Development and Engineering Application of 550 kV Fast SF₆ Circuit Breaker

To address the mitigation of excessive short-circuit currents in power grids and the arcing-resistant technology for large oil-filled equipment, this paper proposes a 550 kV fast SF6 circuit breaker solution, the equipment development and engineering implementation were systematically executed to validate the technology. A new electromagnetic repulsion trip device is used to replace the traditional electromagnet, achieving rapid conversion of the control valve oil circuit and reducing the mechanism activation time from the conventional <inline-formula> <tex-math notation="LaTeX">$10\sim 14$ </tex-math></inline-formula> ms to within 4 ms; by enhancing the operating power of the hydraulic disc spring mechanism, the output force is increased, and the buffer design is optimized, reducing the opening time from <inline-formula> <tex-math notation="LaTeX">$19\sim 25$ </tex-math></inline-formula> ms to within 8 ms; the design of SF6 arc-extinguishing chamber is improved and optimized from the aspects of contact gap, arc-blowing pressure, and electric field distribution, reducing the short arcing time from <inline-formula> <tex-math notation="LaTeX">$12\sim 14$ </tex-math></inline-formula> ms to within 8 ms. The successful development of the 550 kV fast SF6 circuit breaker achieves a breaking current of 63 kA, a breaking time of no more than 25 ms (approximately half that of conventional circuit breakers). The developed fast circuit breaker has been successfully applied in the Shunjiang sub-station 500kV short-circuit current flexible suppression demonstration project, and further enhances reliability with pilot applications for arcing-resistant of converter transformers at the Dongping and Bangguo converter stations of the Jinshang-Hubei and Longdong-Shandong &#x00B1;800 kV ultra-high voltage direct current transmission projects, respectively, with good application prospects.