This thesis discusses applications of phasor measurement units to power system monitoring and synchronous generator modeling. Adjustments to a previously developed PMU placement algorithm are described which observe generator and tie line flows explicitly and reduces the number of PMUs required for a system, still observing the major dynamic components of a system. This adjusted methodology leaves some buses unobserved. A method for estimating the state of the unobserved region is developed based on using constant admittance or constant current load models. These models are accurate for a small neighborhood around the operating point when they were calculated. To determine the maximum error expected for any given system estimate, an equation relating the maximum error in the voltages to the maximum change in load power is derived. Once the issue of power system monitoring has been presented, the application of PMUs to the synchronous generator modeling is explored. This thesis deals with the on-line identification of the generator transient model using a recursive version of the generalized least squares algorithm. Simulations have been performed to demonstrate the validity and difficulties with these methods. / Master of Science

<p dir="ltr">Advancements in astronomical imaging all-sky surveys are revolutionising the field of time domain astronomy. However, the immense volume of alert data presents a critical bottleneck in maximizing scientific returns from these surveys. Effectively analyzing alert streams to discover transients in unexplored physical parameter spaces is crucial for enhancing scientific output. Building robust infrastructure to identify, prioritize, and execute efficient follow-up strategies on alert streams from all-sky surveys becomes critical. My thesis confronts this challenge through a multidisciplinary approach, by integrating statistical methods, machine learning algorithms, and hydrodynamical simulations to constrain transient explosion properties and motivate effective follow-up initiatives. </p><p dir="ltr">I analyze a sample of 45 Type II supernovae from the Zwicky Transient Facility (ZTF) public survey using a grid of hydrodynamical models in order to assess whether theoretically driven forecasts can intelligently guide follow-up observations supporting all-sky survey alert streams. I estimate several progenitor properties and explosion physics parameters, including zero-age main-sequence (ZAMS) mass, mass-loss rate, kinetic energy, ⁵⁶Ni mass synthesized, host extinction, and the time of the explosion. This work involves simulations of real-time of evolving incomplete light curves of the sample (∆t < 25 days, ∆t < 50 days, all data) leading to the conclusion that certain physical parameters exhibit greater reliability as indicators of true values during early epochs. This study emphasises the vital role of real-time modeling of transients, supported by multi-band synthetic light curves tailored to survey passbands, for identifying interesting transients based on their progenitor and explosion properties and determining critical epochs for follow-up observations.</p><p dir="ltr">In my thesis, I report multi wavelength observations and characterization of the ultraluminous transient AT 2021lwx (ZTF20abrbeie; aka“Barbie”) identified in the ZTF alert stream, that was flagged as an anomaly by the Recommender Engine For Intelligent Transient Track-ing (REFITT). From a spectroscopically measured redshift of 0.9945, and slowly fading g and r light curves spanning over 1000 observer-frame days that peak with an absolute magnitude of Mr = −25.7 mag, AT 2021lwx has an extraordinary peak pseudo-bolometric luminosity of log (Lmax/[erg/s]) = 45.7. The total radiative energy is over 10⁵³ erg, and as of today, the transient continues to decline slowly following a t^−5/3 power-law. Modeling available photometry with MOSFiT suggests that AT 2021lwx is a tidal disruption event (TDE) candidate involving a ≈ 14 or 15 solar mass star accreting onto a supermassive black hole (SMBH) with mass M_BH ≈ 10⁸ solar mass. But, intriguingly, no host galaxy associated with the theorized SMBH is detected yet. The Pan-STARRS non-detections do not definitively exclude the existence of a galaxy hosting AT 2021lwx. Utilizing EzGal, upper limits on the stellar mass for different stellar population models were determined. These upper limits suggest that a 10¹⁰ solar mass host galaxy cannot be ruled out.</p><p dir="ltr">The enhanced sensitivity of upcoming large-scale all-sky surveys enables the early detection of transients, providing unique insights into their progenitor systems, an example being detection of shock cooling emission (SCE) in light curves of stripped-envelope supernovae(SESNe). Leveraging a statistically significant sample of these events with early detections from all-sky surveys presents an invaluable opportunity to constrain their environments, pro-genitors, and explosion properties. In my final study contributing to this thesis, I analyze a sample of 16 SESNe identified from the ZTF survey, characterised by prominent shock cooling emission features in their light curves. By modeling the SCE and the radioactive peak in these transients, I derive estimates of progenitor radius, mass of the extended envelope and explosion properties of SESNe. This analysis yields upper limits and ranges for the compactness and envelope structures of the SESN progenitors that exhibit SCE in their light curves. I conclude my thesis with a summary of the findings and their future applications.</p>

