Red Eléctrica faces a problem in the voltage control of its lines. The growing integration of renewable energies and the drop in demand is causing high fluctuations in voltage levels which can end up causing blackouts.
The Almaraz II plant (Cáceres) yesterday notified the Nuclear Safety Council of an automatic shutdown of its plant. The event, which occurred while the unit was operating at full power, occurred when the generator voltage regulator returned to automatic mode. A few hours before, said regulator had been switched to manual due to the oscillations recorded in the high voltage network. The drop in voltage in the electric generator caused the turbine protections to trip and automatically stopped the reactor.
Another example of this situation – caused by the level of rainfall – occurred during the DANA in Valencia. The Cofrentes plant had to lower its power before the instability in the network voltage – due to the fall of towers – could cause an automatic shutdown and acted as a sink for the reactive energy that was generated to avoid a blackout.
The National Markets and Competition Commission (CNMC) has put on the table an analysis of the situation of voltage control within the review of network remuneration.
The growing integration of renewables has meant a greater contribution of reactive energy to the system. On the other hand, the drop in consumption has reduced the need to transport active energy through the networks and has caused a lower consumption of reactive energy, which has resulted in an increase in system voltage that leads the regulator to predict scenarios in the short and medium term where this effect may increase.
On the limit
The CNMC explains that the tensions in the transmission network have not suffered significant variations thanks to the application of tension control measures, but highlights that the values have remained at high levels.
For the organism, “at some moments, “The tensions in the transmission network have reached maximum values close to the thresholds allowed by the regulations, even exceeding them at specific times.”.
According to Competition, a plan has been carried out to install reactors in the transportation network, but the use of this resource has reached the point of exhaustion.
The organization chaired by Cani Fernández maintains that the decoupling of lines from the transportation network by voltage control has followed the same trend as the use of reactances, that is, they have remained open for longer in the system, although it explains that has been reduced in recent years by the installation of these locking systems.
Given this diagnosis, the supervisor indicates that in order to keep voltages within the margins, in recent years the application of measures (reactances and opening of lines) has been intensified, so the system “is losing room for action in the face of possible exceptional situations” and indicates that sometimes “It is necessary to connect generation due to technical restrictions due to exhaustion of measures.” It is precisely at this point where nuclear power plants could become a key player in maintaining said voltage control, according to sources in the sector.
The National Markets and Competition Commission has also observed that with respect to tension control service providers, there has been room for improvement.
The agency reveals that in recent years the price signal sent to consumers regarding the penalty for reactive power consumption has led to the installation of capacitor banks that, in many cases, cause overcompensations in reactive power consumption and, Because they remain coupled over time (even during off-peak hours), they have a negative effect on system voltages when there are overvoltage problems.
The most affected would be electro-intensive consumers (steel and railway) whose facilities have capacitor banks that allow them to control the reactive during flat and peak hours, which was encouraged at the time to satisfy the needs of the system, but now they do not have the capacity to disconnect said equipment in the valley period. To avoid the penalty, consumers would have to invest between 120 and 200 million to replace the equipment with others that provide greater flexibility.
The CNMC estimates that demand is responsible for 13% of the reactant discharged into the network and assures that it is the one that is supporting the extra cost of the restrictions to resolve tension problems, which according to the organization’s data reached 370 million euros in 2022.
What is reactive energy and why is it compared to beer foam?
Reactive energy appears in electrical installations when devices are used that need to create magnetic and electric fields for their operation (refrigerator motors, elevators, freezers or transformers). This energy causes loss of useful power in the facilities, overheating of electrical conductors, lower performance of electrical appliances, voltage drops and disturbances in the electrical network, which induces a series of costs that must be transferred to the users who use them. induce, according to the National Markets and Competition Commission.
With the massive installation of renewables, the system today requires as a priority to reduce reactive injection during off-peak hours. Therefore, reactive energy is compared to when we order a beer, we pay for the entire glass, which would be equivalent to the apparent power, but the part we want the most (the beer) is the active power. And the foam, the last thing we want, is the reactive power.
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