Dark current measurements in pressurized SF6: Influence of relative humidity and temperature

Current measurements in pressurized gases at high electric field are performed using electrodes with coaxial geometry. To identify the main mechanisms involved in “dark current” measured, the influences of electrode roughness, gas pressure, relative humidity and temperature have been investigated. The experimental results reveal that charge injection from the electrode constitute the main mechanism responsible for dark current. The latter is considerably modified when relative humidity RH is changed via the influence of pressure and temperature. The measured current shows an exponential increase versus electric field and also versus RH. It is thus assumed that water adsorbed on the electrodes induces an enhancement of charge injection from the electrode surface.