Effect of Spacer Insulation Material Permitivity on the Electric Field of 150 kV Three-Phase GIS Spacer

This paper reports electric field intensity minimization in a three-phase 150 kV GIS spacer with aim to reduce the maximum electric field intensity (Emax) in the spacer, especially around the triple junction area, where conductor, spacer, and SF6 gas meet. Some modifications on the spacer material are conducted to minimize the maximum value of electric field intensity in it, including applying Functional Graded Material (FGM) method, which is a relatively new technique that is proven to reduce electric field intensity in the most effective way. An already designed three- phase 150 kV GIS spacer made from epoxy resin with relative permittivity of 3.5 is provided as the initial model. A double layer FGM method is used in this research where the spacer material is modified to have two different materials combined, consisting of epoxy resin with relative permittivity of 3.5 which is placed in the middle area of the spacer, and Titanium Dioxide (TiO2) with relative permittivity of 8.4 which is placed around the triple junction area. Each modification is performed through simulation using Comsol Multiphysics software for electric field distribution simulation by modeling the initial spacer designed in 3D, and by applying three-phase supply voltage with Vmax of 150 kV to the phase conductors, the electric field distribution specifically the maximum electric field intensity for each voltage phase angle is monitored. The result shows that the Emax in the spacer which is originally 138 kV/cm can be reduced from 10% up to 59%. The most significant reduction in electric field intensity is given by the FGM method, resulting Emax of 56 kV/cm.