Influence of barrier on corona discharge activity in liquid nitrogen under AC voltages adopting UHF technique

In liquid nitrogen insulation, the corona inception voltage is high with barrier in the electrode gap. The breakdown voltage of needle-plane gap has increased with barrier positioned near high voltage needle electrode. The current signal injected due to corona discharge in liquid nitrogen insulation, at the point of its inception and during streamer formation, have rise time, in negative and positive cycle of the AC voltage are about 2.9 ns and 2.5ns respectively and the characteristics has not altered due to barrier insulation. The UHF signal generated by corona discharges, in the liquid nitrogen electrode gap (with/without barrier) have frequency contents between 0.5-1.5 GHz. The magnitude of UHF signal formed due to corona activity (with barrier) on inception and at higher voltages (not at point of near breakdown) shows inverse relationship. Corona discharge followed with breakdown studies analyzed using zero span analysis. Phase resolved partial discharge signatures obtained due to corona discharges indicates that phase window at which corona discharge occurs become narrow with barrier in the electrode gap.