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Mtanga, Jameson Joseph. "Dynamic modeling and vibration control of high-voltage overhead transmission lines." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5022.
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Includes abstract.Includes bibliographical references (leaves 140-144).
The problem of the dynamic behavior of overhead power transmission lines under wind and other excitations is an important one, since it allows an optimal design and positioning of vibration dampers for the cables. Excessive sway and oscillation of power lines need to be avoided, as they can lead to damage of the lines and power interruptions. The relatively high flexibility of the cables, coupled with the large spans and large sags involved, make the dynamic response of the system highly nonlinear. In this study, we numerically investigate the damped free-vibration response of systems of cables of particularly large spans (120, 200 and 400m).
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Naredo, V. José Luis A. "Communication frequency response of high voltage power lines." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26725.
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Several methods for calculating the electrical phase and modal parameters of overhead transmission lines are described in this thesis; then, a graphical method for evaluating communication frequency response of delta transmission lines -based on the guidelines given by W. H. Senn [12,13,14]- is developed. The graphical method, combined with the parameters calculation methods, obviates the need of large mainframe computers for the analysis of power line carrier (PLC) systems.
A new technique for assessing coupling alternatives, based on Senn's method, is developed. The technique is applied to generate coupling recommendations; it is found that many of the current recommendations given elsewhere [21] are not reliable.
Finally, future work to be done in this field is proposed.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Crnojacki, Zorica. "Extra high voltage transmission corridor siting : technical, public, institutional and regulatory considerations /." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-10032007-171749/.
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Callanan, Judith Marie. "Assessing the property market impact of stigma removal : high voltage overhead transmission lines removal in Wellington, NZ." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/71885/2/Judith_Callanan_Thesis.pdf.
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This thesis advances the understanding of the impact of stigma on property values. A case study in Wellington, New Zealand, enabled hedonic modelling and an empirical analysis to determine the impact of the stigma from the high voltage transmission line structure and how long the stigma remained after removal.
The results reveal a substantial difference between the discount applied to individual properties while the structure is in place, as compared to the overall increase in neighbourhood value once the structure, which created the stigma, is removed.
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Martinho, Lucas Blattner. "Numerical modeling of electromagnetic coupling phenomena in the vicinities of overhead power transmission lines." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-28062016-152807/.
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Les phénomènes de couplage électromagnétique entre les lignes aé- riennes de transmission d\'énergie et des structures voisines sont inévitables, surtout dans les zones densément peuplées. Les effets indésirables découlants de cette proximité sont variés, allant de l\'établissement des tensions dangereuses à l\'apparition de phénomènes de corrosion dus au courant alternatif. L\'étude de cette classe de problèmes est nécessaire pour assurer la sécurité dans les alentours de la zone d\'interaction et aussi pour préserver l\'intégrité des équipements et des dispositifs présents. Cependant, la modélisation compl ète de ce type d\'application implique la représentation tridimensionnelle de la région d\'intérêt et nécessite des méthodes numériques de calcul de champs spécifiques. Dans ces travaux, des problèmes liés à la circulation de courants électriques dans le sol (ou de couplage dit conductif) seront abordés avec la méthode des éléments finis. D\'autres problèmes résultants de la variation temporelle des champs électromagnétiques (ou de couplage dit inductif) seront aussi considérés et traités avec la méthode PEEC (Partial Element Equivalent Circuit) généralisée. Plus précisément, une condition limite particulière sur le potentiel électrique est proposée pour tronquer le domaine de calcul dans l\'analyse par éléments finis des problèmes de couplage conductif et une formulation PEEC complète pour la modélisation de problèmes de couplage inductif est présentée. Des con gurations tests de complexités croissantes sont considérées pour valider les approches précédentes. Ces travaux visent ainsi à apporter une contribution à la modélisation de cette classe de problèmes, qui tendent à devenir communs avec l\'expansion des réseaux électriques.Electromagnetic coupling phenomena between overhead power transmission lines and other nearby structures are inevitable, especially in densely populated areas. The undesired effects resulting from this proximity are manifold and range from the establishment of hazardous potentials to the outbreak of alternate current corrosion phenomena. The study of this class of problems is necessary for ensuring security in the vicinities of the interaction zone and also to preserve the integrity of the equipment and of the devices there present. However, the complete modeling of this type of application requires the three- -dimensional representation of the region of interest and needs specific numerical methods for field computation. In this work, the modeling of problems arising from the flow of electrical currents in the ground (the so-called conductive coupling) will be addressed with the finite element method. Those resulting from the time variation of the electromagnetic fields (the so-called inductive coupling) will be considered as well, and they will be treated with the generalized PEEC (Partial Element Equivalent Circuit) method. More specifically, a special boundary condition on the electric potential is proposed for truncating the computational domain in the finite element analysis of conductive coupling problems, and a complete PEEC formulation for modeling inductive coupling problems is presented. Test configurations of increasing complexities are considered for validating the foregoing approaches. These works aim to provide a contribution to the modeling of this class of problems, which tend to become common with the expansion of power grids.
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Lawson, Allan Brett. "Environmental impact assessment in the routing of high voltage overhead transmission lines : theory and practice in South Africa." Master's thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/16103.
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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).
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Hussin, Mohd Fahmi. "Voltage transducer for fault monitoring on high voltage overhead lines." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/65731/.
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Overhead lines are the backbone of electrical power transmission. In most cases, the overhead line provides the best economic and practical solution for energy transmission. Nevertheless, overhead lines suffer more faults due to the vulnerability of the overhead lines to adverse weather condition, transient overvoltage and falling trees. An extensive literature review of existing condition monitoring and impulse a voltage measurement technique of overhead lines are covered in this work, and ultimately leads to the development of the proposed voltage transducer. Although conventional transducers such as voltage transformers and voltage dividers are widely used for monitoring and voltage measurement, yet they have several drawbacks in terms of their size and cost. These are the key factors that limit their widespread deployment for monitoring and measuring voltage on overhead lines and, in particular, rural areas. The proposed transducer is based on a non-contact capacitive voltage probe developed at Cardiff University. However, the proposed transducer uses a high voltage conductor rather than the ground as a measurement reference. The proposed transducer is based on a cylindrical-shaped in order to avoid sharp edges, which can initiate a partial discharge effect. Commercial numerical field computation software packages are used to assist in the development of the proposed transducer for simulation of the electric field distributions around the HV conductor and the transducer. The computed electric field magnitudes obtained on the sensing probe surface are then used for calibration of the proposed transducer. The proposed transducer is developed using low cost materials and tested in a laboratory environment with a low amplitude impulse supply using a surge generator and the corresponding output voltage amplitude obtained from the transducer was validated against a low ac voltage supply using variable output voltage source. The effects of variation in the input voltage, the integrating capacitor inserted between the HV conductor and the sensing probe and height of the transducer above ground on the output voltage amplitude are also investigated. The developed transducer is subsequently tested in field experiments using test overhead lines with low and high voltage supplies. Only a single-phase measurement setup was used in this test as there is only one voltage transducer fabricated in this work. Therefore, each phase of the overhead line was tested individually. Results obtained from the laboratory and field experiments have demonstrated the suitability of the developed transducer for measuring both ac and impulse voltages, which would be useful for fault monitoring on the high voltage overhead lines. However, the computed results obtained from the simulation demonstrated the presence of end-effects at the transducer sensing probe edges. Therefore, an improved design was proposed in this work by introducing a floating electrode between the sensing probe and the guard electrode, with the aim to reduce the fringing effects by preventing the sensing probe from sensing unwanted electric field. The physical development of this improved transducer design is yet to be initiated, and is thus proposed for future work.
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Ahmed, Yasir E. "Modelling of microshocks associated with high voltage overhead lines." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.625456.
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Microshocks can be described as the unpleasant discharges experienced by people capacitively coupled to high voltage equipment once a contact is established between their finger-tips and another object at different potential. The situations in which these discharges occur are complicated and very limited research has been conducted so far in this area. The work presented in this thesis aims to enhance the understanding of the microshocks phenomenon, and in particular, focuses on exposure to microshocks by overhead transmission line workers before developing mitigation techniques to prevent the linesman from receiving microshocks or at least minimising the sensation level associated with receiving the discharges. Results of a survey that included 102 linesmen and conducted to determine the implications of different factors on the frequency and intensity of microshocks are presented. Experimental setups and activities that took place inside and outside the High Voltage laboratory to simulate the environment at which linesmen became subjected to microshocks are discussed. Initially, a simplified 2-dimensional metallic test object "Stickman", which simulates a human body, was placed in various positions relative to a lattice tower structure inside the laboratory. Measurements of induced voltages and currents on the object as a result of capacitive coupling have been made. To accurately represent the structure and shape of the human body, a 3- dimensional test object "Cylinderman" has been designed and introduced to the experimental setup replacing Stickman. Experiments have been modelled successfully using the commercial software package CDEGS (Current Distribution and Electromagnetic Interference, Grounding and Soil Structure Analysis). The software package is shown to be capable of accurately modelling simple objects made of thin conductors as well as complicated structure such as the transmission tower. Furthermore, models of realistic and complicated scenarios under which linesmen experience Microshocks have been developed. Discharge voltage waveforms recorded of human subjects experiencing microshocks have been captured successfully. By examining these waveforms it was concluded that skin impedance dictates the level of voltage drop during discharge. In addition to investigating the effectiveness of earthing the body through the footwear to prevent microshocks from occurring, experiments that lead to the identification of a novel mitigation technique are detailed. The technique aims to increase the charging capacitance to ground -represented originally by the shoe capacitance- to reduce the induce voltage on the individual. Details of a filed patent are also included.
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Langlois, Sébastien 1981. "Design of overhead transmission lines subject to localized high intensity wind." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99775.
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Wind loading considered in the design of overhead transmission lines is based on extreme values of synoptic wind, i.e. boundary layer wind originating from largescale meteorological pressure systems. Localized high intensity wind (HIW) storms such as tornadoes and downbursts are a different type of extreme wind frequently causing failures of overhead lines. This thesis covers the design aspects of overhead transmission lines when subject to localized HIW storms. A comprehensive review of the literature is included on the effects of such wind storms on lines and on mitigation measures. Furthermore, several options for the design of self-supporting transmission towers against localized HIW are discussed based on numerical simulations of several simple load cases on four examples of lattice structures.
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Cameron, Gordon. "Steady state inductive influence of high voltage transmission lines." Thesis, University of Canterbury. Electrical and Electronic Engineering, 1993. http://hdl.handle.net/10092/5592.
