Impediments to survivability of the electric power grid and some collaborative EE-CS research issues to solve them (original) (raw)

arXiv (Cornell University), 2022

Critical infrastructures are defined as those physical and cyber-based systems that are essential to the minimum operations of the economy and the government [1, 2]. Since they provide crucial support for the delivery of basic services to almost all segments of society, they form the backbone of any nation's economy. As one of the most complex, largescale networked systems, electric power system has become increasingly automated in the past few decades. However, the increased automation has introduced new vulnerabilities to equipment failures, human errors [3, 4, 5, 6, 7], weather and other natural disasters [8, 9], and physical and cyber-attacks [2, 10]. The ever-increasing system scale and the strong reliance on automatic devices increase the likelihood of turning a local disturbance into a large-scale cascading failure [11, 12, 13, 14, 15, 16]. This kind of wide-area failure may have a catastrophic impact on the whole society. Reports of recent major power system blackouts [17, 18, 19, 20, 21, 22, 23, 24] have shown how several events ranging from minor equipment failure and operator errors to severe weather events (such as forest fires, hurricanes and winter storms) have triggered widespread system wide power disruption affecting millions of customers. This necessitates the development of a framework which would assess the vulnerability of the power grid subjected to any of these events, and thereby allowing energy policy makers to identify critical components in the grid and subsequently allocate budgets to harden them. Statistical analysis of more than 400 blackouts in USA from 1984 to 1999 indicates that a large blackout, though rare, is more likely to occur than expected (heavy tails of a power law distribution) [25]. Therefore, large blackouts require more attention not only due to their higher probability of occurrence, but also due to the enormous societal damage caused by such events. Following this observation, several works [12, 26, 27, 28, 29, 30, 31, 32, 33, 34] have proposed multiple failure models to represent the system dynamics leading to a cascading outage. They have studied cascading failures in power grids using quasi-steady state analysis with DC power flow. With any reactive power component being ignored and the assumption of a flat voltage profile, the DC power flow analysis may produce good approximations under some circumstances, e.g., when performing steady-state planning level studies. However, the increased penetration of converter-based generator technologies, loads and transmission devices have contributed to newly evolved dynamic stability behaviors of the power grid [35]. Major cascading outages are caused when transient rotor angle stability and voltage stability of the power grid are affected [22, 36, 37, 38]. Therefore, a simple cascading failure model based on DC power flow analysis is not a suitable tool to simulate such events. In this paper, we consider the AC power flow model to accurately simulate the actual operating point in the power system. Several physics-based models have been used to study cascading failures in power grid networks and interdependent power and communication networks [39, 40, 41, 42, 43, 44, 45, 46]. The authors have considered the effect of connectivity between layered networks on the cascade probability in each network, and used the sandpile dynamics [47] to represent the cascade tripping of loads in the power grids. These papers are useful in that one can often either obtain analytical results, or carry out large number of simulations to get a detailed understanding of cascade dynamics. The physics based models are simplified models capable of showcasing mechanistic possible behavior of complex network systems, rather than providing precise predictions which requires engineering models with a large number of parameters [46]. The models fail to replicate the actual system conditions in a power grid where a node (or bus) trips due to under-voltage or under-frequency and not due to overload. Further, stability of a power system subjected to cascading events is evaluated either from the network structure point of view (evaluating the degree distribution of nodes) [42, 39, 41, 43] or from the convergence of steady-state power flow solution [26, 27, 28, 29, 30, 31, 32]. Such measures do not necessarily cover all possibilities of grid instability [35], as non-linear mechanisms such as rotor angle stability or voltage collapse are not accurately captured in these methods [36]. In this work, dynamic transient analysis has been used to assess stability of the power system. The reports of certain major blackouts [23, 22] suggest that cascades need not propagate locally due to the complex non-linear nature of the power grid. Furthermore, [24] discusses the various reasons leading to the historic 1996 WSCC outage, the most important being the operation of relays. Based on the NERC data, in more than 70% of the major disturbances, failures in protective relays are found to be a contributing factor [30]. Among these failures, a failed protection system that remains dormant in normal operating conditions and becomes exposed when an abnormal condition in the system forms, is the most troublesome to tackle [48]. Such failures are termed as hidden failures and these are capable of causing widespread cascading failures in the power system network leading to a major blackout [49]. This is equivalent to the human immune system where an immune response following immunization might be more damaging

Energy Infrastructure Survivability, Inherent Limitations, Obstacles and Mitigation Strategies

The blackout of August 14, 2003 affected 8 states and fifty million people and could cost up to 5billion2.YetanotherpressreleaseclaimsitmayhavecostOhiomanufacturers5 billion 2 . Yet another press release claims it may have cost Ohio manufacturers 5billion2.YetanotherpressreleaseclaimsitmayhavecostOhiomanufacturers1.1 billion, based on a poll of 275 companies. Preliminary reports 3 indicate the outage progressed as a chain of relatively minor events, rather than a single catastrophic failure. This is consistent with previous cascading outages, which were caused by a domino reaction 4 . The increasingly ubiquitous use of embedded systems to manage and control our technologically complex society makes our homeland security even more vulnerable. Therefore, knowing how vulnerable such systems are is essential to improving their intrinsic reliability/survivability (in a deregulated environment knowing these important properties is equally essential to the providers).

