Abstract
In this paper it is studied and analyzed the impact of different security performance indices on a contingency screening and ranking algorithm. The proposed filtering technique consists of three modules, with different complexity levels. The contingencies are ranked in accordance with severity indices that allow assessing the influence of the overloads and voltage limit violations in the power network. The developed software package was applied to the IEEE 118 Test Power System. The simulation results that were produced using two different sets of security indices were compared, showing a satisfactory agreement The simulation was carried out considering a monotonous increase of the load level as well as a random one. For the different solutions the computing times were also obtained. Finally, some conclusions that provide a valuable contribution to the understanding of the Electric Power System security analysis are pointed out. © 2003 IEEE.

Abstract
In this paper it is proposed an efficient steady-state contingency classification using the Rough Set Theory. This approach allows the evaluation of the importance of particular attributes and the elimination of redundant attributes from the decision domain. Moreover, the construction of a minimal subset of independent attributes ensuring the same quality of classification as the original set. The elimination of redundant attributes can help in identification of strong non-redundant classification rules. The developed methodology produces a classification of the system operation in four possible states. The methodology developed by the authors was applied to a test power network and the results obtained were analysed. Finally, some conclusions that provide a valuable contribution to the understanding of the power system security analysis are pointed out.

Abstract
In this paper it is used a hybrid approach to study and analyse the tripping effect of one or more generators in the transient stability of a multimachine power system. This efficient and robust approach combines the advantages of the time domain integration schemes to compute the initial system trajectory with the equal area criterion. The transient stability assessment is obtained using stability indices. Consequently, the time domain simulation is only computed during a short integration period. This early termination procedure reduces drastically the computing time. The software package TRANsySTEM developed by the authors was applied to a multimachine test power network. The results obtained with this hybrid formulation were compared with the solutions produced by a time domain simulation program. Finally, some conclusions that provide a valuable contribution to the understanding of the generators tripping effect in the transient stability problem are pointed out.

Abstract
In this paper it is studied and analysed the influence of the selective load shedding in the dynamic voltage stability assessment of the BPA test power network. The outage of a 500 kV overhead transmission line was simulated. Different values of emergency load shedding were used to avoid voltage collapse. The automatic voltage regulators of the generating units and the turbine speed governors were modelled. Different load models were used and the under load tap changers were also taken into account. The simulation results were obtained using the commercial transient software package EUROSTAG, developed by Electricité de France and Tractebel Energy Engineering. Finally some conclusions that provide a better understanding of the voltage collapse phenomena are pointed out.

Abstract
Sliding mode controllers are derived for the control of the average output voltage in DC/DC power converters. The controller design is carried out on the basis of well-known bilinear models of such circuits. A cascaded control structure is chosen for ease of control realization and to exploit the motion separation property of this power converter. The performance of the proposed sliding mode controllers is tested for the buck and boost converter type. The numerical simulations will demonstrate the efficiency of sliding mode techniques in this field as a powerful alternative to other existing methods. © 2003 IFAC.

Abstract
This paper describes a surveillance system for forest environments and protected natural areas. The surveillance system has a capacity for detecting fires and other ecological crimes. The system uses a digital camera that is controlled remotely by a system operator. Using the software the operator may choose to zoom a special spot or even take measures to strategically fight the fire right before it becomes uncontrollable. Since this system is operated in the middle of forests, aspects like effectiveness, robustness and reliability are crucial. In positioning the camera, the system uses a stepper motor for the vertical movement of the camera and a DC motor for the horizontal movement. The system also captures information about the temperature, humidity, wind speed and direction. All the processing is realized by a PIC16f877 microcontroller. © 2003 IEEE.