Reducing the Vulnerability of Electric Power Grids to Terrorist Attacks

Final Project ReportThis project (‘Reducing the Vulnerability of Electric Power Grids to Terrorist Attacks’) is collaborative research with the Naval Postgraduate School (NPS), under the sponsorship of the U.S. Department of Energy. The research at The University of Texas focuses on analyzing cascading outages in large-scale electricity grids, both as a standalone tool and also as a component to eventually be added to the Vulnerability of Electric Grids Analyzer (VEGA) [1]. We refer to the proposal (Wood, Salmeron and Baldick 2003), and references therein, for detailed background on the problem of electric power-grid vulnerability. In that document, goals were established for this research and its critical importance. One aspect of that research, conducted primarily at University of Texas at Austin (UT), is the development of a cascading analysis tool, building on the experiences of a prototype tool developed by Commonwealth Associates and described in a white paper [2]. This development is aimed at including the short-term effects of cascading outages into the analysis of network vulnerability. In addition to integrating representation of cascading outages into VEGA, informal feedback from industry suggested that it was also important that for this research to develop a standalone cascading analysis tool. Development as a standalone tool has also facilitated the division of activities between NPS and UT. This report details the development of the prototype standalone tool. Future work includes extending the types of initial disturbances that can be considered and integration of the tool with VEGA.DOE Research Project DE-FG02-05ER2567

Impact Assessment of Hypothesized Cyberattacks on Interconnected Bulk Power Systems

The first-ever Ukraine cyberattack on power grid has proven its devastation by hacking into their critical cyber assets. With administrative privileges accessing substation networks/local control centers, one intelligent way of coordinated cyberattacks is to execute a series of disruptive switching executions on multiple substations using compromised supervisory control and data acquisition (SCADA) systems. These actions can cause significant impacts to an interconnected power grid. Unlike the previous power blackouts, such high-impact initiating events can aggravate operating conditions, initiating instability that may lead to system-wide cascading failure. A systemic evaluation of "nightmare" scenarios is highly desirable for asset owners to manage and prioritize the maintenance and investment in protecting their cyberinfrastructure. This survey paper is a conceptual expansion of real-time monitoring, anomaly detection, impact analyses, and mitigation (RAIM) framework that emphasizes on the resulting impacts, both on steady-state and dynamic aspects of power system stability. Hypothetically, we associate the combinatorial analyses of steady state on substations/components outages and dynamics of the sequential switching orders as part of the permutation. The expanded framework includes (1) critical/noncritical combination verification, (2) cascade confirmation, and (3) combination re-evaluation. This paper ends with a discussion of the open issues for metrics and future design pertaining the impact quantification of cyber-related contingencies

An optimal proportional integral derivative tuning for a magnetic levitation system using metamodeling approach

A magnetic levitation system (MLS) is a complex nonlinear system that requires an electromagnetic force to levitate an object in the air. The electromagnetic field is extremely sensitive to noise which can cause the acceleration on the spherical object, leading it to move into the unbalanced region. This paper presents a comparative assessment of controllers for the magnetic levitation system using proportional integral derivative (PID) controller based optimal tuning. The analysis was started by deriving the mathematical model followed by the implementation of radial basis function neural network (RBFNN) based metamodel. The optimal tuning of the PID controller has offered better transient responses with the improvement of overshoot and the rise time as compared to the standard optimization methods. It is more robust and tolerant as compared to gradient descent method. The simulation output using the radial basis based metamodel approach showed an overshoot of 9.34% and rise time of 9.84 ms, which are better than the gradient descent (GD) and conventional PID methods. For the verification purpose, a Simscape model has been developed which mimic the real model. It was found that the model has produced about similar performance as what has been obtained from the Matlab simulation

The detection, prevention and mitigation of cascading outages in the power system

This dissertation studies the causes and mechanism of power system cascading outages and develops new methods and new tools to help detect, prevent and mitigate the outages. Three effective solutions: a steady state control scheme, a transient stability control scheme, and an interactive system-wide and local scheme have been proposed using those new methods and tools. A steady state control scheme can help detect and prevent the possible cascading outage at its initial slow steady state progress stage. It uses new methods and new tools to solve the line overload, congestion or bus high/low voltage problems. New methods, such as vulnerability index (VI), margin index (MI), network contribution factor (NCF), topology processing and selected minimum load shedding (SMLS), and new tools, such as transmission network control based on a network contribution factor (NCF) method, generator control based on a generator distribution factor (GDF) method, and load control based on a load distribution factor (LDF) method have been proposed and developed. A transient stability control scheme can help prevent and mitigate the possible cascading outage at its transient progress stage if there is enough time to take action. It uses one Lyapunov direct method, potential energy boundary surface (PEBS) method, and sensitivity analysis of transient energy margin for fast stabilizing control. The results are verified by the accurate time-domain transient stability analysis method. The interactive scheme takes advantage of accurate system-wide and local information and analysis results, uses some techniques from both steady state control and transient stability control, works at both the system-wide level and local substation level, monitors the system all the time, and takes actions when needed to help detect, prevent and mitigate the possible cascading outage. Comprehensive simulation studies have been implemented using the IEEE 14- bus, 24-bus, 39-bus and 118-bus systems and promising results show the ability of the proposed solutions to help detect, prevent and mitigate cascading outages

