This monograph focuses on the modern power system and its reliable operation on a national scale. The contents focus on the analysis and root cause of different power system blackouts, the introduction of a phasor measurement unit incorporating a polygon-shaped graphical algorithm for out-of-step protection of the synchronous generator, predictive out-of-step protection, dual-slope relay setting, novel apparent stability concept, among others. This volume will be beneficial to academia and industry during the testing, development, and modeling of protective relays for generators, transformers, and transmission lines.