Computation of electric field for FGM spacer using U-shape insulator in GIS

The Gas Insulated Substation (GIS) have various advantages like compactness, immunity from environmental conditions, high operational reliability, low maintenance cost. In a number of GIS installations, the main design considerations involved in gas insulated equipment are at cone insulator, gas and metal interface. Hence there is a need for control of electric stress in order to reduce internal discharges, surface discharges to the enclosure surface. In conventional approach, in order to reduce such distortion of electric field, many techniques applied like, control of the spacer shape, additional shielding of electrodes for relaxation of electric field around spacer and low permittivity material of spacer, etc., from this point of view the new techniques of Functionally Gradient Material (FGM) spacer has been proposed in this paper. The applicability of FGM spacer for gas insulated power apparatus has been verified. In the FGM spacer, a spatial distribution of permittivity for the control of the electric field distribution in and around the spacer is used. The electric field calculations for several types of FGM spacers have been carried out using Finite Element Method (FEM). The electric field distribution along the radial distance of the spacer insulator has been obtained for various FGM materials and results are compared.