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Harmonic current flows within High Voltage transmission lines induce voltages in neighbouring metallic conductors be they fences, pipelines, other transmission lines or telecommunications cables. These voltages may endanger organisms which come into contact with the conductors or impair the operation of electrical systems connected to them. Under steady state operating conditions the induced voltages are seldom of sufficient magnitude to be hazardous, however they are on occasions severe enough to impair telecommunications services. With the increasing use of non-linear loads within the power system, harmonic current flows and hence the incidence of telecommunication interference can be expected to rise.
Many potential interference problems may be avoided by the coordination of telecommunication and electricity transmission systems. The most cost effective time to engineer solutions to interference problems is during the design of the system. A need exists therefore for methods which accurately quantify the ability of High Voltage transmission lines to cause interference.
This thesis is concerned with methods, both experimental and analytical, for determining the Inductive Influence or ability of a transmission line to cause interference. Existing models for the mutual impedance of conductors in the presence of the earth are reviewed. Numerical studies of the factors effecting the inductive influence of single and three phase transmission lines are reported. Measures for reducing the inductive influence through the use of alternative transmission line geometries and continuously grounded earth wires are investigated. New measures for quantifying the inductive influence are proposed, which are superior to existing measures due to the inclusion of the effect of frequency, earth resistivity, current sequence and transmission line geometry on the inductive influence. Comparisons are made between a digital computer model of the New Zealand inter-island HVDC link, and measured currents using a non-invasive crossed loop antenna system. The accuracy of the new methods is confirmed, as is the need for sensitive equipment when undertaking such investigations.
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Černín, Kamil. "Reconstruction of conductor movement and monitoring of high voltage lines." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218765.
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Tahle práce se zabývá monitorováním venkovních vysokonapěťových vedeních, což mohou být vedení od 70kV do 400kV. Senzory jsou umístěny na vodiči a hlavní myšlenkou je vyhodnotit mechanické chování vodičů, a to od nízkých frekvencí (zlomky Hz) až po vysoké frekvence (desítky Hz). Tahle práce se zabývala pohyby o nízkých frekvencích a vysokých amplitudách a popsala možnosti sestavení těchto pohybů na základě měření ze senzorů. Konkrétně se jedná o pohyby v případě silného větru, zkratu, opadávání ledu nebo dalších. Všechno tohle pomáhá operátorů dělat rozhodnutí ohledně provozování sítí. Vývoj zahrnuje přidání/kombinaci nových senzorů, popsání matematického algoritmu potřebného k sestavení pohybu na základě toho co bylo změřeno, ať už se jedná o hodnoty získané simulací, laboratorním testem nebo reálným měřením na vedení.
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Chen, Shelley L. "Programs for calculating high temperature ampacity and sag for overhead electrical conductors." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/17933.
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Flazi, Samir. "Etude du contournement electrique des isolateurs haute tension pollues : critere d'elongation de la decharge et dynamique du phenomene." Toulouse 3, 1987. http://www.theses.fr/1987TOU30266.
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Etude de l'aspect statique du contournement, on montre experimentalement que les criteres de wilkins et hampton ne s'appliquent qu'au modele d'obenaus. Mise en evidence de l'importance du champs electrique au voisinage de la decharge. Etude detaillee de la conduction electrolytique et de son evolution pendant le contournement
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Najafi, Syed Ahmed Ali. "Energy Harvesting From Overhead Transmission Line Magnetic Fields." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1548448189459464.
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Brown, Martin. "High voltage soliton production in nonlinear transmission lines and other pulsed power applications." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364003.
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Sims, Sally Caroline. "The impact of high voltage overhead power lines on the value of residential property in the United Kingdom." Thesis, Oxford Brookes University, 2004. https://radar.brookes.ac.uk/radar/items/47d4ec9e-e187-4218-b8da-5371c528a5da/1.
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This thesis investigates the impact of electricity distribution equipment on the value of residential units in the UK. This is a complex task, due to the potential influence on the market from the publics' perception of a perceived link between living in close proximity to high voltage overhead power lines (HVOTLs) and a number of adverse health effects. A review of the literature revealed that no previous studies had been undertaken within the UK to establish the impact of HVOTLs on house prices and as such, identified a gap in knowledge within the UK and provided a focus for this thesis. Due to a lack of available transaction data in England, investigating the impact on house price relies entirely on the use of qualitative research methods. Therefore to test the accuracy of the results from the perceptual study, a benchmark was developed using transaction data obtained from a residential housing estate in Blackwood, Scotland where a HYOTL was present. The thesis begins with an overview of the current planning and development controls relating to the siting of electricity distribution equipment and the subsequent development of land near HYOTLs. A critical review of the literature is presented which, due to the perceived relationship between living near HVOTLs and a health risk, includes literature on other related areas, for instance, property stigma, risk analysis and scientific and epidemiological studies on the possible health effects. ' A multimethod approach is adopted towards data gathering, using both qualitative and quantitative research paradigms. Buyers' and valuers' perceptions of the impact of a HYOTL on value are obtained using postal surveys and interviews. Additional information is gathered from the electricity utilities, residential developers and government planning departments. Using a case study approach and a hedonic pricing methodology (to enable the relationship between a HYOTL and house price to be explored), selling price data and asking price data from three locations were gathered and analysed. Regression analysis established that a INOTL near a residential unit does have an impact on house price, although this impact is not always negative. The results from three case studies, the opinion surveys and the interviews are compared, indicating that opinion surveys may result in an underestimation of the impact of a HYOTL on selling price and, by contrast, appraisers may overestimate the negative impact of HVOTLs on asking price when marketing a house. The results suggest reliance on one method may prove misleading and therefore the use of a multimethod approach towards data collection may improve the reliability of findings.
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Elmas, Erinc Evren. "Protection Of Transmission Lines Against Switching Overvoltages." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605607/index.pdf.
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Any switching action or lightning stroke on a transmission system causes excessive of voltage, which are propagated through the equipment. The withstand capability of the electrical equipment to these overvoltages is dependent on the rate of rise, peak value and the duration of these overvoltages and are especially critical to information technology (IT) equipment.
Whenever there is a probability of these overvoltages appearing across the electrical equipment, they should be limited to a safe value by the application surge arresters of the metal oxide type. However, surge arresters are expensive, an optimal location for these should be found so as to minimise the number of surge arresters used.
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Kapuduwage, Sarath, and skapuduwage@hotmail com. "Fault Location on the High Voltage Series Compensated Power Transmission Networks." RMIT University. Electrical and Computer Engineering, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080418.120506.
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Nowadays power transmission networks are capable of delivering contracted power from any supplier to any consumer over a large geographic area under market control, and thus transmission lines are incorporated with FACTs series compensated devices to increase the power transfer capability with improvement to system integrity. Conventional fault location methods developed in the past many years are not suitable for FACTs transmission networks. The obvious reason is that FACTs devices in transmission networks introduce non-linearity in the system and hence linear fault detection methods are no longer valid. Therefore, it is still a matter of research to investigate developing new fault detection techniques to cater for modern transmission network configurations and solve implementation issues maintaining required accuracy. This PhD research work is based on developing an accurate and robust new fault location algorithm for series compensated high voltage transmission lines, considering many issues such as transmission line models, configurations with series compensation features. Building on the existing knowledge, a new algorithm has been developed for the estimation of fault location using the time domain approach. In this algorithm, instantaneous fault signals from the transmission line ends are measured and applied to the algorithm to calculate the distance to fault. The new algorithm was tested on two port transmission line model developed using EMTP/ATP software and measured fault data from the simulations are exported to the MATLAB space to run the algorithm. Broad range of faults has been simulated considering various fault cases to test the algorithm and statistical results obtained. It was observed that the accuracy of location of fault on series compensated transmission line using this algorithm is in the range from 99.7 % to 99.9% in 90% of fault cases. In addition, this algorithm was further improved considering many practical issues related to modern series compensated transmission lines (with TCSC var compensators) achieving similar accuracies in the estimation of fault location.
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Tong, Sai-kit. "A computer-aided measurement system for monopolar high-voltage direct-current coronating lines /." [Hong Kong] : University of Hong Kong, 1986. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12321771.
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湯世傑 and Sai-kit Tong. "A computer-aided measurement system for monopolar high-voltage direct-current coronating lines." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1986. http://hub.hku.hk/bib/B31207467.
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van, Rensburg Karel Jensen. "Analysis of arcing faults on distribution lines for protection and monitoring." Thesis, Queensland University of Technology, 2003. https://eprints.qut.edu.au/15800/1/Karel_van_Rensburg_Thesis.pdf.
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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.
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van, Rensburg Karel Jensen. "Analysis of arcing faults on distribution lines for protection and monitoring." Queensland University of Technology, 2003. http://eprints.qut.edu.au/15800/.
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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.
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Cheong, Wai Jing. "Accurate fault location in TCSC high voltage transmission lines using combined wavelet transform and artificial neural network." Thesis, University of Bath, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425674.
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Mohd, Noor Mohd Junaizee. "Application of knowledge-based fuzzy inference system on high voltage transmission line maintenance." Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/16050/1/Mohd_Junaizee_Mohd_Noor_Thesis.pdf.
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A majority of utilities conduct maintenance of transmission line components based on the results of routine visual inspection. The inspection is normally done by inspectors who detect defects by visually checking transmission line components either from the air (in helicopters), from the ground (by using high-powered binoculars) or from the top of the structure (by climbing the structure).
The main problems with visual inspection of transmission lines are that the determination of the defects varies depending on the inspectors' knowledge and experience and that the defects are often reported qualitatively using vague and linguistic terms such as "medium crack", "heavy rust", "small deflection". As a result of these drawbacks, there is a large variance and inconsistency in defect reporting (which, in time, makes it difficult for the utility to monitor the condition of the components) leading to ineffective or wrong maintenance decisions. The use of inspection guides has not been able to fully address these uncertainties.
This thesis reports on the application of a visual inspection methodology that is aimed at addressing the above-mentioned problems. A knowledge-based Fuzzy Inference System (FIS) is designed using Matlab's Fuzzy Logic Toolbox as part of the methodology and its application is demonstrated on utility visual inspection practice of porcelain cap and pin insulators. The FIS consists of expert-specified input membership functions (representing various insulator defect levels), output membership functions (indicating the overall conditions of the insulator) and IF-THEN rules. Consistency in the inspection results is achieved because the condition of the insulator is inferred using the same knowledge-base in the FIS rather than by individual inspectors. The output of the FIS is also used in a mathematical model that is developed to suggest appropriate component replacement date.
It is hoped that the methodology that is introduced in this research will help utilities achieve better maintenance management of transmission line assets.
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Mohd, Noor Mohd Junaizee. "Application of knowledge-based fuzzy inference system on high voltage transmission line maintenance." Queensland University of Technology, 2004. http://eprints.qut.edu.au/16050/.
