Toronto during the 2003 Northeast blackout, which required black-starting of generating stations. Source: https://en.wikipedia.org/wiki/Black_start

Black starts

Large blackouts can be quite devastating and it isn’t easy to restart the electric grid again.

This is typically done by designated black start units of natural gas, coal, hydro, or nuclear power plants that can restart themselves using their own power with no help from the rest of the electrical grid.  Not all power plants can restart themselves.

After a brief introduction to black starts, I have a recent example of one in Venezuela to give you an idea of how hard restarting a grid can be.

Clearly a renewable grid running mainly on wind and solar will crash a lot, and without hydropower or fossil fuels to restart the grid (which are finite and won’t be available at some point), the idea we can just do stuff when the grid is up and wait it out for when the grid is down isn’t going to work.  This is a huge problem for a 100% renewable system that may not be solvable.  Microgrids don’t solve anything, manufacturing and industry require mind-boggling amounts to electricity to stay in business.

Alice Friedemann   www.energyskeptic.com  author of “When Trucks Stop Running: Energy and the Future of Transportation”, 2015, Springer and “Crunch! Whole Grain Artisan Chips and Crackers”. Podcasts: Practical Prepping, KunstlerCast 253, KunstlerCast278, Peak Prosperity , XX2 report

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In regions lucky enough to have hydropower (just 10 states have 80% of the hydropower in the U.S.) this is usually the designated black start source since a hydroelectric station needs very little initial power to start, and can put a large block of power on line very quickly to allow start-up of fossil-fuel or nuclear stations.

Wind turbines are not suitable for black start because wind may not be available when needed (Fox 2007) and likewise solar power plants suffer from the same problem.

The impact of a blackout exponentially increases with the duration of the blackout, and the duration of restoration decreases exponentially with the availability of initial sources of power. For several time-critical loads, quick restoration (minutes rather than hours or even days) is crucial. Blackstart generators, which can be started without any connection to the grid, are a key element in restoring service after a widespread outage. These initial sources of power include pump-storage hydropower, which can take 5-10 minutes to start, to certain types of combustion turbines, which take on the order of hours.

For a limited outage, restoration can be rapid, which will then allow sufficient time for repair to bring the system to full operability, although there may be a challenge for subsurface cables in metropolitan areas. On the other hand, in widespread outages, restoration itself may be a significant barrier, as was the case in the 1965 and 2003 Northeast blackouts. Natural disasters, however, can also lead to significant issues of repair—after Hurricanes Rita and Katrina, full repair of the electric power system took several years (NAS)

Restoring a system from a blackout required a very careful choreography of re-energizing transmission lines from generators that were still online inside the blacked-out area, from systems from outside the blacked-out area, restoring station power to off-line generating units so they could be restarted, synchronizing the generators to the interconnection, and then constantly balancing generation and demand as additional generating units and additional customer demands are restored to service.

Many may not realize it takes days to bring nuclear and coal fired power plants back on-line, so restoring power was done with gas-fired plants normally used for peak periods to cover baseload needs normally coal and nuclear-powered. The diversity of our energy systems proved invaluable (CR).

Restarting the grid after the 2003 power outage was especially difficult.

The blackout shutdown over 100 power plants, including 22 nuclear reactors, cutoff power for 50 million people in 8 states and Canada, including much of the Northeast corridor and the core of the American financial network, and showed just how vulnerable our tightly knit network of generators, transmission lines, and other critical infrastructure is.

The dependence of major infrastructural systems on the continued supply of electrical energy, and of oil and gas, is well recognized. Telecommunications, information technology, and the Internet, as well as food and water supplies, homes and worksites, are dependent on electricity; numerous commercial and transportation facilities are also dependent on natural gas and refined oil products.

Newman, L. H. 2018. Why it’s so hard to restart Venezuela’s power grid. Wired.com

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.

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.”

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. 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.

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.

“Reenergizing a grid in some ways is more of a shock to the system than it operating in its norm,” Yardley says. “If infrastructure is aging, and there’s a lack of maintenance and repairs, as you try to turn it back on and try to balance the loads you may have stuff that’s not going to come back up, infrastructure that’s been physically damaged or that was in such a bad state of repair that reenergizing it causes other problems.”

Crews attempting to deal with black-starting a frail and brittle grid also face major safety considerations, like explosions. “You have a maintenance issue and a manpower issue, because it’s extremely dangerous to reenergize a system if you have gear that hasn’t been maintained well,” Yardley notes.

Venezuela has faced years of power instability since about 2009, including two major blackouts in 2013 and a power and water crisis in 2016. At times the blackouts were caused in part by weather conditions like El Niño, but overall they have established a pattern of poor planning, mismanagement, and lack of investment on the part of the government. President Maduro has repeatedly overseen rationing efforts resulting in erratic power and has even set official national clocks back to put the country’s morning commute in daylight.

References

CR. September 4 & 23, 2003. Implications of power blackouts for the nation’s cybersecurity and critical infrastructure protection. Congressional Record, House of Representatives. Serial No. 108–23. Christopher Cox, California, Chairman select committee on homeland security

Fox, Brendan et al; Wind Power Integration – Connection and System Operational Aspects, Institution of Engineering and Technology, 2007 page 245

NAS. 2012. Terrorism and the Electric Power Delivery System. National Academy of Science

NAS. 2013. The Resilience of the Electric Power Delivery System in Response to Terrorism and Natural Disasters. National Academy of Science