Future Modern Distribution Networks Resilience: From Passive Operation to Strategic Active Paradigms

By Mohammadreza Daneshvar and Behnam Mohammadi-Ivatloo

Future Modern Distribution Networks Resilience examines the combined impact of low-probability and high-impact events on modern distribution systems’ resilience. Using practical guidance, the book provides comprehensive approaches for improving energy systems’ resilience by utilizing infrastructure and operational strategies.

Divided in three parts, Part One provides a conceptual introduction and review of power system resilience, including topics such as risk and vulnerability assessment in power systems, resilience metrics, and power systems operation and planning. Part Two discusses modelling of vulnerability and resilience evaluation indices and cost-benefit analysis. Part Three reviews infrastructure and operational strategies to improve power system resilience, including robust grid hardening strategies, mobile energy storage and electric vehicles, and networked microgrids and renewable energy resources.

With a strong focus on economic results and cost-effectives, Future Modern Distribution Networks Resilience is a practical reference for students, researchers and engineers interested in power engineering, energy systems, and renewable energy.

• Reviews related concepts to active distribution systems resilience before, during, and after a sudden disaster
• Presents analysis of risk and vulnerability for reliable evaluation, sustainable operation, and accurate planning of energy grids against low-probability and high-impact events
• Highlights applications of practical metrics for resilience assessment of future energy networks
• Provides guidance for the development of cost-effective resilient techniques for reducing the vulnerability of electrical grids to severe disasters

• Language: English
• Publisher: Elsevier Science
• Release date: Feb 23, 2024
• ISBN: 9780443160875

Book preview

Chapter 1: Introduction and literature review of resilience concept in power systems

Ghazal Rahmani-Sane¹,², Sasan Azad¹,², Kamran Jalilpoor¹,², and Mohammad Taghi Ameli¹,²     ¹Department of Electrical Engineering, Shahid Beheshti University, Tehran, Iran     ²Electrical Networks Research Institute, Shahid Beheshti University, Tehran, Iran

Abstract

The influence of electricity on various aspects of daily routine, including commercial enterprises, healthcare providers, and residential complexes, is profound. Nonetheless, significant power outages across the globe have disrupted society's regular operation, particularly while the world is experiencing increasing reliance on secure, imperishable, and cost-effective energy sources. The vast and complex networks spanning continents are even susceptible to far-reaching consequences from local events. Furthermore, the projected 48% increase in global energy consumption by the year 2040 will place additional strain on aging power grids worldwide. Subsequently, the existing infrastructure has been forced to perform at higher levels, rendering the entire power system and its underlying components more vulnerable to deliberate cyber-physical attacks and unplanned natural hazards. Thus, this chapter presents a detailed exposition of the definition and concept of power system resilience, providing valuable insights and perspectives to inform further research, policy formulation, and implementation in the energy sector.

Keywords

Extreme events; Power system resilience; Resilience curve; Resilience measures

1.1 Introduction

1.2 Resilience in power systems and its importance

1.3 Understanding resilience

1.4 Resilience curve

1.4.1 Resilience triangle

1.4.2 Resilience trapezoid

1.5 Resilience measures

1.5.1 Short-term resilience measures

1.5.2 Long-term resilience measures

1.6 Taxonomy of strategies employed for enhancement of power systems' resilience

1.6.1 Preevent preparation

1.6.2 Corrective actions and emergency response

1.6.3 Restoration actions

1.7 Conclusion

References

1.1. Introduction

The power systems are the fundamental framework of the national economy and infrastructure. Reliable power availability plays a pivotal role in determining the nation's strength, as it directly impacts daily operations and other critical national infrastructures [1]. The global operation and planning of distribution network infrastructures are subordinated to sufficiency and security reliability principles. These fundamental principles ensure that distribution networks can operate safely against common threats, providing consumers with high-quality supply and minimal interruptions. However, additional considerations are essential beyond the classical reliability to maintain a continuous power supply [2].

Infrequent natural catastrophes and purposeful assaults threaten power systems' security and operational stability. As an integral component of vital infrastructure, the power system is susceptible to severe weather phenomena, including inundations, earthquakes, storms, snow, and human-related elements that may lead to line or equipment failures and impact public welfare. In the past few years, nature-induced disasters like the 2019 Typhoon Lekima have caused power disruptions, impacting around 6 million individuals in China. In the same year, Typhoon Faxai inflicted significant harm to transmission cables and towers in Japan, depriving nearly 1 million consumers of electrical power [3]. In 2021, Texas experienced a profound electricity emergency caused by an unprecedented ice storm [4]. The ice accumulation within the natural gas transmission pipeline and the icing of wind turbine blades led to the cessation of 18,000MW of power generation.

