Activity of moving metallic particles in prebreakdown state in GIS

The paper presents experimental results of measurements of prebreakdown activity, caused by free metallic particles in GIS, obtained using a phase resolved partial discharge (PRPD) analysis and acoustical measurements. The numerous parameters characterizing prebreakdown activity of particles were identified and analyzed. These included phase resolved distribution of charge, maximum charge, average charge per period, or per pulse, a balance of charge in positive and negative half-wave of voltage, pulse rate (number of pulses per period) for electrical and acoustic methods. The measurements were conducted in a compartment of real GIS, and Al as well as Cu particles of different shapes were investigated. The pressure varied from 150 to 550 kPa, however most measurements were taken at 450 kPa. A discharge model which takes into account the effect of a free metallic particle in GIS is presented.