An Integrated Approach for Reliability Evaluation of Electric Power Systems Considering Natural Gas Network Reliability

With the rapid increase of demand for electric power and the growing complexity of the electric system, the reliable operation of electric systems is facing new challenges. Meanwhile, natural gas has been widely used in transportation, electricity generation, and heating. In addition, gas-fired turbines play a growing vital role in the generation of electricity. However, all the facilities in a natural gas network are subject to failures. The operation of gas-fired turbines will be affected by the status of natural gas network, and the insufficient supply of natural gas may cause the output of gas turbine units to reduce to zero. This power decrease may further influence the operation of power systems. Therefore, it is quite urgent to quantify the influence of natural gas networks on the power system reliability. A deep understanding of the operation of natural gas network is needed to quantify the impact that natural gas networks will bring to the power system reliability. The main facilities in a natural gas network are natural gas pipelines, compressor stations and natural gas sources. Additionally, the mathematical failure models have been developed for these facilities to build a reliability analysis framework for the gas network. The mass flow of natural gas at different failure conditions is analyzed by the maximum flow algorithm. Case studies are conducted on a modified Europe Belgium natural gas network to analyze the influences of different failures on the maximum flow of natural gas. The main problem discussed in this thesis is related to how the natural gas network operation status influences the reliability of power system. The coupling unit is the gas-fired turbine between and electric and gas infrastructures, while the simplified gas-fired turbine model used in this work shows a linear relation among the power generation and the mass flow of natural gas. In this thesis, reliability evaluation is performed based on the hierarchical level II which contains the generation system and the transmission system. The optimal power flow analysis has been conducted for the reliability evaluation. Based on the results of power flow, the status of load shedding can be obtained in a power system. Then, system reliability states can be determined. Failure statuses of both the natural gas network and electric system are simulated by Monte Carlo Simulation. Case studies are conducted on the RTS-79 system and the modified Europe Belgium natural gas network by using MATLAB and IBM CPLEX. The results indicate that the reliability of system decreases

Reliability Evaluation and Defense Strategy Development for Cyber-physical Power Systems

With the smart grid initiatives in recent years, the electric power grid is rapidly evolving into a complicated and interconnected cyber-physical system. Unfortunately, the wide deployment of cutting-edge communication, control and computer technologies in the power system, as well as the increasing terrorism activities, make the power system at great risk of attacks from both cyber and physical domains. It is pressing and meaningful to investigate the plausible attack scenarios and develop efficient methods for defending the power system against them. To defend the power grid, it is critical to first study how the attacks could happen and affect the power system, which are the basis for the defense strategy development. Thus, this dissertation quantifies the influence of several typical attacks on power system reliability. Specifically, three representative attack are considered, i.e., intrusion against substations, regional LR attack, and coordinated attacks. For the intrusion against substations, the occurrence frequency of the attack events is modeled based on statistical data and human dynamics; game-theoretical approaches are adopted to model induvial and consecutive attack cases; Monte Carlo simulation is deployed to obtain the desired reliability indices, which incorporates both the attacks and the random failures. For the false data injection attack, a practical regional load redistribution (LR) attack strategy is proposed; the man-in-the-middle (MITM) intrusion process is modeled with a semi-Markov process method; the reliability indices are obtained based on the regional LR attack strategy and the MITM intrusion process using Monte Carlo simulation. For the coordinated attacks, a few typical coordination strategies are proposed considering attacking the current-carrying elements as well as attacking the measurements; a bilevel optimization method is applied to develop the optimal coordination strategy. Further, efficient and effective defense strategies are proposed from the perspectives of power system operation strategy and identification of critical elements. Specially, a robustness-oriented power grid operation strategy is proposed considering the element random failures and the risk of man-made attacks. Using this operation strategy, the power system operation is robust, and can minimize the load loss in case of malicious man-made attacks. Also, a multiple-attack-scenario (MAS) defender-attack-defender model is proposed to identify the critical branches that should be defended when an attack is anticipated but the defender has uncertainty about the capability of the attacker. If those identified critical branches are protected, the expected load loss will be minimal

Reliability in a smart power system with cyber-physical interactive operation of photovoltaic systems and heat pumps

