ABSTRACT
This chapter provides an overview of alternate approach using “symmetrical components”. Using symmetrical components, analysis is greatly simplified because calculations are a function of load or fault condition rather than a function of source voltage. The basic premise underlying symmetrical components is that calculations, for any load or fault condition, can be developed using single phase methods. Symmetrical components utilize a unit vector, designated “a,” to transform phase quantities to sequence quantities and to transform sequence quantities to phase quantities. When using symmetrical components, transformers are represented as “star equivalents.” Three-phase power systems are difficult to model and analyze using traditional methods, that is, using loop equations and node equations when transformer turns ratios and transformer winding connections are included in the calculations. Calculations are developed using per unit quantities for voltage, current, and impedance as per unit quantities eliminate the need to use transformer turns ratios and conversions throughout calculations.
