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.

I. Introduction

Gas-insulated substations (GISs) have been widely put into operation in the power grid due to their high operational security and easy maintenance [1]–[4]. High-voltage (HV) circuit breakers (CBs), as a key equipment within the GIS, can quickly cutoff the fault current when the power system fails and prevent other electrical equipment from being damaged, thus ensuring the safe operation of the power grid [5], [6]. However, the on-site experimental data show that the allowed number of consecutive switching operations of the HV CBs in full capacity is around several tens, therefore it is of a large potential security risk after a long period of multiple switching operations [7]–[9]. With the advancement of today’s construction of ultrahigh-voltage projects, the voltage level of CBs continues to increase. Once the CB fails, it may not only damage the end-loaded transformers and lines but even cause serious equipment explosions [10]. Therefore, the stability of CBs is closely related to the safety of the power system, and a reliable condition assessment method is needed to detect early-stage defects in HV CBs.