Fault Detection for High-Voltage Circuit Breakers Based on Time-Frequency Analysis of Switching Transient E-Fields

A noninvasive approach for high-voltage (HV) circuit breaker (CB) diagnosis, based on the time frequency analysis of the transient electric fields (E-fields) radiated due to switching operations outside the enclosure [switching transient E-fields (STEFs)], is presented in this paper. By use of a synthetic test platform, this paper measures the STEFs generated by CBs working in both normal and fault status and analyses their primary parameters, such as the amplitude, the center frequency, and the number of pulses. The correlation between the different working status of the CBs and the time-frequency characteristics of their STEFs is established. Based on the comparison and analysis of the main features, the STEFs could reflect the operating states and serve as an indicator of the early insulation defect of the HV CBs. The proposed defect detection method has been validated experimentally, which makes the most of the high changing rate of the induced current on the CB enclosure that itself is a weak signal and hard to capture by traditionally adopted means. This method can further be a useful reference of defect or fault diagnosis for the switchgear in operation.