Preventing Earth Faulting during Switching of Disconnectors in G.I.S. including Voltage Transformer

Switching of disconnectors in G.I.S. in the presence of an inductive voltage transformer can give rise to extreme conditions which can seriously affect their dielectric withstand capacity. The case is studied in detail. A description of the various overvoltages generated by disconnector operation shows that they can reach 2.3 - 2.5 PU in real G.I.S. configuration. A synthetic test circuit in full phase opposition can reproduce the main voltage parameters and following an appropriate test procedure, check the capacity of the disconnector switching in these conditions. The present article gives general information on the behavior of the insulation between arc and enclosure.