The concepts of measurements and analysis in power system harmonics are discussed in this elaborative book. The rise in the usage of power electronics equipment has led to significant distortions. An ideal AC power system is purely a sinusoidal wave, both voltage and current. However, the increasing existence of non-linear loads changes the aspects of voltage and current from the perfect sinusoidal wave. This alteration from the perfect wave is reflected by the harmonics and although its effects vary based upon the type of load, it affects the effectiveness of an electrical system and can create extensive damage to the system and infrastructure. Establishing ideal power quality after a good design and devices leads to productivity, efficiency, competitiveness and profitability. However, nobody can promise the ideal power quality when there is a good design, if the accurate tests and working methods from the collected information are not properly assured at every moment; this entails processing the actual information accurately. This book discusses harmonics analysis, ranging from the actual measurement data to the study of various industrial environments and electronic tools.