Abstract: the B phase spring mechanism of the circuit breaker did not store energy and failed to close, reDuring the operation of a CT20 type circuit breaker from hot standby to operation in a 220kV substatiosulting in non full phase operation and inconsistent three-phase protection action of the main body. This article analyzes the reasons for the abnormal energy storage of the circuit breaker and the possible impacts, and proposes improvement measures from the aspects of equipment installation design, operation and maintenance, which is of great significance for the safe and reliable operation of the power grid.