The major cause of failure of DC-GIS is due to presence of foreign particles causing partial discharges in the insulation structure. It is realized that the levitation voltage of a particle in GIS is independent of polarity of applied DC voltage and operating pressure. It is observed that particle movement in GIS radiates electromagnetic waves and the bandwidth of the signal lies up to 2 GHz. Increase in applied voltage/pressure has not altered the frequency content in the UHF signal measured. It is observed that absolute charge injected due to partial discharge formed due to particle movement increases with increase in voltage/ ambient pressure. It is also realized that partial discharge magnitude and the UHF signal amplitude have good correlation and show a proportionate increase. © 2009 FEI STU.