Study of the Bus Voltage Magnitude to Monitor Power Quality in the Distribution System

Power quality disturbances can be observed as sags, swells, transients, and harmonics, and can affect customers at varying levels of intensity. It is the responsibility of the utility to supply customers with power, however power quality disruptions can occur during distribution. Traditionally, only voltage information is used to conduct power quality monitoring at the distribution level. It is common to record the RMS values of the bus voltages and to identify abnormal operations based on when a sag or swell occurs. This paper proposes a tool consisting of an algorithm and an accompanying graphical user interface (GUI) that can display historical voltage bus data, analyze the data, and provide the user with information that details voltage behavior outside of a user-defined threshold. The GUI gives the user the interactive ability to import data and set the desired threshold. The algorithm then detects events in the imported data outside of the chosen threshold. It also provides the user with event durations, magnitudes, local maximums, and area. The efficacy of the algorithm was verified by comparing the output determined by the algorithm versus the conclusion drawn by a human observer. Additionally, this paper provides a brief overview of two power quality curves: the Computer and Business Equipment Manufacturers' Association (CBEMA) curve, and the Information Technology Industry Council (ITIC) curve. These curves have been utilized in past decades as the common mechanisms to identify voltage variations and the duration of disturbances. Although these curves have proven to have great merit for use as tolerance curves, they may not capture all the necessary details of the events for power quality characterization.