Playing Other Roles
Rachana Gururaj and M. Granger Morgan are with the Department of Engineering and Public Policy, Carnegie Mellon University. Liza Reed is with the Niskanen Center in Washington, D.C.
For most of us, mention high voltage DC (HVDC), and images spring to mind of transmission lines marching across the landscape with just two conductor bundles, rather than the usual three. Such lines move large blocks of power to customers from far off places like the hydro projects of northern Quebec.
Long distance, overhead HVDC transmission lines are certainly part of the story, but increasingly HVDC is also playing other roles. Often it would be helpful to move a large amount of power using an underground cable rather than an overhead line.
Doing that with HVAC over more than short distances is difficult because of problems created by electric and magnetic fields that are inherent to the alternating nature of that power. Because DC avoids many of these problems, it is far more suitable to move power over significant distance using cables.
For example, HVDC cables on the sea floor are used to move power to shore from offshore wind platforms. Europe leads in harnessing offshore wind with installed capacity of roughly twenty-two gigawatts in 2019. Today there are hundreds of miles of DC cables crisscrossing the North Sea, some moving power from offshore platforms, some connecting the power systems of Scandinavia, the UK, and the EU.