On the other hand, Recent cyber-attacks launched on power grids have exhibited a marked escalation in terms of their intricacy and refinement. The Ukraine cyber-attack is an example that occurred on December 23, 2015 [5]. It was one of the most notable and widely reported cyber-attacks targeting critical infrastructure, leaving 225,000 customers without electricity for several hours. Consequently, it has become imperative to ensure that specific vital loads remain functional despite unforeseen circumstances, particularly within military or critical microgrid contexts [6]. At this particular time, the power system should have adequate flexibility to adapt to grave disturbances while maintaining its full functionality; it should promptly restore itself after resolving the disturbance. This crucial characteristic of the behavior of infrastructure systems in power grids is known as resilience [7]. A resilient power system can anticipate, respond quickly, recover promptly from shocks, reduce their duration, or provide alternative means of meeting energy service needs with minimum vulnerability against changed external events. The quantitative evaluation of infrastructure resilience in a given scenario can be achieved by analyzing resilience curves, which depict the progression of system performance over time [8]. Given that resilience encompasses short-term and long-term measures, it offers a comprehensive approach to address immediate shocks and sustained disruptions. Short-term resilience measures concentrate on swift reaction, ensuring prompt recovery, and reducing the immediate impact of an event. Conversely, long-term resilience measures involve strategic planning, infrastructure enhancements, and adaptive approaches to bolster the system's ability to withstand and adjust to future risks. By integrating both short-term and long-term perspectives, resilience emerges as a dynamic and proactive approach that promotes preparedness, response, recovery, and adaptation amid evolving threats and uncertainties. It enables systems and organizations to rebound from disruptions and learn, evolve, and become more flexible over time.

The study of resilience concepts and definitions in power systems has garnered considerable attention in recent years, reflecting the increasing recognition of the need to enhance the reliability and adaptability of these critical infrastructures. Several notable works have contributed significantly to understanding resilience in power systems. For instance, Ref. [9] comprehensively analyzes grid resilience and reliability, focusing on emerging electric infrastructure. Reference [10] reviews measures for enhancing power system resilience, categorizing them into resilience-based planning, response, and restoration. It explores commonly used approaches, methods, and techniques in each category, discusses challenges in the context of high renewable energy penetration, and identifies future trends for improving resilience. Reference [11] addresses the need to quantify the impact of disruptive events on power system performance and proposes resilience metrics for evaluation. It reviews quantitative power system resilience metrics using a standardized framework, categorizing them and identifying specifications. A research gap is evident in the current literature, where more attention should be given to the specific discussion and analysis of resilience definitions, the resilience curve, and the underlying conceptual framework. While studies have touched upon these aspects to some extent, a comprehensive examination and synthesis of these critical components need to be improved, highlighting the necessity for future research to delve deeper into refining and clarifying the understanding of resilience in various domains. Hence, this chapter aims to fill the existing research gap and provide valuable insights for researchers, practitioners, and policymakers in effectively fostering resilience in diverse domains. The findings of this study have the potential to contribute to more informed decision-making, improved system design, and the development of proactive strategies to enhance resilience and ensure the reliable functioning of critical systems in the face of future challenges.

This chapter will analyze the factors that contribute to power outages on a global scale at first. Then presents a comprehensive overview and introduction to the resilience concept of power systems and the importance of constructing resilient infrastructure to ensure the continuous supply of electricity to end-users even in the face of disruptions. The significant differences between resilience and reliability concepts will be discussed, and studying and comprehending the resilience curve, which is a representation of various stages of resilience throughout a disaster, will ultimately lead to the completion of the resilience definition with the ultimate goal of facilitating future research endeavors in this domain.

1.2. Resilience in power systems and its importance

Power systems are of remarkable significance for social production and economic development. It is imperative that these systems are not only reliable during normal weather conditions but also resilient against extreme weather events since the power system is designed to effectively cope with low-probability high-risk (HILP) occurrences such as natural calamities and cyber-attacks. A few examples of HILPs that can affect power infrastructure are the Tohoku Earthquake in Japan and Hurricanes Katrina and Sandy in the United States [12]. Another significant example pertains to the deluge in Queensland, which resulted in substantial destruction to poles, substations, transformers, and even overhead wires. Consequently, approximately 150,000 customers were subjected to power outages. The adverse impact of extreme weather events on the power system is undeniable; Although the probability of such events occurring may be low, their consequences are severe enough to warrant the implementation of preventive measures to minimize their effects.

