The per unit impedance of a transformer is
Right Answer is:
The same whether computed from primary or secondary side
The Per Unit value of any quantity is defined as the ratio of actual value to the base value.
PU value = actual value/base value
Per unit system in transformers:
The per-unit impedance of a transformer is the same whether computed from the primary or secondary side so long as the voltage bases on the two sides are in the ratio of transformation (equivalent per phase ratio of a three-phase transformer which is the same as the ratio of line-to-line voltage rating).