Online Diagnosis for Mechanical Faults in GIS Disconnector with Residual Voltages of VFTO

The mechanical performance of the isolating switch in gas insulated switchgear (GIS) is crucial to the safety of the power grid, but existing methods cannot directly observe the contact stroke, and the accuracy needs improvement. Through theoretical and simulation analysis, this paper reveals a strong correlation between the residual voltage of very fast transient over-voltages (VFTO) and the contact opening distance. Then, the first-order difference of the residual voltage in the whole process waveform of VFTO is extracted as the discriminant feature. Furthermore, for the extremely unbalanced problem of the training samples in practice, the one-class support vector machine (OCSVM) is utilized to realize the online diagnosis task. Experiments show that this method can effectively identify typical mechanical faults such as sticking and rusting of the GIS isolating switch shaft.