Venezuela's massive, nationwide power outages, which began on Thursday, have so far resulted in at least 20 deaths, looting, and loss of access to food, water, fuel, and cash for many of the country's 31 million residents. Late Monday, the United States said its diplomats would leave the US embassy in Caracas, citing deteriorating conditions. As the societal impacts intensify and Venezuela's internal power struggle continues, the country is clearly struggling to restart its grid and meaningfully restore power—a problem exacerbated by its aging infrastructure.

Reenergizing a dead grid, a process known as a black start, is challenging under any circumstances. But statements from Venezuelan president Nicolás Maduro, opposition leader Juan Guaido, and other officials have largely failed to explain details of what caused the country's outage or a plan for restoration. Government statements and reports indicate that the blackout stems from a problem at the enormous Guri dam hydropower plant in eastern Venezuela, which generates 80 percent of the country's electricity. And the already arduous process of restoring power seems hobbled by years of system neglect. It's also unclear whether Venezuela has the specialists, workforce, and spare equipment available on the ground to triage the situation quickly.

"The challenge with black start is always just knowing specifically what happened," says Nathan Wallace, director of cyber operations and a staff engineer at secure grid companies Cybirical and Ampirical Solutions. "It sounds like there may be lack of maintenance and some mismanagement. And typically if a system hasn’t been maintained, that means they really don’t have the visualization needed to understand the state of the system in real time. If the procedure for black start is not accurately representing the state of the system, there can be problems."

"The challenge with black start is always just knowing specifically what happened." Nathan Wallace, Cybirical and Ampirical Solutions

A black start generally involves seeding power from an independent source—like small diesel generators or natural gas turbines—to restart power plants in an otherwise dead transmission network. This process is often called bootstrapping. Hydroelectric plants in particular can be designed to essentially black-start themselves. In these plants, water—often from a dam, as in the case of Guri—flows through a turbine, which spins it, powering an electric generator. Since it takes relatively little independent energy to open the water intake gates and potentially generate a lot of power very quickly, hydroelectric plants can work well for black start. It is unclear whether Venezuela's Guri plant is designed with this scenario in mind.

What makes any black-start process especially complicated is the need to load balance a system, so that as power surges through, the supply from the generator matches the demand. Otherwise the generation plant will run too fast or be exhausted, causing the system to fail again.

"It’s a large stepwise process to build up load, build up generation, build up more load, build up more generation until they’ve got enough reliability to go to the next element of the system," says Michael Toecker, a grid security engineer and founder of the firm Context Industrial Security. "If a utility has issues with maintenance, or has a history of operational issues, or they don’t have a plan, or that plan is outdated, or if they don’t have a really good understanding of the limitations of the grid system, everything the utility is attempting to do becomes far more difficult."

Venezuela's grid is based on a classic model of bulk power generation. From a centralized plant—in this case, Guri—substations transform electricity from low to high voltage so it can be transmitted all over the country and then converted back down to lower voltage for local distribution. This is fairly typical in small countries, though some prioritize adding diverse generation or connecting with neighboring grids to increase redundancy. Black-start researchers and practitioners say, though, that any model has pros and cons. While distributed systems don't have a single point of generation failure, they can be more difficult to black start if they do go down, since more generation sites need to be bootstrapped and there are more loads to balance.

"It’s extremely dangerous to reenergize a system if you have gear that hasn’t been maintained well." Tim Yardley, University of Illinois

Regardless of the setup, the crucial component of all black starts is understanding what caused the outage, having the ability to fix it, and working with a system that can handle the power surges and fluctuations involved in bringing power back online. Without all of these elements in place, says Tim Yardley, a senior researcher at the University of Illinois focused on industrial control crisis simulations, black starts can be prohibitively difficult to execute.