Pilot project for the evaluation of the sag performance of some Brazilian network busbars

The Brazilian electric energy market can be characterized as a functionally unbundled model, which implies that generation, transport-transmission and distribution-and commercialization activities are segregated. Considering the ample institutional experience in Brazil, ONS-the exclusive Brazilian Independent System Operator (ISO)-has been working diligently to bring into force all the previous concerns with respect to the question of power quality. To this end and with the support of ANEEL-the Brazilian Electric Energy Regulating Agency-ONS has been stimulating a broad debate which market players that require access to the transmission system, government organs, universities and research centers have been taking part in. Regarding voltage sags and swells, it has been clearly observed that the amount of information readily available in Brazil was not sufficient as to permit conclusions to be safely made. For that reason, a pilot project, a measurement survey, has been initiated. This project has as its prime motivation the quality of power at the end consumer and has striven to achieve the immediate objectives of identifying the main causes and mechanisms of sag and swell propagation in the system, as well as to subsidize the definition and characterization of the phenomenon and its indices. The main results of the project have made clear that the performance of a homogeneous family of bars follow a lognormal statistical distribution, as the present paper intends to show.