Application of short-time energy analysis in condition monitoring of circuit breakers

To avoid the drawback that the closing moment of circuit breakers are difficult to measure in online condition monitoring, the application of short-time energy (STE) analysis in the event time detection of the vibration signal was investigated. The quantitative analysis shows that STE method can significantly improve the signal-to-noise ratio (SNR), which facilitates determining the commencement of the vibration event from an adverse environment. This approach was applied to a ZN12-35 type vacuum circuit breaker for analyzing the vibration signals during the closing operation. The closing moments of three poles were gained accurately by STE analysis, and some mechanical parameters such as closing-simultaneity and closing time were calculated correctly. Moreover, a VS1-12 type vacuum circuit breaker was tested via analyzing the vibration signals under the condition of the single pole short-circuit current. The influences of different peak currents on the measurement system and closing simultaneity of the circuit breaker were discussed. The test results show that STE analysis has a measurement accuracy of 0.2 ms after selecting a proper window function.