Survey of harmonic current unbalance in public low voltage networks

The paper presents a survey of harmonic current unbalance in public low voltage networks based on measurements of 130 German grids. To ensure a representative set of sites, the selection is based on a classification schema that considers different consumer, generation and network configurations. New individual and aggregated harmonic unbalance indices, which have been recently introduced starting from a harmonic and interharmonic unbalance theory, are applied for the analysis. The results show that fundamental as well as harmonic currents have unbalances higher than 10% and the unbalance levels increase further with the harmonic order. Exceptional high current unbalance levels have been found in some networks with shopping centers and office buildings as unbalance issues have not been taken properly into account at the design stage. The analysis suggests that harmonic studies in public LV networks have to take into account harmonic current unbalances in order to obtain realistic results.