Humidity Dependent Charge Formation in Air under DC field Below Partial Discharge Inception

This study investigates the influence of humidity, electric field strength, and electrode geometry on charge formation and accumulation dynamics at electrode-air-polymer interfaces under DC conditions below the partial discharge inception level. Utilizing a structured test matrix with varying voltages and electrode radii, experiments were conducted in a controlled environment where humidity levels ranged from 40% to 90%. The results reveal that lower voltage levels and larger electrode radii significantly heighten sensitivity to humidity changes, affecting charge accumulation patterns at the dielectric-air interface. Notably, high humidity conditions (~98% RH) demonstrated that water condensation on electrodes can inhibit charge generation. Surface potential measurements with a Kelvin probe is utilized to quantify these effects, highlighting the complex interaction among air humidity, electric field strength, and time in influencing charge formation. This study enhances the understanding of charge dynamics critical for improving the reliability and performance of HVDC insulation systems.