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A majority of utilities conduct maintenance of transmission line components based on the results of routine visual inspection. The inspection is normally done by inspectors who detect defects by visually checking transmission line components either from the air (in helicopters), from the ground (by using high-powered binoculars) or from the top of the structure (by climbing the structure).
The main problems with visual inspection of transmission lines are that the determination of the defects varies depending on the inspectors' knowledge and experience and that the defects are often reported qualitatively using vague and linguistic terms such as "medium crack", "heavy rust", "small deflection". As a result of these drawbacks, there is a large variance and inconsistency in defect reporting (which, in time, makes it difficult for the utility to monitor the condition of the components) leading to ineffective or wrong maintenance decisions. The use of inspection guides has not been able to fully address these uncertainties.
This thesis reports on the application of a visual inspection methodology that is aimed at addressing the above-mentioned problems. A knowledge-based Fuzzy Inference System (FIS) is designed using Matlab's Fuzzy Logic Toolbox as part of the methodology and its application is demonstrated on utility visual inspection practice of porcelain cap and pin insulators. The FIS consists of expert-specified input membership functions (representing various insulator defect levels), output membership functions (indicating the overall conditions of the insulator) and IF-THEN rules. Consistency in the inspection results is achieved because the condition of the insulator is inferred using the same knowledge-base in the FIS rather than by individual inspectors. The output of the FIS is also used in a mathematical model that is developed to suggest appropriate component replacement date.
It is hoped that the methodology that is introduced in this research will help utilities achieve better maintenance management of transmission line assets.
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Krige, Ernst. "Harmonic interaction between weak AC systems and VSC-based HVDC schemes." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71704.
Full textAbstract:
Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: The implementation of the Caprivi Link Interconnector (CLI) High Voltage Direct Current (HVDC) scheme in 2010 connecting the weak Namibian and Zambian Alternating Current (AC) transmission networks via overhead line is based on Voltage Source Converter (VSC) technology. This world-first combination of attributes presents a unique opportunity to study harmonic interaction between weak AC systems and VSC-based HVDC schemes. Relatively few publications exist that focus on AC and DC harmonic interaction and very few refer to VSC HVDC schemes. Because weak AC systems are much more prone to harmonic distortion than strong AC systems, there is a clear motivation for more detailed work in this field. In order to understand the context wherein AC and DC harmonic interaction exists, the fields of AC power system harmonic analysis and resonance, VSC switching theory, HVDC scheme configurations, Pulse Width Modulation (PWM) techniques and frequency domain analysis techniques are discussed. This thesis then presents the concept of Harmonic Amplitude Transfer Ratio (HATR) by a theoretical analysis of AC and DC harmonic interaction due to the fundamental component, as well as harmonic interaction due to scheme characteristic harmonics and is compared to the simulation results obtained from different software solutions. Simulation and modelling techniques for AC and DC harmonic interaction are discussed including AC and DC systems modelling. The theoretical results and simulation results are compared to the results obtained from a real life case study on the CLI HVDC scheme where a harmonic resonance condition occurred. The correlation of these three sets of results confirms the validity of the theories presented and possible mitigation of the case study resonance problems is explored. The results and conclusion highlight a variety of interesting points on harmonic sequence components analysis, VSC zero sequence elimination, AC and DC harmonic interaction due to the fundamental component and the HATR for different PWM methods, AC and DC harmonic interaction due to scheme characteristic harmonics, modelling techniques and mitigation for the resonance conditions experienced in the analysed real life case study.
AFRIKAANSE OPSOMMING: Die implementering van die Caprivi Skakel Tussenverbinder (CLI) hoogspannings- gelykstroom (HSGS) skema in 2010 wat die swak Namibiese and Zambiese Wisselstroom (WS) transmissienetwerke verbind via „n oorhoofse lyn is gebasseer op Spanningsgevoerde-omsetter tegnologie. Hierdie wêreld-eerste kombinasie van eienskappe verskaf „n unieke geleentheid om harmoniese interaksie tussen swak WS stelsels en Spanningsgevoerde-omsetter Hoogspannings GS stelsels te bestudeer. Relatief min publikasies wat fokus op WS en GS harmoniese interaksie bestaan, en baie min verwys na Spanningsgevoerde-omsetter Hoogspannings GS skemas. Omdat swak WS stelsels baie meer geneig is tot harmoniese verwringing as sterk WS stelsels, is daar „n duidelike motivering vir meer gedetaileerde werk in hierdie veld. Om die konteks te verstaan waarin WS en GS harmoniese interaksie bestaan, word die velde van WS kragstelsel harmoniese analise en resonansie, Spanningsgevoerde-omsetter skakelteorie, Hoogspannings GS skema opstellings, Pulswydte Modulasie (PWM) tegnieke, en frekwensiegebied analiese tegnieke bespreek. Hierdie tesis stel dan die konsep van Harmoniese Amplitude Oordragsverhouding voor deur „n teoretiese analise van WS en GS harmoniese interaksie na aanleiding van die fundamentele komponent, asook harmoniese interaksie a.g.v. harmonieke wat die stelsel kenmerk en word vergelyk met die simulasieresultate verkry uit verskilllende sagteware oplossings. Simulasie- en modelleringstegnieke vir WS en GS harmoniese interaksie word bespreek insluitend WS- en GS stelselmodellering. Die teoretiese resultate en simulasieresultate word vergelyk met die resultate wat verkry is uit „n werklike gevallestudie op die CLI HSGS skema waar „n harmoniese resonansie toestand voorgekom het. Die ooreenkomste tussen hierdie drie stelle resultate bevestig die geldigheid van die teorieë soos uiteengeset voor, en die moontlike verbetering van die gevallestudie resonansie probleme word verken. Die resultate en samevatting beklemtoon „n verskeidenheid punte aangaande harmoniese volgorde-komponent analiese, Spanningsgevoerde-omsetter zero-volgorde uitskakeling, WS en GS harmoniese interaksie na aanleiding van die fundamentele komponent en die Harmoniese Amplitude Oordragsverhouding vir verskillende PWM metodes, WS en GS harmoniese interaksie na aanleiding van skema-kenmerkende harmonieke, modelleringstegnieke, asook verbetering van die resonansie toestande soos ervaar in die analise van die werklike gevallestudie.
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Lee, Jack Monroe Jr. "Seasonal Patterns of Melatonin, Cortisol, and Progesterone Secretion in Female Lambs Raised Beneath a 500-kV Transmission Line." PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/1317.
Full textAbstract:
There is ongoing controversy about the possibility of adverse biological effects from environmental exposures to electric and magnetic fields. These fields are produced by all electrical equipment and appliances including electrical transmission lines. The objective of this environmental science study was to investigate the possible effects of a high voltage transmission line on domestic sheep (Ovis aries L,), a species that can often be found near such lines. The study was primarily designed to determine whether a specific effect of electric and magnetic fields found in laboratory animals also occurs in livestock under natural environmental conditions. The effect is the ability of fields, at levels found in the environment, to significantly depress the normally high nocturnal concentrations of the pineal hormone melatonin. Melatonin mediates the reproductive response to changes in photoperiod in seasonal breeders such as sheep. Factors which modify the production of nocturnal melatonin in sheep can have important effects on the timing of seasonal reproduction including the onset of puberty in this species. Ten female Suffolk lambs were penned for 10 months directly beneath a 500-kV transmission line near Estacada, Oregon. Ten other lambs of the same type were penned in a control area away from the transmission line where electric and magnetic fields were at ambient levels. Serum melatonin was analyzed by radioimmunoassay (RIA) from 6618 blood samples collected at 0.5 to 3-hour intervals over eight 48-hour periods. Serum progesterone was analyzed by RIA from blood samples collected twice weekly beginning when the lambs were 23 weeks old. This hormone was used to measure the onset of puberty. Serum cortisol was also assayed by RIA from the blood samples collected during the 48-hour samples. This was done to assess whether exposure to the transmission line produced stress in the growing lambs. Other supplemental biological data collected included body weight gain, wool growth, and behavior. An extensive study was conducted by engineers from the Bonneville Power Administration (BPA) to measure electric and magnetic fields and noise to which the lambs were exposed. This was accomplished by installing permanent monitors near both the control and line pens. Results showed that lambs in both the control and line groups had the typical pattern of melatonin secretion consisting of low daytime and high nighttime serum concentrations. There were no statistically significant differences between groups in melatonin levels, or in the phase or duration of the nighttime melatonin elevation. Age at puberty and number of reproductive cycles also did not differ between groups. Serum cortisol showed a circadian rhythm with highest concentrations during the day. Cortisol concentrations also seemed to reflect effects of known stressors on livestock, e.g., weaning, introduction to new housing, and vehicle transport. There were, however, no differences in cortisol concentrations between groups. Statistical analyses on other biological parameters revealed no differences between groups for body weight gain, wool growth, or behavior. The electrical monitoring program verified that the line group lambs were exposed to electric and magnetic fields at levels typical of those found beneath commercial 500-kV transmission lines. In summary, the large effect of electric and magnetic fields on melatonin concentrations reported in laboratory animals was not observed in this study of sheep.
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Visser, Abraham Johannes. "Transformerless series dip/sag compensation with a multilevel cascaded inverter." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52592.
Full textAbstract:
Thesis (MScEng)--University of Stellenbosch, 2001.ENGLISH ABSTRACT: This thesis covers the development of a multilevel cascaded inverter for the purpose of costeffective transformerless series dip compensation. Of all known power quality problems, voltage dips are the greatest reason for concern. Dips/sags occur more frequently than outages and therefore tend to be more costly for industry as modem technical equipment becomes all the more sensitive to the quality and reliability of supply. A number of devices already exist to compensate for this problem, but the cost of most of these systems does not always justify the financial losses they compensate for. All of these systems are using transformers and/or large filter components that contribute to the size, price and losses to quite a large extent. Series injection dip compensators offer the advantage of only having to compensate for the decrease in supply voltage during a dip. This results in a significant reduction in the converter ratings and energy storage requirements compared to conventional uninterruptible power supplies or shunt injection power quality devices. Existing inverter topologies, including multilevel inverters, were therefore studied and compared as possible solutions for cost-effective transformerless series dip compensation. On the basis of these considerations the multilevel cascaded inverter seems to be the most cost-effective option. The relatively low harmonic content of its unfiltered output also eliminates the need for a large output filter. A single-phase dip compensator, with this topology, was designed and built according to specifications stated by Eskom, the main utility in South Africa. Batteries as energy storage and automotive MOSFETs as switching components, proved to be most cost-effective options for the specified power ratings. Control algorithms for dip compensation with the multilevel inverter were also developed. Some of these algorithms are based on existing techniques, but two new algorithms were also developed to implement force commutation of the thyristors and to share the power dissipation in the dip compensator. Simulations indicated that these algorithms could be suitable and sufficient for their application. This dip compensator with its control algorithms was tested with a dip generator, developed at the University of Stellenbosch, for different types of loads. The experimental results confirmed the simulations and showed a very good performance for the specified conditions. An optimised design of this dip compensator will make it a cost-effective solution for dip compensation.
