Transient earth voltage measurement in PD detection of artificial defect models in SF ₆

This paper mainly discussed the utilization of transient Earth voltage measurement (TEVM) in partial discharge (PD) detection of gas insulation switchgear. Four typical artificial defect models in SF ₆ such as spikes fixed on high voltage (HV) conductor, suspended metals, voids in dielectric, and metal particles on the surface of dielectric had been used as test objects in ac PD experiments with the aid of the synchronized PD signals sampled from a transient Earth voltage sensor, photomultiplier, Rogowski monitor, and PDCheck system. The measuring results of TEVM results, which included the phase distribution of PD, the relative amplitude, and the pulse number of different voltage thresholds, showed good consistency with three other methods and had better sensitivity of detection in spark or corona PD patterns. For further study, the frequency distributions of the three PD patterns were analyzed and discussed for understanding the different measurement sensitivities showed in different typical defects in SF ₆. In addition, TEVM was applied to detect PD under oscillating impulse voltage. As an example, the needle-plane electrode with short gap was adopted under 613.2-kHz oscillating impulse, which showed the effectiveness in this kind of detection.