Este trabalho descreve a produção e a caracterização de redes de período longo (LPG) e redes de Bragg corroídas como elemento sensor. Tanto a produção quanto às caracterizações das redes de período longo foram realizadas no Laboratório de Laser da UTFPR e a produção e caracterização das redes de Bragg corroídas foram realizadas no Laboratório de Óptica Coerente da Universidade de Aveiro, Portugal. São abordados aspectos referentes aos princípios de produção e funcionamento do dispositivo. São apresentados os resultados obtidos na produção e na caracterização das redes, bem como os sistemas experimentais desenvolvidos para estes fins. O método empregado para a escrita das redes de período longo foi o da aplicação ponto-a-ponto de um arco elétrico, sendo produzidas redes com períodos de 598 e 600 μm operando na terceira janela de transmissão em torno de 1,55 μm. As redes de período longo e as redes de Bragg corroídas foram caracterizadas quanto as suas sensibilidades ao índice de refração, temperatura e deformações longitudinais (esta última caracterização foi realizada apenas para as redes de período longo), assim com a sensibilidade cruzada a estes parâmetros. A resposta das redes de período longo em função da variação do índice de refração do meio externo em duas diferentes situações, uma na presença de gasolina em ambiente hídrico e outra na presença de vapores de hidrocarbonetos ambiente atmosférico, indica a possibilidade da utilização deste dispositivo na detecção de vazamentos de hidrocarbonetos em refinarias ou postos de abastecimentos. Estas redes também foram caracterizadas para monitorar a concentração de cromo (III e VI) em soluções aquosas, os resultados indicam a possibilidades de monitorar em tempo real os processos de tratamento destes produtos, e assim otimizar este processo. As redes de Bragg foram utilizadas para a caracterização de propriedades ópticas de materiais, o resultado obtido para o etanol mostrou boa concordância com os valores apresentados na literatura, indicando que esta é uma técnica adequada para este fim. / This work describes the production and characterization of long period gratings (LPG) and etched fiber Bragg gratings as sensors. Both the production and characterization were carried out at the Laser Laboratory of UTFPR and the production and characterization of etched fiber Bragg gratings were carried out at Coherent Optics Laboratory of University of Aveiro, Portugal. Aspects concerning to the production and operation principles are shown. The results obtained from the grating production and characterization, as well as the experimental set-up developed to these goals are presented. The method used to write the gratings was the application of point-to-point electrical arch discharge, resulting in grating periods of 598 and 600 μm operating at the third window transmission around 1.55 μm. The long period gratings and the etched fiber Bragg gratings were characterized as a function of modification on the refractive index of the external surrounding environment, of temperature changes and strain (this last parameter was carried out only for long period gratings), the cross sensitivity also was characterized. The refractive index response of long period grating at two different conditions, one of them for presence of gasoline blend in water environment and another one for vapors of some hydrocarbon in closed container, points to the use of this device for hydrocarbon leakage detection at refineries and gas stations. Long period gratings e results obtained for ethanol agrees with the data find in literature, showing that this is a good technique for this goal.

