Dissertations / Theses on the topic 'Overhead lines analysis'

Overhead transmission lines are an essential component of power systems, being the most economical means of transmitting electricity from remote sources of generation to the customer. It is, therefore, vital that they be protected and maintained in service to ensure the security of the supply to the end-user, and to protect the capital investment of the power companies. Arcing faults are a common phenomenon on power systems and being able to understand the effects of fault arcs is important for power system protection. Numerical algorithms can be developed that locate the position of and analyse faults on power systems. The aim of this thesis is to develop accurate models of arcing faults and to develop numerical algorithms that can operate successfully on different power system topologies under various fault conditions. Comprehensive literature reviews have been completed the areas of electrical arcs and fault location algorithms. Existing arc models are investigated and new alternative methods of simulating them are proposed. A new method of modelling the elongation of secondary arcs is devised in this thesis and verified using real arc data. A new ‘AirArc’ model for use in fault simulations is proposed and its accuracy is verified by comparison with the behaviour of a real arc. Three new numerical algorithms, developed for this thesis, for fault location and analysis, based upon the synchronised sampling of voltage and current data at both ends of the line, are derived and their accuracy tested for a number of different network topologies and fault scenarios. Finally, there is a chapter summarising the work completed for this thesis, drawing conclusions from that work and suggesting further work that could be undertaken in the future.

