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For the size reduction and the enhancing reliability of electric power equipment, the electric field stress around solid insulators should be considered enough. For the relaxation of the field stress, the application of FGM (Functionally Graded Materials) with spatial distribution of dielectric permittivity (¿-FGM) can be an effective solution. In this paper, we investigated the applicability of ¿-FGM for reducing the electric field stress on the electrode surface with contact to the solid dielectrics, which was one of the important factors dominating a long-term reliability of the insulating spacer. Firstly, we carried out numerical simulation of electric field to confirm the reduction of the electric stress by U-shape permittivity distribution. Secondly, we investigated the fabrication feasibility of ¿-FGM with the U-shape distribution. Thirdly, we estimated the longterm electrical insulation performance of the ¿-FGM. Finally, we verified the applicability and the fabrication technique of the ¿-FGM to solid dielectrics for improvement of the electric stress and the long-term insulation performance in electric power equipment.
Kurimoto et al. (Mon,) studied this question.