A general purpose cascaded pi section representation of a transmission line for a Transient Network Analyzer was designed. The pi sections modeled single and double circuit lines at 34.5, 69, 138, 345 and 765 KV levels. Representations of mutual impedances produced by nontransposition and mutual impedances and electrostatic coupling in double circuit lines are included in the model. Line data was collected for the above mentioned transmission line configurations. Impedance and capacitance matrices were calculated for each line. The matrices were scaled to model voltage levels. Equations were derived relating these matrices to model component values. Inductors were designed for the model. Finally, the pi sections were built and tested. Test results indicate steady state responses were generally correct to five percent. Maximum steady state error measured was 8 .6 percent. Results from the transient response tests were indicative of lines represented by very few pi sections. / M.S.

Os afundamentos de tensão são reduções de curta duração entre o 10% a 90% da magnitude de tensão eficaz. Usualmente, estes afundamentos são associados com falhas no sistema de energia elétrica, mas podem ser causados pela elevada corrente de partida de motores de indução ou energização de transformadores. Apesar de sua curta duração, tais eventos podem causar sérios problemas para alguns equipamentos. As conseqüências dos afundamentos de tensão sobre a máquina assíncrona são: perda de velocidade durante o afundamento e picos de corrente e de conjugado que aparecem na queda de tensão e no instante de restabelecimento. Este estudo visa analisar o comportamento da máquina assíncrona diante de afundamentos de tensão e as características destes, devido à influência do motor assíncrono como carga. Enfocando-se neste ponto, é que foram considerados diferentes tipos de afundamentos devido a diferentes falhas, que produziram quedas de tensão nos terminais da máquina assíncrona com variações na magnitude e no argumento de tensão. As simulações foram realizadas aplicando um método numérico tradicional e um método simplificado, o método simplificado lineariza as equações diferenciais elétricas da máquina assíncrona considerando a velocidade mecânica constante, para o cálculo dos transitórios elétricos no início da queda de tensão e no restabelecimento da mesma. Os transitórios obtidos pelo método numérico tradicional (Runge Kutta quarta ordem) e o método simplificado foram comparados, para verificar a precisão deste método com respeito ao numérico tradicional, concluindo-se, que o método simplificado poderá aplicar-se em máquinas de baixo escorregamento e elevada constante de inércia. Além disso, foram realizados experimentos, submetendo o sistema a diferentes quedas de tensão, considerando diferentes magnitudes e durações no afundamento. / Voltage sags are fast reductions between 10% to 90% in the voltage magnitude. Sags are usually associated with system faults, but can also be caused by motors starting or by the transformers energizing. Despite their small duration, such events can cause serious problems for a wide range of equipments. The consequences of voltage sags on the induction machine are: decrease of the speed during the sag and current and torque peaks in the voltage drop and recovery times. This study aims to analyze the behavior of the induction machine during voltage sags and find the characteristics of these sags due to the influence of the induction motor as load, taking into account the different voltage sags types due to different fault types, considering variations in the magnitude, phase angle voltage and variations of the mechanical load of the motor. The simulations were carried out by means of a linear and simplified induction motor model using Matlab, this simplified method separates the electric transient of the mechanical transient, resulting in a large speed of calculation when compared with the numerical method (fourth order Runge-Kutta). The transients obtained by the simplified method were compared with the calculated by the numerical method. Besides, the experiments were carried out under the same bases as the simulations, submitting the system to different voltage drops during several intervals of time.

