Estudos de transitórios eletromagnéticos são importantes fontes de informação para que os transformadores sejam dimensionados de maneira correta. No entanto, para que tais estudos sejam bem sucedidos, os modelos utilizados devem refletir com fidelidade o comportamento do equipamento. Este trabalho mostra como os elementos do modelo de um transformador são influenciados pelas dimensões geométricas de sua parte ativa. Também introduz uma formulação alternativa, para o transformador saturável (STC) do ATP, desenvolvida dentro do programa MATLAB. Os ramos RL foram representados usando o Método de Integração Trapezoidal e a magnetização foi equacionada pelo Método da Compensação. Uma das contribuições que esta dissertação oferece é a possibilidade de identificar erros numéricos que ocorrem em simulações do ATP, bem como permitir a interpretação de resultados que apresentem oscilações numéricas. / Electromagnetic transient studies are an important source of information to develop transformer dimensioning. But, for the success of that purpose, it is important the models which are being used reflect with fidelity the behavior of the machine. This lecture presents how the transformer model elements are influenced by the active part geometrical dimensions. It also introduces an alternative formulation for the ATP saturable transformer (STC), written inside the MATLAB program. The RL branches are represented using the Trapezoidal Rule and the magnetization by the Compensation Method. One of the contributions of this dissertation is the possibility to identify numerical errors that occur in ATP simulations, and also permit numerical oscillatory results interpretation.

In this thesis models for the simulation of transient phenomena in high voltage direct-current systems are developed. The new converter model is versatile and the solution algorithm is free from numerical oscillations. A new generic inverter control described in this thesis is based on a predictive approach. Steady-state and transient simulations of two-terminal and multi-terminal (i.e., a parallel converter system) high voltage direct-current systems are carried out using the new converter system model. Comparison between the two-terminal transient simulation results and the high voltage direct-current simulator outputs shows good agreement. An alternating-current/direct-current initialization procedure for the Electromagnetic Transients Program (EMTP) has been investigated and a novel initialization algorithm has been suggested in this thesis. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The successful application of HVDC transmission links requires correct predictions of the performance of the dc link and the ac system to which it is interconnected. Whatever the system configuration, the steady-state, dynamic and transient behaviour of the associated dc and ac systems are mostly interdependent. To simulate these phenomena with digital computers, converter stations must be modelled in more detail than as simple dc sources. This thesis discusses the development and implementation of a converter model which enables the converter bridge circuits to be represented in detail and the valve ignition to be controlled in the constant current mode. The model has been added to the U.B.C. Electromagnetic Transients Program to permit simulations of the complete ac/dc system. It is used to analyze the harmonics during steady-state operation, and to compare the results with those obtained from conventional (approximate) formulae. In a transient case, the new model gives closer agreement with field measurements than the simplified model used before. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Transient pressures subsequent to simultaneous power failure at all pumps of a multistage pumping system are analysed. Distributing pumping stations along a pipeline, rather than placing all of the required pumps within one pumping station, significantly reduces transient pressure fluctuations within the system. A computer program using the FORTRAN language is developed to analyse multistage pumping systems, with appropriate surge controls, in the event of such a power failure. These surge controls consist of valves, vacuum breakers, air chambers and reservoirs; with other controls easily added as they develop. Boundary conditions determining system controls are not developed as a part of this thesis, but are described for completeness. By comparing the maximum and minimum transient pressures occurring within- single stage and multistage systems, the premise that multistage systems give significantly lower transient pressures than single stage systems is substantiated. This reduction in transient pressures allows for possible savings in costs, as pipe wall thicknesses and the size of large, expensive control structures may be reduced. Examples demonstrating the use of the program are included. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Distributed energy production in the form of renewable energy sources are expected to increase in the coming years, a consequence of this is instability of the power grids due to the stochastic nature and lack of inertia of renewable energy sources. In addition, small and local, so called island grids, are on the rise and these system may present an even higher sensitivity to frequency fluctuations. In these applications gas turbines are an attractive option owing to the quick start capabilities, flexible fuel options and reliable operation. The aim of this thesis is to evaluate the transient capabilities of the Siemens SGT-750 double shaft and SGT-800 single shaft industrial gas turbines in island grid settings, through simulations of substantial load increases in varying ambient settings. Furthermore the possibility of using hydrogen fuel as a renewable option to the standard natural gas will be evaluated. This thesis provides a model of a simple island grid for load sharing between two or three turbines. The model was tuned to real life test data for the two gas turbines considered. In order to evaluate the capabilities of the turbines simulations were run in cold (-30 oC), hot (30 oC) and ISO (15 oC) conditions, evaluating the maximum instant load increase capabilities. Case studies were also run on island grids containing two or three turbines in order to determine the frequency response in case of an event. Case A regarded a scenario in which two turbines ran on 50% of rated power and one tripped, case B regarded three turbines working on 33% of rated power and one tripped out. Lastly, the maximum load increase cases with hydrogen fuel mixes (25, 50, 75 and 100% hydrogen by volume) were considered. The results suggest that the SGT-750 and SGT-800 gas turbines are capable of handling scenarios on reasonably dimensioned power systems, with both machines capable of recovering instant load increases of over 50% of the rated power. The findings shows thats hort periods (<10 s.) of allowed overfiring temperatures are necessary for the transient performance for the most extreme scenarios of high ambient temperatures and large loadincreases (around 50% of rated power). Furthermore an empirical κ-parameter, related to inertia and operational stability is discussed in order to compare GT load increase capability. The relevance of inertia and dynamic response is discussed and conceptually simulated to highlight the their role in gas turbine transient response. The hydrogen simulations, aside from the 75% case, showed little difference from natural gas in transient scenarios. The 75% hydrogen fuel consisting of high amounts ofinert gas however, rendered the turbine unable to withstand substantial load increases. The hydrogen simulation results are suggested to be accounted for by the rather simple combustion system and the energy densities of the gases.

