Partial discharge characteristics at low pressures in dry air and argon

Characteristics of partial discharges (PD) in two gases (air and argon) under pressures in the range of 0.1 to 760 Torr, and 60 Hz AC energization are discussed for an energized needle grounded plane electrode arrangement. The most significant conclusion of the study is that the frequency content of PD current pulses for all the tests conducted is much lower at low pressures than at atmospheric pressure. In general, the frequency content of PD current pulses at low pressures is outside the detection range of typical commercially available PD equipment.