The dielectric behavior of dry-air in a quasi-uniform field gap

초록

In this paper, in order to evaluate the capability of alternative insulation gases for SF6 in power distribution system equipment, the dielectric behavior and physical phenomena of dry-air gas in a quasi-uniform electric field are investigated experimentally. The gas pressure ranges from 0.2 MPa to 0.6 MPa. Breakdown voltage-time (V-t) and 50% impulse breakdown voltage (BDV50) characteristics in dry-air are analyzed as functions of the applied voltage shape, polarity, and gas pressure in detail. As a result, the breakdown development mechanisms for the positive and negative polarities are investigated as a fundamental streamer mechanism. The BDV for the positive polarity is higher than that for the negative polarity in two applied voltage waveforms. The BDV50 in dry-air gas is higher than 150 kVp above 0.4 MPa gas pressure in the negative polarity. The BDV50 increases linearly with increasing gas pressure in both polarities, regardless of the applied voltage shape and polarity. The voltage-time curves are dependent on the rise time of the impulse voltage and gas pressure.