CONCLUSIONS This paper demonstrates that increasing humidity has different effects on the breakdown voltage of non-uniform field configurations at 30 kHz and 60 Hz. For certain non- uniform field configurations, such as the hemispherical rod/plane, there was no corona prior to breakdown when the gap was in the range of 8-45 mm. The breakdown voltage for this configuration was independent of humidity. For the rod/rod and conical rod/plane configurations, the presence of corona was dependent on the gap spacing. When there was corona (glow) prior to breakdown, the breakdown voltage tended to reduce with humidity. For the long gaps (125-1000 mm) in all configurations, there was corona (streamers) prior to breakdown, yet the breakdown voltage is essentially independent of humidity. Independent of the humidity in the air, for non-uniform gaps exhibiting corona prior to breakdown, the breakdown voltage at 30 kHz is significantly lower than that at 60 Hz. This difference is seen to increase with the gap length. In the range of gaps studied, the difference in breakdown voltage at 30 kHz when compared to that at 60 Hz is seen to increase from 20% to 70%. The reasons for the observed results have been explained in terms of ionic mobility and space charge.