The simulations are performed in PSS®NETOMAC, which is equivalent to EMTP and approvedin many transient studies carried out in the past. Typically, a number of switching actions aresimulated for a time span of a few microseconds to a few tens of microseconds, and themaximum occurring VFT voltage within the GIS and at the transformer terminals is extracted.These maximum voltages are compared to the BIL value of the installation and thetransformer, taking into account a safety factor of 1.15 (as mentioned in IEC 60071-2)..