In operational practice power system security analyses are usually conducted with respect to "credible" contingencies, such as almost all N-l contingencies and some N-2 contingencies suggested by operational experience. Moreover it is normally conducted in an off-line approach. The paper presents an extensive analysis performed on a realistic network representative of the Italian HV grid by means of a Dynamic Security Assessment (DSA) application tool. The paper is aimed at proposing some improvements for the DSA tool through an integration between the original simulator environment and MATLAB functions, used to automatically generate different scenarios to be processed. The goal of this study is to analyze different scenarios and investigate the possibility to correlate some network parameters (such as reactive margins, voltages, etc.) to the Voltage Stability margin provided by a DSA tool.

The paper presents the preliminary results of an on-going research activity concerning the application of ANN (artificial neural network) for on-line identification of potential harmful states in power systems (contingency screening). The necessity of on-line static security assessment with a good degree of confidence and the evaluation of indices for successive indications to power system operators of possible remedial actions is deeply felt in the new context of liberalized electrical energy markets. The paper addresses primarily the use of ANN for contingency screening. It describes and reports the activity for choosing the most suitable ANN structure and training the ANN for a realistic power system. The chosen ANNs are then trained and used to assess the security state of a larger power system representing an equivalent model of the Italian HV grid

The paper presents a technical overview of a large research project on Dynamic Security Assessment (DSA) supported by EU. Transient Stability Assessment and Control, which was one of the main goals of the project, is taken into consideration by presenting the fundamental theoretical methodology and possible applications. A specific prototype installation for a realistic power system is then reported by presenting and commenting some of the obtained results.

This paper presents a technique for identifying a dynamic power system equivalent using Artificial Neural Network (ANN). The power system is divided into two parts: internal system, also called retained system or the study system, and the external system which is equivalenced by the neural network. The approach uses only measurements at interconnection nodes where retained and reduced systems are interfaced. The equivalent is an input-output equivalent where the inputs are voltages at interconnection nodes and the outputs are currents flowing through interconnection lines. The neural network will be interfaced with the study system through interconnection variables, i.e. voltages and currents, and will provide the dynamic behavior of the external system. Test results will provide the robustness of the proposed methodology in developing dynamic equivalents.

The authors introduce an exotic financial hedging tool in order to replicate interruptible load supply contracts. This derivative tool should guarantee the ISO the possibility of using interruptible resources "when" and "where" it actually needs them. A methodology, based on nonlinear programming, is proposed in order to give the technical tool necessary to exploit, on real-time operation, all control resources ensured by energy markets and by the proposed financial contracts. In the formulation, static and dynamic security constraints are taken into account. Moreover, costs related to control actions are minimized through the introduction of a pure economical objective function. The procedure has been implemented and tested on a representation of the Italian national grid.

In this paper, a contract curtailment proce- dure for the management of power systems in a deregu- lated environment is presented. A method to evaluate corrections on power exchanges in bilateral contracts is proposed in order to guarantee the static and dynamic security. The cost of curtailment for each transaction is evaluated concurrently to the solution of a dynamic opti- mization problem. The procedure has been implemented on an actual and detailed representation of the Italian national grid. Test results are presented. security constraints are integrated in the same formula- tion. The distribution of curtailment among transactions is strongly influenced by the formulation of objective functions and other features. In (5-6), curtailment de- pends on the willingness-to-pay of each customer, whereas in the definition of rules for the Transmission Loading Relief for the WSCC (7), some LIFO priority lists are taken into account. In this paper, the proposed contract curtailment strat- egy is based on the sensitivity of each transaction to the static and dynamic performances of the system. Moreo- ver, the objective function is related to the firmness of transactions. This feature can be exploited by ISO to minimize curtailment costs, taking into account the presence of firm and interruptible loads. The procedure has been implemented on an actual and detailed representation of the Italian transmission system. Test results are presented.

The paper provides an overview of existing programs for including load as an actor in power sy stem management and control. The possible roles for load in electrical energy systems are recalled and specific interest is devoted to Interruptible Loads. Examples of applica tions for a realistic power system such as the Italian one are provided. Some preliminary results are shown.

SOMMARIO Si forniscono nel seguito alcune informazioni relative agli obiettivi essenziali ed ai principali risultati ottenuti nell'ambito di due progetti di Ricerca di Sistema (SICURE e CONSISTE), svolti in collaborazione con i Politecnici di Bari, Milano e Torino e con le Università di Genova e Pavia, che hanno affrontato il tema della sicurezza e del controllo con l'obiettivo di sviluppare e rendere disponibili un insieme di funzioni che permetta al sistema elettrico nazionale di mantenere un alto livello di affidabilità, anche in presenza di maggior sfruttamento della rete e di competizione economica tra i diversi operatori del settore. Le funzioni sviluppate potranno essere applicate sia in sede di stabilizzazione e regolazione del sistema elettrico in condizioni di funzionamento normale, sia in fase di controllo preventivo e correttivo delle condizioni di allarme o di emergenza, sia in sede di ripristino del sistema a partire da una condizione di black-out parziale o totale.

The paper presents a technical overview of a large research project on Dynamic Security Assessment (DSA) supported by EU. Transient Stability Assessment and Control, which was one of the main goals of the project, is taken into consideration by presenting the fundamental theoretical methodology and possible applications. A specific prototype installation for a realistic power system is then reported by presenting and commenting some of the obtained results.