Voltage unbalance in low voltage distribution networks

SUMMARY This paper presents a methodology for measuring, monitoring and controlling voltage unbalance in electrical power distribution networks. The distribution of single-phase and double-phase loads along the network and their random instant demand values can be considered as the main causes to voltage unbalance in three-phase distribution systems. The work considers voltage unbalance measurements carried out in a Brazilian distribution company located in the State of Paraná, namely COPEL – Companhia Paranaense de Energia. Since voltage unbalance gradually affects equipment, this disturbance should be dealt with by statistical analysis. Regarding voltage regulation and voltage unbalance, a worldwide tendency is to consider their monitoring and measuring on 10 minute intervals along a 1 week period. Thus, this paper aims at:-studying the opportunity of using digital simulations for the analysis of voltage unbalance disturbances;-comparing field measurements and results from simulations;-proposing preliminary standards regarding voltage unbalance to be applied in low and medium voltage distribution systems in Brazil.