Electricity is a crucial form of energy in our societies, and transmission lines are key elements to ensure the reliability of electric power grids. Continuity of service is the main preoccupation of electric utilities, and this continuity may be disrupted by a large variety of sources and accidents. Transmission lines, by their intrinsic topology, remain the grid components that are the most exposed to climatic sources of disruption.The most common and important source of dynamic loads on transmission lines results from wind effects on the towers and conductors. Conductors are particularly sensitive to wind effects as they are long and relatively flexible (compared to their supports) and are literally wind-catching structures in the power grid infrastructure. In cold climates, wind and ice have compounding effects on lines and give rise to the most severe design loading conditions. Therefore, accurate prediction of the wind pressure on overhead conductors is essential to conduct a reliable assessment of the line response, in terms of both electrical clearances and conductor loads transferred to supports. Spatial randomness of wind loads on overhead lines has already been addressed by stochastic analysis methods and is now taken into account in design with the use of so-called span factors. Further gains in wind load accuracy can be obtained by examining the physics of wind effects on conductors, in both non-iced and iced conditions, with improved predictions of lift and drag forces determined from fluid-structure interaction (FSI) analysis.The traditional design method to apply wind load on transmission lines is to convert the design wind speed to a static pressure through Bernoulli's equation where the pressure is proportional to the air density and the squared wind speed. In this approach the fluid-structure interaction of wind and line components is ignored: wind is considered as a quasi-static load on conductors and supports, while special instability effects due to particular wind conditions such as vortex shedding (Aeolian vibrations) and flutter (cable galloping) are accounted for separately with specific mitigation solutions if necessary.In gusty wind conditions with high turbulence intensity, conductors may experience large horizontal displacements that affect their surrounding wind flow. A physically accurate wind load evaluation on conductors is possible by computational wind-structure interaction analysis. To date, largely due to its high computational cost and the lack of experimental data to validate computational models, an advanced fluid-structure analysis framework for wind-cable interaction has not been developed. In this study a new approach based on FSI analysis to evaluate equivalent wind loads on conductors is developed. The first step in such an approach is accurate evaluation of wind pressure on conductor. For this purpose the FSI analysis is carried out in two dimensions where the detailed bare and iced conductor section geometry and surrounding air flow are modeled, considering a given incident wind speed. The conductor cross section is assumed to be supported on flexible supports to study the interaction between the conductor motion and the air flow. FSI analysis yields both the fluid and structure response. Of particular interest is the wind pressure field on the conductor section, which allows the computation of the resultant drag and lift forces. This process is repeated for several cross sections along the span and the resulting forces provide the effective span wise wind load distribution on the conductor. This wind loading is then used as input in a separate 3-D computational nonlinear dynamic analysis model to predict the line response. This dynamic analysis of the line section can be detailed to represent very realistic line sections including conductors, suspension links and supporting towers.
Nos sociétés sont fortement dépendantes de l'électricité, et il ne fait pas de doute que la fonctionnalité des lignes de transport est déterminante pour assurer la fiabilité des réseaux électriques modernes. En effet, la continuité de l'approvisionnement en électricité reste la préoccupation majeure de toutes les compagnies d'électricité, et cette continuité du service peut être compromise par une multitude d'incidents ou d'accidents sur l'ensemble du réseau. Parmi toutes les sources possibles de charges dynamiques sollicitant les lignes de transport, celles provenant des effets du vent sur les pylônes et les conducteurs restent les plus fréquentes. Les conducteurs de lignes sont particulièrement vulnérables aux effets du vent car les portées sont longues et flexibles (comparé aux pylônes) et leur présence physique dans le réseau en font des structures exposées à toutes les intempéries qui peuvent survenir sur le territoire couvert. Cette vulnérabilité est encore plus grande dans les climats nordiques où les effets combinés du givrage atmosphérique et du vent créent des scénarios de charges de conception parmi les plus critiques et donc susceptibles de contrôler la conception finale des lignes. Il nous apparaît donc essentiel de comprendre la dynamique des fluides des effets du vent pour prédire avec réalisme et un degré de précision raisonnable la pression du vent exercée sur les conducteurs. Une meilleure évaluation des charges dues au vent permettrait par le fait même des prédictions plus réalistes de la réponse des lignes aux charges de vent, non seulement en terme de déplacements et dégagements électriques mais aussi en terme des charges nettes transférées aux pylônes par les conducteurs. La nature aléatoire des effets du vent sur les conducteurs a déjà fait l'objet de nombreuses études scientifiques et les méthodes d'analyse stochastique modernes permettent de cerner la question : les méthodes de conception simplifiées qui sont suggérées dans les normes et guides tiennent compte de ces effets en utilisant un coefficient de portée global qui ajuste à la baisse les efforts calculés au pylône sous des charges supposées synchrones et uniformes le long des conducteurs. Cette recherche ne concerne pas cet aspect de la question. Nous croyons que des gains de précision appréciables dans la prédiction des charges de vent sur les lignes sont possibles par une meilleure modélisation de la physique des effets du vent sur les conducteurs, dans les conditions givrées ou non, en utilisant les techniques d'analyse qui tiennent compte des interactions dynamiques fluide-structure. Ces interactions sont ignorées dans les méthodes d'analyse conventionnelles qui consistent simplement à calculer une pression statique proportionnelle à la vitesse carrée du fluide selon l'équation classique de Bernoulli. Bien sûr, les concepteurs ne négligent pas la considération des vibrations éoliennes ou du galop des conducteurs, mais ces phénomènes sont traités séparément et n'influencent pas le calcul des charges sur les pylônes. Dans cette recherche, nous nous intéressons aux conditions de vent de rafale avec grande turbulence qui caractérisent les tempêtes de vent. Ces vents forts et turbulents créent de grands déplacements des conducteurs qui modifient les conditions d'écoulement d'air. Une évaluation plus précise de ces conditions est possible par analyse computationnelle des interactions vent-conducteur.Les bases théoriques de la physique des phénomènes en présence sont connues mais aucun cadre d'application numérique n'a été proposé jusqu'à maintenant, en partie à cause des coûts numériques élevés mais aussi dû au manque de données expérimentales pouvant valider ces modèles computationnels.Nous avons développé un tel cadre d'analyse computationnelle dans cette recherche et l'avons illustré dans un cycle complet, du calcul des charges au calcul de la réponse d'une section de ligne, avec plusieurs exemples pratiques à chacune des étapes de développement

