Some experiments on positive point-to-plane corona and spark breakdown of compressed gases

A test pressure vessel for the investigation of electrical discharges in gases at pressures up to 1 000 lb/in2 is described. The electrical insulating properties of compressed air, nitrogen, dichlorodifluoromethane (commercially known as Freon 12 or Arcton 6) and sulphur hexafluoride, as well as certain mixtures of these gases, are compared; a hemispherically-tipped point-to-plane electrode configuration and direct voltages were used. Pronounced maxima obtained in the spark-breakdown-voltage/gas-pressure characteristics for the electronegative gases and gas mixtures are shown to be associated with the establishment of corona at the anode. Corona-current/voltage characteristics for some of the gases tested are included.