The connectivity of the power grid is increasing with the internet of things, and low carbon technologies being deployed to help enhance smart grid performance and reliability. Meanwhile, they also increase the digital complexity and dependency of cyber assets, which might be vulnerable to cyber-physical threats, and hence may impact the reliability of power systems. Due to cyber-threats’ unpredictable nature, the interactive operation of low carbon technologies with cyber-physical systems is becoming a challenging task for smart grids. This thesis proposes novel mathematical frameworks to estimate the availability of photovoltaics and heat pumps with cyber-physical components. These frameworks are developed to quantify the level of risk posed by cyber-threats to the interactive operation of photovoltaics and heat pumps, using Markov-Chains. The availability framework considers the severity of random cyber-attacks on photovoltaics and the probability of cyber-threats with mean time to detection-time on heat pump operation. Sensitivities of the repair times of cyber-physical component for photovoltaics and sensitivities of cyber-attack-detection time for heat pumps are also evaluated. The impact of cyber threats on the interactive operation of photovoltaics and heat pumps are considerable and inconsistent, however the propagation of cyber-threats can be restricted by appropriate means of photovoltaics. For heat pumps, operational reliability substantially decreases due to the unavailability of their control panel. Contributions of this thesis include an availability model for photovoltaic configurations, an innovative approach to assess the reliability of a photovoltaic integrated power system with cyber-physical interactions, the availability estimation of heat pump with variable detection time, and an enhanced cyber-intrusion process model for reliability analysis of heat pumps. The findings offer insight into the impact of cyber-physical system availability and its importance on power system reliability

Cyber-Based Contingency Analysis and Insurance Implications of Power Grid

Cybersecurity for power communication infrastructure is a serious subject that has been discussed for a decade since the first North American Electric Reliability Corporation (NERC) critical infrastructure protection (CIP) initiative in 2006. Its credibility on plausibility has been evidenced by attack events in the recent past. Although this is a very high impact, rare probability event, the establishment of quantitative measures would help asset owners in making a series of investment decisions. First, this dissertation tackles attackers\u27 strategies based on the current communication architecture between remote IP-based (unmanned) power substations and energy control centers. Hypothetically, the identification of intrusion paths will lead to the worst-case scenarios that the attackers could do harm to the grid, e.g., how this switching attack may perturb to future cascading outages within a control area when an IP-based substation is compromised. Systematic approaches are proposed in this dissertation on how to systematically determine pivotal substations and how investment can be prioritized to maintain and appropriate a reasonable investment in protecting their existing cyberinfrastructure. More specifically, the second essay of this dissertation focuses on digital protecting relaying, which could have similar detrimental effects on the overall grid\u27s stability. The R-k contingency analyses are proposed to verify with steady-state and dynamic simulations to ensure consistencies of simulation outcome in the proposed modeling in a power system. This is under the assumption that attackers are able to enumerate all electronic devices and computers within a compromised substation network. The essay also assists stakeholders (the defenders) in planning out exhaustively to identify the critical digital relays to be deployed in substations. The systematic methods are the combinatorial evaluation to incorporate the simulated statistics in the proposed metrics that are used based on the physics and simulation studies using existing power system tools. Finally, a risk transfer mechanism of cyber insurance against disruptive switching attacks is studied comprehensively based on the aforementioned two attackers\u27 tactics. The evaluation hypothetically assesses the occurrence of anomalies and how these footprints of attackers can lead to a potential cascading blackout as well as to restore the power back to normal stage. The research proposes a framework of cyber insurance premium calculation based on the ruin probability theory, by modeling potential electronic intrusion and its direct impacts. This preliminary actuarial model can further improve the security of the protective parameters of the critical infrastructure via incentivizing investment in security technologies

Reliability Evaluation of Line Switching Operations and Investigations into Incomplete Data Issues

