The paper reports about the role of humidity on the breakdown of air in non-uniform
fields at 30 kHz – a frequency within the VLF/LF bands used for long distance
communication. Experiments were conducted using rod/rod and rod/plane
configurations with gap lengths ranging from 8 to 1000 mm. The results indicate that
the breakdown voltage at 30 kHz is affected by humidity with varying impact based on
gap length. Short (8-45 mm) gaps show a reduction in the breakdown voltage with
humidity, while no significant variation is observed for long gaps (125-1000 mm).
Breakdown voltages are observed to be markedly lower for 30 kHz when compared to
the same gap at 60 Hz. Breakdown mechanisms for explaining this phenomenon are
proposed. A correction factor to calculate breakdown voltage as a function of humidity
for VLF is presented