The “Sistema Eléctrico Patagónico Interconectado (SFPI)” is an elechic system that involves the Argentina south region. This electric system is isolated fiom the other one in the north of the country. The 60% of its load is consumed by an aluminum production plant consisting of two 160 MW series of 200 electrolytic cells each one. Dynamic and transient stability studies carried out over this system, taking into Bccount present and future situations, with load and genedon grown at the aluminum plant and in the remaining system, require adequate modeling of this particular load. Tests and simulations canied out to obtain the electrolytic process load model are &scribed. Statistical behavior of the aluminum plant load variations is analp4 to estimate the spinning reserve in the system. By the way, available load shedding mechanisms at the aluminum plant, as a system control element, were tested and the results are analyzed.Este trabajo también fue presentado en la I Conferencia Internacional del Área Andina del IEEE (IEEE-ANDESCON) (Isla Margarita, Venezuela, septiembre de 1999).Instituto de Investigaciones Tecnológicas para Redes y Equipos Eléctricos (IITREE