Research in this dissertation is mainly focused on two topics: reliability evaluation of line switching operations and the investigation into incomplete data issues observed in reliability evaluation. A method is proposed for studying the reliability implications of line switching operations in power systems. This method is designed to explore previously overlooked areas, study objectives and study measures, in reliability evaluation of line switching operations. Line removal test is proposed to obtain simulation data of the system, and then with risk analysis and impact analysis, six reliability indices are used to evaluate reliability performance of each transmission line in the system. Weibull distribution is used to reconstruct distributions of reliability indices which provide variance analysis and worst-case scenario comparisons. Eventually, with results obtained, categorization for line switching operations is introduced to classify all transmission lines based on their reliability performance. The categories provide reliability implications of line switching operations and can be used for guidance in actual operations. This method is tested in two case studies: IEEE Reliability Test System (RTS) and IEEE 118-bus system. Both case studies validate the effectiveness of this method. A contingency ranking (CR) method is introduced as a pre-selection method to create a hybrid reliability evaluation method. The objective is not only to speed up the simulation but also to provide analytical analysis of state space. The differences between event-based and yearly-based indices are analyzed to better understand the results of the proposed method. Two case studies on IEEE RTS and IEEE 118-bus system conclude that this method have high accuracy in identifying critical lines with a significant improvement in calculation speed. To resolve incomplete data issues observed in reliability evaluation, mathematical conditions are derived for the probabilities obtained from the Markov model using transition rates to be identical with those obtained from the state residence times. This research provides guidance on building or recovering transition rate matrix in the absence of complete data. This research also shows equivalent transition rates with implicit assumption of exponential distribution is not affected by the probability distribution of state residence times in steady state analysis

Modelo de ciberseguridad en las Unidades de medición fasorial (PMU) del nuevo sistema inteligente de supervisión y control avanzado de tiempo real (ISAAC) del sistema eléctrico Nacional

El mapa de implementación del proyecto Sistema Inteligente de Supervisión y Control Avanzado (ISAAC) desarrollado por la compañía XM SA ESP, está basado en dispositivos PMU (Unidades de medición fasorial) los cuales hacen parte de la infraestructura eléctrica colombiana, éstos, son la base para el control de la frecuencia, sirven para dar respuesta efectiva de la oferta y demanda de energía. Éste proyecto ha definido un modelo de ciberseguridad del proyecto ISAAC, para lo cual, se estableció (i) Una estimación de los riesgos asociados a ciberataques sobre dispositivos de supervisión PMU, (II) se definió un modelo para la implementación de controles, que reduzcan los niveles de riesgos sobre los dispositivos de supervisión PMU y (III) se implementó un ambiente de prueba que permita valorar los resultados del modelo propuesto y el impacto de los controles de seguridad sobre las funcionalidades de los equipos. Este proyecto no contempla la implementación de elementos de seguridad en su diseño ni controles complementarios sobre las PMU, Los ciberataques cada vez más complejos y elaborados (ataques de hombre en el medio, alteración de datos, ataques de denegación de servicios distribuidos, suplantación, inserción de código, botnet, entre otros), el surgimiento de grupos especializados en construir software malicioso (malware, troyanos, APTS -amenazas persistentes en el tiempo, secuestro de información), el ciberespionaje y la situación compleja de nuestro país hacen que sea necesario la implementación de controles y modelos de ciberseguridad para proteger la infraestructura que soporta el sistema eléctrico Dado lo anterior en éste trabajo de maestría, se diseñó un modelo de ciberseguridad para los elementos PMU en el proyecto ISAAC asociado al sistema eléctrico colombiano, que permite realizar una operación confiable y segura, mitigando con ello riesgos y mejorando la resiliencia ante posibles eventos de ciberseguridad sobre dichas PMU.The implementation map of the Intelligent Advanced Monitoring and Control System (ISAAC) project developed by the company XM SA ESP, is based on PMU devices (Fasorial measurement units) which are part of the Colombian electrical infrastructure, these are the basis for frequency control, they serve to effectively respond to the supply and demand of energy. This project has defined a cybersecurity model of the ISAAC project, for which, it was established (i) An estimate of the risks associated with cyber attacks on PMU monitoring devices, (II) a model for the implementation of controls was defined, which reduce the risk levels on the PMU monitoring devices and (III) a test environment was implemented to assess the results of the proposed model and the impact of safety controls on the functionalities of the equipment. This project does not include the implementation of security elements in its design or complementary controls on PMUs, The increasingly complex and elaborate cyberattacks (man-in-the-middle attacks, data alteration, attacks on denial of distributed services, impersonation, code insertion, botnet, among others), the emergence of groups specialized in building malicious software (malware , Trojans, APTS - persistent threats over time, kidnapping of information), cyber espionage and the complex situation of our country make it necessary to implement controls and cybersecurity models to protect the infrastructure that supports the electrical system Given the above in this master's work, a cybersecurity model was designed for the PMU elements in the ISAAC project associated with the Colombian electricity system, which allows a reliable and safe operation, thereby mitigating risks and improving resilience to possible events cybersecurity about these PMU