AFRIKAANSE OPSOMMING: Hierdie tesis dek die ontwikkeling van 'n multivlakwisselrigter, in kaskade, met koste-effektiewe transformatorlose duik kompensasie as mikpunt. Van al die bekende toevoerkwaliteit probleme wek duike in die spanning die meeste kommer. Duike kom meer gereeld voor as kragonderbrekings en neig daarom om 'n groter onkoste te wees vir die industrie soos wat moderne tegnologiese toerusting al hoe meer sensitief raak vir die kwaliteit en betroubaarheid van die toevoer. 'n Aantal toestelle wat vir hierdie probleem kompenseer bestaan reeds, maar die koste van hierdie stelsels regverdig nie altyd die finansiële verliese wat hulle moet elimineer nie. Al hierdie stelsels gebruik transformators en/of groot filter komponente wat grootliks bydra tot die grootte, prys en verliese van hierdie stelsels. Serie-injeksie kompenseerders het die voordeel dat hulle net kompenseer vir die verlies in die toevoerspanning tydens die duik. Dit het 'n beduidende vermindering in die omsetterkenwaardes en energiestoorvereistes tot gevolg in vergelyking met ononderbroke kragbronne (UPS) of newe-injeksie toevoerkwaliteit toestelle. Daarom IS bestaande wisselrigtertopologië, insluitende multivlakwisselrigters, bestudeer en vergelyk as moontlike oplossings vir koste-effektiewe serie duik-kompensasie. Van al hierdie moontlikhede lyk die multivlakwisselrigter, in kaskade, na die mees koste-effektiewe opsie. Die relatiewe lae harmoniese inhoud van sy ongefilterde uittree elimineer die behoefte aan 'n groot uittreefilter. 'n Enkelfase duik kompenseerder, met hierdie topologie, is ontwerp en gebou volgens die spesifikasies wat vasgestel is deur Eskom, die hoof elektriese kragvoorsiener in Suid-Afrika. Dit het geblyk dat batterye, en MOSFETte uit die motorbedryf, die mees koste-effektiewe opsies bied vir onderskeidelik die energiestoor en skakelkomponente. Beheeralgoritmes VIr duik kompensasie met die multivlakwisselrigter is ook ontwikkel. Sommige van hierdie algoritmes is gebaseer op bestaande tegnieke, maar twee nuwe algoritmes is ook ontwikkel vir die kommutering van die tiristors en die deling van die drywingsverkwisting in die duik kompenseerder. Simulasies dui aan dat hierdie algoritmes geskik en voldoende kan wees vir hulle toepassing. Hierdie duik kompenseerder met sy beheeralgoritmes is getoets vir verskillende tipes laste met 'n duikgenerator wat ontwikkel is by die Universiteit van Stellenbosch. Die eksperimentele resultate bevestig dit wat verkry is uit die simulasies en wys 'n goeie werkverrigting vir die gespesifiseerde kondisies. 'n Geoptimeerde ontwerp van hierdie duik kompenseerder sal dit 'n koste-effektiewe oplossing maak vir duik kompensasie.
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Mishra, Chinmaya. "Design and implementation of low power multistage amplifiers and high frequency distributed amplifiers." Texas A&M University, 2004. http://hdl.handle.net/1969.1/2775.
Full textAbstract:
The advancement in integrated circuit (IC) technology has resulted in scaling down of device sizes and supply voltages without proportionally scaling down the threshold voltage of the MOS transistor. This, coupled with the increasing demand for low power, portable, battery-operated electronic devices, like mobile phones, and laptops provides the impetus for further research towards achieving higher integration on chip and low power consumption. High gain, wide bandwidth amplifiers driving large capacitive loads serve as error amplifiers in low-voltage low drop out regulators in portable devices. This demands low power, low area, and frequency-compensated multistage amplifiers capable of driving large capacitive loads. The first part of the research proposes two power and area efficient frequency compensation schemes: Single Miller Capacitor Compensation (SMC) and Single Miller Capacitor Feedforward Compensation (SMFFC), for multistage amplifiers driving large capacitive loads. The designs have been implemented in a 0.5??m CMOS process. Experimental results show
that the SMC and SMFFC amplifiers achieve gain-bandwidth products of 4.6MHz and 9MHz, respectively, when driving a load of 25Kδ/120pF. Each amplifier operates from a ??1V supply, dissipates less than 0.42mW of power and occupies less than 0.02mm2 of silicon area.
The inception of the latest IEEE standard like IEEE 802.16 wireless metropolitan area network (WMAN) for 10 -66 GHz range demands wide band amplifiers operating at high frequencies to serve as front-end circuits (e.g. low noise amplifier) in such receiver architectures. Devices used in cascade (multistage amplifiers) can be used to increase the gain but it is achieved at an expense of bandwidth. Distributing the capacitance associated with the input and the output of the device over a ladder structure (which is periodic), rather than considering it to be lumped can achieve an extension of bandwidth without sacrificing gain. This concept which is also known as distributed amplification has been explored in the second part of the research. This work proposes certain guidelines for the design of distributed low noise amplifiers operating at very high frequencies. Noise analysis of the distributed amplifier with real transmission lines is introduced. The analysis for gain and noise figure is verified with simulation results from a 5-stage distributed amplifier implemented in a 0.18??m CMOS process.
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Lang, Ian Dewi. "The degradation of all-dielectric self supporting cables installed in high potential electro-magnetic fields : a theoretical and practical evaluation of optical fibre cables strung independently on overhead power transmission lines." Thesis, University of South Wales, 2001. https://pure.southwales.ac.uk/en/studentthesis/the-degradation-of-alldielectric-self-supporting-cables-installed-in-high-potential-electromagnetic-fields(5a7dee38-9f9b-40f8-8259-2e3d5386e292).html.
Full textAbstract:
The operational life of all-dielectric self supporting (ADSS) optical fibre cables installed on high voltage over-head power transmission lines is limited by sheath degradation caused by induced electrical activity on the cable's surface. The work presented in this thesis describes research completed to quantify this degradation. This has resulted in a novel analysis method being developed and used to associate product testing with field trial results. The analysis is based on evaluating the magnitude of recorded electrical activity and fitting an appropriate distribution to the data to describe relative electrical arcing power. This innovation was possible due to the completion of a comprehensive review of the theories dealing with the generation of the electrical activity, followed by a detailed analysis. Where appropriate, worked examples are given in the thesis to demonstrate these theories. As a result of this work three proposals have been made to simplify future analyses. They are: approximating the relevant variables to span related polynomial functions, relating capacitive coupling to the space potential, and the superposition of assumed functions. The work is supported by results presented of extensive practical testing and simulations carried out by the author. These include analyses of the resulting cable damage, some of which has not been discriminated between in previous work. The completed analysis of tested products has also identified, previously not quantified, degradation accelerants. The work classifies these accelerants into extrinsic installation and intrinsic product factors. The thesis presents and reviews the implication of the electrical degradation resistance of sheaths applied to slotted-core and advance multi-loose tube (MLT) optical fibre cable designs. This has lead to the evaluation of three generations of sheath technology, which varied from low smoke compound technology, through to bimodal polyethylene. The work also identifies specific methods to limit risk to products. They include the use of pre-blended materials and the need to assure both sheath surface finish quality and cable longitudinal water blocking. Finally, the thesis summarises the development of new and previously investigated proposed degradation mitigation systems. Selected possible solutions were then evaluated using tests and analysis methods developed by the author, and compared with those of other notable works. This has resulted in the filing of two patents. As a result of this research a solution has been trialed and proposed to the collaborating company. This will allow optical fibre cable to be installed in high potential fields for the prescribed lifetime, overcoming previous limitations.
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Roets, Hendrik Adriaan. "Effect of altitude on audible noise generated by AC conductor corona." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71810.
Full textAbstract:
Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Power utilities are expected to keep the cost of electricity as low as possible. They are also expected to be environmentally friendly and, amongst other things, not to produce unacceptable audible noise. When the electric field on a conductor is high enough corona is produced and this is accompanied by audible noise. Air pressure, which is directly related to altitude, has an effect on the voltage at which corona will start. It is more difficult to ionise the air at sea level (high air pressure) than at high altitude (low air pressure). Altitude does not only affect the corona inception voltage, but also the intensity of the audible noise. A thorough scan of literature revealed that there is very little evidence of prior research work on the effect of air density on corona under fair weather (dry) conditions. In South Africa, transmission lines are built at altitudes higher than 1800 m above sea level. The cost of a 400 kV line is in the region of R2M per km. It is important to predict the noise levels under a proposed line accurately, before it is energised. This research indicated that the altitude correction for conductor corona audible noise, under dry conditions, might be steeper than the general accepted correction of 1 dB/300m. This correction, however, appears to be valid for heavy rain conditions. Under heavy rain conditions the corona is mainly determined by the water droplets, whereas under dry conditions the condition of the conductor plays the biggest role. The air density therefore has a bigger effect on the corona performance under dry conditions. The implication of a steeper altitude correction for dry conditions is that too low noise levels will be predicted for a higher altitude, which could lead to complaints. On the other hand, predictions for lower altitudes will be too conservative.
AFRIKAANSE OPSOMMING: Daar word van kragvoorsieners verwag om die koste van elektrisiteit so laag as moontlik te hou. Hulle is verder onder druk om omgewingsvriendelik te wees en om onder andere nie onaanvaarbare hoorbare geraas te veroorsaak nie. Wanneer die elektriese veld op ‘n geleier hoog genoeg is, kan korona ontstaan wat dan hoorbare geraas veroorsaak. Die lugdruk, en daarom die hoogte bo seevlak, beïnvloed die spanning waarby ‘n geleier in korona sal gaan. Dit is moeiliker om die lug te ioniseer by seevlak (hoë lugdruk) as hoog bo seevlak (lae lugdruk). Die hoogte bo seevlak beïnvloed daarom nie net die spanning waarby korona sal begin nie maar ook die intensiteit van die hoorbare geraas. Dit wil voorkom of die effek van hoogte bo seevlak, op hoorbare geraas, a.g.v. geleier korona tot op datum baie skraps nagevors is. Baie min kon in die literatuur gevind word op die effek onder droë toestande. In Suid-Afrika is dit nodig om transmissielyne op hoogtes van 1800 m en hoër te bou. So ‘n lyn (400 kV) kos in die omgewing van R2M per km. Dit is daarom van uiterste belang om die geraasvlakke wat ‘n beplande lyn sal veroorsaak, akkuraat te bepaal, voordat so ‘n lyn aangeskakel word. Hierdie navorsing het gewys dat die effek van hoogte bo seespieël op hoorbare korona geraas onder droë toestande groter kan wees as wat algemene aanvaar word. Die helling van die korreksiefaktor vir hoogte bo seevlak blyk steiler as 1 dB/300 m te wees vir droë toestande. Die implikasie hiervan is dat geraas voorspellings vir hoër hoogtes bo seespieël te laag sal wees en die vir lae hoogtes te konserwatief kan wees. Die navorsing stem egter saam met die korreksiefaktor van 1 dB/300 m onder swaar reën toestande. Dit wil voorkom of die invloed van die waterdruppels op geleier korona groter is as lugdruk. Onder droë toestande speel die toestand van die geleier 'n groter rol en is die effek van lugdruk groter.
