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This literature review supports a project to develop methods to improve U.S. national security using a federation of microgrids powered with solar photovoltaic technology.

Literature Review

Social and ecological resilience: are they related?

Source: Adger, N. "Social and ecological resilience: are they related?" Progress in Human Geography, 24(3), 347-364, 2000.

Abstract This article defines social resilience as the ability of groups or communities to cope with external stresses and disturbances as a result of social, political and environmental change. This definition highlights social resilience in relation to the concept of ecological resilience which is a characteristic of ecosystems to maintain themselves in the face of disturbance. There is a clear link between social and ecological resilience, particularly for social groups or communities that are dependent on ecological and environmental resources for their livelihoods. But it is not clear whether resilient ecosystems enable resilient communities in such situations. This article examines whether resilience is a useful characteristic for describing the social and economic situation of social groups and explores potential links between social resilience and ecological resilience. The origins of this interdisciplinary study in human ecology, ecological economics and rural sociology are reviewed, and a study of the impacts of ecological change on a resource-dependent community in contemporary coastal Vietnam in terms of the resilience of its institutions is outlined.

  • Resilience relates to the functioning of an ecological system
  • Ability of the system to absorb disturbances- before the system changes structure
  • Ecological economists: resilience is the key to sustainability
  • Social resilience: looks at dependency of social system on the environment (natural resources for example)

Error and attack tolerance of complex networks

Source: Albert, R., Jeong, H., Barabasi, A. "Error and attack tolerance of complex networks." Nature, 406, 378-382, 2000.

Abstract

Many complex systems display a surprising degree of tolerance against errors. For example, relatively simple organisms grow, persist and reproduce despite drastic pharmaceutical or environmental interventions, an error tolerance attributed to the robustness of the underlying metabolic network1. Complex communication networks2 display a surprising degree of robustness: although key components regularly malfunction, local failures rarely lead to the loss of the global information-carrying ability of the network. The stability of these and other complex systems is often attributed to the redundant wiring of the functional web defined by the systems' components. Here we demonstrate that error tolerance is not shared by all redundant systems: it is displayed only by a class of inhomogeneously wired networks, called scale-free networks, which include the World-Wide Web3, 4, 5, the Internet6, social networks7 and cells8. We find that such networks display an unexpected degree of robustness, the ability of their nodes to communicate being unaffected even by unrealistically high failure rates. However, error tolerance comes at a high price in that these networks are extremely vulnerable to attacks (that is, to the selection and removal of a few nodes that play a vital role in maintaining the network's connectivity). Such error tolerance and attack vulnerability are generic properties of communication networks.

  • Article focuses on complex networks as a whole- including social networks
  • Principle is held constant however- when a small number of nodes is affected- measured by number of connections to node- communication remains unaffected
  • Informed attacks will target most connected nodes
  • Author's label this sort of scale-free system as "inhomogeneous"- explaining the different number of linkages/sizes of each node

Security Challenges for the Electricity Infrastructure

Source: Amin, A. " Security Challenges for the Electricity Infrastructure." Computer, 35 (4), 8-10, 2002.

Abstract

Because critical infrastructures touch us all, the growing potential for infrastructure problems stems from multiple sources, including system complexity, economic growth, deregulation, terrorism, and even the weather. Electric power systems constitute the fundamental infrastructure of modern society. A successful terrorist attempt to disrupt electricity supplies could have devastating effects on national security, the economy, and every citizen's life. Yet power systems have widely dispersed assets that can never be absolutely defended against a determined attack. Indeed, because of the intimate connections between power systems and society's other infrastructures, we need to consider three different kinds of threats: attacks upon the power system; attacks by the power system; and attacks through the power system

