MODELS AND TOOLS TO SUPPORT THE DECISION MAKING FOR ELECTRICITY SECURITY

Security of power systems, as a critical infrastructure, is a global concern because continuous, reliable supply of electricity is substantial for the economy of modern countries and the well-being of people. Thus electricity security is a key concern for the utilities, the operators and the authorities in charge. From one side, the threats to the supply of electricity have changed dramatically throughout the last decade; additional to the traditional natural (lightning, flood, etc.) and accidental ones (component failure, untimely intervention of protections, etc.), new threats represented by highly organized malicious attacks needs to be considered in the light of the development of national and international terrorism and crime. Moreover, renewable energy sources and more smart equipment are being utilized extensively, the infrastructures are growing in complexity and vulnerability and in parallel, information flows and operational methods are being developed rapidly which consequently result in a huge growth in different types of emerging threats to the power system infrastructures. From another side, keeping a required level of security after materialization of threats to the power systems implies a required level of investment to secure the infrastructure. New technologies and innovation in the energy sector can greatly enhance the ability of the system to prevent and cope with security threats and incidents. Multiple available options and proposals of measures and investments need to be decided and selected for limited budgets. Therefore, there is a need for panoramic understanding of how and where to allocate limited budgets for the preparedness of the system against potential failures or ceasing the evolution of the cascades at a restrained level. The decision on the implementation of a set of selected feasible countermeasures needs to be taken through a scientific evidence based approach. Therefore, special tools are needed to support decision making process aiming at modeling the impacts of various threats, quantifying the consequences of the disruption in the supply of electricity and eventually carrying out cost/benefit trade off of the investment to improve the security level. This thesis aims to introduce a proposed framework of supporting decision making for electricity infrastructure security, whose objective is to ensure the ability of the power system to withstand some level of impacts from threats by means of the enhancement of the infrastructure. The decision needs to assess the investments, with medium/long term perspective, off-line, and carry out a tradeoff analysis between them and benefits given a proper estimation of the costs of the failure. As prerequisite, firstly threats to power system need to be classified and mapped to triggering events which directly affect the physical networks including ICT layers. A materialized threat (set of triggering events) provokes a sequence of cascading failures and counteractions in the grid. The simulation and analysis of the cascades leading to blackouts are extremely intricate due to various time scales, multiple interacting automatic and human-driving actions, and the large set of possible countermeasures. To design protective schemes, guiding investments and supporting policy decision making on reinforcing the system, the simulation of post-contingency evolution of cascading events is crucial. In this thesis, I also present a simulation framework which provides snapshots of system operational status during cascading failures, modelling both behaviors of the system and human/automatic actions, and considering the actions for minimizing load-shedding or maximizing the restoration of the unserved loads. The conceptual framework is implemented as a software tool to simulate system behaviors and actions like automatic countermeasures, human interventions and optimal operational strategies to defend and restore the system. It can be used as a key component of the decision support system to evaluate investments on the countermeasures and the potential costs of different threats. The software with its developed algorithm has been applied to study the countermeasures to enhance the security of two realistic regional EU power transmission networks.