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Silveira, Patrícia Oliveira da. "Planejamento de sistemas de transmissão em área com fonte de geração intermitente, apoiado no uso de tecnologias avançadas." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-27062017-105858/.
Full textAbstract:
O Brasil é um país de dimensões continentais, onde existe uma considerável distância entre a geração e os principais centros de consumo. Dessa forma, o estudo e desenvolvimento de novas tecnologias de transmissão a longas distâncias é de fundamental importância para o desenvolvimento do país. A solução mais utilizada atualmente é a transmissão em corrente alternada. Entretanto a transmissão em corrente continua também é uma solução viável para longas distâncias. O sistema brasileiro é composto principalmente por linhas 500 kV em corrente alternada (também há 230; 345; 440 e 750 kV), bem como em corrente continua (em ±600 e ±800 kV). O presente estudo apresenta uma solução de transmissão em corrente alternada por linhas de 1000 kV, que se mostrou mais econômico na transmissão de potências superiores a 3.500 MW e distâncias de 1400km. Nos próximos anos, a geração de energia elétrica no Brasil será expandida de forma significativa, ocorrerá um aumento principalmente na geração de energia eólica e solar, localizadas em sua maioria na região Nordeste do país. Esse aumento na geração exigirá a transmissão de grandes blocos de energia elétrica por distâncias significativas, devido à falta de proximidade entre a geração e os principais centros consumidores, que estão localizados no Sudeste. Neste estudo, serão mostradas as etapas de definição de condutor economicamente mais adequado e projeto da geometria da torre. Com base nos dados obtidos, será feita a avaliação do desempenho da linha 1000 kV, durante a operação normal de fluxo de carga, curtos-circuitos e estabilidade.Brazil, a country of continental proportions, have significant distance between the power generation centers and the main consumer centers. In such way, the study and development of new transmission technologies over long distances is of fundamental importance for the development of the country. Nowadays, the most commonly used solution is alternating current transmission. However, direct current transmission is also a viable solution for long distances. The Brazilian system mainly consists of 500 kV alternating current lines (along with 230, 345, 440 and 750 kV) and direct current lines (± 600 and ± 800 kV). This study provides a solution for transmission in alternating current by lines of 1000 kV, which proved to be more economical in power transmission over 3,500 MW and distances beyond 1400km. In the coming years, the electric power generation in Brazil will expand significantly; a boost will take place mainly in wind and solar power generation, located mostly in the Northeast of the country. This generation expansion will require transmission of large blocks of electric power over considerable distances, due to the lack of proximity between generation sites and main consumer centers located in the Southeast. This study will show the setting stages of the most economically applicable conductor and tower geometry design. Based on the data obtained, the performance of the 1000 kV line will be evaluated during the regular load flow operation, short circuits and stability.
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Bailey, Etienne Benjamin. "Understanding local public responses to a high-voltage transmission power line proposal in South-West England : investigating the role of life-place trajectories and project-related factors." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/17948.
Full textAbstract:
With a projected increase in electricity demand and low-carbon energy generation in the UK, expansion of the existing transmission grid network is required. In going beyond the NIMBY concept, Devine-Wright (2009) posited a place-based approach that highlights the roles of place attachment and place-related symbolic meanings for understanding public responses to energy infrastructure proposals. This PhD research investigated two overarching and interrelated research aims. The first sought to enlarge our understandings of the processes of attachment and detachment to the residence place by investigating the dynamics of varieties of people-place relations across the life course (people's 'life-place trajectories'), thus addressing the limitation of studies adopting a 'structural' approach to the study of people-place relations. This research, in a second instance, sought to better understand the role of people's life-place trajectories and a range of project-based factors (i.e. procedural and distributive justice) in shaping people's responses to a power line proposal. This research focussed on the Hinckley Point C (HPC) transmission line proposal and residents of the town of Nailsea, South-West England. A social representations theory framework was usefully applied to this research by acknowledging that people's personal place relations and their beliefs about proposed place change, are situated and embedded within wider social representations of place and project. A mixed methods approach was employed comprising three empirical studies. The first consisted of twenty-five narrative interviews, the second a set of five focus group interviews, and the third a questionnaire survey study (n=264) amongst a representative sample of Nailsea residents. Triangulating findings across the three studies produced a novel set of key findings. By elaborating five novel 'life-place trajectories', this PhD research moved beyond structural approaches to the study of people-place relations and made a novel contribution to our understandings of the processes and dynamics of attachment and detachment to the residence place across the life course. This research further confirmed the existing typology of people-place relations and revealed a novel variety termed 'Traditional-active attachment'. Life-place trajectories were instrumental in informing divergent representations of the nearby countryside which were more or less congruent with objectified representations of the HPC project. Future studies investigating place and project meanings should be sensitive to these trajectories. Interestingly, place as a 'centre of meaning' rather than a 'locus of attachment' (or non-attachment) emerged as particularly salient for understanding responses to the project. Project-based factors were salient in informing participants' responses toward the project. A perceived imbalance between high local costs and an absence of local benefits was seen to result in distributive injustice and opposition toward the project. However, improved perceived procedural justice following National Grid's announcement of siting concessions in the spring of 2013, was seen to ameliorate local trust in the developer and project acceptance.
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Valuntaitė, Vaida. "The Investigation and Assessment of the Man-made Ozone Formation and Dispersion." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090608_190741-86415.
Full textAbstract:
The dissertation comprises the general characteristic of the work,
5 chapters, conclusions and recommendations, references and list of published works on the topic of the dissertation. The dissertation covers 149 pages,
78 illustrations, 17 tables.
In introduction chapter the problem topicality is considered, the aims and tasks of the work are formulated, the novelty of the research is described, the author’s reports and publications as well as the dissertation structure are presented. Chapter 1 is intended for the review of literature. The survey of ozone sources in working premises and the environment air is presented as well as methods of the ozone concentration determination and its dispersion simulation are discussed. At the end of the chapter conclusions are formulated and the dissertation tasks are concretized. In chapter 2 the methodology of the ozone concentration determination with the ozone analyzer and passive samplers as well as the measurement methods of aerosol particles and meteorological, microclimatic parameters are described. In chapter 3 the results obtained during experimental investigations are discussed: the ozone concentration changes near technogenic sources of this pollutant, the influence of meteorological and microclimatic parameters on the ozone concentrations changes, the relation of aerosol particles with the ozone concentration. Ozone concentrations measured by different methods are compared and the results of comparative measurements are... [to full text]Disertaciją sudaro įvadas, 5 pagrindiniai skyriai, darbo išvados ir rekomendacijos, literatūros sąrašas, publikacijų sąrašas. Bendra disertacijos apimtis – 149 puslapiai, 80 iliustracijų, 17 lentelių. Įvadiniame skyriuje nagrinėjamas problemos aktualumas, formuluojamas darbo tikslas bei uždaviniai, aprašomas mokslinis darbo naujumas, pristatomi autoriaus pranešimai ir publikacijos, disertacijos struktūra. Pirmasis skyrius skirtas literatūros apžvalgai. Jame pateikta ozono šaltinių darbo patalpose ir aplinkos ore apžvalga, aptariami ozono koncentracijos nustatymo ir jos sklaidos modeliavimo metodai. Skyriaus pabaigoje formuluojamos išvados ir konkretinami disertacijos uždaviniai. Antrajame skyriuje aprašomi ozono koncentracijos nustatymo ozono analizatoriumi ir pasyviaisiais kaupikliais metodika bei aerozolio dalelių ir meteorologinių, mikroklimato parametrų matavimo metodai. Trečiajame skyriuje aptariami eksperimentinių tyrimų metu gauti rezultatai apie: ozono koncentracijos kitimą prie technogeninių šio teršalo šaltinių, meteorologinių ir mikroklimato parametrų įtaką ozono koncentracijos pokyčiams, aerozolio dalelių sąryšį su ozono koncentracija. Lyginamos ozono koncentracijos matuotos skirtingais metodais ir aptariami lyginamųjų matavimų rezultatai. Ketvirtajame skyriuje pateikti RISK programa sumodeliuoti ozono sklaidos nuo šaltinio rezultatai. Penktajame skyriuje pasiūlytas technologinis sprendimo variantas, leidžiantis sumažinti ozono koncentracijas prie technogeninių... [toliau žr. visą tekstą]
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Chromík, Aleš. "Vyvedení výkonu z rozvodny 110/22 kV Moravany u Brna." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220293.
Full textAbstract:
The aim of this Master’s thesis is the design and reconstruction of the high voltage distribution network for the company E. ON with focus on calculation of the stabilized operation and on the planning of new cable taps from the transformer substation Moravany u Brna. The first part of the theoretical analysis of the work deals with the inclusion of the distribution network into the power system and with principles of development and construction of high voltage networks. The second part includes a general calculation of stabilized operation of the power distribution network and a familiarization with the program PAS Off - Line Bison 4.0. The practical part of the thesis is focused on the calculation of the stabilized operation at the current state of transformer substation Moravany u Brna using the PAS Off - Line Bizon 4.0 V programme. This part also contains the design of six new cable lines which are needed to strengthen the power distribution in the southern part of the city Brno. The closing part of this chapter constitutes of a outdoor and indoor cable line renovation. These cables are connected to the transformer substation Moravany u Brna and a calculation of stabilized operation is also included in this part.
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Yang, Yi. "Power line sensor networks for enhancing power line reliability and utilization." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41087.
Full textAbstract:
Over the last several decades, electricity consumption and generation have continually grown. Investment in the Transmission and Distribution (T&D) infrastructure has been minimal and it has become increasingly difficult and expensive to permit and build new power lines. At the same time, a growing increase in the penetration of renewable energy resources is causing an unprecedented level of dynamics on the grid. Consequently, the power grid is congested and under stress.
