Abstract
When the PET film was placed on the anode, the breakdown voltage with a DC-ramp voltage (0.5kV/s) was much lower than that for the oil alone as long as the film was thin and it increased with increasing the film thickness. These results suggested that the complete breakdown was caused by the film reakdown due to negative charge deposition.
The breakdown voltage for the case of the film on cathode was slightly higher than that for oil alone and it was scarcely changed by the change in the film thickness. It was suggested that the discharge in the oil caused the complete breakdown of the composite. However, when the composite whose cathode was screened with the film was subjected to a constant dc voltage for a long period, it was assumed that the complete breakdown was induced by the film breakdown caused by the deposition of positive ions.
