Tanya Weaver Tue 5 Aug 2025
Collected at: https://eandt.theiet.org/2025/08/05/new-circuit-breaker-design-could-unlock-use-direct-current-power-grid
Researchers have developed a new semiconductor-based circuit breaker that could enable broader integration of direct current into the electric grid.
Traditional circuit breakers in the grid work well with alternating current (AC), which is easier to interrupt as it changes direction 60 times per second.
With direct current (DC) flowing in only one direction, it is more challenging to interrupt.
However, DC is more attractive for the electric grid as it flows with less resistance through power lines, wasting less power. This means power grid capacity could be increased while energy costs reduced.
It also means that current wouldn’t have to be converted between DC-based power electronics and an AC-based grid.
However, the challenge with a DC-based grid is the lack of medium-voltage circuit breakers for DC.
Traditional mechanical breakers rely on a physical gap that is less effective at stopping DC, which is capable of sparking across a gap in an arc of explosive energy.
Researchers from Oak Ridge National Laboratory (ORNL) in Tennessee, operated by the US Department of Energy, decided to tackle this challenge.
“Once you go to DC, that ‘zero current’ moment is gone – and without it, a mechanical switch isn’t fast enough to stop a fault before heat builds up and a fire starts,” said Prasad Kandula, lead researcher who leads ORNL”s grid systems hardware group.
The research team developed a new type of semiconductor-based circuit breaker that offers both speed and greater safety for DC systems. To avoid the possibility of arcing, the current is routed away through the semiconductor-based device.
Kandula and his team selected an industry-accepted semiconductor called a thyristor, which Kandula points out is a base technology that is “robust, efficient and inexpensive”.
ORNL’s engineers built and tested a circuit breaker prototype to interrupt a current at 1,400V in less than 50 microseconds — four to six times faster than had been demonstrated with thyristors previously.
To prove the technology could be scaled up to handle higher voltages, the researchers connected the breakers in a series and tested them at an 1,800V capacity.
The researchers say they are now working on adding to the series for eventually scaling up to 10,000V, anticipating the larger energy demands of future DC grids.
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