Power quality has become an important issue in recent times when many utilities around the world find very difficult to meet energy demands which leads to load shedding and power quality problems. This book on power quality written by experts in their fields will be of great benefit to professionals, engineers and researchers. This book comprises of 16 chapters which are arranged in two sections. Section one covers power quality monitoring, classification, and analysis aspects. Power quality enhancement, reactive power compensation and voltage sag mitigation of disturbances in transmission and distribution system are presented in the second section. Brief discussion of each chapter is as follows