Switching operations in a gas insulated substations 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 terminal
over voltages can arise close to the transformer BIL. The suppression of VFTO is very
important in GIS systems. Different techniques are applied to 245 kV GIS model. The
simulation used ATP-EMTP package program to evaluate the VFTO at the sensitive
points in GIS. The different results are compared to determine the effective mitigation
method. The results show that the wave steepness and the amplitudes of VFTO can be
reduced to about 1Pu with less oscillation frequency. |
