A widespread blackout like the one that plunged Spain and Portugal into darkness this spring is unlikely to happen in the U.S., according to a leading grid reliability expert. The U.S. electrical grid is better prepared than Spain to handle surges in voltage that caused the blackout.
Mark Lauby, senior vice president of the North American Electric Reliability Corp., briefed federal regulators Thursday, June 26, on the April blackout that cut power to the entire Iberian Peninsula for up to 18 hours. The collapse happened in just 27 seconds after a series of power failures. The cause of the failure has been hotly contested, but U.S. officials agreed with Spain’s determination that renewable energy was not to blame.
The blackout was the result of a cascading “engineering and operations challenge,” Lauby said, involving the failure “to manage the grid’s static and dynamic voltage.” But when it comes to U.S. vulnerability to a similar crisis, Lauby declared, “It appears that we’re on the right track.”
The Spain blackout ignited a debate over the future of electric grids, which resources should be prioritized and how the system can be managed to keep the lights on. As the U.S. faces surging electricity demand, U.S. regulators are looking to learn from the European failure.
How does the electric grid maintain stability?
Electric grid operators need to maintain a delicate balance of frequency and voltage, otherwise critical equipment can be damaged. The frequency is the rate at which electric current changes direction in an alternating current (AC) system. Whereas voltage is more like the pressure or force utilized to move those electrons through the current.
If the voltage becomes too high, it can damage or even fry electrical equipment. If voltage is too low, the system cannot deliver sufficient power to meet demand.
The electrical grid is built to run at a frequency of 60 hertz, which is maintained by balancing electricity supply and demand. Traditional power plants are big spinning machines, so they have a natural inertia that can absorb slight changes in the frequency. However, wind, solar power, and batteries – sometimes referred to as inverter-based resources – do not possess the same natural inertia to absorb frequency fluctuations.
In the initial aftermath of the Spain blackout, there was widespread speculation that renewable energy, with its lack of natural inertia, was responsible for plunging the country into darkness. Spain’s grid is powered by 60% renewable energy, and critics have argued that this makes it vulnerable to blackouts because it lacks sufficient inertia.
Some questions still remain around the blackout, and a larger European electric reliability organization is conducting its own investigation into the incident. However, a report published by the regional grid operator suggests that while frequency played a role, the main problem was a failure to manage voltage spikes.
What caused Spain’s grid to collapse so quickly?
According to a report from Red Eléctrica, the county’s grid operator, Spain’s problems began with frequency oscillations between the Spanish and Portuguese grids around noon on April 28. Grid operators successfully dampened the shift in frequency by reducing how much power was exported to neighboring France and turning on an additional transmission line. But these corrective measures to manage frequency caused voltage to increase.
When high voltage is detected, substations can automatically trip offline to avoid equipment damage. One substation went offline, and with it, the grid lost 355 megawatts of generation. Seconds later, another 1.5 gigawatts of wind and solar installations disconnected from the grid to avoid damage from high voltage.
As the Red Eléctrica report puts it, ”with each generation disconnection, the system voltage increased and this in turn caused the disconnection of additional generation,” until the entire Iberian Peninsula and part of southern France went dark.
In Spain, traditional power plants are supposed to help manage voltage fluctuations. In his report to U.S. Federal Energy Regulatory Commission members, Lauby said those power plants failed to provide adequate voltage control when needed most.
“Most of the conventional generation with dynamic voltage control did not act as expected,” he said.
After reviewing Lauby’s presentation, FERC commissioner David Rosner concluded, “This was not any particular resource’s fault.”
How does the US grid differ from Spain’s system?
American grid operators already require both conventional power plants and renewable energy installations to help control voltage, a crucial difference from Spanish regulations. In Spain, laws governing the electric grid dictated that traditional power plants were responsible for voltage control, but many failed during the emergency.
The U.S. also has continuous monitoring of voltage levels on the grid and requirements for power plants and inverter-based resources to keep their voltage control equipment updated. This enhanced monitoring and requirements are one of the primary reasons that regulators are not too worried about a similar crisis afflicting the North American grid.
Lauby highlighted another advantage being deployed on the grid: synchronous condensers. These are spinning machines that can be installed at strategic locations on the grid to help control unexpected voltage fluctuations. As an added benefit, synchronous condensers have their own inertia that can dampen changes in frequency.
Lauby also pointed to the proliferation of grid-scale batteries in parts of the U.S. – something that has not caught on to the same degree in Spain. Batteries also help manage changes in the frequency and voltage of the grid because they can release or absorb power at a moment’s notice.
