This recommended practice encompasses the monitoring of electric power quality of single-phase and polyphase ac power systems. As such, it includes consistent descriptions of electromagnetic phenomena occurring on power systems. The document also presents definitions of nominal conditions and of deviations from these nominal conditions, which may originate within the source of supply or load equipment, or from interactions between the source and the load. Brief, generic descriptions of load susceptibility to deviations from nominal conditions are presented to identify which deviations may be of interest. Also, this document presents recommendations for measurement techniques, application techniques, and interpretation of monitoring results so that comparable results from monitoring surveys performed with different instruments can be correlated. While there is no implied limitation on the voltage rating of the power system being monitored, signal inputs to the instruments are limited to 1000 Vac rms or less. The frequency ratings of the ac power systems being monitored are in the range of 45â€"450 Hz. Although it is recognized that the instruments may also be used for monitoring dc supply systems or data transmission systems, details of application to these special cases are under consideration and are not included in the scope. It is also recognized that the instruments may perform monitoring functions for environmental conditions (temperature, humidity, high frequency electromagnetic radiation); however, the scope of this document is limited to conducted electrical parameters derived from voltage or current measurements, or both. Finally, the definitions are solely intended to characterize common electromagnetic phenomena to facilitate communication between various sectors of the power quality community. The definitions of electromagnetic phenomena summarized in table are not intended to represent performance standards or equipment tolerances. Suppliers of electricity may utilize different thresholds for voltage supply, for example, than the ± 10% that defines conditions of overvoltage or under voltage in table . Further, sensitive equipment may malfunction due to electromagnetic phenomena not outside the thresholds of the table criteria.