Evaluation and trends of power quality indices in distribution system

An integrated electrical energy and power quality monitoring system was implemented over more than 250 location in the electric power distribution system of ELEKTRO, a utility company in the south-east of Brazil. Harmonics, short-duration voltage variation (voltage sags, voltage swells and interruptions), voltage imbalance, frequency deviation, and other power quality disturbances were monitored over more than 2 years. Measurements in substations and distribution feeders at different voltage levels (138kV, 88kV, 69kV, 34,5kV and 13,8kV) were acquired and stored in a specific energy and power quality database. Statistical analysis and characterization of typical quantities, such as magnitude and duration of phenomena as well as trends of historical indices and analysis to estimate its tendencies for the near future were the main investigation in this work. Therefore, this work contributed to broad the view of the specific electric power system behavior to power quality disturbances, with the objective of providing quick answers to customer's power quality problems and to foster the improvement of the electric distribution system performance.