Casceding failuers in power grids

F ew people consider the complexity of power grid operation when they flip a switch to light a room. Power grids provide electricity to billions of individuals around the globe, often with higher than 99.9% reliability. Because the social structures in most developed countries rely on high-reliability electricity, massive social disruption can result when the power grid fails to deliver energy to customers-urban transportation systems grind to a halt, heating and cooling systems stop, computer systems shut down, and vital services like water, sewer, and communications quickly degrade. In some cases, blackouts can uncover major social unrest, as occurred in the 1977 New York City blackout, which led to widespread rioting and the arrest of more than 3,000 individuals.

1 Structural Vulnerability of Power Grids to Disasters

2016

Natural Disasters like hurricanes, floods or earthquakes can damage power grid devices and create cascading blackouts and islands. The nature of failure propagation and extent of damage is dependent on the structural features of the grid, which is different from that of random networks. This paper analyzes the structural vulnerability of real power grids to impending disasters and presents intuitive graphical metrics to quantify the extent of damage. Two improved graph eigenvalue based bounds on the grid vulnerability are developed and demonstrated through simulations of failure propagation on IEEE test cases and real networks. Finally this paper studies adversarial attacks aimed at weakening the grid's structural resilience and presents two approximate schemes to determine the critical transmission lines that may be attacked to minimize grid resilience. The framework can be also be used to design protection schemes to secure the grid against such adversarial attacks. Simulations on power networks are used to compare the performance of the attack schemes in reducing grid resilience.

Structural vulnerability of power grids to disasters: Bounds and reinforcement measures

2015 IEEE Power & Energy Society Innovative Smart Grid Technologies Conference (ISGT), 2015

Designing survivable power systems

2008 IEEE/PES Transmission and Distribution Conference and Exposition, 2008

Survivability, or the ability to provide power to consumers/loads in spite of multiple simultaneous faults caused by natural or hostile disruptions, is a desirable feature of any power system. Topology (or design) is a key factor determining survivability of the power system. In our study, we develop mathematical and numerical tools to analyze the topological survivability of utility power systems. A new web topology of enhanced survivability is suggested.

Resilience Assessment in Distribution Grids: A Complete Simulation Model

Energies

For several years, the increase of extreme meteorological events due to climate change, especially in unusual areas, has focused authorities and stakeholders attention on electric power systems’ resilience. In this context, the authors have developed a simulation model for managing the resilience of electricity distribution grids with respect to the main threats to which these infrastructures may be exposed (i.e., ice sleeves, heat waves, water bombs, floods, tree falls). The simulator identifies the more vulnerable network assets by means of probabilistic indexes, thus suggesting the best corrective actions to be implemented for resilience improvement. The fulfillment of grid constraints, i.e., loading limits for branches and voltage limits for buses, under actual operating conditions, is taken into account. Load scenarios extracted from available measurements are evaluated by means of load flow analyses in order to choose, among the best solutions identified, those compatible with...

Power System Resilience: Current Practices, Challenges, and Future Directions

IEEE Access, 2020

The frequency of extreme events (e.g., hurricanes, earthquakes, and floods) and manmade attacks (cyber and physical attacks) has increased dramatically in recent years. These events have severely impacted power systems ranging from long outage times to major equipment (e.g., substations, transmission lines, and power plants) destructions. This calls for developing control and operation methods and planning strategies to improve grid resilience against such events. The first step toward this goal is to develop resilience metrics and evaluation methods to compare planning and operation alternatives and to provide techno-economic justifications for resilience enhancement. Although several power system resilience definitions, metrics, and evaluation methods have been proposed in the literature, they have not been universally accepted or standardized. This paper provides a comprehensive and critical review of current practices of power system resilience metrics and evaluation methods and discusses future directions and recommendations to contribute to the development of universally accepted and standardized definitions, metrics, evaluation methods, and enhancement strategies. This paper thoroughly examines the consensus on the power system resilience concept provided by different organizations and scholars and existing and currently practiced resilience enhancement methods. Research gaps, associated challenges, and potential solutions to existing limitations are also provided. INDEX TERMS Critical review; extreme events; power system resilience; resilience definitions, metrics, and enhancement strategies.

Impediments to survivability of the electric power grid and some collaborative EE-CS research issues to solve them (original) (raw)

Related papers