When in calculated scheme there is a transformer with tap changer, the position of tap changer ir taken into account when calculating. The calculated result depends on the position of tap changer and the changed voltage.
It is not possible to perform the calculations if parts with different voltage levels are shortened. For example, to this scheme:
In this case, there are two parallel lines with the same line length and the same transformers, except the tap changer position of the first transfomer is different than the position of other. In this case, it is not possible to calculate the short circuit current.
