Research on partial discharge characteristics of protrusion defect in GIS under oscillating lightning impulse voltage

In order to ensure the safe operation of the gas insulated switchgear (GIS), on-site impulse withstand voltage test is becoming more and more important. Oscillating impulse voltage is very suitable for the field test due to its high generating efficiency. By detecting the partial discharge when conducting on-site impulse withstand voltage test, the insulation state of GIS can be overall known. The protrusion is a typical a
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nd harmful defect in GIS, so it is very significant to research the partial discharge characteristics of protrusion in GIS under oscillating lightning impulse voltage. In this paper, we applied oscillating lightning impulse voltage on a 330kV GIS which was set a protrusion at the conductor and we measured the partial discharge by the inner UHF sensor at the same time. We analyze the variation of discharge position, maximum discharge amplitude and discharge number with the increasing of voltage and compare the results of different frequencies voltage. Our studies show that the partial discharges mainly occur at the peak of the oscillating lightning impulse voltage. With the increasing of the voltage amplitude, the maximum discharge amplitude and discharge number also increase. And with the increasing of the voltage frequency, the partial discharge inception voltage increases. The results of this paper are helpful for the on-site impulse withstand voltage test.