Based on an examination of 140 instances of power outages from previous years, it was found that nearly half (47.86%) of these incidents were attributed to equipment failures or internal factors within the power system. The remaining outages were primarily caused by natural disasters, which accounted for approximately 30.71% of the total occurrences. Malfunctions, vandalism, supply shortages, and cyber-attacks are other causes, as shown in Fig. 1.1. It is of significance to note that the power system is directly impacted by said events through the occurrence of multiple transmission line outages, which may subsequently lead to voltage violation or load loss [13].

• Natural disasters: As shown in Fig. 1.1, the weather is the primary factor responsible for power outages. There has been an observable upsurge in the prevalence of severe incidents transpiring across the globe. The operational dependability and robustness of the entire power infrastructure, comprising electrical components, have been significantly impacted by extreme events, including ice disasters, wildfires, or floods. Ice storms, as one of natural disasters, are classified as rare meteorological phenomena that can have severe repercussions despite their infrequent occurrence. That necessitates the implementation of preventive measures to alleviate their impact. For instance, the ice disaster in Southern China in 2008 caused extensive damage to power grid equipment and disrupted power supplies in certain regions. This event impaired over 36,000 transmission lines and affected approximately 27 million individuals [14]. On the other hand, other natural disasters such as wildfires, hurricanes, or light Strikes may significantly impact transmission lines, manifesting in various ways, especially short-circuit faults (SCF). Notably, large fires can inflict damage on transmission towers and poles, particularly those made of wood, resulting in the complete collapse of the line. Furthermore, the smoke, soot particles, and ions emitted during such fires can diminish the electric strength of insulation strings insulating conductors from both tower structures and the surrounding air, an insulating medium between said conductors. This phenomenon has the potential to result in insulation failure and subsequent flashovers, either between the conductors and the tower structure or among the conductors themselves [15,16]. Ultimately, in contrast to the previous meteorological events, precipitation, and inundation do not inflict harm upon aerial transmission lines but profoundly impact substation apparatus.

Figure 1.1  Factors responsible for power outages that occurred globally in previous years.

• Equipment failure: Power systems are complex networks that use various equipment, such as transformers, generators, and transmission lines, to function effectively. When any of these components fail, it can cause significant disruptions to the power supply, leading to blackouts and other related issues. Therefore, it is essential to have effective maintenance strategies in place to prevent equipment failure. Additionally, having backup systems and redundancy measures can help mitigate the impact of equipment failure on power systems.

• Cyber-attacks: Although the digital devices in the power grid have indisputable benefits, they concurrently introduce potential cyber vulnerabilities in the smart grid. The exploitation of said vulnerabilities could lead to deleterious impacts on the overall performance of the grid, as malicious actors would be able to exert disruptive influence [6]. Safeguarding organizational assets against malevolent attacks is crucial to achieving business continuity objectives. The majority of organizations are cognizant of security threats and have devoted considerable resources to formulating a security strategy. This strategy delineates the technology, policies, personnel, and procedures necessary to address security breaches. Nevertheless, cyber incidents persistently escalate, and assailants frequently devise novel methods to inflict harm. Given the arduousness of preventing cyber-attacks, emphasis should be placed on promptly responding to and recuperating from such attacks. The cyber-resilient approach must be predicated on the latest threats and necessitates continuous enhancement [17].

• Vandalism: A notable consequence of an infrastructure that experiences a partial collapse is power outages, which can ultimately result in financial losses for manufacturers and other parties involved. The collapse of the distribution system is typically linked to the actions of vandals who may have a vested interest in steel tower angle bars, earth wires, nuts, and other crucial elements on the pylon. These pylons are commonly situated away from human habitations and are primarily found in fields. These vandals are commonly enticed by the prospect of accessing copper wires and transformer oil, which is applied in various market contexts. This issue remains pervasive in developing nations [18].

• Supply shortage: The supply insufficiency in power systems alludes to an occasion whereby the demand for electrical energy surpasses the obtainable supply. This prevailing circumstance can be attributable to a plethora of factors ranging from demographic upsurge to industrialization and the prevalence of severe meteorological conditions along with insufficient investment in the infrastructure associated with power. In the advent of a supply shortfall, adverse ramifications such as power outages, blackouts, and brownouts may ensue with deleterious economic and societal implications.

