Simulation Models and Implementation of a Simulator for the Performability Analysis of Electric Power Systems Considering Interdependencies

Abstract

Electric Power Systems (EPS) become more and more critical for our society, since they provide vital services for the human activities. At the same time, obtaining dependable behaviour of EPS is an highly challenging task, both in terms of defining effective business management and in terms of analysis of dependability and performability attributes. A major concern when dealing with EPS is the understanding and the evaluation of the interdependencies between Electric Infrastructures (EI) and the Computer-based Control System (CCS), which controls the status and the activities of EI. Studies on these interdependencies are only at an early stage of development. Major difficulties are the complexity of the infrastructures under analysis and the lack of well-established models and tools for dealing with them. This paper presents an ad-hoc simulator for the evaluation of dependability and performability measures in EPS. The system model the simulator is based on focuses on interdependencies between EI and CCS. Most existing modeling approaches in EPS does not provide explicit modeling of interdependencies among the composing subsystems, so that the cascading or escalating phenomena cannot be deeply analyzed. Our stochastic model is composed by separated and simple, but representative, submodels representing the dynamics of EI and different policies of reactions to disruptions and reconfigurations triggered by CCS. In this way, the simulator aims at providing explicit modeling of the interdependencies between the main subsystems, so the impact on the dependability and performability of the cascading or escalating failures can be analyzed. In this paper, we describe the simulator and highlight the design choices.

Interdependency Analysis in Electric Power Systems

“…Such operations are not considered in detail but they are abstracted at two levels, on the basis of the locality of the EI state considered by ITCS to decide on proper reactions to disruptions (the same approach adopted in [4]). Each level is characterized by an activation condition (that specifies the events that enable the ITCS reaction), a reaction delay (representing the overall computation and application time needed by ITCS to apply a reconfiguration) and a reconfiguration strategy (RS), based on generation re-dispatch and/or load shedding.…”

“…The output values of RS 2 () for P and F are derived by solving an optimization problem to minimize the change in generation or load shedding, considering more sophisticated system constraints, as described in [4]. The reconfiguration strategy RS 1 () is applied immediately, while RS 2 () is applied after a time needed to RT S to evaluate it.…”

“…Some simplifying assumptions have been made to represent the power flow through the transmission grid, following the same approach used in [4,5,6,7]. Therefore, the state and the evolution of the transmission grid are described by the active power flow F on the lines and the active power P at the nodes (generators, loads or substations), which satisfy linear equations for a direct current (DC) load flow approximation of the AC system.…”

Model-Based Evaluation of the Impact of Attacks to the Telecommunication Service of the Electrical Grid

“…The arming operation is immediately activated when an EI fault happens, but it requires more time than RS1 to be accomplished. Initially, the set of DSO SSs to be involved in the load shedding strategy is derived by solving an optimization problem to minimize the change in generation or load shedding, under additional system constraints, as described in (Romani, Chiaradonna, Di Giandomenico & Simoncini, 2007).…”

Quantification of dependencies between electrical and information infrastructures

“…The output values of RS 2 () are derived by solving an optimization problem to minimize the change in generation or load shedding, under additional system constraints, as described in [34]. The reconfiguration strategy RS 1 () is applied immediately, while RS 2 () is applied after a time needed by RTS to evaluate it.…”