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On August 8, a vacuum-based rapid circuit breaker with a rated voltage of 363kV, rated current of 5000A, and an opening time of just 1.2ms was successfully tested in Xi'an, Shaanxi. Developed by State Grid Ningxia Electric Power Co., Ltd. and tested at the Electric Apparatus Research Institute, this groundbreaking device passed the breaking test with a short-circuit current of 80kA. This marks a significant milestone in power system protection technology.
The fast-breaking capability of this circuit breaker plays a crucial role in ensuring the safe and stable operation of the power grid. As a bus-coupling circuit breaker, it allows parallel operation of busbars under normal conditions, enhancing system reliability. In the event of a nearby busbar short-circuit fault, the circuit breaker quickly isolates the fault within one cycle, significantly reducing the short-circuit current and preventing it from exceeding standard limits. This not only improves grid stability but also prevents large-scale outages and minimizes damage to equipment.
Additionally, the circuit breaker's ability to rapidly cut off fault currents reduces the stress on other grid components, lowering the need for costly upgrades. For new energy stations and sensitive loads, this technology ensures that faulty lines are quickly removed, avoiding cascading failures and production losses. This enhances the overall quality and reliability of power supply.
This achievement builds on earlier challenges faced by the State Grid Corporation in 2016, when ultra-high voltage grids experienced severe short-circuit current overloads, threatening grid safety and economic efficiency. In response, the company initiated a key research project to develop a 363kV/5000A/63kA fast circuit breaker. The project involved collaboration between State Grid Ningxia Electric Power Co., Ltd., Nanrui Group, Anhui Huidian Technology, Xi'an Jiaotong University, and Chongqing University.
Through this initiative, researchers developed a high-voltage vacuum circuit breaker capable of breaking short-circuit currents within 20ms using advanced technologies such as multi-vacuum interrupter configurations, ultra-fast repulsive mechanisms, and rapid identification of current amplitude and phase. These innovations enable reliable and efficient fault clearance, supporting the development of smarter and more resilient power systems.
The successful implementation of this technology not only strengthens China’s independent innovation and manufacturing capabilities but also lays the foundation for future smart grid infrastructure. With its potential to enhance grid safety, reduce operational risks, and improve economic efficiency, this breakthrough holds great promise for the future of power systems worldwide.
July 25, 2025