To compound the situation, the utilities do not possess detailed information on the status and operating margins on their assets in order to use them optimally. The task of monitoring asset status and optimizing asset utilization for the electric power industry seems particularly challenging, given millions of assets and hundreds of thousands of miles of power lines distributed geographically over millions of square miles. The lack of situational awareness compromises system reliability, and raises the possibility of power outages and even cascading blackouts.
To address this problem, a conceptual Power Line Sensor Network (PLSN) is proposed in this research. The main objective of this research is to develop a distributed PLSN to provide continuous on-line monitoring of the geographically dispersed power grid by using hundreds of thousands of low-cost, autonomous, smart, and communication-enabled Power Line Sensor (PLS) modules thus to improve the utilization and reliability of the existing power system.
The proposed PLSN specifically targets the use of passive sensing techniques, focusing on monitoring the real-time dynamic capacity of a specific span of a power line under present weather conditions by using computational intelligence technologies. An ancillary function is to detect the presence of incipient failures along overhead power lines via monitoring and characterizing the electromagnetic fields around overhead conductors. This research integrates detailed modeling of the power lines and the physical manifestations of the parameters being sensed, with pattern recognition technologies. Key issues of this research also include design of a prototype PLS module with integrated sensing, power and communication functions, and validation of the Wireless Sensor Network (WSN) technology integrated to this proposed PLSN.
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Alles, Joan. "Investigations on flashover of polluted insulators : Influence of silicone coating on the behavior of glass insulators under steep front impulse." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC058.
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Cette thèse s’inscrit dans le cadre de l’amélioration du comportement électrique des isolateurs de lignes haute tension ; l’objectif est d’assurer une meilleure fiabilité et qualité d’alimentation en énergie électrique. Ce travail a été motivé par la nécessité de répondre à trois questions liées au comportement des isolateurs verre en zone polluée. La première porte sur la recherche d’une méthode permettant de calculer la tension de contournement des chaînes polluées selon le type d’isolateur et ses caractéristiques. La deuxième question concerne la différence de comportement entre les isolateurs en verre et les isolateurs en porcelaine de type « outerrib » ; ce type d’isolateurs présente une forme spécifique adaptée aux environnements à forte pollution. Les tensions de contournement ainsi que les trajectoires de l’arc sur les isolateurs en verre sont très différentes de celles observées avec les isolateurs en porcelaine. Et la troisième question est relative à la défaillance des isolateurs recouverts de silicone lors des essais en chocs (des impulsions de tension) à front raide. En effet, les isolateurs recouverts d’une couche de 0.3 mm (ou plus) de silicone hydrophobe explosent lorsqu’ils sont soumis à des impulsions de tension à front raide d’amplitude très élevée pendant un temps très court. Différents mécanismes pouvant être à l’origine de l’explosion/éclatement des isolateurs recouverts d’une couche de silicone sont discutés. Il ressort des différents tests et analyses que le mécanisme le plus probable semble être la fragmentation par plasma. En effet, suite à l’application d’une tension à front raide, d’amplitude très élevée, des canaux (fissures) microscopiques prennent naissance là où le champ électrique est le plus intense. L’application répétitive des chocs de tension conduit au développement de décharges dans ces canaux (rupture diélectrique de l’air) c’est-à-dire des arcs (canaux de plasma) qui se développent/propagent dans le volume de l’isolateur. La puissance déchargée (c’est-à-dire l’énergie stockée dans les condensateurs du générateur en des temps très courts) dans ces canaux à chaque choc étant très élevée, elle conduit à l’explosion de l’isolateur après quelques chocs (parfois 5 ou 6 suffisent): c’est la fragmentation par plasmaThis thesis deals with the improvement of the electrical behavior of insulators of high voltage lines; the objective is to ensure better reliability and quality of power supply. This work was motivated by the need to answer three questions related to the behavior of glass insulators in polluted areas. The first one concerns the search for method for calculating the flashover voltage of polluted chains according to the type of insulator and its characteristics. The second question concerns the difference in behavior between glass insulators and "outerrib" porcelain insulators; this type of insulator has a specific shape adapted to environments with high pollution. The flashover voltages as well as the trajectories of the arc on glass insulators are very different from those observed with porcelain insulators. And the third issue is the failure of silicon-coated insulators during shock tests (pulses) with a steep front. Indeed, insulators coated with a layer of 0.3 mm (or more) of hydrophobic silicone explode when subjected to very high amplitude steep-edge voltage pulses for a very short time. Different mechanisms that may be responsible for the explosion / puncturing of insulators covered with a layer of silicone are discussed. It appears from the various tests and analyzes that the most probable mechanism seems to be plasma fragmentation (cracking). Indeed, following the application of a steep front voltage, of very high amplitude, microscopic channels (fissures) originate where the electric field is most intense. The repetitive application of impulse voltages (shocks) leads to the development of discharges in these channels (breakdown of the air), i.e.; arcs (plasma channels) which develop / propagate in the volume of the insulator. The discharged power (i.e.; the energy stored in the capacitors of the generator in a very short times) in these channels (cracks) at each shock being very high, leads to the explosion of the insulator after some shocks (5 to 6 sometimes): it is the fragmentation by plasma or plasma cracking
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Martinho, Lucas Blattner. "Modélisation numérique des phénomènes de couplage électromagnétique dans les alentours des lignes aériennes de transmission d'énergie." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAT030/document.
Full textAbstract:
Les phénomènes de couplage électromagnétique entre les lignes aériennes de transmission d'énergie et des structures voisines sont inévitables, surtout dans les zones densément peuplées. Les effets indésirables découlants de cette proximité sont variés, allant de l'établissement des tensions dangereuses à l'apparition de phénomènes de corrosion dus au courant alternatif. L'étude de cette classe de problèmes est nécessaire pour assurer la sécurité dans les alentours de la zone d'interaction et aussi pour préserver l'intégrité des équipements et des dispositifs présents. Cependant, la modélisation complète de ce type d'application implique la représentation tridimensionnelle de la région d'intérêt et nécessite des méthodes numériques de calcul de champs spécifiques. Dans ces travaux, des problèmes liés à la circulation de courants électriques dans le sol (ou de couplage dit conductif) seront abordés avec la méthode des éléments finis. D'autres problèmes résultants de la variation temporelle des champs électromagnétiques (ou de couplage dit inductif) seront aussi considérés et traités avec la méthode PEEC (Partial Element Equivalent Circuit) généralisée. Plus précisément, une condition limite particulière sur le potentiel électrique est proposée pour tronquer le domaine de calcul dans l'analyse par éléments finis des problèmes de couplage conductif et une formulation PEEC complète pour la modélisation de problèmes de couplage inductif est présentée. Des configurations tests de complexités croissantes sont considérées pour valider les approches précédentes. Ces travaux visent ainsi à apporter une contribution à la modélisation de cette classe de problèmes, qui tendent à devenir communs avec l'expansion des réseaux électriquesElectromagnetic coupling phenomena between overhead power transmission lines and other nearby structures are inevitable, especially in densely populated areas. The undesired effects resulting from this proximity are manifold and range from the establishment of hazardous potentials to the outbreak of alternate current corrosion phenomena. The study of this class of problems is necessary for ensuring security in the vicinities of the interaction zone and also to preserve the integrity of equipment and devices there present. However, the complete modeling of this type of application requires the three-dimensional representation of the region of interest and needs specific numerical methods for field computation. In this work, the modeling of problems arising from the flow of electrical currents in the ground (the so-called conductive coupling) will be addressed with the finite element method. Those resulting from the time variation of the electromagnetic fields (the so-called inductive coupling) will be considered as well, and they will be treated with the generalized PEEC (Partial Element Equivalent Circuit) method. More specifically, a special boundary condition on the electric potential is proposed for truncating the computational domain in the finite element analysis of conductive coupling problems, and a complete PEEC formulation for modeling inductive coupling problems is presented. Test configurations of increasing complexities are considered for validating the foregoing approaches. These works aim to provide a contribution to the modeling of this class of problems, which tend to become common with the expansion of power grids
Fenômenos de acoplamento eletromagnético entre linhas aéreas de transmissão de energia e outras estruturas vizinhas são inevitáveis, sobretudo emáreas densamente povoadas. Os efeitos indesejados decorrentes desta proximidadesão variados, indo desde o estabelecimento de potenciais perigosos até o surgimento de processos de corrosão por corrente alternada. O estudo desta classe de problemas é necessária para a garantia da segurança nas imediações da zona de interação e também para se preservar a integridade de equipamentos e dispositivos ali presentes. Entretanto, a modelagem completa deste tipo de aplicação requer a representação tridimensional da região de interesse e necessita de métodos numéricos de cálculo de campos específicos. Neste trabalho, serão abordadas as modelagens de problemas decorrentes da circulação de correntes elétricas no solo (ditos de acoplamentocondutivo) com o método dos elementos finitos. Também serão considerados problemas produzidos pela variação temporal dos campos eletromagnéticos (ditos de acoplamento indutivo), que serão tratados com o método PEEC(Partial Element Equivalent Circuit) generalizado. Mais especificamente, uma condição de contorno particular sobre o potencial elétrico é proposta para o truncamento do domínio de cálculo na análise de problemas de acoplamento condutivo com o método dos elementos finitos, e uma formulação completa tipo PEEC para a modelagem de problemas de acoplamento indutivo é apresentada. Problemas teste de complexidades crescentes são considerados para a validação das abordagens precedentes. Estes trabalhos visam fornecer desta forma uma contribuição à modelagem desta classe de problemas, que tendem a se tornar comuns com a expansão das redes elétricas
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Wan, Jie-Jyun, and 萬倢君. "Optimal Sensor Placement for Conductor Temperature Estimation of Overhead Extra-High Voltage Power Transmission Lines." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/00965799148018975076.
Full textAbstract:
碩士國立臺灣大學
生物產業機電工程學研究所
102
Dynamic thermal rating (DTR) technique is an effective and proper method to manage transmission lines in power system. Dynamic thermal rating utilizes on-line thermal sensors to monitor the operating temperature of overhead transmission lines, and calculates the ampacity margin of the transmission lines. The power transmission efficiency could be improved while under the safe condition. However, deploying a large number of thermal sensors may not be a viable option, because of high equipment costs and increasing the structural complexity of the power grid. A case study of the 345 kV extra high voltage transmission lines in central Taiwan was presented. The goal in this study is to allocate the minimum number of thermal sensors. Using the measurements where deploy the thermal sensor, the conductor temperature of whole transmission lines can be efficiently accurate estimation. This paper proposed an allocating placement method which is using the proper orthogonal decomposition (POD) for temperature feature extraction, and then using the memetic algorithm (MA) for determining the minimum number of thermal sensors and the optimal sensor placement to track the temperature of transmission lines and accurately estimate the full conductor temperatures. The results show that this method can be made only needs the one-fifth of sensors to estimate the conductor temperature of entire transmission line spans with high accuracy. The average mean square error is less than 1. This method can provide the operating power system a dependable technique for thermal capacity increment and the evaluation of overload risk.