  • Attacks on power system: infrastructure is primary target (substations, transmission towers, entire regional grid, etc.)
  • Attacks by power system: Utilizing infrastructure to attack populations. An example includes utilizing power plant cooling towers to release chemical or biological agents
  • Attacks through the power system: Attacks on utility networks, further damaging computer/telecommunications infrastructure
  • Important to identify important vulnerabilities, and responding accordingly with appropriate policies
  • Major problem- easy to exploit the weaknesses of current centralized control system
  • Solution- decentralize into smaller, local systems (distributed generation)
  • Current grid system is highly reliant on high-speed data transfer, increasing susceptibility to security breaches
  • Strategy to prepare for security threats includes preventing cascading damage; sectioning off attack cites, securing critical controls and communication from hackers, provide ongoing security assessments
  • Infrastructure Security Initiative- 2 year program funded by electric power industry to develop and apply key technologies to improve electric grid security system

Cascade-based attacks on complex networks

Source: Motter, A., Lai, Y. "Cascade-based attacks on complex networks." Physical Review, 66(6), 65102-1-65102-4, 2002.

Abstract

We live in a modern world supported by large, complex networks. Examples range from financial markets to communication and transportation systems. In many realistic situations the flow of physical quantities in the network, as characterized by the loads on nodes, is important. We show that for such networks where loads can redistribute among the nodes, intentional attacks can lead to a cascade of overload failures, which can in turn cause the entire or a substantial part of the network to collapse. This is relevant for real-world networks that possess a highly heterogeneous distribution of loads, such as the Internet and power grids. We demonstrate that the heterogeneity of these networks makes them particularly vulnerable to attacks in that a large-scale cascade may be triggered by disabling a single key node. This brings obvious concerns on the security of such systems.

  • Small average distance between nodes
  • Highly organized distribution of links per node
  • In power transmission grid, each node deals with a load of power, removal of nodes changes the balance of power flows and leads to redistribution of flows across the network
  • Cascading failures occur after redistribution of loads, domino effect, can either stop after few steps or shutdown a larger fraction of the network
  • If node has relatively small load, removal may not have huge effect; When load is relatively large, node's removal has potential to significantly affect loads at other nodes
  • nodes with largest number of links will have higher loads, therefore more likely to have cascading failure under intentional attack

Attack vulnerability of complex networks

Source: Holme, P., Kim, B. "Attack vulnerability of complex networks." Physical Review, 65(5), 56109-1-56109-14, 2002.

Abstract

We study the response of complex networks subject to attacks on vertices and edges. Several existing complex network models as well as real-world networks of scientific collaborations and Internet traffic are numerically investigated, and the network performance is quantitatively measured by the average inverse geodesic length and the size of the largest connected subgraph. For each case of attacks on vertices and edges, four different attacking strategies are used: removals by the descending order of the degree and the betweenness centrality, calculated for either the initial network or the current network during the removal procedure. It is found that the removals by the recalculated degrees and betweenness centralities are often more harmful than the attack strategies based on the initial network, suggesting that the network structure changes as important vertices or edges are removed. Furthermore, the correlation between the betweenness centrality and the degree in complex networks is studied.

  • Attack network by either reducing total number of lines in the network or destroying nodes in the network
  • Can attack by cutting off communication in networks or breakdown server in network

Toward more robust infrastructure: observations on improving the resilience and reliability of critical systems

Source: Little, R. "Toward more robust infrastructure: observations on improving the resilience and reliability of critical systems." System Sciences, Proceedings of the 36th Annual Hawaii International Conference, 1-9, 2002.

Abstract

Civil infrastructure provides the range of essential services generally necessary to support a nation's economy and quality of life - arguably entire economies rely on the ability to move goods, people, and information safely and reliably. Consequently, it is of the utmost importance to government, business, and the public at large that the flow of services provided by a nation's infrastructure continues unimpeded in the face of a broad range of natural and manmade hazards. From a comprehensive vulnerability assessment and hazard mitigation standpoint, it is necessary to look beyond the effects of an event on a single system and instead seek to understand the perturbed behaviors of a complex, "system of systems". Making our infrastructure systems inherently safer when stressed also will require more than just improved engineering and technology. The events of September 11 demonstrated that these complex systems also have critical institutional and human components that need to be understood and integrated into design and operational procedures.

