Partial discharge characteristics initiated by metallic particles in N2, CO2, dry air and SF6 at AC voltages

This paper reports partial discharge (PD) properties initiated by moving metallic particles in N2, CO2, dry air and SF6 at AC voltages. Using a 168 kV actual GIS bus, PD signals like electromagnetic (EM) waves and PD magnitude (apparent charge) were measured when a metallic particle contacts the high voltage conductor (crossing) at 0.55 MPa. The voltage phase characteristics of the PDs distributed between 0 and 180 degrees and between 270 and 360 degrees. The PD magnitude was larger in negative voltage phase and at nearly the peak of voltage phase. Detecting mobile metallic particles (3 mm) in CO2 and dry air would be possible in the same or easier level than the case in SF6. The particle detection by the PDs during its crossing would be very difficult in N2, but the PDs could be measured…