Effect of humidity on the breakdown characteristics of air in non-uniform fields at 30 kHz

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.