Abstract
This work presents a system to manage wind turbines maintenance through a predictive model. The system is based on specific maintenance software and hardware for data acquisition and also on algorithms for prediction based on time series. The maintenance software is called SMIT - (Terology Integrated Modular System). The acquisition system can be interconnected with professional, industrial and low cost acquisition systems. The communication channel is based on IP networks, using clock synchronization for data sampling. A time series prediction algorithm runs on low cost hardware, working as a monitoring trigger of the central system.

Abstract
Lightning caused around 26% of the total number of faults in the Portuguese Transmission system in the analysed period. Based on historical data, this study uses incident data from 2001 until 2008 (2157 faults in overhead lines) and lightning data from 2003 until 2008 (around 1.65 million cloud-to-ground flashes). The performance of the lightning monitoring system is analysed and the statistical analysis of the incidents caused by lightning is made. Therefore, several indicators are presented, such as average failure rate per 100km and the percentage of these faults from the total. In addition, month and hour fault distributions are shown and the overhead lines with the worst performance in terms of lightning are identified. The aim of this analysis is to characterize this type of faults in order to evaluate the impact caused by lightning on an operational level. It will be one of the many inputs of a risk assessment methodology. © 2009 IEEE.

Abstract
Voltage stability has become one of the most important issues in electrical power systems. The power system ability to maintain acceptable bus voltage is a very important characteristic of a network. This paper analyzes the performance of line stability indices. These indices were tested in IEEE 14 and IEEE 57 busbar test systems, with satisfactory results. Simulation results show that using line stability indices the most critical line and the weakest bus of the system can be correctly identified.

Abstract
This paper proposes the use of available PMU measurements for establishing network observability State estimation is an important EMS application for providing real time, reliable and qualitative information on the system state. The observability analysis is the necessary function of the whole network state estimation. This paper addresses the incorporation of PMU measurements with the purpose of full network observability. The methodology is validated by the results on IEEE 14, 30 and 57 bus test system.

Abstract
This paper aims to characterize accurately each incident main cause, to analyse their occurrence with the intrinsic characteristics of the Portuguese territory, including geographical and meteorological data, and to define the requirements and guidelines to use this information as input for a risk assessment methodology, whose main purpose is to support control room operators in their continuous task.

Abstract
Nowadays the total sum of Distributed Generation (DG) in the Portuguese Distribution Network (DN) is extremely significant. Previously, load shedding schemes were designed without taking into consideration this type of generation. In this paper, the Portuguese Electrical System is studied through a static analysis using real data, and the new relay parameters to be applied in substations are evaluated, continuously bearing in mind the strict coordination with those of the DN. In order to achieve these purposes, an algorithm was developed to rank possible candidate substation feeders to the load shedding plan, using Ms Excel to process data and perform the calculations. The obtained results show that by using the designed algorithm it is possible to find a systematic process for determining under-frequency relay parameters considering the trade-off between shedding critical consumers and shedding DG. © 2009 IEEE.