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"A theoretical and experimental investigation into fire induced flashover of high voltage transmission lines." Thesis, 2005. http://hdl.handle.net/10413/2930.
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This thesis documents a research study of High Voltage transmission line faults induced by fire. Conductor to conductor and conductor to ground flashovers have been experienced by electricity utilities around the world under conditions of veld and sugar cane fires. These types of faults are unpredictable and negatively impact line reliability and quality of supply. This is a crucial problem when the revenue of the industry is sensitive to voltage dips. Electricity utilities have taken a preventative approach, like clearing vegetation from the line servitude in order to decrease the frequency of line faults. There has also been a drive to collaborate with sugarcane farmers in order to have harvesting fires planned with utilities. Some success has been achieved with these initiatives however there still remains a large number of faults. The focus of this study is on the mechanism of fire-induced flashover. Previou s work has displayed the existence of two theories. The first theory suggests that flashover is due to the reduction in air insulation strength caused by a reduced air density that results from the thermal effect of the fire. The second theory suggests that small particles present in the fire cause electric field distortions that induce flashover. This study is focused on a theory , which indicates that flashover is induced due to an enhanced electric field which is a result of the conductive properties of the flames present in the air gap (the flame conductivity theory). The effects of particles and a reduced air density is said to support this mechanism that is the primary reason for flashover. This thesis present s a summary of the literature where firstly an understanding of air insulation behavior is displayed. Thereafter specific interest is given to the effect of fire and flames wherein the physics of flames are discussed. This then leads to the description of the flame conductivity theory. Chapter 4 deals with a simulative investigation into the effect a conducting flame has on the electric field distribution. This is looked at with a varying flame conductivity and gap length in mind. The simulations specifically cover the 275 kV and 400 kV line configurations. The simulative investigation results in a mapping of electric field enhancement against conductivity values and gap sizes. Thus a flashover probability is assessed by using the two factor flashover criteria when analyzing the electric field stresses. The objective of the experimental work in this study is to obtain insight on how the flame geometry and orientation affects flashover and the dependence of flashover on gap size. Tests involving a fire beneath a conductor were carried out for different gap sizes . Experimentation with particles above a flame was also conducted. It was concluded that flame structure does have an impact on flashover since a flame with sharp edges is more likely to cause flashover. Particles have a reducing effect on air insulation strength. This is mainly due to the fact that the particle reduces the effective air-gap size. No significant effect over and above this is noticed . For gaps spanned by clean Liquid Petroleum Gas (LPG) flames flashover voltage increases as gap-length increases with some degree of nonlinearity. Flame resistances and conductivity were approximated from measured currents and voltages.Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2005.
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Ramli, Khairun N., Raed A. Abd-Alhameed, Hmeda I. Hraga, D. T. W. Liang, and Peter S. Excell. "Electromagnetic Field Interaction Between Overhead High Voltage Power Transmission Line and Buried Utility Pipeline." 2011. http://hdl.handle.net/10454/5468.
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yesThis work presents the development of a new approach of modelling the source excitation and the penetration of structures by continuous propagating electromagnetic (EM) plane waves. The technique incorporates the solution of time-dependent Maxwell¿s equations and the initial value problem as the structures are illuminated by the plane waves. The propagation of waves from source excitation is simulated by solving a finite-difference Maxwell's equation in the time domain. Subgridding method is used to condense the lattice at the point of interest locally for observing field distribution in high resolution. The computational burden due to huge number of time steps has been eased by employing quasi-static approach. An example of induced EM fields near an underground pipeline runs parallel to a 132 kV overhead power transmission line (OHTL) has been presented which paves the way in the development of new approach of EM fields interaction modelling.
MSCRC
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Evert, Cecil Richard. "The detection of fires under high voltage transmission lines." Thesis, 2003. http://hdl.handle.net/10413/4265.
Full textAbstract:
Fires generate heat and propel burning material into the air above and around the core of the fire.
Fires under power lines reduce the breakdown strength of the air insulation due to the influence
the heat and particles have on the electric field surrounding the conductors. The result can be
flashovers and undesirable power supply interruptions in the electrical transmission network with
a considerable impact on Eskom's 275 kV and 400 kV MTS (main transmission system)
networks. Eskom typically experiences a loss in sales, a reduction in the quality of the power
supplied to consumers and disgruntled consumers who in turn experience financial losses due to
a loss in production.
In this thesis, the high frequency characteristics of corona and electrical discharges generated by
the fire phenomena are studied. The influence of the operating voltages on the electric fields, the
potential of different media to initiate ionisation and comparison of conductor construction
(bundling and diameter) are all considered in the measurement of high frequency signals in the
range of frequencies available in the tuned circuits connected to power lines.
The propagation of these high frequency signals is studied both in isolation of other sources of
high frequency signals (within controlled laboratory conditions) and in the real environment
adjacent to all other interfering sources.
Finally the fingerprinting of the varying high frequency signal patterns associated with fires is
considered with a view to implementing an operational early detection device.
Early detection of a fire allows the utility to understand the source of a system fault, manage it
effectively and if possible pre-empt possible failure by means of appropriately applied standard
operating guidelines (SOG) to minimise the impact.Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.
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Nicolae, Dan Valentin. "Non-conventional methods for energy extraction from high voltage transmission lines." Thesis, 2004. http://hdl.handle.net/10352/143.
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Thesis (D. Tech. Electrical engineering) --Vaal University of TechnologyA comprehensive study upon "Non-conventional methods for energy extraction from the high voltage transmission lines" was addressed in this thesis. As defined in this study, a non-conventional method to extract energy is one that does not touch the conductors of the line. The theoretical framework which originated in the Maxwell's equations was presented as a base for discussion of all the methods and the conditions for the extraction to be possible. This study presents various methods such as capacitive and inductive to extract energy from high voltage alternating current transmission lines (HVAC). Although in theory, for high voltage direct current transmission lines (HVDC), the conditions for extraction are not matched, there remain some methods that could still attract interest. The centre point of this thesis is the new power application of the Rogowski coil. This method is analysed in full extent starting from theoretical modelling, computer simulations, design of the actual Rogowski coil and power electronics associated with it, and experimental results on a reduced scale model. In doing this, strong mathematical tools and computer software such as Matlab 6, Quick Field and MathCAD were used. At the end of this thesis, some conclusions are presented together with new ideas for further research in the field.
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Devadiga, Anurag A. "Lightning Shielding Failure Analysis of Ultra High Voltage Power Transmission Lines." Thesis, 2015. http://etd.iisc.ernet.in/2005/3973.
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In India, the natural energy resources (thermal and hydro) are unevenly distributed and are mostly present in the remote areas and the load centers are distributed across various regions of the country. Therefore high voltage lines have become necessary for the devel-opment of large interconnected power networks and for the reliable and economic transfer of power. The increase in electric power demand due to the electric load growth has lead to the expansion of the transmission systems to ultra high voltage levels. Presently, Ultra High Voltage (UHV) power transmission lines are being built to transfer large electric power to distant load centers from the generating stations. Increasing the line voltage increases the surge impedance loading, stability and the thermal capacity of the line.
Lightning is one of the major causes for the line outages and interruptions of UHV power lines. A lightning strike generates a very large voltage leading to insulator puncture, melting, burning and pitting of conductors and the supporting hardware. Lightning can lead to transient over-voltages thus leading to ash-over in the power transmission lines which are dangerous for the power equipments as well as for the human beings working in the vicinity. Ground wires are used for the protection of overhead power transmission lines against a lightning stroke. The overhead ground wires are installed such that the lightning attaches to it and shunts the lightning current to the ground through the tower, thus protecting the phase conductors. Shielding failure happens when the lightning strikes the phase conductor instead of the ground wires. Lightning shielding failure is a major con-cern in UHV lines due to their large height, very high operating voltage and wide exposure area of the phase conductors. The lightning over-voltages injected on the phase conductor (shielding failure) nally reaches the substation causing serious threat to the substation components and can lead to temporary or permanent outage of the power transmission system. There have been cases of very high shielding failure ash-overs of UHV lines and thus lightning attachment to power transmission lines need to be studied in detail to reduce the power system line outages.
Several models such as electro-geometric model (EGM) and leader progression model (LPM) have been developed to study the shielding failure of power transmission lines. EGM has been extensively used to obtain lightning attachment to power transmission lines but in recent years it is seen that EGM is unable to accurately predict the lightning attach-ment to UHVAC lines. The shielding failure rates obtained by EGM does not match with the observed shielding failure rate for UHV lines. For this reason LPM is considered to obtain lightning attachment to UHV lines but LPM in its initial stage do not deal with the detailed physics of the upward leader inception, i.e., corona inception and unstable as well as stable upward leader inception from the object on the ground.
In this thesis a model for the lightning attachment has been developed based on the present knowledge of the lightning physics. The thesis mainly focuses on the modelling of upward leader inception and propagation for lightning attachment to UHV power trans-mission lines. Upward leader inception is modeled based on the corona charge present near the conductor region and the upward leader propagation model is based on the correlation between the lightning induced voltage on the conductor and the voltage drop along the upward leader channel. The present model considers corona inception and modelling of unstable and stable upward leader inception from the ground object for the analysis of the lightning attachment process.
The upward leader inception model developed is compared with the previous inception models and the results obtained using the present and previous models are found to be comparable. Lightning striking distances ( nal jump) for various lightning return stroke current were computed for di erent conductor heights using present lightning attachment model. It is seen that the striking distance increases with the increase in lightning re-turn stroke current and increases with increase in conductor heights. The striking distance computed using the present model matches with the value calculated using the equation proposed by the IEEE working group for the applicable conductor heights of up to 8 m.
The in uence of the conductor operating voltage, cloud electric eld, lightning down-ward leader lateral distance, conductor length, transmission line tower and conductor sag on the upward lightning leader inception are analysed and reported in the thesis. It is found that the lightning attraction to power transmission line increases with increase in conductor positive operating voltage and decreases with increase in conductor negative op-erating voltage. The presence of transmission line tower reduces the lightning attachment to the conductor lines and the probability of lightning strike decreases with the increase in downward leader lateral distance from the conductor lines.
