Characterization of voltage variations through the application of experimental statistics

Currently, power quality problems are more and more acute due to the increasing number of voltage variation sensitive devices that are embedded in the electronic subsystems, and due to the presence of harmonics and unbalance. Non-quality in electrical networks translates into an increase of energy consumption and additional expenses for consumers. In this paper an analysis regarding the voltage variation characteristic parameters using descriptive statistics is done, and experimental data are processed applying statistical methods to a set of data obtained by monitoring the phase voltages for 11 days on the low voltage bus-bars. Using the Statistica software in analysis of the phase voltage data strings, the following integral statistical indices are obtained: arithmetic mean, module, median, minimum, maximum, standard deviation, coefficient of variation. The analysis indicated that the actual means values of phase voltages are close to the upper regulated limit. However, the power quality level regarding the voltage variation is acceptable.