Comparison and Analysis on Very Fast Transient Overvoltage Based on 550kV GIS and 800kV GIS

The transitional process from EHV to UHV not Only brings many technical problems, such as zero drift, resonance overvoltage, quenching of secondary arc current, but also makes the problem of VFTO in GIS caused by operating disconnector increasingly outstanding. With the development of UHV GIS in China, there still exist many works to be done thoroughly for the further study of VFTO characteristics. In this paper, a mathematical model has been set up respectively based on a 500kV GIS and an 800kV GIS to study the amplitude-frequency of VFTO and its effects on power transformers, using FORTRAN and EMTP. The protective effect of shunt resistor of DS has been verified again in suppression of VFTO in 800kV GIS. By comparing and analyzing the calculation results between the two EHV systems, an important reference is provided to accelerate the UHV transmission network for the localization of UHV utilities and GIS manufacture.