Semiconductor-Based Medium-Voltage Circuit Breakers Enhance DC Grid Efficiency

Researchers at Oak Ridge National Laboratory (ORNL), part of the Department of Energy, have developed medium-voltage circuit breakers using affordable thyristor semiconductors to improve the safety and efficiency of direct current (DC) power grids. Led by Prasad Kandula, the team created breakers that operate up to 100 times faster than mechanical switches, addressing a key limitation in DC grid protection.

Unlike alternating current (AC), which oscillates 60 times per second and is easily interrupted, DC flows in one direction, lacking a "zero current" moment. This renders mechanical breakers too slow to prevent faults, risking heat buildup and fires. Tested at ORNL’s Grid Research Innovation and Development Center (GRID-C), the semiconductor-based breakers interrupt currents at 1,400 volts in under 50 microseconds, four to six times faster than prior thyristor-based tests. By connecting breakers in series, the team achieved operation at 1,800 volts, with plans to scale to 10,000 volts for future grid needs.

DC grids reduce energy loss during transmission and eliminate conversion losses between DC electronics and AC grids, supporting applications like AI data centers and multi-directional power flows. The lack of cost-effective medium-voltage DC breakers—capable of handling over 2,000 volts—has hindered adoption. ORNL’s solution uses th...