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. Historically, this was done to simplify numerical calculations that were made by hand. Although this advantage has been eliminated by using the computer, other advantages remain:
• Device parameters tend to fall into a relatively narrow range, making erroneous values conspicuous.
• The method is defined in order to eliminate ideal transformers ...