The San Geronimo B substation connects eight out of Venezuela’s 10 largest cities to the Guri hydropower plant via one of the longest high-voltage lines in the world.
When visited on Sunday, the substation’s usual buzz of high-voltage cross currents had been replaced by total silence. A cow roamed amid the transformers. Several National Guard soldiers and a unit of police commandos were at the substation, but no employees were there.
The substation is vital “to supply the country in a stable way,” said Luis Aguilar, a Venezuelan power industry expert based in Chicago. Its paralysis means power is unlikely to be restored nationally until Tuesday, at the earliest, he said.
The government declared Monday a holiday for schools and public workers.
What caused the blackout has been a source of speculation. A Corpoelec union leader, Ali Briceño, told reporters on Friday that a brush fire under a power trunk line destabilized the grid and caused Guri’s turbines to shut down. The government has struggled to restart the turbines since, he said.
Other experts, including Mr. Aguilar, said the magnitude of the blackout indicated the problem was caused by a major failure inside Guri’s turbines. A Corpoelec supervisor involved in dispatching Guri’s power said he was told by the plant’s managers on Thursday that the plant’s equipment was damaged.
After analyzing power levels across the country, Mr. Aguilar, who consults reinsurance companies on Venezuela’s power sector, said the government has tried to restart Guri four times since the start of the blackout on Thursday.
The latest attempt led to the explosion of a secondary substation near Guri on Saturday.
“Every time they attempt to restart, they fail and the disruption breaks something else in the system, destabilizing the grid yet further,” said Mr. Aguilar. “Obviously, they are hiding something from us,” he said of the government.
Restarting the turbines requires skilled operators who can synchronize the speed of rotation on as many as nine of Guri’s operational turbines. Experts said the most experienced operators have long left the company because of meager wages and an atmosphere of paranoia fed by Mr. Maduro’s ever-present secret police.