Os afundamentos de tensão são reduções de curta duração entre o 10% a 90% da magnitude de tensão eficaz. Usualmente, estes afundamentos são associados com falhas no sistema de energia elétrica, mas podem ser causados pela elevada corrente de partida de motores de indução ou energização de transformadores. Apesar de sua curta duração, tais eventos podem causar sérios problemas para alguns equipamentos. As conseqüências dos afundamentos de tensão sobre a máquina assíncrona são: perda de velocidade durante o afundamento e picos de corrente e de conjugado que aparecem na queda de tensão e no instante de restabelecimento. Este estudo visa analisar o comportamento da máquina assíncrona diante de afundamentos de tensão e as características destes, devido à influência do motor assíncrono como carga. Enfocando-se neste ponto, é que foram considerados diferentes tipos de afundamentos devido a diferentes falhas, que produziram quedas de tensão nos terminais da máquina assíncrona com variações na magnitude e no argumento de tensão. As simulações foram realizadas aplicando um método numérico tradicional e um método simplificado, o método simplificado lineariza as equações diferenciais elétricas da máquina assíncrona considerando a velocidade mecânica constante, para o cálculo dos transitórios elétricos no início da queda de tensão e no restabelecimento da mesma. Os transitórios obtidos pelo método numérico tradicional (Runge Kutta quarta ordem) e o método simplificado foram comparados, para verificar a precisão deste método com respeito ao numérico tradicional, concluindo-se, que o método simplificado poderá aplicar-se em máquinas de baixo escorregamento e elevada constante de inércia. Além disso, foram realizados experimentos, submetendo o sistema a diferentes quedas de tensão, considerando diferentes magnitudes e durações no afundamento. / Voltage sags are fast reductions between 10% to 90% in the voltage magnitude. Sags are usually associated with system faults, but can also be caused by motors starting or by the transformers energizing. Despite their small duration, such events can cause serious problems for a wide range of equipments. The consequences of voltage sags on the induction machine are: decrease of the speed during the sag and current and torque peaks in the voltage drop and recovery times. This study aims to analyze the behavior of the induction machine during voltage sags and find the characteristics of these sags due to the influence of the induction motor as load, taking into account the different voltage sags types due to different fault types, considering variations in the magnitude, phase angle voltage and variations of the mechanical load of the motor. The simulations were carried out by means of a linear and simplified induction motor model using Matlab, this simplified method separates the electric transient of the mechanical transient, resulting in a large speed of calculation when compared with the numerical method (fourth order Runge-Kutta). The transients obtained by the simplified method were compared with the calculated by the numerical method. Besides, the experiments were carried out under the same bases as the simulations, submitting the system to different voltage drops during several intervals of time.

Os afundamentos de tensão são reduções de curta duração entre o 10% a 90% da magnitude de tensão eficaz. Usualmente, estes afundamentos são associados com falhas no sistema de energia elétrica, mas podem ser causados pela elevada corrente de partida de motores de indução ou energização de transformadores. Apesar de sua curta duração, tais eventos podem causar sérios problemas para alguns equipamentos. As conseqüências dos afundamentos de tensão sobre a máquina assíncrona são: perda de velocidade durante o afundamento e picos de corrente e de conjugado que aparecem na queda de tensão e no instante de restabelecimento. Este estudo visa analisar o comportamento da máquina assíncrona diante de afundamentos de tensão e as características destes, devido à influência do motor assíncrono como carga. Enfocando-se neste ponto, é que foram considerados diferentes tipos de afundamentos devido a diferentes falhas, que produziram quedas de tensão nos terminais da máquina assíncrona com variações na magnitude e no argumento de tensão. As simulações foram realizadas aplicando um método numérico tradicional e um método simplificado, o método simplificado lineariza as equações diferenciais elétricas da máquina assíncrona considerando a velocidade mecânica constante, para o cálculo dos transitórios elétricos no início da queda de tensão e no restabelecimento da mesma. Os transitórios obtidos pelo método numérico tradicional (Runge Kutta quarta ordem) e o método simplificado foram comparados, para verificar a precisão deste método com respeito ao numérico tradicional, concluindo-se, que o método simplificado poderá aplicar-se em máquinas de baixo escorregamento e elevada constante de inércia. Além disso, foram realizados experimentos, submetendo o sistema a diferentes quedas de tensão, considerando diferentes magnitudes e durações no afundamento. / Voltage sags are fast reductions between 10% to 90% in the voltage magnitude. Sags are usually associated with system faults, but can also be caused by motors starting or by the transformers energizing. Despite their small duration, such events can cause serious problems for a wide range of equipments. The consequences of voltage sags on the induction machine are: decrease of the speed during the sag and current and torque peaks in the voltage drop and recovery times. This study aims to analyze the behavior of the induction machine during voltage sags and find the characteristics of these sags due to the influence of the induction motor as load, taking into account the different voltage sags types due to different fault types, considering variations in the magnitude, phase angle voltage and variations of the mechanical load of the motor. The simulations were carried out by means of a linear and simplified induction motor model using Matlab, this simplified method separates the electric transient of the mechanical transient, resulting in a large speed of calculation when compared with the numerical method (fourth order Runge-Kutta). The transients obtained by the simplified method were compared with the calculated by the numerical method. Besides, the experiments were carried out under the same bases as the simulations, submitting the system to different voltage drops during several intervals of time.

