Improvement of reliability of closing latch in spring type operating mechanism of high voltage circuit breakers

Occasionally closing operation failures occurred when a spring type operating mechanism was used to operate a high voltage circuit breaker with higher loads. This kind of failures is a high risk for circuit breakers. The objective of this paper is to propose a concept of reset time difference of a trip-open unit and to improve the reliability of closing operation of a high voltage circuit breaker with a spring type operating mechanism based on the reset time difference. In a spring type operating mechanism, there is a big latch and a small latch in a trip-open latch unit. In a close operation of a high voltage circuit breaker driven by a spring type operating mechanism, there is a time lag between the big latch and the small latch when they reach their final latched positions. And we definite the time lag as the reset time difference (T_R). The experimental results showed that the reliability of closing operation can be guaranteed with T_R was higher than 10ms. And T_R increased with an increase of a preload of the big latch spring. And the bounces of the small latch were the most significant factor to cause a closing operation failure. An improvement from the point of view of time reset difference (T_R) enhanced the reliability of closing operation of a high voltage circuit breaker.