Customers specify non-auto transformers for network applications when separate grounding systems between the high voltage and low voltage is required.
Substation non-autotransformers, like the autotransformers, transfer the incoming high voltage to the next voltage level. As an example, incoming high voltage of 400 kV would be transferred down to 220 kV.
In general they are equipped with on-load tap changers (OLTC) and are connected to the grids by bushings and cables. Non-autotransformers are built-in core form with windings facing full power, that is, HV windings and LV windings are galvanically separated.