April 10, 2025

Experts discuss the causes behind large-scale power outages, the existing gaps to prevent them, and, if they occur, how to quickly restore electricity.

Multiple emotional states ran through the eight million Chileans who, on February 25, starting at 3:16 p.m., were affected by an unexpected and widespread power outage—both in terms of surface (from the regions of Arica and Parinacota to Los Lagos) and time (about 8 hours on average for most users).

What caused it? An alleged failure in the Nueva Maitencillo–Nueva Pan de Azúcar transmission line, operated by ISA Interchile. To clarify the situation, the National Electric Coordinator (CEN) requested the U.S.-based consultancy Electric Power Research Institute (EPRI) to conduct an independent technical study. At the same time, the role of Transelec in the slow service recovery is being investigated.

Regarding potential failures that can trigger events of this magnitude, Christian Scholz, Director of Development at Energie, states that in general, “they are very few, since the electrical system is designed and built with redundancies to guarantee its stability. However, to preserve operational safety, it is essential to apply proper security criteria, which are defined in current technical standards and regulations.”

On this point, Daniel Olivares, Director of the Civil Engineering in Energy program at the School of Engineering and Sciences of Universidad Adolfo Ibáñez, explains that Chile’s National Electric System (SEN), like many others worldwide, applies a security criterion known as N-1.

“This means the system must be operated so that a single failure (e.g., a generation unit or a transmission circuit) should not trigger a cascading shutdown of other SEN elements or interrupt the supply to customers. Consequently, failures that involve the loss of two or more elements, depending on their criticality, could lead to power outages and eventually partial or total blackouts.”

He adds that the Technical Standard for Security and Service Quality establishes a classification for failure severity, identifying a set of extreme contingencies for which the CEN could resort to special measures such as system segmentation into islands and partial load shedding. These actions are part of the Defense Plan Against Extreme Contingencies (PDCE), aimed at avoiding a total blackout.

Lessons and gaps

Offering a different perspective, Javier Bustos, Executive Director of the Association of Electric Customers (Acenor), points out that events like this one “highlight the effects that a failure of such magnitude has on customers. We estimate the country’s loss at nearly 500 million dollars, since many industries were unable to resume normal production even 24 or 48 hours after power was restored.”

He also notes that the massive outage exposed the fact that electric customers have been paying “more than 3 million dollars a year for infrastructure meant for extreme contingencies and service restoration. These payments should be reviewed if it is found that the paid service was not adequately provided.”

According to Acenor’s representative, “free market customers can identify their critical energy uses and evaluate options for self-generation and storage in the event of system failure, and also to reduce consumption during peak hours or manage demand efficiently.”

To prevent unexpected events like the February 25 blackout and their consequences, “it is necessary to focus on test exercises, technical visits, audits, and to enforce oversight of the facilities providing services for contingency management and service recovery. It is unacceptable that, when a failure like this occurs, the SCADA, phone center, and backups of key system facilities do not work.”

He also makes it clear that “there is no evidence that this failure and its propagation would have been prevented with more transmission lines in operation. Before thinking about more infrastructure, it’s necessary to evaluate how the contingency and recovery plans functioned, as well as the actions taken by the CEN.”

To temper expectations, Olivares clarifies that “no electrical system is completely immune to widespread or total blackouts. Statistically, there will always be low-probability, high-impact failures for which it is economically inefficient to prepare, and the rational decision is to let them occur. Their occurrence is uncertain and difficult to predict by nature, but it is not expected that they happen more frequently than once every two decades—if they do, we have a problem.”

Nonetheless, he specifies that the recent total blackout of the SEN exposed several important gaps:

  1. Excessive delays in the system’s ability to meet regulatory compliance, specifically regarding the implementation of the PDCE, which could have prevented the blackout.

  2. Lax application of established procedures, possibly pointing to weaknesses in staff training.

  3. Issues related to the role that distributed energy resources, such as PMGD plants, could play—not worsening, and potentially supporting—the system’s stability during extreme contingencies.

For Scholz, anticipating failures is extremely complex and relies on advanced technologies, such as control systems at power plants and protection equipment. “However, these phenomena occur in just milliseconds, so it is important that the studies conducted consider all possible scenarios that may arise during operations, to anticipate potential situations and preserve system security,” he adds.

Control and communications

Daniel Olivares reveals that the last major blackout also exposed technological gaps related to the availability of control and communications infrastructure, “which is critical for executing the service recovery plan following a total blackout. There are also significant communication gaps with the general population.”

“We must move forward as a country in incorporating mechanisms that allow grid support services to also be provided by renewable technologies, so the system’s evolution contributes positively to its security,” says Christian Scholz, Director of Development at Energie.

These gaps should be addressed by incorporating minimum information requirements for users and competent authorities from the CEN in blackout situations. These, perhaps, should be similar to those applied during natural disasters via the Emergency Alert System.

Also focusing on electricity service recovery post-blackout, the Energie executive notes that recovery plans “are refined, with clear instructions and defined maneuvers. However, they depend on certain resources, such as the ignition of specific power plants, smooth communication, and visibility of grid status, among others. These are key elements that must be properly tested and maintained in order to rely on them at all times.”