Resiliency of Power Systems to Black Swan Hazards: How Ready Are We?

More frequent extreme-weather events are causing widespread power blackouts

26 October 2018

The electric power grid has been called one of the greatest inventions ever made. However, as perfect as it may be, it is still subject to operational interruptions due to the unpredictable randomness in the natural world. Even though the rapid development of science, technology, and engineering have made the interruptions relatively rare, they still occur, often with disastrous results. The most significant outcome of natural disasters is a blackout due to a complete system shutdown known as “Black Swan” events. These adversely can impact communities for an extended period of time—from days and weeks to months.  

The chair of IEEE Smart Grid, Pete Wung, and the editor in chief of the monthly IEEE Smart Grid eNewsletter, Panos Moutis, offer this excerpt of an article written by an international group of scholars from Chile, the United Kingdom, and Australia. It focuses on the dire hazards of these Black Swan events, and how current technical expertise and technology could effectively predict and resolve the disastrous results through novel smart grid programs and applications. The original article was published in the September edition of the IEEE Smart Grid eNewsletter, “A Special Issue on Grid Resiliency in Smart Grid,” and can be found in the IEEE Smart Grid Resource Center.

The catastrophic impacts of natural hazards and extreme-weather events are happening worldwide. Several events in Europe this year severely affected electrical power systems and other critical infrastructures, including severe wildfires in the Mediterranean region of Greece. There were flash floods in France and other countries, while severe droughts and heat waves affected all of Europe, creating heavy demand on the electricity system. During the last week of June, for example, high temperatures in the United Kingdom resulted in an increase of 860 megawatts in demand, the equivalent of an additional 2.5 million households.

Some people say that the extreme-weather events are due to climate change and that, as such, their severity and frequency will increase. For some countries—like Chile, which experiences more than 450 earthquakes each year measuring at least 4.5 on the Moment magnitude scale (4.5Mw)—we may have to think twice before we characterize such events as high-impact and low-probability (or frequency).

It is becoming more critical than ever to consider widespread blackouts—known as black swans because of their rarity—in the operational and reinforcement planning of power systems. The assessment and planning tools that we use, however, might be unable to deal with the new challenges.

RESILIENCY

Motivated by real-world experiences and considerations, we conducted joint research work that has provided advanced tools for assessing and mitigating the impact of disastrous events on power systems. These tools  go beyond the traditional N-1/N-2 security assessment, which is key when analyzing the impact of events that could result in the simultaneous loss of multiple assets, possibly in a short period. These tools have been effectively and consistently used to assess the impact of windstorms and floods on Great Britain’s transmission network, as well as the impact of earthquakes on the Chilean transmission network.

Our work has also highlighted the need for suitable resiliency metric systems, for example, based on the so-called multiphase resiliency trapezoid. The trapezoid describes the phases where a power system might be during a disturbance: disturbance progression, post-disturbance degraded state, and restorative state. By using these metric systems, bottlenecks in the response and recovery of a power system can be identified and the effectiveness of different resiliency strategies can be compared. Overall, the results clearly demonstrate that the use of traditional reliability indices in such studies—which do not take into proper account risk considerations—can significantly underestimate the severity of the problem.

The “resiliency trilemma” therefore arises as to whether the electrical infrastructure should be made bigger, stronger, or smarter. In fact, in many instances it may be more efficient to have a smarter and more responsive strategy to accelerate the recovery of the system rather than the “traditional” solution of making the system bigger (more redundant).

That has been shown in case studies in Chile through a risk-based planning approach, subject to budget constraints, which minimizes risk exposure to large earthquakes, those measuring above 7Mw. The results indicate that an optimal planning portfolio should consider a wide range of investments including new transmission lines (to provide redundancy), substation reinforcement (to provide robustness), and an array of distributed energy resources organized in microgrids (to provide rapid restoration to critical zones in the system).

FLEXIBILITY

Indeed, a more risk-based planning approach would naturally recommend a diversified set of measures that would allow network operators to deal with unforeseen events, better adapting power system operation to the remaining power infrastructure resulting from extreme events. In this outlook, our results also suggest that flexible transmission systems such as flexible alternating-current transmission and high-voltage direct-current transmission technologies can better manage and reroute power flows after a catastrophic event occur. Using the remaining power infrastructure more efficiently can improve the network’s resiliency.

However, how ready is the power engineering industry in making the shift from the traditional reliability-oriented paradigm to a more resiliency-oriented, risk-based engineering one? The need for this shift is becoming even more critical considering significant changes and uncertainties in the power systems landscape, such as the increasing penetration of intermittent renewable sources as demonstrated in the South Australia blackout of September 2016.

THE FUTURE

There is clearly still a lot to do, and building a resilient electrical power infrastructure is a daunting task that involves technical and commercial considerations. Regulation and market mechanisms should, in fact, be in place to incentivize the power industry to consider resiliency issues in its long-term planning, as well as to enable emerging technologies and maximize their use.

Yes, there are challenges to overcome with many of the technologies, but there are also benefits that are still to be fully exploited.

The road map toward resilient power systems should be a collective effort by all the key actors—from the increasingly active end users and distribution system operators all the way up to regulators and policymakers.

Mathaios Panteli is a lecturer in power systems at the University of Manchester’s School of Electrical and Electronic Engineering, in the United Kingdom.

Rodrigo Moreno is an assistant professor at the Universidad de Chile’s electrical engineering department, in Santiago, and a research associate at the Imperial College London’s electrical and electronic engineering department in the United Kingdom.

Pierluigi Mancarella is the chair professor of electrical power systems at the University of Melbourne, Australia, and part-time professor of smart energy systems at the University of Manchester in the United Kingdom.

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