Moreover, what if it were possible to enhance the sustainability of the power system without incurring additional maintenance costs? The importance of resilience in power infrastructure cannot be underrated since disruptions to power systems may lead to severe consequences, ranging from inconvenience and economic losses to life-threatening situations. For example, massive power outages can lead to food spoilage, loss of heating or cooling in extreme weather conditions, and disruption of medical services. Resilient power infrastructure can help mitigate these risks by providing backup systems that can kick in during emergencies or by implementing measures that prevent disruptions from occurring in the first place. This may include redundant systems, backup generators, smart grid technologies that enable rapid response to outages, and robust maintenance procedures. In addition to reducing risks associated with disruptions, resilient power infrastructure also has broader benefits for society. For example, it can support the transition toward renewable energy sources by enabling more efficient integration of intermittent sources such as solar and wind power into the grid. While a solution that achieves these objectives may seem captivating, the path toward a more robust infrastructure is fraught with obstacles. The implementation of innovative technologies that have been demonstrated to prolong the lifespan of designs could result in unfavorable financial and environmental outcomes. To transition away from outdated and expensive design approaches, it is imperative that we first establish a clear definition of resilience.

1.3. Understanding resilience

Numerous scholars have tried to provide a clear definition of the power system's resilience, but a standardized definition has not yet been established. Resilience derives from the Latin word resilio, and Holling in 1973 CS. first defined it as system persistence and the capability of the system to absorb disturbances and changes while preserving its initiate state [19]. Jaeseok Choi et al. in Ref. [12] defined the resilience of a power system as the ability of the power system to promptly return to its original state from external shocks, including natural calamities that are rare but impactful. An alternative definition is based on [6], in which power system resilience refers to the ability of the system to continue providing energy to critical loads despite adverse events. Jason Bird, Florida resilience practice at Jacobs Engineering Group, defines this concept as decreasing the likelihood of negative events, improving dependability and reliability, and ensuring uninterrupted operation in the face of all shocks and stressors an asset or system may encounter over its lifespan [20]. Wendy McBay, vice president of marketing at Tensar International Corporation, explains this concept: resilience in infrastructure is the merging of innovation and constructing and engineering our roads and bridges to withstand the test of time, elements, and mother nature. To develop infrastructure that benefits future generations, adopting a different thought and action process involving building resilience is essential [20]. While there might be slight differences between these definitions, the notion of resilience in any field (including power systems) can generally be expressed as the capability of a system to anticipate and withstand external shocks, recover its preshock state as expeditiously as possible, and adapt to become better prepared to future disastrous events [21]. Considering the definition of resilience, it becomes apparent that resilience typically comprises three stages that align with the definition: predisruption, during disruption, and postdisruption. The majority of resilience studies are conducted within the corresponding stage, as illustrated in Fig. 1.2.

The concept of resilience is occasionally used instead of network security and reliability. Nevertheless, it is crucial to understand that these two concepts are entirely distinct. While a network could be reliable, it may lack the required resilience [22]. Thus, it is essential to differentiate between the concepts of reliability and resilience. Consequently, the following elucidations aim to facilitate differentiation between the concepts of resilience and reliability, as presented in Table 1.1 [2,23].

Figure 1.2  The definition of resilience.

Table 1.1

It can be concluded that an efficient power network can be defined as one that exhibits reliable performance in the presence of temporary faults and is resilient enough to withstand natural disasters and severe mishaps at the same time [22]. In the past, extensive research has been conducted on power system reliability, emphasizing preserving high reliability from causes within the system rather than external factors such as natural disasters. However, in light of natural disasters resulting from climate change, there is a growing need for research to enhance the resilience of power systems. Such research is crucial in mitigating the harm caused by natural calamities and establishing effective recovery plans.

Enhancing the power systems' resilience against climate change and HILPs is a crucial and imperative matter that warrants attention. Consequently, the present study utilizes a dimensional analytic methodology to differentiate between short-term measures (i.e., actions taken before, during, and after the weather event) and long-term strategies (i.e., scheduling of power systems to ensure adequate resilience and robustness against future weather events and climate change).

1.4. Resilience curve

The empirical resilience curve representing the degree of resilience demonstrated in the face of a disaster as a function of time is a crucial topic in grid resilience. Fig. 1.3 highlights the primary resilience characteristics that power grids must possess to navigate the varying circumstances associated with disasters, including extreme storms that successfully pass through the grid [9]. Additionally, an empirical resilience curve has been used to help recognize the success of other resilience development strategies before and after a disaster incident [24,25]. The metric resilience method reflects the extent of resilience degradation, which correlates with the severity of disasters and extreme weather events. The postdisturbance-deteriorated state (PDS) refers to the phase of postdisturbance deterioration, also known as the recovery period. The PDS must be specified with greater precision to minimize power supply interruptions, particularly to critical loads of immense importance, such as healthcare facilities, community centers, fire stations, military bases, data centers, contact centers, and water delivery centers. The resilience curve in Fig. 1.3 can be categorized into five sections: robustness or resistance, resourcefulness or redundancy, response or recovery, postrestoration state, and infrastructure recovery. These categories distinguish the different phases of grid resilience, such as regular operation, disaster occurrence, infrastructure recovery, and grid restoration. The horizontal axis denotes the timeline of the disaster, while the vertical axis represents the level of resilience or grid functionality.

