Officials were searching for answers early Wednesday after a power failure blacked out large swaths of Brazil and Paraguay for more than two hours late Tuesday.
The failure of three transmission lines at Itaipu, the world's largest operating hydroelectric plant, created a domino effect that cut energy to 16 of 27 states in Brazil, including the country's two largest cities, Sâ£o Paulo and Rio de Janeiro, and affected an estimated 60 million people. Airports in several cities were briefly shut down, and passengers had to be pulled from subway cars in Sâ£o Paulo when the system lost power.
Electricity system operators were quick to dismiss the possibility of sabotage at the Itaipu dam and assigned initial blame to an unexplained atmospheric event possibly exacerbated by heavy rains. It was the first time that Itaipu had failed so completely in its 25 years of operation, energy officials said late Tuesday.
Energy experts in both countries said Wednesday that the major blackout was a cautionary sign of the dangers of interconnection and showed the vulnerability in Brazil's transmission system.
"The interconnection system is necessary in a country that uses a lot of hydroelectric plants, but it needs to better managed," said Luiz Pinguelli Rosa, a physics professor at the Federal University of Rio, speaking on television.
The power failure recalled the blackout of August 2003 in the northeastern United States, the country's most widespread electrical blackout in history, which affected 10 million people in southeastern Canada and 45 million people in eight American states.
For Brazilians, Tuesday night's blackout brought back painful memories of energy shortages in 2001, which led the country to step up its push for more natural gas and hydroelectric power generation. The president at the time, Fernando Henrique Cardoso, instituted nine months of energy rationing, and the country's perceived energy fallibility was blamed for a considerable decline in Mr. Cardoso's popularity as he ended his second term in office.