Abstract
Covering an electrode with a dielectric layer improves the performance of SF6 gas-insulated systems. This time, the authors evaluated the influence of charge accumulation of the coated electrode surface on the breakdown characteristics and measured the charge amount on the coated electrode surface. Results of the breakdown voltage measurements showed that, without the charge elimination, both the absolute value and the dispersion of the breakdown voltages enlarged. On the other hand, the influence of the charge accumulation was not observed for the minimum breakdown voltages. By measuring the surface potential of the coated electrode, two results were obtained. First, as for negative voltage application, if the electric field of the coated electrode tip exceeded the critical ionization electric field of SF6 gas, but breakdown did not occur, a positive surface potential was observed. On the other hand, if breakdown occurred, the surface potential hardly changed. Second, as for positive voltage application, if breakdown occurred, a negative surface potential was observed. On the other hand, if breakdown did not occur, the amount of the surface potential varied depending on the electrode system and the SF6 gas pressure.
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