Computation of very fast transients in 400 kV gas insulated substations caused by disconnector switching

Digital simulation of very fast transients due to disconnector operation in a 400 kV gas insulated substation (GIS) is considered. The breaking of small capacitive currents by a disconnector when the buses are unloaded has been considered as an important switching phenomenon. Transient overvoltages are computed and discussed for different switching conditions and points of buses as well as for different points at grounding enclosure. The effects of the usual techniques for dumping of overvoltage levels are considered as well. Criteria for GIS modeling in the digital simulation of very fast transients are proposed.