GEORGE FARRELL et al

The Art of Protecting Electrical Systems, Part 2: System Analysis

This is the second article in the continuing series “The Art of Protecting Electrical Systems.” In this article, some of the concepts underlying the study of electrical systems are outlined: linearity, superimposition, the Thevenin equivalent circuit, the sinusoidal forcing function, vector representation, the single-phase equivalent circuit, symmetrical components and the per-unit method. Understanding these concepts is necessary for comprehending the material that will following in the series. For the most part, calculation steps for the circuits discussed are not shown in detail. Such calculations will be addressed later. Linearity An electrical circuit is shown in Figure 2.1.