ONS and agents effort to face short voltage variations in Brazil

The special power quality group was created in response to an increased interest in power quality, by the Brazilian electricity sector and in alliance with the Brazilian independent system operator - ONS current revision of the grid procedures [2000], specifically those items that affect the quality of electric energy. The work counted on the participation of diverse Brazilian agents - especially those that require access to the transmission system such as the distribution and consumer companies, universities, independent consultants, research centers and the ANEEL - the Brazilian electric energy regulating agency. The group was divided into subgroups to better contribute to the study of power quality aspects. Among those aspects special attention is given to voltage reliability, harmonics, voltage fluctuations, voltage variations (including unbalance), and short voltage variations. In spite of the fact that the short voltage variation is the most highlighted aspect of power quality in the eyes of the Brazilian technical community, a consensus is still incipient as to the best way to approach this phenomenon not only because of the frequency of the ever growing load sensibility but also because of the complexity demand in their analysis. This paper resumes the activities of the subgroup focusing on short voltage variation work which until now has dealt with the classification of the phenomenon, the definition of an amply acceptable nomenclature, the establishment of the minimum monitoring standards and also the establishment of the criteria diagnostics by simulations, the historical data analysis and the ample Pilot Monitoring Program underway since 2001.