The 2019 Argentina and Uruguay Blackout

At about 7am on Sunday 16 June 2019, with demand around 13,200 MW, a short circuit hit the 500 kV line from Colonia Elía to Mercedes, close to the Colonia Elía substation. For about two months one of two parallel lines in that corridor had been out of service, so a temporary connection had joined the Campana substation to the remaining line in a T shape.

The protections on the T shaped line opened it in a way the control scheme did not expect. A scheme meant to cut about 1,200 MW of generation in the northeast, called the DAG, did not act because it was programmed for a different mode of operation. Without that cut, the big hydro plants at Yacyretá and Salto Grande lost synchronism and a block containing Uruguay and part of northeast Argentina split away. The rest of the Argentine grid lost about 3,200 MW of supply against 12,800 MW of demand, several generators tripped early, load shedding could not stabilise it and the system collapsed.

Restart was slow, with several power stations failing to start at the first attempt and control centres disagreeing during the black start. A study by the engineering faculty of the University of Buenos Aires, requested by the regulator ENRE, concluded that the protections did not act as expected and that the generation cutback scheme was not adequate, and it weighed the share of responsibility of the transmission company, generators, distributors and large users stage by stage. Its simulations suggested the system would have stabilised had that scheme worked, though without certainty that no protection would have tripped.