should be clear whether the quantity is a voltage, current, or other unit of measurement.

Purpose

There are several reasons for using a per-unit system:
* Similar apparatus (generators, transformers, lines) will have similar per-unit impedances and losses expressed on their own rating, regardless of their absolute size. Because of this, per-unit data can be checked rapidly for gross errors. A per unit value out of normal range is worth looking into for potential errors.
* Manufacturers usually specify the impedance

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