Review on modeling and simulation of interdependent critical infrastructure systems

Urban ecological infrastructure: an integrated network for ecosystem services and sustainable urban systems

A method for risk modeling of interdependencies in critical infrastructures

Complex networks have been studied intensively for a decade, but research still focuses on the limited case of a single, non-interacting network. Modern systems are coupled together and therefore should be modelled as interdependent networks. A fundamental property of interdependent networks is that failure of nodes in one network may lead to failure of dependent nodes in other networks. This may happen recursively and can lead to a cascade of failures. In fact, a failure of a very small fraction of nodes in one network may lead to the complete fragmentation of a system of several interdependent networks. A dramatic real-world example of a cascade of failures (‘concurrent malfunction’) is the electrical blackout that affected much of Italy on 28 September 2003: the shutdown of power stations directly led to the failure of nodes in the Internet communication network, which in turn caused further breakdown of power stations. Here we develop a framework for understanding the robustness of interacting networks subject to such cascading failures. We present exact analytical solutions for the critical fraction of nodes that, on removal, will lead to a failure cascade and to a complete fragmentation of two interdependent networks. Surprisingly, a broader degree distribution increases the vulnerability of interdependent networks to random failure, which is opposite to how a single network behaves. Our findings highlight the need to consider interdependent network properties in designing robust networks.

http://absimage.aps.org/image/MAR10/MWS_MAR10-2009-001087.pdf

Catastrophic cascade of failures in interdependent networks

SUMMARY
A resilience index is used to quantify preventive measures, emergency measures, and restoration measures of complex systems, such as physical infrastructures, when they are subjected to natural disasters like earthquakes, hurricanes, floods, etc. Interdependencies among these systems can generate cascading failures or amplification effects, which can also affect the restoration measures right after an extreme event and generate a reduction of the resilience index. In this article, a method is proposed to evaluate the physical infrastructure resilience of a region affected by a disaster considering infrastructure interdependency. It is illustrated using available restoration curves from the March 11 2011 Tohoku Earthquake in Japan. The weights assigned to each infrastructure, which are used to determine resilience, are evaluated using the degree of interdependency indices which are obtain by time series analysis. Results show that the weight coefficients thus obtained do not influence the resilience index significantly; however, the methodology proposed is unbiased from subjective judgment and is able to identify the critical lifelines. Furthermore, the results of the case study presented here suggest that to obtain meaningful estimation of the weight coefficients, it is necessary to consider the period range between two perturbations (e.g., main shock and aftershock). Future infrastructure disruption data (from this and other earthquakes) would be needed to generalize this finding that will allow also to quantify the changes in the restoration curves caused by the magnitude and distance of the shocks from the epicenter, as well as the intrinsic properties of the physical infrastructures. Copyright © 2014 John Wiley & Sons, Ltd.

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Physical infrastructure interdependency and regional resilience index after the 2011 Tohoku Earthquake in Japan

https://www.sintef.no/globalassets/project/vulnerability-and-security/publications/papers/ress_risk-analysis-of-critical-infrastructures_2012.pdf

Risk analysis of critical infrastructures emphasizing electricity supply and interdependencies

A comprehensive framework for vulnerability analysis of extraordinary events in power systems

There is an increasing trend towards using the concept of risk assessment as an important tool in distribution system asset management. The paper presents a framework of three main stages in the process of risk management for distribution companies being ‘Risk Study Planning’, ‘Risk Scenario Identification’, and ‘Risk Modelling – Analysis – Decision Making – Communication’. A description of risk related challenges for distribution companies is also presented – based on a survey performed among distribution companies in Norway, Finland and France. The results show six main categories of challenges which contribute to the total risk picture.

/pdf/a-risk-based-approach-to-distribution-system-asset-4w6m6vmj4v.pdf

A risk based approach to distribution system asset management and a survey of perceived risk exposure among distribution companies

Correct operation of the protection system is of vital importance for the reliability and security of supply. Information of protection system faults is therefore important for different purposes such as quality of supply regulation and as input data to security and reliability analysis. This paper provides a comparative review of the Norwegian and Finnish fault statistics for line and transformer protection systems at the voltage levels 132 - 400 kV for the period 1999 - 2004. Unwanted operation is the major fault type, particularly for transformer protection. Human causes dominate by roughly 50 %, technical faults count for 20 - 30 % while there are large portions of faults where the cause is not identified. In Norway 20 % of the total energy not supplied at these voltage levels are caused by the protection. The corresponding portion in Finland is only 4 %.

/pdf/protection-system-faults-a-comparative-review-of-fault-1zl7zqbxlx.pdf

Protection System Faults -- a Comparative Review of Fault Statistics

This paper describes a framework and methodology for risk and vulnerability analysis including extraordinary events in power systems. The framework is based on a bow-tie structure and identifies threats, unwanted events, barriers and consequences. Application of the methodology is shown for a real case analyzing extraordinary events in a transmission system. In this case the consequence is unacceptable, but the risk is moderate due to the low probability for the event to occur. The case study and experience so far indicates that one of the most challenging parts of a risk and vulnerability analysis is how to identify the vulnerable operational states and extraordinary events.

Oddbjørn Gjerde

Papers

Risk analysis of critical infrastructures emphasizing electricity supply and interdependencies

A comprehensive framework for vulnerability analysis of extraordinary events in power systems

A risk based approach to distribution system asset management and a survey of perceived risk exposure among distribution companies

Protection System Faults -- a Comparative Review of Fault Statistics

Risk and vulnerability analysis of power systems including extraordinary events