This thesis describes an investigation into the influences of arcing and conductor deflection due to magnetic forces on the accuracy of fault locator algorithms in electrical distribution networks. The work also explores the possibilities of using the properties of an arc to identify two specific types of faults that may occur on an overhead distribution line. A new technique using the convolution operator is introduced for deriving differential equation algorithms. The first algorithm was derived by estimating the voltage as an array of impulse functions while the second algorithm was derived using a piecewise linear voltage signal. These algorithms were tested on a simulated single-phase circuit using a PI-model line. It was shown that the second algorithm gave identical results as the existing dynamic integration operator type algorithm. The first algorithm used a transformation to a three-phase circuit that did not require any matrix calculations as an equivalent sequence component circuit is utilised for a single-phase to ground fault. A simulated arc was used to test the influence of the non-linearity of an arc on the accuracy of this algorithm. The simulations showed that the variation in the resistance due to arcing causes large oscillations of the algorithm output and a 40th order mean filter was used to increase the accuracy and stability of the algorithm. The same tests were performed on a previously developed fault locator algorithm that includes a square-wave power frequency proximation of the fault arc. This algorithm gave more accurate and stable results even with large arc length variations. During phase-to-phase fault conditions, two opposing magnetic fields force the conductors outwards away from each other and this movement causes a change in the total inductance of the line. A three dimensional finite element line model based on standard wave equations but incorporating magnetic forces was used to evaluate this phenomenon. The results show that appreciable errors in the distance estimations can be expected especially on poorly tensioned di stribution lines.New techniques were also explored that are based on identification of the fault arc. Two methods were successfully tested on simulated networks to identify a breakingconductor. The methods are based on the rate of increase in arc length during the breaking of the conductor. The first method uses arc voltage increase as the basis of the detection while the second method make use of the increase in the non-linearity of the network resistance to identify a breaking conductor. An unsuccessful attempt was made to identifying conductor clashing caused by high winds: it was found that too many parameters influence the separation speed of the two conductors. No unique characteristic could be found to identify the conductor clashing using the speed of conductor separation. The existing algorithm was also used to estimate the voltage in a distribution network during a fault for power quality monitoring purposes.

Includes bibliographies.
This study resulted from a perception held by the author that more attention is afforded to complying with the procedural elements of Environmental Impact Assessment (EIA) in South Africa, than to ensuring the validity of its technical content. The routing of high voltage overhead transmission lines provides a relevant field of study in which to address this perception. An initial literature review to contextualise the perceived problem showed that the questionable validity of the technical content of EIA was one of six shortcomings identified. To address the problem, an inductive approach was adopted to focus on the interpretation and prediction activities of EIA and two propositions, stated as research questions for discussion, were developed. These referred to the theoretical question of whether methods are specified for high voltage overhead transmission line EIAs, and to the practical question of whether the environmental impacts that are known to result from transmission line projects are effectively addressed in such EIAs in South Africa. Investigating these questions provides insights into whether the technical content of transmission line EIA is sufficiently rigorous in South Africa. The method of study takes the form of a sequentially more focused examination of the literature on EIA, from the strategic level, to the sectoral level and culminating at the project level. EIA methods specified for linear developments were identified at the sectoral level, while at the project level the known environmental impacts that result from high voltage overhead transmission lines were determined. A theoretical background was compiled in this way, which allowed for comparison with the practice as determined from benchmark and case study Environmental Impact Reports (EIRs).

