In this book the authors describe the main computer modelling techniques that, having gained universal acceptance, constitute the basic framework of modern power system analysis. Some basic knowledge of power system theory, matrix analysis and numerical techniques is presumed, although several appendices and many references have been included to help the uninitiated to pick up the relevant background. An introductory chapter describes the main computational and transmission system developments which influence modern power system analysis. This is followed by three chapters on the subject of load or power flow with emphasis on the Newton-Raphson fast-decoupled algorithm. Chapter 5 describes the subject of a.c. system faults. The next two chapters deal with the electromechanical behaviour of power systems. Chapter 6 describes the basic dynamic models of power system plant and their use in multi-machine transient stability analysis. More advanced dynamic models and a quasi-steady-state representation of large converter plant and h.v.d.c. transmission are developed in Chapter 7. A description of the Electromagnetic Transients Program with the marriage between Bergeron’s and Trapezoidal methods is presented in Chapter 8, and a generalization of the multi-phase models described in Chapter 3 is used in Chapter 9 as the framework for harmonic flow analysis. Chapter 10 describes the state of the art in power system security and optimization analysis. Finally, Chapter 11 deals with recent advances made on the subject of interactive power system analysis and developments in computer graphics with emphasis on the use of personal computers.