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

Final report on Assessment of the candidate Projects of Energy Community Interest (PECI) and Projects for Mutual Interest (PMI)

A REKK és a DNV GL konzorciuma a 2013-as első PECI lista kiválasztásában nyújtott tanácsadó munkája után 2016-ban is támogatást nyújtott a második PECI lista kiválasztáshoz. A konzorcium kialakított egy projekt értékelési módszertant, majd az elfogadott módszertan alapján értékelte a benyújtott infrastruktúra projekteket. Az értékelés egy előzetes vizsgálatból és egy modellezési és indikátor számítási szakaszból állt. Az előzetes értékelés során megvizsgáltuk, hogy a benyújtott projektek megfelelnek-e a 347/2013 EU rendelet Energy Community által adoptált változatában szereplő általános és specifikus kritériumoknak, illetve a benyújtott projektadatokat verifikáltuk. Az előzetes kritériumoknak megfelelt 31 projektet (12 villamos energia hálózati és 17 gázhálózati és 1 olaj infrastruktúra) értékeltük. A villamosenergia és gázhálózati infrastruktúra projektek esetében a módszertan két lépésen alapult. Első lépésben a modellezésen alapuló költség haszon vizsgálatát végeztük el a projekteknek és kiszámítottuk a társadalmi nettó jelenértékét. Ez az indikátor szerepelt az elemzésben a legnagyobb súllyal (60%). Második lépésben a nem monetizálható hasznok esetében további indikátorok (a rendszerbiztonság, a projektek előrehaladottsága, a piaci versenyhez elősegítése, stb.) kerültek kialakításra, az indikátorok 1-5 skálán pontokat kaptak és a súlyokkal beszorozva megkaptuk minden egyes projekt összpontszámát. Az ily módon sorrendbe állítható projektlista és a részletes érzékenységvizsgálatok eredménye alapján hozta meg a tagállamok képviselőiből álló csoport a döntését az előzetes PECI/PMI listáról

Assessing the criticality of interdependent power and gas systems using complex networks and load flow techniques

Gas and electricity transmission systems are increasingly interconnected, and an attack on certain assets can cause serious energy supply disruptions, as stated in recommendation (EU) 2019/553 on cybersecurity in the energy sector, recently approved by the European Commission. This study aims to assess the vulnerability of coupled natural gas and electricity infrastructures and proposes a method based on graph theory that incorporates the effects of interdependencies between networks. This study is built in a joint framework, where two different attack strategies are applied to the integrated systems: (1) disruptions to facilities with most links and (2) disruptions to the most important facilities in terms of flow. The vulnerability is measured after each network attack by quantifying the unmet load (UL) through a power flow analysis and calculating the topological damage of the systems with the geodesic vulnerability (v) index. The proposed simulation framework is applied to a case study that consists of the IEEE 118-bus test system and a 25-node high-pressure natural gas network, where both are coupled through seven gas-fired power plants (GFPPs) and three electric compressors (ECs). The methodology is useful for estimating vulnerability in both systems in a coupled manner, studying the propagation of interdependencies in the two networks and showing the applicability of the v index as a substitute for the UL index

GIS-based method to assess seismic vulnerability of interconnected infrastructure: A case of EU gas and electricity networks

Our study concerns the interconnected European Electricity and Gas transmission grid where we address two important issues of these interdependent critical infrastructures. First we assessed the response under seismic hazard for each independent network; then we analysed the increased vulnerability due to coupling between these two heterogeneous networks. We developed a probability reliability model that encompasses the spatial distribution of the network structures using a Geographic Information System (GIS). We applied the seismic risk assessment of individual network facilities and presented the results in the form of the system fragility curves of the (independent and dependant) networks in terms of various performance measures - connectivity loss, power loss, and impact on the population. We characterized the coupling behaviour between the two networks as a physical dependency: here the electricity grid, in part, depends on the gas network due to the generation capacity of gas-fired power plants. The dependence of one network on the other is modelled with an interoperability matrix, which is defined in terms of the strength of coupling; additionally we consider how the mechanical-structural fragility of the pipelines of the gas-source supply stream contributes to this dependence. In addition to network-wide assessment, damage was also evaluated at a local level by examining the performance status of each and every electricity distribution substation in the electricity grid. Finally, the comprehensive geographical distributions of performance loss at the European level can be visualized on a GIS tool; showing, as expected, that the highest direct damage in southeast Europe.JRC.DG.G.5-European laboratory for structural assessmen

Gas models and three difficult objectives

Competition, security of supply and sustainability are at the core of EU energy policy. The Commission argues that making the European gas market more competitive (completing the internal gas market) will be instrumental in the pursuit of these objectives. We examine the question through the eyes of existing models of the European gas market. Can model tell us anything on this problem? Do they confirm or infirm the analysis of the Commission appearing in fundamental documents such the Green Paper, the Sector Inquiry or the new legislation package? We argue that results of existing models contradict a fundamental finding (paragraph 77) of the Sector Inquiry. We further elaborate on the basis of the economic assumption underlying the models, that changing the assumptions implicitly contained in paragraph 77 cast doubts on a large part of the reasoning justifying the completion of the internal gas market. We also explain that models could help arriving at a better definition of the relevant market, which is so important in the reasoning of the Commission. Last we also find model results that question the effectiveness of ownership unbundling. As to security of supply, we explain that models can also contribute to assess the value of additional infrastructure in the context of security of supply, but this potential seems largely untapped. Last we note that sustainability has not yet penetrated models of gas markets. We conclude by suggesting other area of immediate concern, possibly of higher technical difficulty, that modellers could address in future research.

