As more countries turn toward renewable energy, the prospects of larger power grids becomes possible, especially as renewable-rich countries start sharing with renewable-poor countries. Thoughts of a supergrid in Europe might pull together Scandinavian hydroelectric dams, German wind farms, Spanish and even African solar farms. One of the problems though, that over long distances, alternating current [AC] lines lose power.
The solution, of course, is to transmit using direct current [DC], and for decades, DC lines have transmitted power from faraway hydroelectric dams to localized grids. Long-distance DC lines maintain their voltage better, work well underground and underwater, but connecting these to larger grids, such as the European supergrid, isn’t safe enough.
To protect intact portions of the grid from a downed section, circuit breakers need to cut power to the broken section, otherwise the whole grid loses power. Mechanical DC circuit breakers proved to be too slow, and transistor breakers prohibitively expensive. Power company ABB recently developed a new high-powered DC hybrid circuit breaker that shuts off power in under 5ms, which could make it safe to connect high-powered DC lines across thousands of miles of a supergrid.
“Ordinarily, if something goes wrong anywhere, all the power goes off,” says Claes Rytoft, ABB’s chief technology officer. “The breaker can cut out the faulty line and keep the rest healthy.” Now that ABB’s devised an efficient and fast DC circuit breaker, they’re working on algorithms to control it to work in concert with lower voltage AC grids on the local level.