Dielectrically Graded Spacer for 126-kV GIS: Design and Construction Strategy

Dielectrically graded insulation (DGI) serving as an embodiment of functionally graded materials in electrical insulation field displays extraordinary insulation strength compared with conventional uniform composite materials. In recent years, the design and fabrication of DGI toward industrial applications have become urgent issues. Here, we reported a construction strategy of DGI for gas-insulated equipment. A topology optimization method was applied to optimize the electric (
$E$
) field distribution of a 126-kV disk-type spacer with actual size. The spatial distribution of relative permittivity (
$\varepsilon _{r}$
) inside spacer was designed to improve the
$E$
-field distributions along the spacer surface and near the triple junction region. Influences of design parameters on
$\varepsilon _{r}$
distributions and the resultant
$E$
-field mitigation degree were analyzed. Appropriate values of design parameters that balance the structure processability and
$E$
-field mitigation results were selected. A three-layer dielectrically graded spacer, including high, medium, and low
$\varepsilon _{r}$
regions, was constructed based on the topology optimization results. In addition, the influence of the area of design domain on the optimization results was analyzed. Numerical results indicate that the
$E$
-field distribution of designed dielectrically graded spacers is significantly improved compared with that of a homogeneous spacer. In the situation with simplified electrode configuration, the maximum
$E$
-field strength along the spacer and at triple junction area could be decreased by 10.5% and 43.4%, respectively. This three-layer DGI construction strategy is promising to apply industrially.