Orientadores: Jose Pissolato Filho, Sergio Kurokawa
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: O objetivo deste trabalho é calcular os parâmetros longitudinais e transversais de linhas de transmissão trifásica a partir das correntes e tensões nas fases das mesmas. Serão utilizadas equações desenvolvidas no domínio modal considerando as obtenções de correntes e tensões em um terminal da linha enquanto o outro terminal permanece em aberto ou em curto-circuito. Inicialmente é apresentada a teoria básica de linhas de transmissão partindo do pressuposto de que tais linhas são melhores representadas através do modelo de parâmetros distribuídos. Assim através da análise de circuitos elétricos e das leis de Kirchhoff são encontradas as equações diferenciais de segunda ordem de tensão e corrente que caracterizam a linha de transmissão. Em seguida é apresentada a metodologia para cálculo dos parâmetros da linha que utiliza a idéia de impedância equivalente de circuito aberto e curto-circuito quando um dos terminais está em aberto e em curto-circuito respectivamente. Utilizando o Toolbox SimPowerSystem do MatLab são simuladas a obtenção das correntes em linhas de transmissão trifásica de 330 kV, 440 kV e 500 kV, todas com comprimento igual a 500 km. De posse de tais correntes são calculados os parâmetros das linhas de transmissão e comparados com seus valores reais, mostrando a viabilidade da metodologia empregada e que o erro obtido com tal metodologia é menor do que o erro entre os parâmetros reais das linhas após construção e seus parâmetros de projeto existente nos bancos de dados das empresas.
Abstract: The objective of this work is to calculate the longitudinal and transversal transmission line parameters using phase currents and voltages. Developed equations are used, in the modal domain, considering current and voltages found between a line terminal and an open line terminal, and a short-circuit terminal. . Initially, the basic transmission line theory is presented assuming that these lines are best represented by distributed parameters model. Therefore, through the analysis of electric circuits and Kirchhoff's laws , second order differential equations for voltage and current are found, which characterizes the line transmission. Next it is shown the method to calculate the line parameters, which uses the concept of open circuit and short-circuit equivalent impedance when one of the terminals is open or in short-circuited respectively. Using the Toolbox of MatLab, SimPowerSystem, estimated currents are simulated in a three-phase transmission line of 330 kV, 440 kV and 500 kV, all with the length of 500 km. The found values are used to calculate parameters of lines transmission and to compared them with their real values, showing that the calculation is possible and that the error obtained with this method is smaller than an error between the real line parameters after construction and those of existing project in the data base of companies.
Mestrado
Energia Eletrica
Mestre em Engenharia Elétrica

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Fundação Parque Tecnológico Itaipu
In this dissertation the modeling of an expert system to support analysis in medium voltage overhead lines is presented, allowing simulations of different networks in a web environment. Based on object-oriented methodology, this system follows as a demonstration of the application of artificial intelligence to act on problems relating to the Electrical Power Distribution Systems. With its implementation, it was possible to automate the processing of data for the calculation of power flow, showing through interface, information necessary for carrying out the analysis in these systems. The modeling of the backward forward sweep method was attached to the proposed model, and was employed as the expert system inference engine, and a heuristic model was established to power flow solution, with the property to adapt to the characteristics of networks, with representation of balanced or unbalanced loads, and with two types of mechanisms to suggest improvements and diagnostics on networks with problems in voltages profiles.
Neste trabalho é apresentada a modelagem de um sistema especialista para suporte à análises em redes de média tensão, possibilitando simulações de diversas redes em ambiente web. Baseado na metodologia orientada a objetos, este sistema segue como uma demonstração da aplicação de inteligência artificial para atuar em problemas relacionados com os Sistemas de Distribuição de Energia Elétrica. Com a sua implementação foi possível automatizar o processamento de dados para o cálculo do fluxo de potência, apresentando por meio de interface gráfica, as informações necessárias para a realização das analises nestes sistemas. Acoplando a modelagem do método backward forward sweep no modelo proposto, empregando-a como motor de inferência do sistema especialista, foi estabelecida uma modelagem de solução heurística para o fluxo de potência, com a propriedade de se adaptar às características das redes, com representação de cargas balanceadas ou desbalanceadas, e com dois tipos de mecanismos para sugestão de melhorias e diagnósticos em redes com problemas nos perfis de tensões.

