Comparison between suppressing approaches of very fast transients in gas-insulated substations (GIS)

In this paper, first transient waves in the gas-insulated substation (GIS) are analyzed and methods for suppression of very fast transients (VFTs) in GISs are introduced. For suppressing VFTs, four methods are presented, including suppression by terminal components, capacitance components, adopting a resistor-fitted disconnector, and ferromagnetic rings. Finally, these approaches are compared with each other. These methods can be divided into two groups. The first group contains the methods (such as terminal components and reconfiguration) that can be used after installation of the GIS and during the operation of the GIS. The second group contains the methods (such as the resistor-fitted disconnector and ferromagnetic rings) that must be used as an extra limitation before installation and during the design of the GIS. Advantages of the first group are simplicity and the low cost of implementation along with producing minimal changes in the installed GIS. The main advantage of the second group is estimation of all factors during the design of the GIS. Finally, the best approach for the suppression of VFTs is chosen based on the criteria of the transient waves and feasibility.