Partial discharge characteristics in UHF-band of composite insulation system including various artificial defects in transformer

Experiments of partial discharge (PD) current pulse and phase resolved PD characteristics were performed using various artificial defects in oil/pressboard composite insulation system in oil-filled transformer. As artificial defects, we used barrier insulation model-in-oil, oil wedge model, air void model, floating electrode model, and oil gap model. As a result, it was found that the rise time, fall time, and pulse width of each PD current pulse differed depending on each model. Moreover, we confirmed the existence of PD-radiated electromagnetic wave with frequency UHF band for the defects. It was shown from these results that UHF method is applicable for detecting PD originating from the defects and identifying the defect types in oil-filled transformer.