| Work Detail |
Some media outlets have speculated that the April 28 blackout in Spain could have been caused by an offline solar plant, but DNV grid analyst Andrea Mansoldo tells pv magazine that it was likely due to a combination of grid weakness and low-frequency oscillations. Several European media outlets have speculated that solar energy may have caused the massive blackout in Spain on April 28, but Spanish Prime Minister Pedro Sánchez stated in a press conference this week that renewable energy was not to blame for the incident. There is speculation that the blackout in Spain could have been due to a solar plant located in the southwest of the country, which apparently disconnected from the grid, Andrea Mansoldo, principal consultant at the Norwegian technical consultancy DNV GL Group, told pv magazine . Mansoldo noted that the facility in question could be the 150 MW Gemasolar solar thermal plant located near Fuentes de Andalucía, in the province of Seville. If 150 MW are suddenly lost from the grid, the grid is able to cope with this easily, he said. ESTC plants, on the other hand, are not intermittent like photovoltaic installations and operate exactly the same as conventional electricity systems. It should also be noted that the Spanish grid operator, Red Eléctrica de España (REE), manages a generation mix with nuclear power plants, and therefore, in the transmission planning criteria, the NG contingency, i.e., also the loss of a nuclear generator, is checked from a safety perspective. This means that adequate resources are also made available to cope with capacity losses much larger than the loss that could have been caused by the disconnection of the 150 MW Gemasolar plant. Mansoldo dismissed speculation that the blackout was due to an excess of renewable energy, stating that restrictions easily resolve these types of problems. The problem arises when you want to increase the share of renewables, not reduce it, he explained. Spain depends on a mix of combined-cycle gas, nuclear energy, and renewables, which is not the best configuration to provide sufficient inertia for the entire system. He argued that losing the entire capacity of a 500 MW solar plant is unlikely, as photovoltaic projects are more reliable than conventional plants. He said that with a 500 MW installation, hundreds of generators would not fail simultaneously unless there was a drastic change in system frequency, away from the nominal 50 Hz in Europe. In this case, circuit breakers will open the main circuit from the grid to prevent damage to the connecting equipment, he explained. To that end, the grid code dictates the rules and thresholds for when this can occur, and protections will be established accordingly. Note that this can apply to solar, wind, hydro, and conventional generators, not just renewables. Mansoldo rejected the other three theories that have circulated in the media in recent days: atmospheric vibration, a cyberattack, and the disconnection of the Spain-France interconnection. “First, the investigation will clarify the sequence of events and the actual causes, effects, and consequences,” he said. “The atmospheric phenomenon hypothesis seems a bit fanciful to me. This type of event occurs under particular humidity conditions that trigger the so-called corona effect on power line conductors, especially high-voltage lines, which increases power losses. Consider that the grid typically has 2% losses, and this atmospheric event can theoretically increase this value to 5%. This additional 3% could create a partial imbalance in Spains 25 GW of load, but the event materializes gradually in the system, regardless of temperature variations, so the capacity margin can compensate for it. However, it is quite unlikely that these high humidity levels will occur across the entire grid at the same time.” He also noted that the load increase from 6 a.m. (CEST) to noon is much more severe, and the grid operator is accustomed to managing these consumption variations. Regarding the cyberattack theory, Mansoldo, along with Antonio Delgado Rigal, CEO of AleaSoft Energy Forecasting, said that REE had already ruled out any modification to the generation plan from an external source. Mansoldo suggested that the loss of the Spain-France interconnector could be a possible triggering event. However, it is a contingency included in the TPC (Transmission Power Controller), and REE is involved in both the planning and operation of these types of contingencies and studies the appropriate corrective measures to ensure the system is resilient, he said. In this case, everything depends on the actual scenario used in the case study, and in specific situations with a high percentage of renewables and grid weaknesses, fluctuations can be exacerbated, generating conditions that lead to generation disconnection. This means that if the safety parameters dictated in the grid code are exceeded, this can occur with any type of generation technology. The main problem behind the blackout, according to Mansoldo, is that the Spanish electricity system was operating under unusual conditions, with a high penetration of renewables in a large interconnected grid, which can be prone to low-frequency oscillations unless properly damped. The superposition of this behavior with some generation contingencies can exacerbate frequency oscillation, generating widespread generation disconnection conditions, increasing generation and load imbalances, and causing system collapse, he said. In this case, the interconnection disconnection of the ENTSO-E transmission system is triggered to prevent the collapse from spreading throughout the Eurozone. Most utilities have already undertaken activities to counteract the consequences of renewable energy deployment in terms of maintaining a robust transmission system, at least during transient events. Mansoldo said that Statcom, E-Statcom, and synchronous capacitor technologies are gaining attention as potential solutions to provide inertia to power grids during transients and prevent fluctuations like those observed in Spain. The Italian grid operator, Terna, currently uses 28 synchronous condensers for central and southern Italy, explains Mansoldo. This seems to work quite well when it comes to handling large fluctuations. We need to wait for a proper investigation, which, by examining the information recorded before and after the event, can help engineers define the root cause, explain the consequences, and suggest possible mitigations, Mansoldo added. This will confirm whether the outage was caused by solar power, an interconnector disconnection, abnormal system behavior, or superimposed contingencies. Overall, it must be said that once again the transmission system proved to be the elephant in the room, that there can be no transition without proper transmission system planning and operation, Mansoldo concluded. This suggests avoiding words like acceleration, rapid, and speedy within energy transition implementation processes, as haste can be bad advice and slow down the process of allowing for a detailed, step-by-step approach to understanding transmission planning and the operation of the future energy system. |
