Due to its geographical characteristics, Spain has more than ten electricity systems. The largest of these is the Peninsular grid, through which more than 200 gigawatt hours flow annually. There are also the power systems of the islands of La Palma, El Hierro, La Gomera, Tenerife, and Gran Canaria, the connections between Fuerteventura and Lanzarote, and the autonomous cities of Ceuta and Melilla. Although the unified Balearic system has been connected to the Peninsula since 2012, it remains somewhat isolated.
This Monday, an outage occurred on the Peninsula, which, according to Red Eléctrica Española, supplies approximately 94% of Spain’s electricity needs. Beatriz Corredor, President of Red Eléctrica, described the system as the “best” in Europe despite Monday’s incidents because it relies on a diverse energy mix.
Together with thermal power plants (coal, combined cycle, and fuel/gas) and nuclear power plants, the system has an installed capacity of approximately 50,000 megawatts. An additional 45,000 megawatts comes from renewable energy sources such as wind, hydro, photovoltaics, solar thermal, renewable heat, combined cycle power plants, cogeneration, waste, turbines, and pumps.
The system is also interconnected with France, Portugal, Andorra, and Morocco. These international connections were crucial in resolving the major blackout and restoring light to households. However, only a limited amount of electrical energy is available; Morocco’s capacity is only 1,400 megawatts, while the French connection has nearly 3,000 megawatts. The French government systematically refuses to increase the flow of electricity, even though work is underway on a submarine cable in the Bay of Biscay to achieve a capacity of 5,000 megawatts.
In total, Spain’s installed capacity exceeds 130,000 megawatts. However, this theoretical maximum generation capacity is never fully utilized, as it is generally not required. During peak consumption, the output only reaches 40,000 to 45,000 megawatts.
The entire system is interconnected via an electricity transmission network. There are more than 34,500 kilometers of high-voltage lines, including medium- and low-voltage distribution lines. The total length of these lines exceeds 600,000 kilometers.
The high-voltage lines and over 400 transformer stations belong to Red Eléctrica, while the medium- and low-voltage lines are owned by various electricity companies that supply electricity to businesses, organizations, and households.
Cecoel: The Monitoring Center
The Electric Control Center (Cecoel), based in Madrid, is responsible for the operation and coordinated real-time monitoring of the national electricity system’s generation and transmission facilities. The goal is to maintain a constant balance between the energy demand and the energy produced. For this purpose, Cecoel continuously receives, analyzes, and processes approximately 240,000 pieces of data.
Cecoel receives real-time information about facilities not owned by Red Eléctrica from control centers set up to transmit telemetry data in real time. It also continuously monitors the status of the network and its individual components, as well as their electrical parameters. This is done via a telecommunications network that acts on control variables to ensure the security and quality of supply.
The system controls and manages demand fluctuations and unavailability situations at the generating plants. This is done according to redundancy criteria: if one line or plant fails, others immediately take over the load, ensuring backup generators are always available.
SCADA and Cyberattacks
SCADA (Supervisory Control and Data Acquisition) systems are used to regulate electrical flow. These systems allow substations to be controlled, the distribution of electrical flow to be monitored, and automated measures to be taken. A potential cyberattack could have been directed against the SCADA system.
As we all learned this week, the network must always be in balance; supply must be proportional to demand. Since electricity cannot be stored in large quantities, everything happens in real time. Red Eléctrica’s main function is to “ensure a constant balance between the energy required (demand) and the energy produced (generation), in order to deliver the required amount of energy where and when it is needed.” This process occurs continuously, adjusting production in tenths of a second.
“This means that in Spain, the same amount of energy must be produced every tenth of a second as consumed,” explains Marcos Rupérez, Professor at the OBS Business School. For example, if we turn off the light in the living room, a Spanish plant immediately reduces production output and synchronizes all generation and consumption sources. “It’s an extremely critical and unstable system where everything can collapse in a matter of seconds if something fails,” the expert adds.
To understand Monday’s historic power outage, it’s important to understand how alternating current flows through the power grid works. This current oscillates, meaning it doesn’t move in one direction but oscillates at a frequency of 50 times per second. Rupérez explains that it’s a wave that moves in opposite directions 50 times per second. This value must be stable and synchronized throughout the national grid. “In other words, all generation plants must not only operate at these 50 hertz, but they must also do so synchronously, like a large orchestra playing without delays,” he explains.
Imbalance between generation and consumption
What happens when there is an imbalance between energy supply and demand? If the grid cannot react in time to correct the frequency deviation, a chain event occurs in which all control panels shut down.
That’s exactly what happened. If the frequency drops below 50 hertz, wind farms and solar power plants are automatically shut down; combined-cycle and nuclear power plants also shut down for safety reasons. “The grid shows 0 MW synchronized because it is not possible to maintain the common voltage,” writes Gonzalo García in “Hybrids and Electrics.”
Rupérez explains that this happened because most generation plants are ordered to shut down if the frequency deviates too much from 50 hertz. This is a safety measure. The entire grid, both generation and consumption, is designed for this frequency. “Basically, what happened is that there was an area where the grid frequency was destabilized because an event that is still being investigated spread throughout the grid and led to a collapse,” says Rupérez.
Unstable Renewables and Necessary Upgrades
Current renewable energy sources (photovoltaics and wind) are considered unstable and accounted for 70% of generation at the time of the blackout. Only a few sources, such as nuclear, gas, and hydroelectric power plants, ensured frequency stability. When the local outage occurred, the grid was unable to maintain the frequency, causing the fault to spread and a large part of the grid to collapse.
“Photovoltaics is the technology least capable of providing stability to the grid when there are imbalances between generation and demand,” explains engineer Manuel Moral, professor of the Master’s degree in Renewable Energy Transition at the European University. “It has the least capacity to respond to such fluctuations and ensure stability,” he adds.
Although renewable energies do not currently contribute to grid stabilization, there are technologies such as grid formation that could make this possible. Antonio Turiel, a doctor of theoretical physics at the Autonomous University of Madrid and a researcher at the CSIC, argues that electricity companies are unwilling to invest in modernizing the transmission grid. “This was not implemented because it was more cost-effective to operate grids without stabilization systems.” Turiel also points out that the power outage would have been less severe if the combined cycle power plants (which were idle) had been operating. These were stopped because the electricity companies suffered losses due to negative prices.
