Dielectric behaviour of compressed air in a slightly divergent field-measurements versus simulations - [gas insulation applications]

The dielectric behaviour of technical air was investigated in a slightly divergent electric field (coaxial arrangement) varying the gas pressure and the voltage polarity as well. The investigated pressure range was from 300 to 750 kPa. The HV electrode was made of aluminium and the roughness degree of its surface was close to real applications (technical surface). Predictions performed using the streamer inception criteria are in good agreement with the experimental results if a protrusion on the HV electrode is taken into account within the simulation model. The poor dielectric strength of air compared to SF/sub 6/ is highlighted.