Based on conventional static line rating method, the actual current carrying capability of overheadconductors cannot be judged. Due to continuous increment in electricity demand and the difficultiesassociated with new line constructions, the overhead lines are therefore required to be rated based on amethod that should establish their real-time capability in terms of electricity transmission. The methodused to determine the real-time ampacity of overhead conductors not only can enhance their transmissioncapacity but can also help in allowing excessive renewable generation in the electricity network. In thisdiploma work, the issues related to analyzing an impact of wind power on periodical loading of overheadline as well as finding its static and dynamic ampacities with line current are investigated in detail.Initially, in this project, the investigation related to finding a suitable location for the construction of a 60MW wind farm is taken on board. Thereafter, the wind park is integrated with a regional grid, owned byFortum Distribution AB. In addition to that, the electricity generated from the wind park is also calculatedin this project. Later on, the work is devoted to finding the static and dynamic line ratings for‘VL3’overhead conductor by using IEEE-738-2006 standard.Furthermore, the project also deals with finding the line current and making its comparison withmaximum capacity of overhead conductor (VL3) for loading it in such a way that no any violation of safeground clearance requirements is observed at all. Besides, the line current, knowing the conductortemperature when it transmits the required electricity in the presence of wind power generation is also animportant factor to be taken into consideration. Therefore, based on real-time ambient conditions withactual line loading and with the help of IEEE-738-2006 standard, the conductor temperature is alsocalculated in this project.At the end, an economic analysis is performed to evaluate the financial advantages related to applying thedynamic line ratings approach in place of traditional static line ratings technique across an overheadconductor (VL3) and to know how much beneficial it is to temporarily postpone the rebuilding and/orconstruction of a new transmission line. Furthermore, an economic analysis related to wind power systemis taken into consideration as well to get familiar with the costs related to building and connecting a 60MW wind farm with the regional grid.

碩士
大葉大學
電機工程研究所
90
The purpose of this study is to examine the effects of EMP coupling on overhead transmission lines. First, a theoretical model of multiconductor transmission line is derived and used to obtain the transfer function of an EMP coupling to the transmission line. On the basis of this function, the coupling effects of two-conductor and multiconductor transmission lines are analyzed by varying the incident angle, the termination impedance and the associated dimension. The proximity effect is also discussed. Finally, the lossy ground effect is investigated by varying the lossy parameters, and the wire to ground distance.

碩士
崑山科技大學
電機工程研究所
103
ABSTRACT Lightning strike is a natural phenomenon. The insulators of transmission systems will be flashover and causing the breakers trip if the lightning surge invades. The outages of power system are then resulted. The parameters that affect lightning transients of power transmission system include tower characteristics、ground resistance and lightning surge characteristics (front time and peak values). In this thesis, the ATP/EMTP package is used to simulate the back flashover transient voltage of 161kV overhead transmission system. tower caused by lightning strikes. The multi-story model of tower is adopted. The different ground resistance and lightning characteristics are considered in the simulations. The performances of line arresters installed are also observed. The data obtained can be used as references for lightning protection design.

碩士
國立臺灣海洋大學
電機工程學系
98
Abstract “Lightning” is a kind of energy which is very hard to be controlled. A lightning stroke produces high voltage and large current that will cause the damage of everything which is attacked by the lightning stroke directly. Besides, lightning stroke can damage the people, animals, and objects around indirectly. Then the overhead transmission lines erected in open fields are much easier to be attacked by thunderbolt. The damage of transmission lines and related equipments caused by lightning stroke will result in enormous economic losses, especially for those factories in Science Park. Thus the science industry has set up very high standard on the quality and reliability of electric power supply. Therefore, the utility makes every endeavor to improve lightning protections. This thesis studies the design of lightning protection by analyzing the lightning stroke and explaining every kind of lightning protective measure. Moreover, the thesis also investigates the sheltering capability of all lightning protective measures and the terminal voltage of the insulators under lightning by using the T-Flash software, and the probability of being attacked by the lightning is also examined. It is found that adopting two overhead ground lines with a minus five-degree sheltering angle will be a better protective structure, with even better performance by adding the line arrestor. Keywords: Lightning Protection Method, Power Quality, Power Reliability, Lightning Sheltering, Impulus Flashover Voltage

碩士
崑山科技大學
電機工程研究所
103
Most of the transmission lines locate at the wild or mountain area which with high lightning density. The flashover accidents occur in transmission lines if struck by lightning during thunderstorm day. Voltage drop and line tripped caused by lightning transient results in equipment damage and manufacturing loss. The reliability and quality of power will be seriously affected. In this thesis, type of transmission line tower used by TPC and mitigation methods against lightning are introduced first. ATP/EMTP package is used for lightning simulation of 161 kV transmission lines with different conditions. Then the effect with line arresters installed is observed by simulations.

