What are the reasons for the reduction in the opening and closing speed of circuit breakers?

During the use of a circuit breaker, adjusting the opening and closing speeds properly is a reliable condition to ensure its operation. Correct testing is a direct method to verify whether the speed is qualified and to analyze the reasons for unqualified speed. Therefore, analyzing the correct testing methods for circuit breaker speed and the reasons for speed reduction is of profound significance for correctly judging the operation of circuit breakers