Este trabalho descreve a produção e a caracterização de redes de período longo (LPG) e redes de Bragg corroídas como elemento sensor. Tanto a produção quanto às caracterizações das redes de período longo foram realizadas no Laboratório de Laser da UTFPR e a produção e caracterização das redes de Bragg corroídas foram realizadas no Laboratório de Óptica Coerente da Universidade de Aveiro, Portugal. São abordados aspectos referentes aos princípios de produção e funcionamento do dispositivo. São apresentados os resultados obtidos na produção e na caracterização das redes, bem como os sistemas experimentais desenvolvidos para estes fins. O método empregado para a escrita das redes de período longo foi o da aplicação ponto-a-ponto de um arco elétrico, sendo produzidas redes com períodos de 598 e 600 μm operando na terceira janela de transmissão em torno de 1,55 μm. As redes de período longo e as redes de Bragg corroídas foram caracterizadas quanto as suas sensibilidades ao índice de refração, temperatura e deformações longitudinais (esta última caracterização foi realizada apenas para as redes de período longo), assim com a sensibilidade cruzada a estes parâmetros. A resposta das redes de período longo em função da variação do índice de refração do meio externo em duas diferentes situações, uma na presença de gasolina em ambiente hídrico e outra na presença de vapores de hidrocarbonetos ambiente atmosférico, indica a possibilidade da utilização deste dispositivo na detecção de vazamentos de hidrocarbonetos em refinarias ou postos de abastecimentos. Estas redes também foram caracterizadas para monitorar a concentração de cromo (III e VI) em soluções aquosas, os resultados indicam a possibilidades de monitorar em tempo real os processos de tratamento destes produtos, e assim otimizar este processo. As redes de Bragg foram utilizadas para a caracterização de propriedades ópticas de materiais, o resultado obtido para o etanol mostrou boa concordância com os valores apresentados na literatura, indicando que esta é uma técnica adequada para este fim. / This work describes the production and characterization of long period gratings (LPG) and etched fiber Bragg gratings as sensors. Both the production and characterization were carried out at the Laser Laboratory of UTFPR and the production and characterization of etched fiber Bragg gratings were carried out at Coherent Optics Laboratory of University of Aveiro, Portugal. Aspects concerning to the production and operation principles are shown. The results obtained from the grating production and characterization, as well as the experimental set-up developed to these goals are presented. The method used to write the gratings was the application of point-to-point electrical arch discharge, resulting in grating periods of 598 and 600 μm operating at the third window transmission around 1.55 μm. The long period gratings and the etched fiber Bragg gratings were characterized as a function of modification on the refractive index of the external surrounding environment, of temperature changes and strain (this last parameter was carried out only for long period gratings), the cross sensitivity also was characterized. The refractive index response of long period grating at two different conditions, one of them for presence of gasoline blend in water environment and another one for vapors of some hydrocarbon in closed container, points to the use of this device for hydrocarbon leakage detection at refineries and gas stations. Long period gratings e results obtained for ethanol agrees with the data find in literature, showing that this is a good technique for this goal.

This thesis investigates the effects of High Voltage Direct Current (HVDC) lines andmulti-terminal grids on power system small-disturbance stability in the presence ofoperational uncertainties. The main outcome of this research is the comprehensiveprobabilistic assessment of the stability improvements that can be achieved through theuse of supplementary damping control applied to HVDC systems.Power systems are increasingly operated closer to stability boundaries in order toimprove their efficiency and economic value whilst a growing number of conventionalcontrolled power plants are being replaced by stochastic renewable generation sources.The resulting uncertainty in conditions can increase the risk of operational stabilityconcerns and should be thoroughly evaluated. There is also a growing necessity toexplore the potential improvements and challenges created by the introduction of newequipment, such as HVDC systems. In recent years, HVDC systems have become moreeconomically competitive and increasingly flexible, resulting in a proliferation ofprojects. Although primarily installed for power transmission purposes, their flexibilityand controllability can provide further benefits, such as the damping of persistentoscillations in the interconnected networks.This work contributes to a number of areas of power systems research, specificallysurrounding the effects of HVDC systems on the small-disturbance stability oftransmission networks. The application and comprehensive assessment of a Wide AreaMeasurement System (WAMS) based damping controller with various HVDC systemsis completed. The studies performed on a variety of HVDC technology types andconfigurations – as well as differing AC test networks – demonstrate the potential forHVDC-based Power Oscillation Damping (POD). These studies include examinationsof previously unexplored topics such as the effects of available modulation capacity andthe use of voltage source converter multi-terminal HVDC grids for POD. Followingthese investigations, a methodology to probabilistically test the robustness of HVDC based damping controllers is developed. This methodology makes use of classificationtechniques to identify possible mitigation options for power system operators whenperformance is sub-optimal. To reduce the high computational burden associated withthis methodology, the Probabilistic Collocation Method (PCM) is developed in order toefficiently identify the statistical distributions of critical system modes in the presenceof uncertainties. Methods of uncertain parameter reduction based on eigenvaluesensitivity are developed and demonstrated to ensure accurate results when the PCM isused with large test systems. Finally, the concepts and techniques introduced within thethesis are combined to probabilistically design a WAMS-based POD controller morerobust to operational uncertainties. The use of the PCM during the probabilistic designresults in rapid and robust synthesis of HVDC-based POD controllers.

