Study of very fast transient overvoltages and mitigation techniques of a gas insulated substation

The very fast transient overvoltages (VFTOs) generated due to switching operations of gas insulated substations (GIS) are dangerous to the equipments connected to the substations. In special cases these transients may cross the Basic Insulation Level (BIL) of the GIS. In this paper, these transient voltages are investigated at the different sensitive locations of a 400 KV GIS. VFTOs of the GIS are calculated using EMTDC/PSCAD software. Hence, the suppression of the VFTOs is also an important field of interest. The suppression techniques to reduce the VFTOs are also discussed in this paper.