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Submarine power production installations use the power of the ocean to generate renewable energy for the population to use. To bring this electricity back to land, use of electrical cables is required. The choice of cable will affect both the quality of received power and the security of the transmission line. To find the inductance and capacitance of these submarine transmission lines, a study of the electric and magnetic fields that are produced due to the power flow on these cables must be performed. The armor that is used to protect the cable from underwater hazards is significant in determining the cable losses and finding the equivalent inductance and capacitance. Finding the inductance and capacitance of the submarine cable will allow for the determination of the two port parameters of the cable. These parameters will allow for the analysis of the transient and steady state performance of the cable.

Transmission line parameters play a significant role in a variety of power system applications. The accuracy of these parameters is of paramount importance. Traditional methods of determining transmission line parameters must take a large number of factors into consideration. It is difficult and in most cases impractical to include every possible factor when calculating parameter values. A modern approach to the parameter identification problem is an online method by which the parameter values are calculated using synchronized voltage and current measurements from both ends of a transmission line. One of the biggest problems facing the synchronized measurement method is line transposition. Several methods have been proposed that demonstrate how the line parameters of a transposed line may be estimated. However, the present case of today's power systems is such that a majority of transmission lines are untransposed. While transposed line methods have value, they cannot be applied in real-world scenarios. Future efforts of using synchronized measurements to estimate transmission line parameters must focus on the development and refining of untransposed line methods. This thesis reviews the existing methods of estimation transmission line parameters using synchrophasor measurements and proposes a new method of estimating the parameters of an untransposed line. After the proposal of this new method, a sensitivity analysis is conducted to determine its performance when noise is present in the measurements. / Master of Science

Accurate value of transmission line parameters is important for power system protection applications, especially for distance relays whose zone settings are based on positive sequence line impedance. The research is devoted to estimating transmission line positive-sequence parameters from synchronized or unsynchronized measurements of voltage and current phasors that are obtained at both terminals of the line. The positive sequence parameters including series impedance and shunt admittance can be linearly estimated. The linear least square algorithm has been derived in this dissertation for different transmission line configurations. The algorithm is able to handle both synchronized and unsynchronized measurements and deal with potential synchronization errors by explicitly modeling the synchronization angle. Sample results are reported to demonstrate the effectiveness of the proposed method. Three types of transmission line models depending on line length (long, medium and short) are studied in this dissertation. Chapter 3 uses unsynchronized data for the long transmission line. The derived method can detect the unsynchronized angle and estimate the positive sequence of long line parameters. The proposed method is examined with negative impacts such as errors on currents and voltages data. These errors are added randomly to one set each time to test the robustness of the developed algorithm. The medium transmission line algorithm derivation is presented in chapter 4. This chapter uses a linear least square to estimate the lumped parameters of a medium transmission line. The two different transmission line circuits are used to model the medium line. The first circuit is a single transmission line with two nodes and is used to evaluate the developed algorithm. The second circuit is a double transmission line. These two lines can have the same or different line parameters or line length. The developed algorithm shows that the proposed method achieves highly accurate results for the estimation of positive sequence line parameters. The short transmission line is studied in chapter 5. The short transmission line uses less data than the long or medium lines because in this model the shunt capacitance is omitted. Thus, the linear estimation yields highly accurate results. Case studies are considered to test the robustness of this developed method. The line temperature mainly affects the series resistance, and the developed algorithms in previous three chapters can accurately estimate the transmission line parameters. To simplify the real-time estimation of line resistance and temperature, the series inductance, and shunt capacitance can be treated as constant and known values. Chapter 6 provides such studies of estimating resistance by treating inductance and capacitance as known values.

This thesis presents a method to obtain the per-unit-length electrical parameters of a given overhead transmission line or underground cable in an unbounded space considering the effect of the ground. This is achieved using a two-dimensional conformal mapping technique, which consists of a modified bilinear transformation to map a semi-open half-space problem into a unit circle. The Helmholtz equations describing the quasi-stationary approximation for the electromagnetic field behaviour are solved using finite element method, with the aid of commonly used commercial software program, COMSOL Multiphysics. The per-unit-length resistance, inductance and capacitance are calculated using the proposed mapping method, the truncation of the original space method and then compared with the analytical solution obtained from Carson's approximation for the overhead lines and Wedepohl's formulation for the underground cables. / October 2016