With the increasing demand for electrical power and the growing need for the restructuring of the power industry, electric power systems have become highly complex with inherent complicated dynamics. Therefore, the study of power system stability has continued to receive significant attention from both academic researchers and industrial practitioners. This thesis focuses on supervisory wide-area control for rotor angle stability of multi-machine power systems using Linear Quadratic Gaussian/Loop Transfer Recovery (LQG/LTR) control theory with guaranteed robustness. The supervisory controllers are developed in both continuous-time and discrete-time framework and their performances and robustness are assessed using both frequency-domain tools, and time-domain simulation results. The impact of the communication time-delays that commonly exist in wide-area power system control on the performance and robustness of the closed-loop system is investigated. In particular, different methods of incorporating such time-delays into the design of the supervisory LQG controller are considered. This thesis proposes a modified supervisory LQG controller that utilizes the Extended Kalman Filter to estimate the unknown/varying time-delays. Simulation results obtained using numerical examples involving non-linear power system models demonstrate the benefits of the proposed scheme for both time-invariant and time-varying delays. The resulting supervisory control scheme is well suited for maintaining power system stability in the presence of communication time-delays.

An islanded power system indicates a geographical and logical detach between a portion<br />of a power system and the major grid, and often accompanies with the loss of system<br />observability. A power system islanding contingency could be one of the most severe<br />consequences of wide-area system failures. It might result in enormous losses to both the power utilities and the consumers. Even those relatively small and stable islanding events may largely disturb the consumers\' normal operation in the island. On the other hand, the power consumption in the U.S. has been largely increasing since 1970s with the respect to the bloom of global economy and mass manufacturing, and the daily increased requirements from the modern customers. Along with the extreme weather and natural disaster factors, the century old U.S. power grid is under severely tests for potential islanding disturbances. After 1980s, the invention of synchronized phasor measurement units (PMU) has broadened the horizon for system monitoring, control and protection. Its real time feature and reliable measurements has made possible many online system schemes. The recent revolution of computers and electronic devices enables the implementation of complex methods (such as data mining methods) requiring large databases in power system analysis. The proposed method presented in this dissertation is primarily focused on two studies: one power system islanding contingency detection, identification, classification and state evaluation algorithm using a decision tree algorithm and topology approach, and its application in Dominion Virginia power system; and one optimal PMU placement strategy using a binary integral programming algorithm with the consideration of system islanding and redundancy issues. / Ph. D.

Today’s electrical transmission &amp; distribution systems, are facing a number of challenges related to changing environmental, technical and business factors. Among these factors are, increased environmental restrictions leading to higher share of production from renewable and uncontrollable sources as well as local environmental concerns regarding construction of new transmission and distribution lines. The re-regulation of the electricity market has created a dynamic environment in which multiple organizations have to coordinate and cooperate in the operation and control of the power system. Finally, the high rate of devel-opment within the ICT field is creating many new opportunities for power system opera-tion and control, thanks to introduction of new technologies for measurement, communi-cation and automation. As a result of these factors, Wide Area Monitoring and Control (WAMC) systems have been proposed. WAMC systems utilize new ICT based technologies to offer more accurate and timely data on the state of the power system. WAMC systems utilize Phasor Measure-ment Units (PMUs) that have higher data rates and are time synchronised using, GPS satel-lites. This allows synchronized observation of the dynamics of the power system, making it possible to manage the system at a more efficient and responsive level and apply wide area control and protection schemes. The success WAMC systems, on the other hand, are largely dependent on the performance of the Information and Communication Technology (ICT) infrastructure that would support them. This thesis investigates the requirements on, and suitability of the ICT systems that support WAMC systems. This was done by identifying WAMC applications and the elicitation of their requirements. Furthermore, a set of simulation projects were carried out to determine the communication system characteristics such as delay and the impact of this delay on the WAMC system. This thesis has several contributions. First, it provides summary and analysis of WAMC application priorities and requirements in the Nordic region. Secondly it provides simula-tion based comparison and evaluation of communication paradigms for WAMC systems. The research documented in this thesis addresses these paradigms by providing a compari-son and evaluation through simulation. Thirdly, the thesis provides insight to the possible sources of delay in WAMC architecture and the impact of these delays on data quality specifically data incompleteness. This provides insight on what applications are important to practitioners and what is the expected performance of these applications, as seen from the power system control and operation point of view.

