National Power Laboratory power quality study 1972 to 1979 revisited

This paper describes the five-year power quality study being conducted by National Power Laboratory (NPL) with a comparison to the Allen-Segall (IBM) and Goldstein-Spetanza (AT&T) studies. The graphics capabilities of the NPL monitoring system are also described with selected waveforms from the study used as examples. Comparisons are based on 1057 site months of the NPL database and the IBM and AT&T study information. Threshold levels for defined disturbances in these comparisons were selected to exactly match the original IBM and AT&T thresholds. This equivalent comparison produces a profile of power quality for 1990-1995 based on the monitor capabilities, definitions, and threshold settings of the 1972 IBM and 1979 AT&T studies. Results of the comparisons show major changes in the number and types of power disturbances, as reported in the original 1972 and 1979 studies. A common result found in all three studies is the need for computer-grade power to protect essential sensitive electronic equipment. A paper coauthored by NPL and Bellcore also concluded that backup powering is needed if commercial AC voltage is used by local exchange carriers for powering fiber-in-the-loop (FITL) systems. Some “typical” waveforms recorded during the study are also shown as examples as to what is happening at the point of utilization