The present lightning attachment model is applied to study the shielding failure of UHV power transmission lines rated for 1200 kV ac (delta and horizontal con guration) and for 800 kV dc (with and without a dedicated metallic return conductor) and thereby the lightning shielding failure ash-over rate is computed for the UHV power transmission lines. It is seen that the lightning shielding rate for UHV power transmission lines depend on the lateral distance of the downward leader channel, instantaneous 50 Hz voltage on the transmission line conductor, height of the transmission line conductor, induced voltages on the conductor and the lightning return stroke current.
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Stubbs, Leigh. "Tapping power from high voltage transmission lines using insulated lightning shieldwires and series compensation." Thesis, 2010. http://hdl.handle.net/10539/7498.
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"Optimum Corona Ring Design for High Voltage Compact Transmission Lines Using Gaussian Process Model." Master's thesis, 2012. http://hdl.handle.net/2286/R.I.15104.
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abstract: Electric utilities are exploring new technologies to cope up with the in-crease in electricity demand and power transfer capabilities of transmission lines. Compact transmission lines and high phase order systems are few of the techniques which enhance the power transfer capability of transmission lines without requiring any additional right-of-way. This research work investigates the impact of compacting high voltage transmission lines and high phase order systems on the surface electric field of composite insulators, a key factor deciding service performance of insulators. The electric field analysis was done using COULOMB 9.0, a 3D software package which uses a numerical analysis technique based on Boundary Element Method (BEM). 3D models of various types of standard transmission towers used for 230 kV, 345 kV and 500 kV level were modeled with different insulators con-figurations and number of circuits. Standard tower configuration models were compacted by reducing the clearance from live parts in steps of 10%. It was found that the standard tower configuration can be compacted to 30% without violating the minimum safety clearance mandated by NESC standards. The study shows that surface electric field on insulators for few of the compact structures exceeded the maximum allowable limit even if corona rings were installed. As a part of this study, a Gaussian process model based optimization pro-gram was developed to find the optimum corona ring dimensions to limit the electric field within stipulated values. The optimization program provides the dimen-sions of corona ring, its placement from the high voltage end for a given dry arc length of insulator and system voltage. JMP, a statistical computer package and AMPL, a computer language widely used form optimization was used for optimi-zation program. The results obtained from optimization program validated the industrial standards.Dissertation/Thesis
M.S. Electrical Engineering 2012
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Wu, Hung-Shuo, and 吳鴻碩. "Optimal Sensor Placement for Extra High Voltage Transmission Lines Based on Dynamic Thermal Rating." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/242gby.
Full textAbstract:
碩士國立臺灣大學
生物產業機電工程學研究所
106
With the increasing demand for electricity, the load on the long-distance extra high voltage (EHV) power grid is getting heavier. However, the construction of a new power grid is time-consuming and costly. In recent years, dynamic thermal rating (DTR) technology is considered to be able to solve this problem. DTR is an effective tool for assisting smart grids in planning and making decisions. It uses real-time weather information to estimate the conductor temperature and ampacity of the overhead transmission lines. Through these crucial information, transmission efficiency can be improved without sacrificing safety. Because DTR relies on real-time and accurate meteorological data, deploying sensors is necessary on transmission lines. However, sensors used in EHV transmission lines are costly, and deploying sensors on each span of the transmission line may not be feasible. Therefore, this study proposes a modified binary particle swarm optimization (MBPSO) to solve this multi-objective optimization problem. The goal is to deploy a minimum number of sensors to achieve ideal sensing performance. This study adopts Quanxing ~ Nantou first line of 345 kV power grid as an example, and uses the hourly meteorological data of the Central Weather Bureau (CWB) from 2013 to 2017 to calculate conductor temperature and ampacity for optimization. The results show that the proposed method only needs to deploy 7.9 % of sensors to effectively monitor more than 96 % of high conductor temperature events occurring across the entire transmission line, and the mean square error in the reconstructed conductor temperature distribution is lesser than 0.8 °C. This method can provide the power company as a reliable technology for increasing transmission current and assessing the risk of overload when operating the power grid system.
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Naidoo, Pathmanathan. "Investigations into the upgrading of transmission lines from HVAC to HVDC." Thesis, 2007. http://hdl.handle.net/10413/2224.
Full textAbstract:
Emanating from the proceedings of CIGRE 2004, a new idea for higher power transmission by recycling and up rating high voltage alternating current transmission lines for high voltage direct current application was presented at the HYDC working group session. To date, there is no known application of the idea. Globally, transmission congestion, power transfer bottlenecks with restricted and limited power transfers and unobtainable servitudes challenge electric power utilities. The literature review shows that since the early sixties, several authors have studied this proposal. However, no applications were done. Admittedly, early HYDC technology was troubled by problems with multi-terminal designs, external insulation breakdown in the presence of DC stress and mercury valve rectifiers struggled with arc backs. To date, power electronic and external insulation technology has grown and matured for confident application both in point to point and multi-terminal application. The economic costs of introducing the DC technology are also more affordable given reducing prices due to higher volume of purchases. With promising developments in insulation and power electronic technology and driven by South Africa's surging growth in the consumption of electrical energy; the subject of upgrading HYAC transmission for HYDC application is revisited. For the research, the emphasis is beyond FACTS and towards a solution that could develop into a new supergrid that could overlay the existing national grid. Thus, the solution is prepared specifically for the case of recycling existing assets for higher power transfers. The working environment is defined by the difficulty in acquiring new powerline servitudes, transmission congestion in complex networks, the need for electrical islands within complex interconnections, and the need for enhanced power system stability and to promote new ancillary services energy management. The focus of this research study was to determine the technical feasibility of upgrading of existing HYAC circuits for HYDC application. It is assumed that the transmission line will remain as is in structure, layout and mechanical design. The changing of external line insulators using live line technology is an accepted modification to the original HYAC line, if required. From the study, we conclude that not all HYAC lines are recommended for upgrade to HYDe. We introduce boundary conditions as a first step towards checking on the suitability of the proposed upgrade from HVAC to HYDC mode. Emanating from this study, the first paper published introduced the initial boundary conditions as being only those lines where the "unused gap" between surge impedance loading and conductor current carrying capability is appreciable and large; generally three to four times surge impedance loading. In the case where the unused gap is the smallest or negligible, then we do nothing. In between, where the unused gap is about two to three times the surge impedance loading, then we can consider active or passive compensation using the HVAC FACTS technology options as proposed by EPRl. Having determined the candidate transmission line configuration for the proposed upgrade to HYDC application, we select the DC operating voltage as based on the voltage withstand capability of external insulation for varying environmental conditions. In addition, the DC voltage will generate allowable electrical fields and corona effects within and outside the transmission servitude. The optimum DC operating voltage would satisfy the conditions of minimum transmission power losses and volt drop for the case of maximum power transfers; within the limits of electrical fields and corona effects.Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.
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Ger, Wei-Jong, and 葛維忠. "Health risk assessment for environmental exposure from high-voltage transmission lines country-wide in Taiwan." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/13999379847529858762.
Full textAbstract:
碩士國立陽明大學
環境衛生研究所
91
The purpose of this study is to survey the power frequency magnetic field (MF) strength of residences from high-voltage (161/345 KV) transmission lines (HVTL). The evaluate short term (spot, 30/60 min) and 24 h MF as surrogates for 72 h MF exposure in residences. Conduct risk assessment for the extra health risks associated with the children aged 0-14 exposed to MF in Taiwan. A total of 80 residences within 70 m of the HVTL were sampled in Hsichuh. The residential magnetic fields were assessed, using EMDEX II at children’s bedroom. The sampling time was 72 h with a sampling rate of 5 min. Statistical analyses use intra-class correlation coefficient (ICC) , specificity/sensitivity and multip regression. The compare the MF of short term/24 h and 72 h show on highest agreement. Houses distance to HVTL and measurement time (weekday/weekend) were determined by residential children’s exposures to MF. Based on the assumption that the children population in Taiwan is homogeneously distributed in each township, and by using the Geographic Information System (Arc View 8.2), it is estimated that 337,174 out of 4,975,970 (or 6.8%) children aged under 15 have resided within 70 m of the HVTL. Considering 72 h measurement, percentages of exposed child population within 70 m of HVTL, the specific relative risk estimates (ranging from 0.8 to 3.4) derived from previous international epidemiological studies, and assessing causal links between power frequency magnetic field and childhood leukemia, it was estimated that 8.4 cases and 6.8 cases childhood leukemia per year could be attributable to exposure to elevated MF emitted from 345 KV and 161 KV power lines in Taiwan. This study showed the residential measurement of short term and 24 h MF can reasonable use to estimates 72 h MF exposure. The HVTL are primacy source of residential magnetic field, and the extra health risks of the children aged 0-14 were mainly. With respect to the uncertainly health risks, need more study in the future.
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Ntshangase, Zola. "A study of fire-induced air-gap voltage breakdown characteristics under HVDC conditions." Thesis, 2012. http://hdl.handle.net/10413/8300.
Full textAbstract:
This dissertation investigates the role that is played by high temperatures of air gaps on the
breakdown voltage levels under DC positive and negative polarity applied voltages. Due to
past experience of AC transmission lines tripping as a result of sugar-cane fires that occur
under these lines during cultivation seasons, this study was initiated to investigate this effect
under DC applied voltages.
Results were obtained from laboratory work conducted and these were closely analysed to
understand the behaviour of air gaps under these conditions. A 17mm2 square-cut brass rodrod
electrode configuration was used to carry out these tests at the various air gap
temperatures. These were induced by a gas burner for both the positive and negative
polarities at 200C – 3000C for the 10 mm – 150 mm air gap range and 200C – 1500C for the
200 mm – 500 mm air gap range. Later particles were introduced into the air gap to
determine the subsequent behaviour. These were introduced vertically from the top into an
air gap via a vibrating micro sieve mechanism to regulate the consistency of the introduction
of these particles in the air gap.
A reduction of 55% and 50% was observed on the breakdown voltage under positive and
negative polarity applied voltages respectively from ambient conditions to 3000C.
Additionally the breakdown behaviour of both negative and positive DC was found to be
linear which is similar to the AC case. However, air gaps subjected to positive DC applied
voltages were found to portray an inferior dielectric strength as opposed to the equivalent
negative DC polarity.
The study found that the effect of particles in the air gap is practically negligible and that for
practical purposes, only the temperature effect plays a role due to the reduced air density at
high temperatures.
Empirical models for both the positive and negative DC polarities have been proposed by the
study that incorporate the effect of the temperature in the air gap to enable the determination
or prediction of the breakdown voltage level at various temperatures. These models may be
utilised for DC transmission line design for servitudes in areas that are known to be prone to
fires.Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.