ABSTRACT
Per-unit is sometimes extended to transient analysis and may include quantities other than voltage, power, current, and impedance. The base value always has the same units as the actual value, forcing the per-unit value to be dimension-less. In many engineering situations, it is useful to scale or normalize quantities. This is commonly done in power system analysis, and the standard method used is referred to as the per-unit system. Representing a complex value in polar form, the angle of the per-unit value is the same as that of the actual value. Actually, in practice, values are selected that force results into certain ranges. The key to successfully using any scaling procedure is to understand how all base values are selected at every location within the power system. If one receives data in per-unit, one must be in a position to convert all quantities to SI units.