The introduction of synchrophasor technology to the realm of power systems has presented a myriad of novel approaches to age-old problems. In this thesis, the questions of instrument transformer calibration and transmission line parameter estimation have been examined. With synchrophasors offering real-time data for analysis, a solution to each individual problem seems feasible. A quandary however arises due to the fact that calibration methods depend on accurate knowledge of line parameters, and estimation of these parameters depend on calibrated measurements. Traditional methods of determining the parameters may not be the most accurate due to a variety of fluctuations possible on the system, which is why real-time estimation could prove beneficial. This work analyzes each problem and a feasible solution and proposes a method to achieve transducer calibration as well as parameter estimation together, while employing synchronized phasor measurements. / Master of Science / Synchrophasor Measurement Units (PMUs) provide the magnitude and angle of the quantity being measured, along with GPS time synchronization. Voltage, current and frequency data can be sent to a central control centre at the rate of 30 or 60 times per second. With a sufficient number of PMUs deployed on the electric grid, system operators now have available essentially a ‘snapshot’ of the system, which aids to monitor the grid, predict abnormal conditions as well as quickly identify troubled areas and accordingly take remedial actions. In order to facilitate the safe and reliable operation of the electric power grid, there are numerous devices that monitor quantities such as voltage, current, frequency etc. Most of these devices however are incapable of handling high levels of voltage and currents that are common to the power network. Instrument transformers (IT) are used to step down the measured quantities to much lower magnitudes that can then be analyzed by downstream devices. Each instrument transformer has a specified transformation ratio. For example, a voltage transformer with a transformation ratio of 100:1 would step down 500V to 5V. With time, these ITs may experience wear which might lead to degradation of its ratio, which would in turn be detrimental for applications relying on accurate measurements. Therefore routine calibration of ITs is desired. Traditional methods of calibration however involve taking the device out of service temporarily. As one can imagine, this is cost, labour and time intensive. With the availability of PMU data, it is now possible to perform calibration of these devices without having to take the device offline, provided we have accurate knowledge of the transmission line parameters. The parameters of a transmission line include the resistance, reactance and susceptance of the line and depend on the type of conductor used, the length and ambient temperature. Therefore seasonal and daily temperature variations can cause changes in the line parameters. With PMU data, we now have the capability to estimate these parameters, so that we have the most accurate idea of the present parameters. However for this, calibrated voltages and currents are required. Herein we face a quandary: we need to calibrate the ITs, which require accurate line parameters, but to estimate the current line parameters we need calibrated voltages and currents. This is the problem this thesis addresses. First, methods to perform both tasks, i.e. instrument transformer calibration as well as line parameter estimation using PMU measurements are analyzed. Finally an iterative method is proposed that can be applied to solve both problems together.

The main aim of this project was to find a practical and accurate method to determine the parameters of a transmission line by using current and voltage measurements. The term line parameters refer to the inherent series resistance and inductance that is found on transmission lines. The line parameters were determined by using the voltage and current measurements from either side of the transmission line. An accurate reference signal is needed to precisely compare the measured signals. The timing signals from GPS units were used to reference the measurements. In a field implementation data transfer of the measured signals would be a necessity which can be accomplished by GPRS modems. Three methods are proposed for determining line parameters. These methods were thoroughly tested in the following ways: 1. A model was built in SIMULINK with known elements and values. The three methods were then applied to the model and simulations were run. The results from the simulations are compared to the known values. 2. A system was built in the laboratory with known parameters. The results gathered from testing the system on all three methods are compared to known values. 3. Finally, the methods were applied to field data from recorders of a utility. This was done to see how well the methods would perform on a real system. Accuracy was determined from what the utility accepts as the correct values. Another focus of the project was to determine the surge impedance loading (SIL) curve from measured data. This curve can be used to determine the loadability limit of the transmission line as well as to visually show at what point the line is operating at any given time. The curve is also useful as it provides insight into the additional reactive power needed for a certain active power transfer. The concept of drawing a SIL curve from actual measurements was first tested by means of simulation. The drawing of the proposed curve is also tested on actual measurements from a transmission line. This investigation posed many challenges. These challenges are discussed in detail in the dissertation. Some of these challenges have easily implementable solutions while others still leave room for further research. The results and findings are published in this document. / Dissertation (MEng (Electrical))--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / MEng / unrestricted

The subject of this thesis is to become familiar with the different parameters describing the lines, and the possibility of modeling data and power models. The thesis also outlined the difference in the mechanical structure of different types of cables. The practical part focuses only on the power cables and measure their basic parameters. Then is created computer model which describes the behavior of cable lines at higher frequencies than are primarily intended. The final section is an experimental network created by the PLC for remote reading of electricity meters, and it measured different transmission properties.