  • Critical infrastructures are: telecommunications, electrical power systems, gas/oil, banking/finance, transportation, water supply, government and emergency services
  • consequences of infrastructure failure can range from benign to catastrophic
  • Mitigating infrastructure failure/damage is a difficult task due to interconnected nature
  • Figure 1 is a good representation of electric grid's connection to every other critical infrastructure
  • Important to focus not only on first order impacts, but second order that propagate, or create cascading failures
  • 3 Types of Infrastructure Failures: cascading, escalating, and common cause
  • Cascading- disruption in one causes disruption in another
  • Escalation- disruption in one exacerbates independent disruption of another
  • Common cause- disruption of two or more at the same time

Reflections on Security

Source: Gent, M., Costantini, L. " Reflections on Security." IEEE Power and Energy Magazine, 1 (1), 46-52, 2003.

Abstract

The North American Electric Reliability Council (NERC) has been responsible for the reliability of the interconnected grid, of which safety and security are essential ingredients, since 1968. NERC has undertaken several key initiatives (many of which began well before September 11) to focus attention on security matters and to encourage electric power industry participants to act. They include: establishing an Information Sharing and Analysis Center for the Electricity Sector (ES-ISAC); developing security guidelines for the electricity sector; deploying a public key infrastructure (PKI); and creating a spare equipment database. NERC's security initiatives are coordinated by the Critical Infrastructure Protection Advisory Group (CIPAG), which reports directly to the NERC board of trustees. The group comprises electric industry experts in the areas of cyber security, physical security, and operational security. Because of NERC's unique position within the industry, CIPAG has become the focal point for security issues within the electricity sector. To ensure the broadest degree of expertise and experience, CIPAG works closely with other industry groups. This coordination is vital to ensuring the electric industry in North America speaks about security with one voice and acts in a coordinated manner.

  • North American Electric Reliability Council (NERC)- responsible for reliability of interconnected grid
  • Interdependence of multiple infrastructures are prime terrorist targets
  • Electricity infrastructure is connected to: economy, nation security, public well-being
  • Security guidelines created- address topics of vulnerability and risk assessment, physical and cybersecurity, and protecting sensitive information
  • This article presents an overview of the NERC's set of initiatives to counter security breaches

Security & Vulnerability in Electric Power Systems

Source: Watts, D. "Security & Vulnerability in Electric Power Systems." North American Power Symposium, 559-566, 2003.

Abstract

Security of supply has been always a key factor in the development of the electric industry. Adequacy, quality of supply, stability, reliability and voltage collapse along with costs have been always carefully considered when planning the future of the electric power system. Since 1982, when world's deregulation process started, the introduction of competition at generation level brought new challenges, while the proper operation of the electric power system still require physical coordination between non cooperative agents. The increasing development of SCADA/EMS systems, the growing number of market participants, and the development of more complex market schemes have been more and more relying on Information Technologies, making the physical system more vulnerable to cyber security risks. Now cyber security risks look bigger than the physical ones. We developed a review of some of the vulnerability risks that actual electric power systems face, showing some implementation issues of it. We also comment some the steps that NERC is leading to ensure a secure energy sourcing to the U.S. Economy.

  • Attack on electric infrastructures could be devastating to economy and public's lives
  • Also touches on attacks upon the power system, Attacks by the power system, and Attacks through the power system
  • This paper focuses on attacks upon the power system
  • Power grid now subject to "new" terrorism that involves disrupting communication systems
  • Strong interdependence of electricity, gas, telecommunications, transportation, and financial infrastructure
  • North American Reliability Council- in charge of reliability of interconnected grid
  • Information sharing and Analysis Centers- security planning and analysis
  • Security guidelines- practices to protect against security breaches (1) Vulnerability and risk assessment, (2) threat response capability, (3) emergency management, (4) Continuity of business processes, (5) communications, (6) physical security, (7) information technology/cybersecurity, (8) employment screening, (9) protecting potentially sensitive information
  • (7)- mitigates threat utilizing intrusion detection, SCADA/EMS systems, firewalls, security protocols
  • (9)- reduces likelihood of hackers using sensitive information to damage critical infrastructure or interrupt operations
  • Some security issues: breaches in wireless firewall, target modems at power plants and substations
  • higher costs come with increased security standards, merging of companies- transition time to create uniformity in cybersecurity systems,
  • To combat this issue- some regions implement mobile substations, to connect to system in the event of a security breach; fencing; (solutions only available for physical attacks)

Structural Vulnerability of the North American Power Grid

Source: Albert, R., Albert, I., Nakarado, G. " Structural Vulnerability of the North American Power Grid." Physical Review, 69, 251031-251034, 2004.