The increasing demand for electricity over the last few decades has not been followed by adequate growth in electric infrastructure. As a result, the reliability and safety of the electric grids are facing tremendously growing pressure. Large blackouts in the recent past indicate that sustaining system reliability and integrity turns out to be more and more difficult due to reduced transmission capacity margins and increased stress on the system. Due to the heavy loading conditions that occur when the system is under stress, the protection systems are susceptible to mis-operation. It is under such severe situations that the network cannot afford to lose its critical elements like the main generation units and transmission corridors. In addition to the slow but steady variations in the network structure over a long term, the grid also experiences drastic changes during the occurrence of a disturbance. One of the main reasons why protection relays mis-operate is due to the inability of the relays to adjust to the evolving network scenario. Such failures greatly compound the severity of the disturbance, while diminishing network integrity leading to catastrophic system-wide outages. With the advancement of Wide Area Measurement Systems (WAMS), it is now possible to redesign network protection schemes to make them more adaptive and thus improve the security of the system. Often flagged for exacerbating the events leading to a blackout, the back-up distance protection relay scheme for transmission line protection and the loss-of-field relay scheme for generator unit protection can be greatly improved from an adaptability-oriented redesign. Protection schemes in general would benefit from a power re-distribution technique that helps predict generator outputs immediately after the occurrence of a contingency. / Ph. D.

In this dissertation, we present vision based scene interpretation methods for monitoring of people and vehicles, in real-time, within a busy environment using a forest of co-operative electro-optical (EO) sensors. We have developed novel video understanding algorithms with learning capability, to detect and categorize people and vehicles, track them with in a camera and hand-off this information across multiple networked cameras for multi-camera tracking. The ability to learn prevents the need for extensive manual intervention, site models and camera calibration, and provides adaptability to changing environmental conditions. For object detection and categorization in the video stream, a two step detection procedure is used. First, regions of interest are determined using a novel hierarchical background subtraction algorithm that uses color and gradient information for interest region detection. Second, objects are located and classified from within these regions using a weakly supervised learning mechanism based on co-training that employs motion and appearance features. The main contribution of this approach is that it is an online procedure in which separate views (features) of the data are used for co-training, while the combined view (all features) is used to make classification decisions in a single boosted framework. The advantage of this approach is that it requires only a few initial training samples and can automatically adjust its parameters online to improve the detection and classification performance. Once objects are detected and classified they are tracked in individual cameras. Single camera tracking is performed using a voting based approach that utilizes color and shape cues to establish correspondence in individual cameras. The tracker has the capability to handle multiple occluded objects. Next, the objects are tracked across a forest of cameras with non-overlapping views. This is a hard problem because of two reasons. First, the observations of an object are often widely separated in time and space when viewed from non-overlapping cameras. Secondly, the appearance of an object in one camera view might be very different from its appearance in another camera view due to the differences in illumination, pose and camera properties. To deal with the first problem, the system learns the inter-camera relationships to constrain track correspondences. These relationships are learned in the form of multivariate probability density of space-time variables (object entry and exit locations, velocities, and inter-camera transition times) using Parzen windows. To handle the appearance change of an object as it moves from one camera to another, we show that all color transfer functions from a given camera to another camera lie in a low dimensional subspace. The tracking algorithm learns this subspace by using probabilistic principal component analysis and uses it for appearance matching. The proposed system learns the camera topology and subspace of inter-camera color transfer functions during a training phase. Once the training is complete, correspondences are assigned using the maximum a posteriori (MAP) estimation framework using both the location and appearance cues. Extensive experiments and deployment of this system in realistic scenarios has demonstrated the robustness of the proposed methods. The proposed system was able to detect and classify targets, and seamlessly tracked them across multiple cameras. It also generated a summary in terms of key frames and textual description of trajectories to a monitoring officer for final analysis and response decision. This level of interpretation was the goal of our research effort, and we believe that it is a significant step forward in the development of intelligent systems that can deal with the complexities of real world scenarios.

