This recommended practice encompasses the monitoring of characteristics of electric power systems. It includes consistent descriptions of conducted electromagnetic phenomena occurring on power systems. This recommended practice presents definitions of nominal conditions and deviations from these nominal conditions that may originate within the source of supply or load equipment or may originate from interactions between the source and the load. Also@ this recommended practice discusses measurement techniques@ application techniques@ and the interpretation of monitoring results. Purpose This recommended practice provides users with a consistent set of terms and definitions for describing power quality phenomena. An understanding of how power quality phenomena affects the power system and end-use equipment is required in order to make monitoring useful. Proper measuring techniques are required to safely obtain useful@ accurate data. Appropriate location of monitors@ systematic studies@ and interpretation of results will enhance the value of power quality monitoring. The purpose of this recommended practice is to assist users as well as equipment and software manufacturers and vendors by describing techniques for defining@ measuring@ quantifying@ and interpreting electromagnetic phenomena on the power system.