Abstract

The magnitude of the August 2003 blackout affecting the United States has put the challenges of energy transmission and distribution into limelight. Despite all the interest and concerted effort, the complexity and interconnectivity of the electric infrastructure precluded us for a long time from understanding why certain events happened. In this paper we study the power grid from a network perspective and determine its ability to transfer power between generators and consumers when certain nodes are disrupted. We find that the power grid is robust to most perturbations, yet disturbances affecting key transmision substations greatly reduce its ability to function. We emphasize that the global properties of the underlying network must be understood as they greatly affect local behavior

  • Over 10^6 km of voltage lines
  • Power now sold over constantly increasing distances
  • Generators, transmission, and distribution substations
  • Connection between two substations does not automatically mean power can be transferred- may have constraints, such as capacity
  • Scale-free networks are resilient to random loss of substation (node), but susceptible to attacks of high-degree hubs
  • Will loss of connected hubs cause breakdown of power grids transmission capability
  • Failure of local line, can overload nearby lines
  • Protection mechanism in place- shut off generating substations to prevent power transmission; this results in outage for all customers
  • Targets to transmission hubs results in large connectivity loss
  • Suggested solution: distributed generation from small local plants

Analysis of Electrical Grid Security Under Terrorist Threat

Source: Salmeron, J., Wood, K., Baldick, R. " Analysis of Electric Grid Security Under Terrorist Threat." IEEE Transactions on Power Systems, 19(2), 905-912, 2004.

Abstract

We describe new analytical techniques to help mitigate the disruptions to electric power grids caused by terrorist attacks. New bilevel mathematical models and algorithms identify critical system components (e.g., transmission lines, generators, transformers) by creating maximally disruptive attack plans for terrorists assumed to have limited offensive resources. We report results for standard reliability test networks to show that the tech- niques identify critical components with modest computational effort.

  • Line interdiction: all lines running physically in parallel at the point of attack are opened; attack on one is an attack on all
  • Transformer interdiction: line representing transformer is opened
  • Generator interdiction: generator is disconnected from the grid
  • Bus interdiction: all lines, generation, and load connected to the bus are disconnected
  • Substation interdiction: all buses at the substation are disconnected; this triggers corresponding bus-interdiction effects
  • This article only focuses on physical attacks to electric system; creates algorithm to solve problem

Microgrid: A conceptual solution

Source: Lasseter, R., Paigi, P. "Microgrid: A conceptual solution." IEEE Power Electronics Specialist Conference, 6, 4285-4290, 2004.

Abstract

Application of individual distributed generators can cause as many problems as it may solve. A better way to realize the emerging potential of distributed generation is to take a system approach which views generation and associated loads as a subsystem or a "microgrid". During disturbances, the generation and corresponding loads can separate from the distribution system to isolate the microgrid's load from the disturbance (providing UPS services) without harming the transmission grid's integrity. This ability to island generation and loads together has a potential to provide a higher local reliability than that provided by the power system as a whole. In this model it is also critical to be able to use the waste heat by placing the sources near the heat load. This implies that a unit can be placed at any point on the electrical system as required by the location of the heat load.

  • Microgrids reduce the need for central dispatch through "intentional islanding"- separation of generation and load from distribution
  • Applying small distributed generation systems allows for the system's efficiency to double
  • Because the microgrid allows for separation from distribution in disturbance events, the system maintains a high level of service

Power System Control Centers: Past, Present, and Future

Source: Wu, F., Moslehi, K., Bose, A. " Power System Control Centers: Past, Present, and Future." Proceedings of the IEEE, 93(11), 1890-1908, 2005.

