Recently, the achievement "Development and Application of 550kV Fast SF6 Circuit Breaker for Explosion Prevention in UHV Converter Transformers," led by the China Electric Power Research Institute (CEPRI), passed the appraisal organized by the Chinese Society for Electrical Engineering (CSEE). The appraisal committee confirmed that the achievement has complete independent intellectual property rights and has reached an internationally leading level.
UHV converter transformers are core equipment for DC transmission. Internal faults can easily generate high-temperature and high-pressure oil and gas, causing shell explosions that seriously threaten grid safety. Traditional SF6 circuit breakers have bottlenecks in fast interruption. Considering the output of the converter transformer protection relay, the total fault clearing time can reach 50-80 milliseconds, making it difficult to achieve timely and effective explosion prevention. To address this, the State Grid Corporation of China (SGCC) initiated a framework project for support. Under the guidance of Academician Chen Weijiang of the Chinese Academy of Sciences, CEPRI, in collaboration with equipment manufacturers (Pinggao Electric, Taikai High Voltage), universities, and provincial power companies, formed a research team to conduct specialized research starting in 2020.
The project achieved comprehensive innovation acceleration, overcoming for the first time multiple core technologies such as electromagnetic repulsion composite tripping, high-power mechanisms and lightweight high-strength transmission, and large-capacity extremely short arc interruption arc-extinguishing chambers. It developed the 550kV fast SF6 circuit breaker with a short-circuit breaking current of 63 kA, a breaking time shortened by approximately half (less than 25 milliseconds), an opening time of less than 9 milliseconds, a mechanical life of 10,000 operations, and an insulation margin of 1.1 times. Key performance and structural dimensions are compatible with conventional circuit breakers. When combined with the fast output of the converter transformer protection, it can shorten the fault clearing time by approximately half, reduce arc energy by about 40%, and significantly lower the risk of explosion.
In 2025, 12 units of the equipment were demonstrated and applied at the ±800 kV Bangguo and Dongping converter stations, operating in good condition. SGCC has begun promoting its application in converter stations nationwide to provide fast protection for converter transformers and valve groups. This achievement breaks the decades-long bottleneck in fast interruption of SF6 circuit breakers, strongly promotes the technological advancement and industrial upgrading of domestic equipment, can be widely applied in ultra-high voltage AC/DC power grids, and provides key equipment support for the construction of new power systems.