Dielectric characteristics of column electrodes with edge in SF₆ Gas under AC Voltage

Abstract

This paper deals with partial discharge characteristics and breakdown characteristics of inhomogeneous field gap in SF₆ gas with AC voltage. The tested gas gap is formed between a high voltage electrode and a protruded column electrode on a grounded electrode. The several columns (φ 30) with sharp edge, cutting edge, rounded edge and a thin column (φ 1) are used as the protruded electrode. The column and gap length are kept 16mm in height, 50mm in gap length, respectively. The gas pressures are changed to 0.1, 0.225, 0.5 MPa, respectively.
At just partial discharge inception voltage, partial discharge happens in negative polarity of column electrode. And it is founded out that partial discharge inception voltage of column electrode, can be estimated with Schumann's equation. The other side, breakdown voltage polarity is changed with gas pressure and inhomogeneousity of the electrode. This tendency of breakdown characteristics with AC voltage is coincident with one with lightning impulse voltage.