Figure 1.3  Resilience curve. Distinct phases of resilience during a disaster are visually distinguished by different colors.

1.4.1. Resilience triangle

As illustrated in Fig. 1.4, the importance of the resilience triangle lies in its capacity to compute the discrepancy between the expected and actual performance of a system and, subsequently, modulate this divergence through various means [26]. Bruneau's theory of the resilience triangle, as proposed in Ref. [27], provides a framework for understanding the functional deterioration of specific assets over the course of an event timeline [28]. This theory serves as a basis for conducting empirical assessments of resilience. In particular, the grid resilience triangle is disaggregated into four distinct phases, each of which changes in response to the evolution of the disaster as time passes.

Figure 1.4  Resilience triangle and its stages during a calamitous event in nature.

Phase A is concerned with reducing the impacts of potential adverse weather events through rigorous planning and periodic assessments of the grid. Notably, grid control measures are vital in improving the system's resilience during this phase [19]. In various situations, the forecast for potential conditions of the power grid is utilized. Historical data can be employed to generate predictions for grid conditions, including statistics on faults in the system, the number of consumers affected, and the duration of the damage. This assessment helps mitigate extreme weather events, and various mitigation strategies can be applied. For example, when expecting heavy precipitation in advance, measures such as installing flood barriers, constructing a water-resistant box for the grid portion, or utilizing a mobile transformer can be taken.

The degradation process takes place in Phase B, which encompasses the period from the time Equation when a severe disaster strikes until the most critical state of the grid is reached, at time Equation . The impact of extreme weather catastrophes is evident in this process, as it showcases the physical strength of the grid, which in turn results in a higher degree of functionality loss. Failure to undertake necessary maintenance measures following the accident will lead to the continued compromised operability of the grid. The malfunctioning of the grid due to physical defects or cascading failures resulting in a loss during a disaster reveals the impact of the deterioration process. Harsh weather conditions can surpass the grid's capacity to resist, leading to physical damage to a component, while overloading other parts of the grid may cause further cascading failures [29].

In the context of grid system restoration, Phase C pertains to the transitional stage, wherein the damaged system undergoes repair and maintenance to achieve a precalamity state. It commences at the onset of replacement activities, marked as Equation , and concludes once the grid has fully regained its preevent functionality. During this stage, the grid remains in its maintenance cycle. The process serves to demonstrate the impact of extreme weather conditions on the grid system and its response, which are assessed by evaluating the restored status of the system components from recovery initiation. Restoration efforts may retrieve 100% or a certain percentage of grid features, contingent upon operational conditions. For example, a defective substation may lead to power loss for consumers in proximity to that substation, and mobile alternatives may fail to meet all customer needs. The operational capacity of the grid is determined by two fundamental factors, namely the restoration period and factor. The restoration period signifies the duration taken to reinstate the service, while the restore component indicates the proportion of grid activity that this operational intervention is capable of restoring. Network service recovery mechanisms such as repair components, rehabilitators, costs, transportation, connectivity, and temporary control are critical in these operations. Therefore, to improve grid resilience, restoration efforts aim to augment operational readiness and decrease restoration time [9].

In the Adaptation State, commonly referred to as Phase D, the electrical grid has undergone a complete restoration and is operating in its preevent state until the next catastrophic natural occurrence, demanding a comprehensive postevent analysis of the recovery process. This analysis serves to distinguish the evaluation of grid stability from the identification of the network's efficiency. Emphasizing the grid's long-term resilience, the Adaptation State represents an extended duration dedicated to scrutinizing past failures, identifying weaknesses in the grid's infrastructure and processes, and introducing and implementing strategic improvement plans. Owing to its contribution to recurrent weather-induced devastations, the Adaptation State becomes an indispensable aspect of grid resilience evaluation, manifesting its capacity to withstand such environmental cataclysms in the future.

One critique of the resilience triangle pertains to the absence of deliberation on the deteriorated state that ensues promptly after the degradation has transpired. In practical terms, when, for example, a cyclone engenders a power outage, it is not currently feasible to instantaneously reinstate the system to its original predisaster condition. Instead, a specific duration of time is obligatory for the initiation and execution of the restorative process. The resilience trapezoid serves as a mechanism to obviate such a shortcoming by recognizing the significance of postthreat degraded states emerging subsequent to the incident or