The detection of the closing moments of a vacuum circuit breaker by vibration analysis

The vibration signals during the closing operation of three-phase vacuum circuit breakers (VCBs) were recorded for detecting the closing moment of each pole. The short-time energy (STE) analysis of the vibration signals with a moving Hamming window is used to derive the closing moments both under no-load conditions and load conditions. By determining a proper length for the moving window, the improved signal-to-noise ratio by the STE analysis greatly facilitates the identification of the closing moments. Under no-load condition, the results obtained from the vibration signals are in good agreement with those measured by the contact timing signals. Under load conditions, it is found that the effect of the making current on the detection results is too tenuous to be neglected. This makes it possible to apply this method to online detection of the closing moments of VCBs.