Switching operations in a Gas Insulated Substations (GIS) generate very fast
transient over voltages (VFTO) which are dangerous for the transformer and
the system insulation because of their short rise time. Under special
circumstances the overvoltages can arise close to the transformer Basic
Insulation Level (BIL). The reduction of VFTO amplitudes is considered
main challenges. Therefore, VFTO in the 220 kV Wadi-Hoff GIS is analyzed
and the worst case for disconnector switching is predicted using EMTP/ATP
in this paper. VFTO mitigation techniques are studied in this work.
Furthermore, proposed techniques are presented for mitigating the VFTO.
The proposed techniques can be used by the maintenance engineers,
transformer designers, and GIS insulation manufactures. The results show
that the proposed techniques highly reduce the VFTO in a simple manner