Revision of Concepts and Approaches for Unbalance Problems in Distribution

The unbalance problem seems to be secondary when requirements of electric power quality are studied. However, unbalance is one of the most frequent problems and involves economic losses. The best known and prominent, is the effect on electric motors. A brief bibliographical survey on the causes and effects, definitions, normative and requirements specially stressing the effect on motors is presented. The attention is centered in the analysis of a typical simple distribution system on which different operative conditions are analyzed. Basically, balanced and unbalanced supply voltage, and balanced and unbalanced loads. In such situations, the power flows are analyzed by their sequence components, and from them an approach for the assignment of responsibilities as function of the load location is presented, considering loads as sources or sinks of unbalanced power. Finally some concepts about a methodological base are presented, intended to allow the control and limits setting for distribution systems