Suppression of VFTO by Disconnector with Opening and Closing Resistor in GIS

During switching operation or earth faults in SF6 gas insulated switchgear(GIS),Very Fast Transient Over-voltage(VFTO) occurs and will stress adjacent equipment or secondary equipment in GIS.With the increasing of GIS voltage level,the effect of VFTO should be taken more consideration.According to the characteristics of 800 kV GIS structure,especially when busbar is relative long(use distribution data simulation with taking into account the frequency characteristic),this paper had made data analysis to 28 deferent connection modes using EMTP program.The calculation effect shows that when open/close resistance on the disconnector is installed or not,the Max.amplitude of VFTO is 1.293 p.u.and 2.976 p.u.respectively.Data show that since the open/close resistance of disconnector has limited effect on VFTO,the amplitude of the VFTO is not high in GIS.When the open/close resistance is larger than 200 Ω,the amplitude of VFTO can be restrained under 1.7 p.u..The amplitude of VFTO has little effect on equipment insulation.This is very important for the insulation design of the adjacent equipment and secondary equipment of 800 kV GIS.