Abstract

In this paper, we review the functions and architectures of control centers: their past, present, and likely future. The evolving changes in power system operational needs require a distributed control center that is decentralized, integrated, flexible, and open. Present-day control centers are moving in that direction with varying degrees of success. The technologies employed in today's control centers to enable them to be distributed are briefly reviewed. With the rise of the Internet age, the trend in information and communication technologies is moving toward Grid computing and Web services, or Grid services. A Grid service-based future control center is stipulated.

  • Information technologies have progressed, while control centers remain stagnant- due to inability to take advantage of technological progression
  • Control centers in transition from centralized to decentralized architecture
  • After Northeast blackout in 1965 digital computers were implemented, introducing idea of system security
  • Control center: power system operations- data acquisition, generation control, network (security) analysis and control
  • Due to online transfer of data, security is now primary concern
  • Security mechanisms must be in place to prevent security breaches: (1) authentication- establish identity, (2) authorization- what is the user allowed to do, (3) confidentiality- only intended recipient can receive message, (4) integrity- ensuring message has not been tampered with
  • Encryption and digital signatures are methods to cybersecurity
  • This paper briefly touches on cybersecurity issues within the electric grid

Modeling cascading failures in the North American power grid

Source: Kinney, R., Crucitti, P., Albert, R., Latora, V. " Modeling cascading failures in the North American power grid." The European Physical Journal, 46(1), 101-107, 2005.

Abstract

The North American power grid is one of the most complex technological networks, and its interconnectivity allows both for long-distance power transmission and for the propagation of disturbances. We model the power grid using its actual topology and plausible assumptions about the load and overload of transmission substations. Our results indicate that the loss of a single substation can result in up to 25% loss of transmission efficiency by triggering an overload cascade in the network. The actual transmission loss depends on the overload tolerance of the network and the connectivity of the failed substation. We systematically study the damage inflicted by the loss of single nodes, and find three universal behaviors, suggesting that 40% of the transmission substations lead to cascading failures when disrupted. While the loss of a single node can inflict substantial damage, subsequent removals have only incremental effects, in agreement with the topological resilience to less than 1% node loss.

  • Interconnected nature of U.S. utilities created to increase reliability of systems
  • Due to this widespread infrastructure, systems are subject to local failures that can translate to a grid-wide outage
  • Breakdown of a single component has the potential to not only affect performance of network, but can create cascading failures in other components
  • Power from any generator is able to reach any distribution substation
  • If external "attack" causes breakdown at one substation, power can be redirected through other substations; this has effects on performance of that substation- if carrying power at a capacity higher than regular load
  • Substations can begin working again if load decreases to below capacity
  • 60% of single substation losses do not result in cascading failures; more targeted attack of susceptible substations causes cascading failures
  • While noting the above, a single substation loss can cause a 25% reduction in efficiency of power grid; vulnerability that must be addressed
  • Suggestions for change include producing power on more localized level- "via environmentally friendly methods"

Energy Infrastructure Defense Systems

Source: Amin, M. " Energy Infrastructure Defense Systems." Proceedings of the IEEE, 93(5), 861-875, 2005.

Abstract

Energy infrastructure faced with deregulation and coupled with interdependencies with other critical infrastructures and increased demand for high-quality and reliable electricity for our digital economy is becoming more and more stressed. The occurrence of several cascading failures in the past 40 years has helped focus attention on the need to understand the complex phenomena associated with these interconnected systems and to develop defense plans to protect the network against extreme contingencies caused by natural disasters, equipment failures, human errors, or deliberate sabotage and attacks. With dramatic increases in interregional bulk power transfers and accelerating diversity of transactions among parties, the electric power grid is being used in ways for which it was not originally designed. As the power grids become heavily loaded with long-distance transfers, the already complex system dynamics become even more important. The potential for rare events but high-impact cascading phenomena represent just a few of many new science and technology challenges. We focus on the lessons learned as well as challenges associated with accomplishing these missions, including recent hardware, software, applications, and algorithmic developments.

