The U.S. power grid doesn’t face the exact risks that led to the collapse of Spain’s and Portugal’s electricity system in April, but its changing resource mix and rising demand create urgent challenges here as well, a U.S. grid security executive told federal regulators Thursday.
Mark Lauby, senior vice president of the North American Electric Reliability Corp., briefed members of the Federal Energy Regulatory Commission on the massive blackout in southwestern Europe as a brutal heat wave across the eastern U.S. pushed power providers to the limit.
In his report, Lauby sought to put an end to finger-pointing about whether the Iberian Peninsula experienced blackouts simply as a result of its reliance on wind power.
“I want to be clear that this is not simply a resource’s fault,” Lauby told FERC commissioners. “People like to point fingers at resources. Rather, it’s an engineering and operational challenge that must be addressed to ensure system conditions are understood and precautions are taken to be ready for system events.”
Lauby didn’t identify who was pointing fingers. But Energy Secretary Chris Wright was one of those who appeared to immediately pin the blackout on Spain’s high percentage of wind power as a warning to the U.S. not to take that path.
“It’s very sad to see what’s happened to Portugal and Spain and so many people there. But you know, when you hitch your wagon to the weather, it’s just a risky endeavor,” Wright told CNBC shortly after the initial blackouts.
FERC Commissioner David Rosner seconded Lauby’s point. “This was not any particular resource’s fault. This was an operational and engineering challenge, or series of challenges,” he said. Failures affected both the region’s wind turbines and conventional fossil fuel plants and were compounded by operator errors.
At the time of the blackout, two-thirds of Spain’s power was coming from wind and solar; nuclear and hydropower added about 10 percent each, and the rest was from fossil fuel generation. A series of disruptions in power flows on the Spanish system that are not fully explained caused high-voltage levels to drop, the Spanish government investigation found. One such disruption may have been improper control settings in a large solar power plant.
Operators responded with measures to dampen the disruptions and restore voltage levels but lost control of the process, Lauby said. One generator shut down, followed by a large loss of other power plants of various types, and the Spanish and Portuguese systems collapsed 27 second after the initial loss.
“It was very quick, and [there was] not much the operators could do,” Lauby said.
A key factor in the loss of control was an obscure but vital factor in power flows over high-voltage lines called reactive power, Lauby explained. The same culprit played a central role in the 2003 Northeast U.S. blackout that cut off power to 50 million people, investigators of that incident found.
Reactive power is created by controlling the relationship between current and voltage, and precise levels must be maintained to allow power to keep flowing.
In Spain’s case, some power plants that were expected to absorb excessive reactive power did not do so. “Not sure why,” Lauby said. Rising voltages caused generators to trip protectively and shut down, putting more stress on the network, pushing systems toward automatic shutdown levels, he added. “It’s kind of a death trap at that point,” he said.
The ability to add or reduce reactive power is a critical component of voltage support and marks a fundamental difference in the U.S. and Spanish systems, he added.
In this country, wind and solar power installations are required to provide dynamic voltage support, but that is not a requirement in Spain, Lauby said. That responsibility is solely with conventional generators, but in the April emergency, some generators failed that mission.
“Most of the conventional generation … with dynamic voltage control did not act as expected,” Lauby said. “By the time control room operators recognized the problem, it was too late,” Lauby said.
Andrew Thompson, a Madrid-based analyst with the Brattle Group consultancy, noted to POLITICO’s E&E News that the investigation showed that some gas, hydro and nuclear plants that are paid for provide voltage control services failed to do so as contracted.
Lauby added, “In hindsight, if operators understood how fragile the system was, they could have planned for additional dynamic voltage support from other plants” and had them standing by. “So, lessons learned.”
But another vital operating issue affecting the U.S. grid has persisted for years and still awaits final resolution, Rosner noted, centered on the ability of solar installations to keep operating during short-term drops in voltage in the surrounding power grid. NERC’s proposal for a new requirement for solar installations to have low-voltage ride-through technology is awaiting a decision at FERC.
“I think it’s absolutely needed,” FERC Chair Mark Christie told reporters following the commission meeting. “It very controversial because people whose ox is gored obviously don’t like it.
“But I have no reason to think that what NERC has proposed is not the proper engineering solution, and that’s what we ought to be supporting,” Christie said.
He did not comment on the status of the proposed regulation as it is still before the commission. “This certainly is an example of the need for better … standards” on this issue, Brattle Group’s Thompson said.
Another recommendation by Spanish authorities resonates for the U.S., said Michael Goggin, vice president of Grid Strategies.
The government’s report urged stronger transmission interconnections with the rest of the European grid system. Had Spain been more interconnected with its neighbors, the initial disturbance would probably have been smaller and more easily contained, noted Goggin, whose firm advocates for a larger, more interconnected U.S. grid to increase competition and resilience.
“It’s so important that we look holistically at all the resources on the grid today and identify whether there are any gaps in our bulk power system reliability standards that would prevent a similar incident from occurring,” Rosner concluded.
“If we don’t do this, it’s just a recipe for failure,” he said.
