JELE_V2_N4_RP3 A. Raghu Ram M. Mohana Rao Journal on Electronics Engineering 2249 – 0760 2 4 14 20 Very Fast Transient Over Voltages (VFTO), GIS, Insulating Flange, MATLAB 7.0. In gas insulated substations(GIS) very fast transient overvoltages(VFTO) are generated due to disconnector switching operations. Disconnector switches are primarily used to isolate the operating sections of HV installation from each other as a safety measure. Very fast transient over voltages at an insulating flange are generated due to propogation of VFTOs on the conductor of a gas bus in GIS.Genaration of VFTOs causes sparkovers across insulating flange of high pressure oil filled cable/GIS interface.The ionised path formed by the sparkovers create low impedance path for power frequency fault current, resulting in flange damage with serious consequences.This paper deals wih the generation of VFTOs across insulating flange and their suppression using shunting bars and capacitors for providing protection have been analyzed and reported using MATLAB 7.0. June – August 2012 Copyright © 2012 i-manager publications. All rights reserved. i-manager Publications http://www.imanagerpublications.com/Article.aspx?ArticleId=1899&issueid=0