Abstract
Taking into account that the non renewable recourses are less and less available worldwide we need to use renewable energies to produce electricity. The wind energy is nowadays the most attractive renewable energy, after hydropower, to produce electricity. Wind energy is the renewable energy source that had a higher growing in the last decades and can be considered a hope in future based on clean and sustainable energy. All over the world, energy companies are investing in technologies to make better use of renewable energy to generate electric power. Wind energy is the renewable energy source that had a higher growing in the last decades and can be considered a hope in future based on clean and sustainable energy. Unlike conventional fuels, wind energy is a massive indigenous power source permanently available in virtually every nation in the world. Wind power delivers the energy security benefits of fuel costs, no long term fuel price risk, and avoids the economic and supply risks that can arise with reliance on imported fuels and political dependence on other countries. The problems resulting by the production of electricity using wind power and by the interconnection of wind parks to the grid are discussed in this paper.

Abstract
In a world with a global market that is continually increasing, the productivity management plays an important key role to keep the competitiveness. The productivity can be achieved through the availability that can be increased through the adoption of efficient maintenance practices, by focusing the organisations on adequate type of maintenance strategy. Condition Based Maintenance (CBM) uses primarily non destructive testing techniques, as environmental indicators, visual inspection, monitoring functioning variables and performance data. This kind of maintenance replaces tasks of scheduled maintenance by warranted interventions predicted by on-condition limits previously defined. The interventions occur only when the equipments presents abnormal symptoms. The intervals of CBM are determined based on the expected delay to fail and are managed through the frequency by which the predictive interventions have to be done. The technological advances are accepted and applied on CBM systems, which includes improved knowledge of failure mechanisms, advancements in, failure forecasting techniques, monitoring and sensor devices, diagnostic and prognostic software, communication protocols, and computer networking technologies. The measurement precision and sensitivity of the Condition Monitoring (CM) techniques are used because they affect the reaction time available to reduce or eliminate the consequences of the functional failure. CBM maintenance tasks must be applicable under the situation of cost effective improvement, including external costs. The base of development of this paper is supported by an integrated system called SMIT (Terology Integrated Modular System), that permits to manage the maintenance itself, including on-condition maintenance, but it is modular enough to permit to associate new features, namely this last approach, in order to maintain the system up-to-date and, always possible, to anticipate the future.

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
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.