Site surveys are generally initiated to evaluate the quality of the power available at a specific location with the aim of avoiding equipment disturbances in a planned installation or of explaining (and correcting) disturbances in an existing installation. Monitoring disturbances of the power supply has been an objective of various site surveys, but results often appear to be instrument-dependent or site-dependent, making comparisons difficult. After a review of the origins and types of disturbances, the authors describe the types of monitoring instruments. A summary of nine published surveys reported in the last 20 years is presented, and a close examination of underlying assumptions is carried out allowing meaningful comparisons which can reconcile some of the differences. Finally, the authors appeal for improved definitions and applications in the use of monitoring instruments.
