Aiming at a better understanding of power system harmonics, this text presents a discussion of this issue, providing a quantitative analysis when possible. Pertinent equations are developed. 80 practical case studies based on real-life work experience come with the text. These are analysed providing the results and commenting on the output. Furthermore, 80 end-of-chapter problems are provided. A detailed solution manual is available. The book can be used as a textbook for undergraduate and graduate students, in short-courses offered by consultants and institutes, as well as a tutorial, reference, or self-study course for practising engineers in the industry and electric utility.