Le travail présenté dans ce mémoire concerne le cadre global de la connaissance de notre atmosphère. L'exploitation des spectres atmosphériques requiert une bonne connaissance des paramètres de raies des molécules qui la composent. En particulier de la vapeur qui en est l'absorbant principal. Des spectres ont été enregistrés avec le spectromètre par transformation de Fourier construit au laboratoire et ceux ci ont été traités en ajustement multi-spectres avec le logiciel MultiFiT. Ce travail se focalise sur la mesure précise des intensités de raie dans deux régions spectrales. A 10 µm, région d'intérêt atmosphérique pour l'instrument IASI, deux études sur les intensités sont présentées. Pour l'isotopologue principal de 1200 à 1400 cm-1, 300 transitions ont pu être mesurées et comparées aux données de la littérature. Le but de ce travail était de déterminer la meilleure base de données pour l'exploitation des spectres IASI. De 1000 à 2300 cm-1, les isotopologues H218O et HD18O ont été étudié à partir de spectres enrichis en 18O. Ce travail a permis de mesurer et d'attribuer un ensemble de 2500 transitions. Enfin ce mémoire propose une révision complète des intensités de la région 1.25µm, qui présentent un important problème dans les bases de données. 39 spectres ont été enregistrés pour cette région avec des échantillons d'eau naturelle. Plus de 11000 transitions ont pu être mesurées et sont comparées aux données de la littérature. Une partie de ces intensités, publiées en 2010, a été exploité par L. Tallis de l'université de Reading. Enfin ce mémoire présente le début d'une exploitation des coefficients d'élargissement obtenus dans la région de 1.25µm. / The work presented in this manuscript concern the knowledge of our atmosphere. In fact, the analysis of atmospheric spectra needs a good understanding of atmospheric molecular species. In particular the water vapor plays a special role as the first absorbent of earth's atmosphere. Spectra were recorded by Fourier transform spectrometer designed in the laboratory and lines parameters fitted with multi-spectra procedure named MultiFiT. The spectroscopic studies focus on lines intensity measurements for two different spectral ranges. The first presented is 10 µm, were two studies have been done. For the H216O isotopologue in the 1200 – 1400 cm-1 range, 300 transitions were measured and compared with literature data. The aim of this work was to determine the best spectroscopic database for IASI recording analysis. In 1000 to 2300 cm-1, H218O and HD18O isotopologue were measured with enriched 18O spectra. Over 2500 transitions were measured and assigned. Also this manuscript presents a huge work done in the 1.25µm region. This range appears in database with an important discrepancy for line intensities. 39 spectra were recorded with water vapor sample in natural abundance. Over 11000 transitions were measured and assigned, comparison to literature data are also presented. A part of this work were published in 2010 and used by L.Tallis, form University of Reading, for atmospheric application. At the end of this manuscript is presented the first comparisons with calculated data done for self broadening coefficients in the 1.25µm region.

Made available in DSpace on 2017-07-10T16:41:33Z (GMT). No. of bitstreams: 1 Dissertacao Joao Felipe Montemezzo2.pdf: 2529334 bytes, checksum: 3e376a51a377760965206d4d5019db7a (MD5) Previous issue date: 2016-04-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Distribution Systems traditionally operate radially and having little information about the operating status of the network, which is estimated by the results of the load flow. The network is formed by multiphase feeders with untransposed lines, which must be added the inclusion of distributed generation, and in some cases, feeders with great extension, resulting in high level of load imbalance. That it must be added the tendency of having to operate the distribution systems more actively and efficiently, considering the greater penetration of distributed generation, storage systems and demand response. It results in the need for reliable tools for operation and planning. Among these tools the load flow is the most used and therefore deserves special attention. However, given the diverse operating conditions, it is necessary that components get modeled appropriately for reliable results. In this context, this work gathers the main mathematical models that can be used to represent lines of distribution systems, and evaluates how they influence the results obtained with load flow. Overhead and underground lines are considered, considering different topological arrangements and loading, for both primary and secondary networks. Moreover, the differences are investigated in the load flow solution considering the conventional and compact networks. Based on the assessments made in the work it is concluded that, due to the topology of distribution systems, the lines can be well represented by the short line model, with self and mutual impedances calculated by modified Carson equations. And the use of compact networks results in lower voltage drops and unbalance between the phases, due to the increased proximity and symmetry between conductors. / Tradicionalmente os Sistemas de Distribuição operam de forma radial e dispondo de poucas informações sobre o estado operativo da rede, o qual é estimado pelos resultados obtidos da execução do fluxo de carga. A rede é formada por alimentadores multifásicos sem transposição entre as fases, ao qual deve ser somado o desequilíbrio de cargas, a inserção de geração distribuída e, em alguns casos, alimentadores com grande extensão, resultando em elevado nível de desequilíbrio entre as fases. A isto deve ser somada a tendência de ter que operar os sistemas de distribuição de forma cada vez mais ativa e eficiente, considerando a maior penetração de geração distribuída, sistemas de armazenamento e resposta da demanda, resultando na necessidade de dispor de ferramentas confiáveis para a sua operação e planejamento. Dentre essas ferramentas o fluxo de carga é, de longe, a que merece maior atenção pelo seu uso extensivo. No entanto, para que seus resultados sejam confiáveis, diante das mais diversas condições operativas, é necessário que os componentes do sistema de distribuição sejam modelados de forma adequada. Nesse contexto, o presente trabalho reúne os principais modelos matemáticos que podem ser utilizados para representar linhas de sistemas de distribuição, e avalia de que forma os mesmos influenciam nos resultados obtidos com o fluxo de carga. São consideradas linhas aéreas e subterrâneas, levando em conta diversas disposições topológicas e condições de carga do alimentador, tanto para redes primárias como secundárias. Além disso, são investigadas as diferenças na solução do fluxo de carga considerando as redes aéreas convencionais e compactas. Com base nas avaliações feitas no trabalho conclui-se que, devido a topologia dos sistemas distribuição, as linhas podem ser bem representadas pelo modelo de linha curta, com as impedâncias próprias e mútuas calculadas pelas equações de Carson modificadas. E a utilização de redes compactas, devido à maior proximidade e simetria entre os condutores, resulta em menores quedas de tensão e desequilíbrio entre as fases.