No description available.

A mathematical model of a power system is created in the Electromagnetic Transients Program (EMTP). The EMTP is an off-line program which produces transients during a fault under different operating conditions and records the three phase voltage data at two computer relay locations. The EMTP simulation results are later played back in real time in a MVME133A computer platform and the digital signals are converted to analog signals through a D/ A board. These analog signals are filtered and provide inputs to the Power Systems Simulator via the power amplifiers. The computer relays, which are being tested, are connected to the Power Systems Simulator. This thesis describes both the EMTP simulation setup and the playback system configuration and algorithm. In addition, the operating procedure for real time playback of an EMTP output file is also described. / Master of Science

Cette thèse présente plusieurs contributions au software developé pour le traitement d’images dans le cadre du LSST. Notre objectif est d'utiliser le code et les algorithmes LSST existants, afin de créer un pipeline dédié à la détection des supernovae de type Ia. Pour la détection des supernovae nous utilisons une technique appelée soustraction optimale d'images qui implique la construction de coadditions. Nous étudions aussi le comportement des différents objets dans le temps et construisons des courbes de lumière qui représentent leur cycle de vie en fonction de l'intensité lumineuse de chaque détection sur plusieurs nuits. Enfin, pour analyser un nombre excessif de candidats, nous utilisons des algorithmes d'apprentissage machine.Notre première contribution concerne le développement des taches de coaddition automatisée adaptées pour construire des images de référence et de science avec un haut rapport signal-sur-bruit. La contribution suivante est lié à l’addition de mesures et l’étude de résidus des images d’analyse de différence, y-compris la sélection des seuils adaptés et l'étiquetage basée sur les valeurs quantitativess des résidus pour identifier les mauvaises détections, les artéfacts et les flux réellement significatifs. Notre suivante contribution est un algorithme pour sélectionner et générer les courbes de lumière candidates. Finalement, on applique une classification machine learning pour trouver des type Ia supernovae en utilisant la méthode random forest. Ces résultats ont permis l’identification des supernovae de type Ia simulées et réelles parmis les candidats avec une haute précision. / This thesis will present several contributions to the software developed for the LSST telescope with the purpose of contributing to the detection of type Ia supernovae. Our objective is to use the existing LSST code and algorithms, in order to create a type Ia supernovae detection dedicated pipeline.Since detecting supernovae requires a special type of processing, we use a technique known as the Optimal Image Subtraction which implies the construction of coadditions. Afterwards, we study the behavior of the different objects through time and build light curves that represent their life cycle in terms of the light intensity of each detection on several nights. Lastly, in order to analyze an excessive number of candidates, we employ machine learning algorithms to identify what curves are more probable to be type Ia supernovae. Our first contribution concerns the development of adapted and automatized coaddition tasks for building high signal-to-noise reference and science images. The next contribution is related to the addition of measurements and study of the residuals on difference image analysis, including the selection with adapted thresholding and the assignation of labels. We also propose, as contributions, an algorithm to select and generate the different candidate light curves through the selection of objects with recurrent detections through time and in the different bandpasses. Finally, we apply the machine learning classification approach to find type Ia supernovae by means of using a random forest classifier and based strictly on geometrical features that are present in the light curves.

This study aims to improve the modeling of partial SCRAM in the BISON plant model for the Forsmark 2 nuclear reactor after power uprate. Validation of the BISON model against tests performed from March to May in 2013 have shown that this is one of the areas in which there is room for improvement. After partial SCRAM is performed, the model underestimates the reactor power, recirculation flow and steam flow when compared to the measurement data. In BISON the partial SCRAM is modeled using a relative control rod effect vector (ASC vector). The aim is to replace the old values in this vector to improve the model. The new model was shown to give an improved result for the reactor power, recirculation flow and steam flow. The study gives recommendations on how to apply the new model and what values of the relative control rod effect vector that can be used in the future.