Risk based multi-objective security control and congestion management

Deterministic security criterion has served power system operation, congestion management quite well in last decades. It is simple to be implemented in a security control model, for example, security constrained optimal power flow (SCOPF). However, since event likelihood and violation information are not addressed, it does not provide quantitative security understanding, and so results in system inadequate awareness. Therefore, even if computation capability and information techniques have been greatly improved and widely applied in the operation support tool, operators are still not able to get rid of the security threat, especially in the market competitive environment.;Probability approach has shown its strong ability for planning purpose, and recently gets attention in operation area. Since power system security assessment needs to analyze consequence of all credible events, risk defined as multiplication of event probability and severity is well suited to give an indication to quantify the system security level, and congestion level as well. Since risk addresses extra information, its application for making BETTER online operation decision becomes an attractive research topic.;This dissertation focus on system online risk calculation, risk based multi-objective optimization model development, risk based security control design, and risk based congestion management. A regression model is proposed to predict contingency probability using weather and geography information for online risk calculation. Risk based multi-objective optimization (RBMO) model is presented, considering conflict objectives: risks and cost. Two types of method, classical methods and evolutionary algorithms, are implemented to solve RBMO problem, respectively. A risk based decision making architecture for security control is designed based on the Pareto-optimal solution understanding, visualization tool and high level information analysis. Risk based congestion management provides a market lever to uniformly expand a security VOLUME , where greater volume means more risk. Meanwhile, risk based LMP signal contracts ALL dimensions of this VOLUME in proper weights (state probabilities) at a time.;Two test systems, 6-bus and IEEE RTS 96, are used to test developed algorithms. The simulation results show that incorporating risk into security control and congestion management will evolve our understanding of security level, improve control and market efficiency, and support operator to maneuver system in an effective fashion

Modeling, Simulation, and Analysis of Cascading Outages in Power Systems

Interconnected power systems are prone to cascading outages leading to large-area blackouts. Modeling, simulation, analysis, and mitigation of cascading outages are still challenges for power system operators and planners.Firstly, the interaction model and interaction graph proposed by [27] are demonstrated on a realistic Northeastern Power Coordinating Council (NPCC) power system, identifying key links and components that contribute most to the propagation of cascading outages. Then a multi-layer interaction graph for analysis and mitigation of cascading outages is proposed. It provides a practical, comprehensive framework for prediction of outage propagation and decision making on mitigation strategies. It has multiple layers to respectively identify key links and components, which contribute the most to outage propagation. Based on the multi-layer interaction graph, effective mitigation strategies can be further developed. A three-layer interaction graph is constructed and demonstrated on the NPCC power system.Secondly, this thesis proposes a novel steady-state approach for simulating cascading outages. The approach employs a power flow-based model that considers static power-frequency characteristics of both generators and loads. Thus, the system frequency deviation can be calculated under cascading outages and control actions such as under-frequency load shedding can be simulated. Further, a new AC optimal power flow model considering frequency deviation (AC-OPFf) is proposed to simulate remedial control against system collapse. Case studies on the two-area, IEEE 39-bus, and NPCC power systems show that the proposed approach can more accurately capture the propagation of cascading outages when compared with a conventional approach using the conventional power flow and AC optimal power flow models.Thirdly, in order to reduce the potential risk caused by cascading outages, an online strategy of critical component-based active islanding is proposed. It is performed when any component belonging to a predefined set of critical components is involved in the propagation path. The set of critical components whose fail can cause large risk are identified based on the interaction graph. Test results on the NPCC power system show that the cascading outage risk can be reduced significantly by performing the proposed active islanding when compared with the risk of other scenarios without active islanding

Dependent Failures And Failure Propagation In Electric Power Systems

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2013Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2013Biz toplam kesinti sayısı dağılımını, cascading sürecinden sonra dallanma yöntemi ve yayılma ortalamasına göre tahmin ettikAn initial number of lines outaged can lead to a cascading propagation of further outages. We estimate the amount by which line outages propagate from standard utility data that is reported to TEİAŞ. We estimate the distribution of the total number of outages after cascading from the amount of propagation and a probabilistic branching process model of the cascading.Yüksek LisansM.Sc

Selection of Line Contingency for Power System Security Analysis

Contingency analysis (CA) has always been an in integral part of power system security analysis. CA is a useful tool at disposal of operation personnel to see effects of future outages on the system. The overload Performance Index (PI) is a good index for ranking the contingencies as per their severity. The PI requires “n” number of DC analysis to create a complete index, where n is no of lines. And for a larger network having a higher multitude of lines, it is time consuming. A new approach has been discussed for ranking the contingencies. This method requires one DC analysis and line outage distribution factor, which is constant for a particular unchanged transmission network