Analysis of VFTO across bushing in 765kV gas insulated substation using EMTP software

Abstract

Due to the opening or closing of circuit breakers and disconnect switches in Gas Insulated Substations (GIS), Very Fast Transient Over-voltages (VFTO) are generated, which will bring an instantaneous change in voltage with a very short rise time and it is normally followed by oscillation having high frequencies. This paper describes the variations of VFTO magnitudes transformer bushing of a 765 kV GIS during different switching operations have been calculated and compared by using EMTP.