Interdependent Energy Infrastructure Simulation System (IEISS)
Research on energy generation and transmission networks such as electric power systems started in the 1970s to assist a variety of federal, state, and local agencies in understanding these infrastructures, track their evolution, identify their strengths and weaknesses, assess their reliability, and analyze their economics. From this long history of research, an extensive set of databases, analysis tools, and science and engineering expertise has developed to answer a broad range of questions important to decision makers and the nation as a whole. Our most innovative and original work in this area has dealt with simulations of the interdependencies between energy infrastructures, where these are treated as coupled nonlinear complex systems, in order to quantify synergistic effects and feedback mechanisms between them. Within NISAC, this work has spanned an array of tasks from urgent quick-turnaround case studies in times of crisis to long-term research projects.
Much of NISAC’s analysis of the electric power industry has emphasized the identification of outage events that may have an impact on the reliable supply of electric power and the development of vulnerability mitigation options and business continuity strategies for decision-makers within federal government.
Inherent attributes of the electric supply system, natural causes, or man-made causes each constitute possible sources of disturbances in the power system. We typically construct detailed transmission-level models of the utilities of interest and then our team of engineers analyzes the models using state-of-the-art power flow simulation tools to identify (i) service and outage areas, (ii) outage duration, (iii) critical system components, (iv) restoration strategies, (v) mitigation options, and (vi) system performance. The goal of these analyses is to determine the electric grid’s ability to supply the aggregate electrical demand and energy requirements of its customers, taking into account outages of system elements.
Since the late 1990s, our work on the electric power grid has expanded into the broader area of energy generation and transmission infrastructures in general. We now consider additional energy networks such as natural gas pipelines. Energy infrastructures typically have “feedback loops” where infrastructures depend upon each other to deliver their product: a gas-fired electric generating plant requires a steady supply of natural gas, for instance, and the natural gas pipelines may possess electric-powered compressors to maintain sufficient pressure. The security of the nation requires ensuring that the nation’s interdependent energy, communication, and transportation infrastructures provide an appropriate quality of service. The interdependency concept is critical to understanding these complex coupled systems and we feel that an inflexible modeling and technology base has hampered the understanding of them in the past. Historically, although existing modeling and simulation technologies do well at analyzing single infrastructures, these technologies have severe limitations when it comes to modeling interdependent infrastructures.
The IEISS Simulation Tool
The Interdependent Energy Infrastructure Simulation System (IEISS), embodied as analysis software tools, aims at developing a comprehensive simulation study of the nation’s interdependent energy infrastructures to address a wide variety of intra- and inter-infrastructure dependency questions. The IEISS analysis tool models infrastructure networks (mostly energy transmission network systems such as electric power systems and natural gas pipelines) and simulates their physical behavior, including the interdependencies between systems (such as when the energy supplied by one system is used to operate components of another system). Each physical, logical, or functional entity in the model has a variety of attributes and behaviors that mimic its real-world counterpart. IEISS is by far the most flexible and highest quality software framework available for the modeling, simulation, and analysis of interdependencies among critical energy infrastructures, allowing analysts to identify and deeply understand the implications of infrastructure interdependencies for normal operations as well as for disruptions, and providing analysts an unprecedented capability to assess, from an interdependencies perspective, the technical, economic, and national security implications.
IEISS supports a diversity of infrastructure analyses. One can accurately identify critical components and vulnerabilities in coupled infrastructure systems, assess how future investments in the systems might affect quality of service, evaluate the effect of policies, and aid in decision-making during crises. Additionally, IEISS is a research tool for investigating fundamental issues related to real-life, nonlinear, coupled, complex networks. The simulation can be used to visualize the interconnectivity between different systems, predict the outcome of incidents affecting the networks, measure the effects of disruptions in service, assess system robustness under varied future plans and forecasts, and identify components critical for the operation of the systems.
A prototype version of the IEISS analysis tool was used in preparation for the 2002 Salt Lake City Olympics. Since then, it has become a general, operational platform been used to study energy interdependencies: In Florida, we assessed dependencies between electricity, natural gas, and petroleum fuels with respect to a hypothetical natural gas pipeline break. We have provided quick-response assessments of impending hurricane landfalls and generally supported energy shortfall contingency planning. The IEISS software has been deployed at government agencies and is used by teams of analysts resident at Los Alamos National Laboratory on a continuing basis.
