China switches on ultra-high-capacity circuit breaker for grid

China has put the world's first 800-kV circuit breaker rated for an 80-kA short-circuit breaking capacity into service in Shaanxi province.

The 80-kA rating, with kA denoting kiloamperes, reflects the breaker's high fault-current interrupting capability. Built with domestically produced core components, the device can cut off a fault within tens of milliseconds, helping prevent large-scale blackouts and damage to connected equipment.

As the grid expands and becomes more interconnected, short-circuit current levels rise, and circuit breakers need a higher capacity.

The launch comes as Northwest China has integrated more renewable energy into the grid and expanded ultra-high-voltage transmission, pushing system short-circuit currents closer to the switching limits of existing breakers.

The equipment was developed under the leadership of the State Grid Shaanxi Electric Power Research Institute in collaboration with Xi'an Jiaotong University and other institutions. It was completed in February 2025 and passed all type tests in a single round in September.

State Grid Shaanxi Electric Power Company said the device would continue to be tested under complex operating conditions, including heavy loads and frequent switching, as engineers work to further refine its performance.