Abstract
The paper presents a study of the convergence characteristics and an assessment of the performance of the algorithm used to solve power system state estimation problem. The algorithm is studied to determine and compare the convergence patterns using several measurement sets consisting of line flows, bus injections, voltage magnitudes and line currents. The algorithm was tested on different IEEE test systems. Results related to the test with IEEE 14 bus bar system are presented.

Abstract
In a global world, the survival and sustainability of industrial companies depends on several factors: production continuity; quantity assurance; quality assurance; competitive prices for products; on time production; flexibility; operational safety and environmental safety. To achieve these goals, sustainable industrial operations must rely on dependable systems and equipments. Dependability is defined as "the collective term describing the availability performance of any simple to complex product" [1]. This definition can be extended for industrial operations, to their reliability and maintainability design characteristics. As there are no perfect systems and equipments designs, component degradation and failures will always occur during their life cycle. So to keep their dependability level during the life cycle good maintenance support is essential. In this paper we will discuss the importance of maintenance to achieve the required dependability and sustainability for industrial production processes and how that can be achieved.

Abstract
An engineering curriculum requires that its future professionals should be fully prepared to accomplish a variety of tasks involving not only theoretical concepts, but also skills acquired through effective practice. In the Instituto Superior de Engenharia de Coimbra (ISEC), Department of Electrical Engineering, preference was given to apply methods integrating technology in the learning and then evaluating the outcomes. Problem-based learning (PBL) was used as an instructional strategy of active learning, and adapted for use in the Lighting Design course. The students are presented with a virtual scenario, quite similar to the real world, where they are required to perform as they would in a real life situation. The emphasis is given to PBL so that they can learn to become autonomous, skilled and explore their own potential as well as improve team work skills/spirit and that can be applied to a wide range of students and subject matters. PBL is introduced to the students as a 'learn by doing' project. The project incorporates aspects of electrical engineering and computing skills. This study analyses the learning process/techniques that help students deal with the complexity of a Lighting Design Project and assesses its effectiveness and impact on the students. Essentially, it encourages them to be in charge of their education. The benefits of PBL in the Lighting Design course are visible in the improvement of the study and analysis of a Lighting Design project. The method may also bring benefits for Electrical Engineering programmes where educators struggle for improved teaching and learning. The simulation was performed using the Dialux 4.3 software package that runs in Windows Vista or XP environment.

Abstract
In this paper it is proposed an efficient contingency screening and ranking algorithm for assessment and classification of multiple contingencies of an Electric Power System using the Rough Set theory. The developed methodology produces a classification of the system operation in five possible states: normal, alert, emergency, in-extremis and restorative. These different operating states correspond to six levels of security: secure, alert, correctively secure, alert no correctable, emergency and restorative. The states can be classified horizontally as secure, that correspond to the normal state and insecure for the remaining ones. The developed computer programs, the SECURsySTEM were applied to the IEEE 118 busbars test power network and results are presented and analyzed.

Abstract
The electrical power production from dispersed energy sources or distributed generation is playing an increasing role in the supply of electricity in the liberalized electricity markets. Distributed generation can have a significant impact on the power flow, voltage profile, stability and the power quality for both customers and electricity suppliers. In this paper it is studied and analysed the influence of a wind farm in the dynamic voltage stability of a power network. A short-circuit in the middle of the transmission line and a significant load demand disturbance situation were simulated. The automatic voltage regulators of the generating units, the turbine speed governors and the double fed induction generator models were taken into account. The simulation results were obtained using the EUROSTAG software package. Finally, some conclusions that provide a better understanding of the dynamic voltage stability are pointed out.

Abstract
This paper describes an integrated wind farm maintenance system, including software, hardware and some algorithms. The approach will imply the optimization of the maintenance planning among different wind towers owned by a company, considering the management of situations where the distances among them have a considerable weight in the maintenance costs. This reason, associated to the generators accessibility and the on-line maintenance variables acquisition, are very important to justify the necessity of improvement of the maintenance planning. This objective is achieved through the application of integrated maintenance management systems to which are associated new functionalities, in parallel with the usual ones in these systems that fit within the on-condition predictive maintenance, including on-line data acquisition modules. Usually, the manufactures construct, deploy and give the means to the suppliers to perform the wind system's maintenance. In some cases, the owners of wind farms can choose the maintenance company. This is a very competitive area, where companies hide the development details and implementations. Another important factor is that, by the first time in last ten years, the three countries with the largest installed power, together, have fallen to a minimum historic, below 40% of the market for wind power in the EU. Definitively, the other European countries encouraged the appearing of programs for installing wind power, with prominence for Italy, Portugal and Netherlands. Within this scenario, the development of maintenance management models for multiple wind equipments is important, and will allow countries to be more competitive in a growth market.