Electric strength of gaseous and liquefied C4-fluoronitrile

For gas-insulated switchgear, an ecologically friendly candidate could be C4-Fluoronitrile (C4-FN), used in gas mixtures, e.g. with CO2. Because of the relatively high dew-point of C4-FN, liquefaction of insulating gas could occur at very low operating temperature. Hence, electric strength and discharge behavior of liquid phase of the insulating gas C4-FN need to be studied. Breakdown voltage and average breakdown field strength are measured by using a hemispherical electrode arrangement according to IEC 60156. Breakdown tests with 50-Hz-AC-voltage are carried out at gas pressures from 0.1 MPa to 0.25 MPa, and with liquefied C4-FN at 20 deg C at different gap distances from 1 mm to 5 mm.