A test system with wide frequency response was designed to measure pulse current shape of partial discharge(PD)based on the PD model and ultra-wideband detection method under direct current voltage. The measuring impedance was tested by square wave with very steep trailing edge and the corona in air under DC voltage was detected
which confirms the validity of the whole system. According to the defect analysis in oil-paper insulation of converter transformer
six corresponding PD defect models were constructed to gain the PD pulse current shapes. The results show that the PD pulse current shapes of the defects in oil under DC voltage get non-oscillatory without overshoot and the characteristic parameters of the pulse current shapes differ from each other for different defect models
which coincides with the discharge model under DC voltage mentioned above.
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