A comprehensive framework for seismic risk assessment of urban water transmission networks

Earthquakes are natural disasters which human beings cannot control, causing significant damage to the economy and society as a whole. In particular, earthquakes affect not only buildings but also lifeline structures such as water distribution, electric power, transportation, and telecommunication networks. The interruption of these networks is critical because it can directly damage the facilities and, at the same time, cause long-term loss of the overall system for society. In recent years, there has been increasing interest in the uncertainties of ground motion, deterioration of pipelines, and interdependency of lifelines. Therefore, it is essential to predict the damage through possible earthquake scenarios and accounting for factors affecting lifeline structures. This study proposes a comprehensive framework to quantify the impact of earthquakes on the connectivity of urban water transmissions. The framework proposes the following steps to predict damage from earthquakes: (1) estimate the ground motion considering the spatial correlation, (2) propose a modified failure probability of buried pipelines considering deterioration, and (3) evaluate the seismic fragility curves of network components and the interdependency among water treatment plants, pumping plants, and substations. For numerical simulations, an actual water network system in South Korea was constructed using graph theory, and the magnitudes and locations of the epicenters were determined based on historical earthquake data. Finally, the reliability performance indicators (e.g., connectivity loss and serviceability ratio) were measured when earthquakes of various magnitudes occurred in the urban area. This framework will enable the prediction of damage from earthquakes and enhance decision making to minimize the extent of damage

Nuevas técnicas para modelizar y analizar la vulnerabilidad de infraestructuras críticas de energía interdependientes

La interdependencia entre las redes de gas y electricidad es motivo de preocupación debido a la creciente utilización del gas para la generación de electricidad en centrales de ciclo combinado y al uso de energía eléctrica de los compresores en la red de gas. Estas redes están sujetas a riesgos de interrupción del suministro derivados de posibles problemas técnicos o amenazas intencionadas. Por lo tanto, resulta conveniente modelizar y analizar la vulnerabilidad de estas infraestructuras críticas de energía interdependientes.En esta tesis doctoral se presenta, en primer lugar, una metodología para analizar conjuntamente los flujos de electricidad y gas. El conjunto de ecuaciones no lineales que representan la operación del sistema de potencia se resuelve utilizando el método de Newton-Raphson, mientras que las ecuaciones en la red de gas se resuelven utilizando el enfoque de transformada análoga-lineal. Se presentan dos casos de estudio para demostrar la simplicidad de la metodología propuesta. Los resultados obtenidos se verifican contra el método Newton-Raphson tradicional con el fin de comprobar la solución alcanzada, encontrando un buen desempeño de la metodología conjunta aplicada. La aplicación del enfoque propuesto permite el análisis de la vulnerabilidad de las infraestructuras energéticas interdependientes. También, se desarrolla una metodología para evaluar la vulnerabilidad estructural de las redes de energía eléctrica y gas acopladas, considerando interdependencias en el proceso de fallos en cascada. La vulnerabilidad se evalúa empleando el índice de desconexión de carga y las medidas de centralidad de vulnerabilidad geodésica e impacto en la conectividad. El estudio muestra una elevada correlación entre el índice de desconexión de carga y el índice de vulnerabilidad geodésica. De esta manera, la teoría de grafos puede usarse como sustituto de los enfoques de flujos de carga que demandan un conocimiento detallado de los parámetros eléctricos e hidráulicos de los sistemas bajo estudio y son computacionalmente más intensivos que los métodos estadísticos de grafos. Como resultado, se propone un nuevo método para estimar la vulnerabilidad de las redes de energía eléctrica y gas conjuntas utilizando el índice de vulnerabilidad geodésica. Asimismo, se estudia el comportamiento de las redes de electricidad y gas natural de España, tanto de manera separada como conjunta. Los resultados muestran que la red de gas natural es menos robusta que la red eléctrica y que la red acoplada es más vulnerable que la red eléctrica ante fallos aleatorios y deliberados. Además, eliminar los nodos más fuertemente conectados de los dos sistemas independientes resultaría una estrategia de ataque eficaz para el rápido colapso de las infraestructuras acopladas interdependientes. Por último, se evalúa la robustez estructural de los planes de expansión de las infraestructuras de electricidad y gas natural en España. Los casos de estudio corresponden a las principales inversiones propuestas por los operadores de los sistemas en 2015-2020. Los resultados demuestran que la construcción de algunas instalaciones para la expansión de ambas redes no mejora la robustez estructural de la red acoplada; sin embargo, cuando se tiene en cuenta todo el programa de inversión se produce una mejora relativa de hasta un 6% con respecto al caso base. La metodología propuesta en esta tesis corrobora que la aplicación de la teoría de grafos es adecuada para analizar la planificación de activos de una infraestructura energética crítica, requiriendo únicamente la topología y el programa de inversiones para evaluar el desempeño de la red acoplada en caso de fallos en cascada. En suma, esta tesis doctoral pone de relieve la importancia de que los sistemas energéticos se aborden como redes acopladas debido a sus fuertes interacciones. Una perturbación en un sistema puede no ser crítica si las infraestructuras están separadas, pero dado que ambas redes son interdependientes, el impacto resultante podría causar fallos en el otro sistema. En otras palabras, las interdependencias aumentan el impacto de las perturbaciones.<br /