  • sources of vulnerability include: natural disasters, equipment failures, human errors, deliberate attacks
  • every crucial economic and social function depends on secure, reliable operation of energy
  • North American Grid: 15,000+ gnerators in 10,000 plants; estimated worth over $800 billion
  • Aug 1996 Blackout cost: $1.5 billion, Aug 2003 blackout cost: $6-$10 billion (ref article for specific black out examples)
  • avg outages since 1984- have affect 700,000 consumers per event annually
  • interconnection of automation and control systems operate on public data networks and allow easy access to anyone around the globe using "inexpensive computer and a modem"

Electric utility responses to grid security issues

Source: Schainker, R., Douglas, J., Kropp, T. "Electric utility responses to grid security issues." Power and Energy Magazine, IEEE, 4(2), 30-37, 2006.

Abstract

This paper discusses the different initiatives that utility decision makers have set in place to address the vulnerability of the US power grid to physical and cyber attacks. One of the efforts to enhance grid security is EPRI's Infrastructure Security Initiative (ISI), which was designed to develop both prevention countermeasures and enhanced recovery capabilities. To protect against cyber attacks, several organizations were also established including the Computer Emergency Response Team (CERT) and the Process Control Systems Forum (PCSF). In addition, EPRI also launched the Energy Information Security (EIS) program to focus on computer-based security breaches. An industry-wide cybersecurity program alliance, called the PowerSec Initiative, was also formed to address the cyberthreat issue as it could impact electric utility operational and control equipment.

  • Electricity drives all nation's critical infrastructure
  • Impossible to secure entire interconnected system
  • Utilities can be impacted by physical attack, resulting in large financial losses
  • Increased industry dependency on internet and computer monitoring makes grid vulnerable to cyber attacks such as: disable protective relays, disabling grid control center computer systems, or send false control signals
  • Cyber security varies with utilities across the U.S.- so improved coordination of security is needed
  • Industry efforts: reinforce infrastructure security, develop list of steps for countermeasures, educate utilities
  • Several countries have added cyber attacks into military preparations
  • Hackers can either breach main firewall of control system or go through a "back door"- through a 3rd party vendor that is linked to utility system
  • Solutions: amp up current cyber security in control and communication networks

How Resource Dependency can influence Social Resilience within a Primary Resource Industry

Source: Marshall, N., Fenton, D., Marshall, P., Sutton, G. "How Resource dependency can influence social resilience within a primary resource industry." Rural Sociology, 72(3),359-390, 2007.

Abstract Maintaining a healthy balance between human prosperity and environmental integrity is at the core of the principles of Ecological Sustainable Development. Resource-protection policies are frequently implemented so as to regulate the balance between resource access and use, however, they can inadvertently compromise the ability of resource users to adapt and be resilient. Resource users who are especially dependent on a resource are more seriously compromised. But how do we define and measure resource dependency? And how do we assess its ability to influence social resilience? In this study, a conceptual model of resource dependency is developed in terms of: (i) occupational attachment, (ii) attachment to place, (iii) employability, (iv) family attitude to change, (v) business size, (vi) business approach, (vii) financial situation, (viii) level of specialisation, (ix) time spent harvesting, and (x) interest in and knowledge of the environment. The model of resource dependency and its effect on social resilience are (quantitatively and qualitatively) tested and explored using the commercial fishing industry in North Queensland, Australia. Results show that occupational attachment and employability were important influences as were business size and approach. Results can be used to identify vulnerability to institutional change and guide policy development processes.

  • Social resilience in this study: how resource users can cope and adapt to changes in resource policy
  • Resilient systems are flexible, prepared for change, essential to prosperous development of society
  • Knowledge of properties that contribute to resilience allow policymakers to design policies that minimize impacts on people and maximize resources- ecosystem goods and services
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Authors Emily Prehoda, Joshua M. Pearce
License CC-BY-SA-3.0
Organizations MOST
Language English (en)
Related 1 subpages, 1 pages link here
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Created September 5, 2015 by Joshua M. Pearce
Modified February 28, 2024 by Felipe Schenone
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