Final answer:
If a phase-to-phase transformer designed for rated voltage on both primary sides has voltage applied to only one, it will result in an unbalanced transformer, where the primary voltage is lower than the secondary voltage.
Step-by-step explanation:
If a phase-to-phase transformer designed to have the rated voltage applied to both primary bushings only has voltage applied to one, it will result in an unbalanced transformer. In this scenario, the primary voltage will be lower than the secondary voltage.
Typically, the primary and secondary voltages of a transformer are tightly coupled, meaning that changes in one will result in corresponding changes in the other. If voltage is applied to only one primary bushing, the magnetic flux in the transformer will not be balanced, leading to an unequal voltage between the primary and secondary sides.