The management of voltage unbalance in a power system is supported by the knowledge on the contribution of a single unbalanced load/source to the total level of voltage unbalance observed at a Point of Common Coupling (PCC) in an interconnected power system with unbalanced loads distributed all over. The theoretical requirements to solve this problem are investigated in this paper. The flow of active and reactive energy in the fundamental frequency sequence components is studied by means of simulation studies. The correlation of various unbalanced loading conditions with the voltage unbalance factor at the PCC is reported and the possibility in the practical application of a single-point measurement method in the assessment of the unbalance is then discussed based on the results obtained