碩士
國立勤益科技大學
電機工程系
106
This study is to analyse and preventtheelectricity stealing for overhead distribution lines. The overhead distribution lines that provide stable power supply to users is the end line of power company power system. Because the materials used in overhead distribution lines are composed of copper, aluminum and steel, they are often stolen effortlessly by thieves for exchanging into money. As soon as stealing event happens, power failure will occur in the area of wire stolen and result in the loss of electricity income as well. Therefore, it is an important internal issues for power company to prevent electricity stealing. This study aims at analyzing the electricity stealing methods with practical cases, elucidating the loss calculation about distribution wires, then judging whether there is electricity stealing in the area by the analyzed loss of electricity supply. Hopefully, it not only prevents the electricity stealing of the thieves but also maintains the stable power supply.

碩士
逢甲大學
資訊電機工程碩士在職專班
94
The purpose of this thesis is to analyze the magnetic distribution of overhead power lines using finite element analysis software FLUX2D. The shielding effect of the overhead power lines shielded by different kinds of magnetic metal with different shapes is also studied. It provides the information for the mitigation of electromagnetic interference radiated from overhead power lines.

The end of the last century saw a meteoric rise in Environmental Impact Assessment (EIA) and its implementation worldwide subsequent to it being legislated by the United States in 1970. The South African Government's Council for the Environment attempted to emulate international developments in EIA and compiled the Integrated Environmental Management (IEM) guidelines of 1989 which delineated the procedure for undertaking EIAs for development projects in South Africa. It was envisaged that these guidelines would ultimately be made law. The period between 1989 and 1997 was a window period when the IEM guidelines were implemented voluntarily. This period therefore constitutes an important era in the history of EIA in South Africa to which constant reference is made and upon which further development in EIA in South Africa has been reliant. The period 1989 to 1997 also coincided with a major increase in the bulk electricity supply to KwaZulu-Natal by Eskom, the national electricity utility. Eskom had actively tracked the evolution of Environmental Management globally and was considered to be at the forefront of Industrial Environmental Management in South Africa and there was therefore an expectation that Eskom would implement the IEM guidelines. In this study twelve EIAs for Eskom powerlines and substations constructed in KZN for the period were analysed and trends in the implementation of the IEM guidelines extrapolated. This study highlights the extent to which the IEM guidelines were implemented. It discusses the problems attendant to its implementation, which were found to be common to the implementation of EIA globally. From this research it became clear that factors external to the IEM guidelines needed to be resolved before the IEM guidelines could be implemented. The administrative requirement was one of the most important and necessary requirements for successful implementation, but this had not been thoroughly anticipated by Eskom nor the guidelines themselves. This required that there was major reform to policy and company procedure, which had to be clearly understood and accepted, before IEM could be effectively implemented. As a consequence, the implementation of the various steps of the IEM guidelines seldom revealed consistent and satisfactory implementation. Even where the IEM guidelines were more closely followed and implemented, previously entrenched technocentrist procedures and ideals persisted and therefore IEM was subverted and implemented with the wrong goal in mind. There was also an expectation that there would be an improvement in EIA practice with time. It was found that there was a greater association between the quality of the EIA conducted and the Eskom Environmental Officer responsible for it, rather than a consistent improvement with time. Thus integration into the project process of environmental procedure is a complex process and it requires firstly that a company is reformed. Reform has subsequently begun to transpire in Eskom. This reform includes education of company employees, which in turn is linked to political will which is necessary to effect the changes required to apply a procedure such as the IEM guidelines. This study reviews the implementation of the IEM guidelines in Eskom during this important development phase. It therefore reflects on a key portion of the history of EIA implementation in this country. The study provides insight into organisational reform and the voluntary commitments required for successful implementation of EIA. Benefit can be drawn from this study for future implementation of EIA even though EIA legislation now exists, as some form of voluntariness, political will and organisational reform is always imperative for ETA's successful and effective implementation.
Thesis (M.Sc.)-University of Natal, Durban, 2003.