Pulsed and DC discharges in supercritical carbon dioxide

This paper reports the experimental results on the breakdown voltage and phenomena in carbon dioxide medium at 298, 304 and 373 K and within the pressure range of 0.1 to 12.0/20.0 MPa under the point-to-plane electrode using negative dc and pulsed discharge. From the experimental results of negative dc discharge, corona discharges with preceding as well as complete breakdown are observed more clearly in liquid and in supercritical phase than in gas phase of carbon dioxide. The calculated electric field intensity on the tip of point electrode at the corona onset voltage is about 450 MV/m; it suggests that corona is triggered by the field emission of electron. The breakdown mechanism of liquid phase can be classified into two categories in comparison with critical pressure of medium. On the other hand, in the experimental result of pulse electric discharge, the time delay of pulse forming and the relevance of the medium density were found.