One of two project reports: The other part is designated as Part A / <p> A fundamental and important part of nuclear reactor development and analysis today is the study of neutronics following a breach in the primary heat transport circuit. In the past, much of this analysis has concentrated on the calculation of the thermalhydraulic changes which occur following a loss of coolant accident and the effects these subsequently have on neutron kinetics. The purpose of this present study is to examine the influence of neutronic parameters on the size and shape of power pulses which result from loss of coolant accidents. The parameters studied are shutdown system delay times, shutoff rod drop curves, and fuel burnup distribution. </p> / Thesis / Master of Engineering (MEngr)

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No / The increasing complexity in the development and manufacturing process of internal combustion engines leads to a higher demand for more effective testing and monitoring methods. Cold engine testing becomes progressively the main End-of-Line test which is used nowadays from automotive engine manufacturers with the purpose of determining the integrity of engine assembly. The present work is focused on the development of a detailed physics-based, lumped-parameter, dynamic model of a single cylinder internal combustion engine coupled with an alternating current transient dynamometer for cold engine testing applications. The overall transient engine test cell model is described based on a two-inertia system model consisting of the engine, the dynamometer and the coupling shaft. The internal combustion engine is modelled based on First Law of Thermodynamics and Second Newton’s Law for rotational bodies. The transient dynamometer is actually an alternating current three-phase induction motor which is modelled according to direct-quadrature axis approach, and its drive unit which is responsible for controlling the speed of the motor using indirect field orientation scheme. The engine and dynamometer are connected through a coupling shaft which is modelled as a compliant member with damping. The model is validated against experimental measurements such as engine cylinder pressure, engine excitation torque and alternating currents of the induction motor. All of the experimental measurements were recorded from an identical single cylinder transient engine test cell using a highly advanced instrumentation system. The described model serves as an ideal platform for developing innovative model-based fault detection and diagnosis techniques for cold engine testing applications. In conclusion, this is presented successfully for two simulated fault cases, a process fault and a sensor fault, proving the functionality and usefulness of the model.

Dispersed low-frequency radio astronomical pulses may result from exploding primordial black holes, gamma ray bursts, supernovae, or mergers of exotic objects, but have not yet been detected. Detection would be of great scientific significance because such events must involve extreme physics. The transient nature of these events makes detection unlikely with traditional instruments due to lack of sensitivity to single pulses and narrow field of view. For this thesis, a low-frequency wide-bandwidth astronomical search instrument has been developed as an alternative approach. This instrument consists of a single dipole which yields all-sky field of view, albeit at reduced sensitivity. The spectrum from 37 - 55 MHz is coherently digitized at 200 million samples per second, recorded, and analyzed off-line for the presence of dispersed pulses. A preliminary survey has been made at a remote site in western North Carolina. In a 20 minute observation, 9 detections greater than 6.5σ occurred, corresponding to pulses of ≤ 20 ms duration and dispersion measures (DMs) ranging from 15 to 70 pc cm⁻³. In addition, groups of pulses were detected ( 5) at DMs of 43.1, 52.1, and 52.2 pc cm⁻³. The possibility of association with known pulsars is considered; however, it is also possible these are due simply to radio frequency interference. Improvements to this instrument and survey technique are suggested. / Master of Science

In order to facilitate the application of solid oxide fuel cells, in conjunction with reduced research and development costs, there is a need for accurate performance models to aid scientists and engineers in component and process design. To this end, an enhanced transient performance model has been developed. The present thesis enhances transient modeling and simulation via characterization of two important transient phenomena. They are bimodal stimuli (i.e., simultaneous changes in reactant supply and load demand) electrical transients, inclusive of the simulation of electrolysis, and the electrochemical light off phenomenon. One key result of the electrochemical light off simulations was that the realization that electrochemical parameters such as cell potential may be used as dynamic control variables during transitional heating of the cell. Reflective of the state-of-the-art in controls and dynamic simulation development, the modeling efforts are completed in the MATLAB computing environment. There is then a tangible software development that accompanies the modeling and simulation exercises and transient insights resolved.