AC power quality studies: IBM, AT&T and NPL

The author describes the National Power Laboratory (NPL) five-year power supply quality study and compares NPL study results to the Allen-Segall (IBM) and Goldstein-Speranza (AT&T) studies. Comparisons are based on equivalent segments of the NPL database and the IBM and AT&T studies. Threshold levels for defined disturbances in these comparisons match the original IBM and AT&T thresholds. This equivalent comparison produces a profile of power quality for 1990-1991 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 from the original studies. A common result found in all three studies is the evident need for computer-grade power to protect sensitive electronic equipment