The balance of supply and demand of energy is the key factor in the stability of power systems. A small disturbance in the supply demand relationship, if not properly handled, can cascade into a major outage, costing millions of dollars to the stakeholders. Proper monitoring and exchange of critical information in real time is the only solution to prevent the instability in this vulnerable system. But, the disparity in the protocols used by power utilities and the lack of infrastructure for information exchange are proving to be hindrance to obtaining a reliable de-regularized power industry. In this thesis, an emerging Sensor Web Enablement (SWE) has been adapted for the wide area monitoring of power systems. SWE and CIM provide a solution to both problems; the heterogeneity of data and the lack of central repository of the data for proper action. The sensor data from utilities that are published in CIM were modeled thorough a SensorML and exposed via a Sensor Observation Service (SOS). This provides a standard method for discovering and accessing the sensor data between utilities and facilitates rapid response functionality to handle contingences.

The advent of synchronized wide-area frequency measurements obtained from frequency disturbance recorders and phasor measurement units has presented the power industry with special opportunities to study power system dynamics. I propose the use of wide-area frequency measurements in identifying system disturbances based on power system post-event modal properties. In this work, power system dynamics are examined from an internal system energy viewpoint. Since an electric power system is composed of coupled rotating machines (large generators) which have air gap magnetic fields that are essentially static, or quasi-static, the power system may be modeled as a system with energy stored in quasi-static magnetic fields. The magnetic fields in the machines do change with time but may be modeled as static as far as wave propagation is concerned. The dynamic model that I develop treats this magnetic energy specifically as potential energy. Each rotating machine also contains an inertia due to the mass and motion of its rotor train and so each machine contains a rotational kinetic energy. Thus the internal system energy for a power system dynamic model may be considered to be contained in potential (magnetic) and kinetic (rotating mass) energies. This notion of internal energy lends itself to the use of a state-space model where each system state is associated with either a kinetic energy or a potential energy. An n-machine system would have a total of 2n states and would thus be a 2n-th order system. For many power system disturbances, I postulate that a linearized version of this model may be used to examine system natural response in terms of frequency and phasor measurements. The disturbances that I will investigate include generator and line outages. For any particular outage, the power system exhibits a very specific natural response in terms of its kinetic and potential energies. Kinetic energy in the system is directly related to each specific machine's rotational speed. I propose that the kinetic energy corresponds directly with bus frequencies through a linear transformation. Likewise magnetic field energy in each machine corresponds directly with a torque angle. The potential energy in the system thus corresponds directly with bus angles through a linear transformation. The primary focus of this work is on frequency deviation modal characteristics – specifically damped oscillation frequencies, mode shapes, and damping ratios. This work presents how specific disturbances on a power system will lead to specific oscillation frequencies in the deviation quantities and that these oscillation frequencies may be used to identify the disturbance. The idea of disturbance identification stems out of previous work done in locating disturbances by using a distributed parameter (DP) model of an electric power system. This DP model, which assumes a wave-like motion of frequency and phase quantities, was used to locate disturbances via a triangulation method. This present work, instead of using a DP model of the power system, assumes lumped parameters and focuses on disturbance identification strictly via modal characteristics – particularly oscillation frequency in the frequency deviations. This model is not concerned with geographic location but focuses on system topology, loading, and machine mass as lumped parameters. Advantages of disturbance identification include mainly reliability enhancements but can also be used in marketing applications. The state-space model used to realize this theory is verified via simulation using small, "academic" systems which should prove useful in classroom settings. Additionally the model is verified on a larger test system in order prove its validity and potential usefulness on large power systems. / Ph. D.