Influence of switching conditions on Very Fast Transient Over-Voltage in 500kV Gas Insulated Substation

With the wide use of extra high voltage gas insulated substation (GIS), very fast transient over-voltage (VFTO) generated by switching operations threatens the insulation of some equipments even the security of power system. For a 500 kV GIS, the model has been built up and the parameters have been selected in this paper. The variations of VFTO magnitudes along the GIS bus nodes during different switching operations of some typical running modes as well as the frequency spectrum have been calculated by electro-magnetic transient program (EMTP). The results indicate that the VFTO caused by disconnecting operations are higher than those caused by closing operations. Switching conditions and running modes could exert an influence on VFTO of different nodes especially for switches operated. From the studies of the protective effect of shunt resistance in DS, it is shown that VFTO peak could be reduced distinctly, which makes shunt resistance a good way to protect the insulation of GIS and other equipments connected to GIS.