show what the data says rather than quietly overriding it; the finer subsea-vs-buried distinction is too inconsistently tagged to assert, which is why the map commits only to the clean two-way overhead/cable split.