Permittivity gradient characteristics of GIS solid spacer

For electrical insulation design of GIS spacer, we need to control electric field distribution around the solid spacer, especially around the triple junction (TJ). For this purpose, we proposed the application of functionally gradient materials (FGM), which has spatial distribution of dielectric permittivity, to the spacer of SF₆ GIS. In this paper, we discussed applicability of FGM with numerical simulation and fabrication conditions. We firstly investigated the field control effect of the FGM spacer with a conical shape, by finite element method (FEM). Secondly, we fabricated FGM spacer with continuously graded distribution of permittivity by applying the centrifugal force. As for the filler material to control the permittivity, we selected TiO₂ rutile crystal particle. In order to obtain the optimum permittivity distribution, centrifugal forces, their application duration, the diameter distribution of filler particles, volume ratio of filler versus resins and so on were controlled.