Research on Breaking Performance of Large-capacity Circuit Breakers with Different Current Levels

The structure of China's power grid is becoming more and more complex, with the capacity increasing. The rated short circuit current of the existing 550 kV switchgear needs to be increased from 63 kA to 80 kA. Self-blast circuit breaker has the characteristics of high reliability and low opening operation power. In order to improve the breaking performance of a 550kV self-blast circuit breaker under the short-line fault (SLF) L90 condition, this paper conducted magnetohydrodynamic simulation analysis under the rated short-circuit current of 63kA and 80kA respectively, and obtained the spatio-temporal distribution and quantitative analysis curve of temperature field and pressure field. The research shows that under the same circuit breaker structure conditions, the temperature and pressure thresholds under the action of 80kA short circuit current are higher than that of 63kA, and the arc hot gas enters the expansion chamber earlier and pushes the check valve to the closed state at the peak current. The high-pressure upstream of the nozzle at peak time and zero crossing time is caused by the arc entering the expansion chamber to heat the gas inside. The research results provide a certain range of key threshold parameters for 550kV 80kA circuit breakers and a reference for structural optimization design.