Identification of incipient discharges in gas insulated system using acoustic emission technique

The reliability of the SF₆ gas filled GIS is adversely affected by the presence of foreign particles in the insulation structure, which initiates partial discharges leading to catastrophic failure of insulation structure. The literature on partial discharge activity study under the composite voltages in GIS is scanty. Having known all this, in the present work, a methodical experimental study was formulated to understand the partial discharge activity under composite voltage formed by AC and DC voltages, in GIS using acoustic emission (AE) technique. The acoustic emission signal parameters Viz. amplitude, rise time of the pulse, duration of the AE signal, counts and the energy content of the AE signal were analysed and the characteristics of discharges under different voltage profiles were explained. Also the influence of gas pressure and polarity of the DC bias voltage under composite voltage formed by AC and DC voltages, on the partial discharge activity were studied in detail.