A preliminary report from Edesur, one of Argentina’s largest electricity distributors, problems with two 500 kV transmission lines were the proximate cause of the national blackout on 16 June. The lines connect the Yacyreta Dam in Paraguay and the Salto Grande Dam on the Uruguay River to the Argentine grid. Argentine Government officials have said that the cause has not yet been finally determined, and that investigations are ongoing. They promised that a comprehensive report would be issued within 10 days.
The Secretariat of Energy attributed the blackouts to the “collapse of the Argentine Interconnection System (SADI).”
According to a memo from Cammesa, which coordinates the sale and delivery of electricity throughout Argentina, a short-circuit disconnected a 500kV transmission line running from the city of Colonia Elía to Belgrano, a neighbourhood in Buenos Aires. At the same time, an automated system disconnected another 500kV line running from the city of Mercedes to Colonia Elía. A third 500kV line, connecting Colonia Elía and Nueva Campana had been taken out of service on 18 April to relocate a tower. High water levels at the Yacyreta Dam and the Salto Grande Dam meant that these facilities were producing close to their maximum output. With the Colonia Elía-Nueva Campana line out of service, the other lines were carrying high levels of power.
It has been speculated that when the Colonia Elía-Belgrano line short-circuited, excess load was placed on other lines. Argentina’s grid has automated systems to isolate such issues and prevent a cascade, but these systems failed to operate, and the system collapsed.