Power quality is a research field and engineering concept concerned with the characteristics of electrical power as supplied to users, specifically focusing on deviations from ideal sinusoidal voltage and current waveforms at rated frequency and magnitude. It investigates phenomena such as sags, swells, harmonics, flicker, transients, and interruptions, analyzing their causes, effects on electrical and electronic equipment, and methods for monitoring, mitigation, and standardization to ensure reliable and efficient operation of power systems and connected loads.