Thesis (M. Eng.)--Memorial University of Newfoundland, 1998. / Restricted until June 1999. Bibliography: leaves 95-98.

Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Unshielded distribution lines has a poor performance during lightning activity. Lightning initiates flashovers between the phases and earth and causes line breakers to trip several times during a lightning storm. In addition equipment like fuses, surge arresters and transformers are damaged by lightning and cause in some cases long power interruptions to customers. The application of line surge arresters on distribution lines is a solution that is implemented worldwide to limit the lightning related problems. This thesis investigated using line surge arresters in conjunction with bushing-mount fuses to decrease nuisance fusing and transformer damage during lightning activity. Two new pieces of equipment (dropout surge arresters and transformer bushingmount fuses) were developed and strategically placed on 4 different distribution lines. Equipment failures decreased by 90 % while financially the project had an excellent return on investment. / AFRIKAANSE OPSOMMING: Distribusie lyne sonder skermdrade presteer swak gedurende weerlig aktiwiteit. Weerlig veroorsaak oorvonking tussen fases en aard geleiers wat lei tot breker klinke. Transformators, sekerings, stuwingsafleiers en ander toerusting word ook deur weerlig beskadig en veroorsaak in sommige gevalle lang toevoer onderbrekings. Installering van lyn stuwingsafleiers op distribusielyne is 'n metode wat wêreldwyd gebruik word om oorvonking en weerligskade te beperk. Hierdie tesis ondersoek die installering van lyn stuwingsafleiers en deurvoerder gemonteerde sekerings om transformator skade en onnodige blaas van sekerings te beperk tydens weerlig aktiwiteit. Nuwe toerusting (uitval stuwingsafleiers en transformator deurvoerder gemonteerde sekerings) was ontwikkel en strategies op 4 verskillende distribusie lyne geïnstalleer. 'n Negentig persent vermindering in toerusting beskadiging is behaal terwyl die projek finansiël 'n goeie opbrengs op belegging meegebring het.

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.

Fault Detection on transmission lines forms an important part of monitoring the health of the power plant and is an indicator of when potential faults can lead to catastrophic failure of equipment. This research analyses the early detection of generator, transmission line faults and also researches methods of fault detection via the application of Artificial Neural Network techniques. The monitoring of the generator voltages and currents, of transmission line performance parameters forms an important monitoring criterion of large power systems. Failures lead to system down time, damage to equipment and it presents a high risk to the integrity of the power system, and affects the operability and reliability of the network. This dissertation therefore deals with fault detection on the Eskom transmission lines from a simulation perspective. Electrical faults have always been a constant source of conflict between transmission lines and power consumers. This dissertation presents the application faults detection on the transmission lines using Artificial Neural Networks. The ANN is used to model and to predict the occurrence of a transmission line fault, and classifies faults according to its transient characteristics. Results show that the ANN can be used to accurately identify and to classify faults, given accurate problem set-up and training. The major contribution of the dissertation is the application of ANNs to predict faults on the transmission lines / Electrical and Mining Engineering / M. Tech. (Electrical Engineering)

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016. / Power grid and system protection advancement greatly depend on technological advances. Advent technologies like digital microprocessor type protective relays facilitate paradigm shifts, providing inimitable beneficial engineering adaptations. Phasor measuring technology provides one such technological advance. The onset and rapid development of the Phasor Measuring Unit (PMU) provides an excellent platform for phasor-based, power system engineering. Power transmission constitutes a critical section in the electric power system. The power system transmission lines are susceptible to faults which require instant isolation to establish and maintain consistent system stability. This research focuses on the study of transmission line protection based on P-Class synchrophasor measurements. The IEEE C37.238-2011 Precision Time Protocol (PTP) paradigm shift facilitates practical application of synchrophasors in protection schemes. Synchrophasor procession and accurate data alignment over wide areas support the hypothesis of a phasor-based transmission line differential protection. This research aims to directly implement P-Class synchrophasors in transmission line differential protection, employing synchrophasors to determine fault conditions and administer corresponding protective actions in wide area transmission lines. The research also aims to evaluate the operational characteristics of the synchrophasor-based transmission line differential protection scheme. The research deliverables include a laboratory scale Test-bench that implements the PMU-based transmission line differential protection scheme, and a differential protection utility software solution that follows guidelines specified by the C37.118-2011 standard for synchrophasors. The findings stand to evaluate performance of the PMU-based line differential protection scheme, verifying the protection model as an alternate, practical and feasible backup protection solution. The research deliverables include a synchrophasor-based current differential algorithm, software utility for implementing the PMU-based protection scheme and a Test-bench for concept and feasibility validation.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017. / Transmission lines are a vital part of the electrical distribution system, as they provide the path to transfer power between generation and load. Factors like de-regulated market environment, economics, etc. have pushed utilities to operate transmission lines close to their operating limits. Any fault, if not detected and isolated quickly will cascade into a system wide disturbance causing widespread outages for a tightly interconnected system operating close to its limits. Current differential criterion is used with success to protect various elements in power systems, i.e. transmission lines, power transformers, generators and busbars. The alpha plane differential relaying system provides sensitive protection for transmission lines, security and dependability for external faults. This thesis focuses on three terminal alpha plane differential protection with the aim to develop a complete test method using OMICRON test universe software essentially defining security, dependability and sensitivity of the alpha plane characteristic. The research analyses the three terminal alpha plane characteristic and existing primitive test methods and develops an improved test method using IEC 61850 standard. The primitive methods are time consuming and result in unnecessary prolonged outages. These methods have been discussed and improved in the thesis by implementing IEC 61850 standard. First the standard IED Capability Description (ICD) file is modified by developing new logical nodes using AcSELerator Architect and XML Maker software. Then the developed logical nodes, three terminal differential protection alpha plane characteristic with its additional infeed/outfeed check logic, and the developed test method are tested simultaneously using Test Universe software. A laboratory test bench is built using three SEL311L relays, two CMC 356 Omicron injection devices, PC, MOXA switch, CMIRIG-B time synchronising unit, SEL 2407 satellite synchronised clock, and a DC power supplier. The test method developed in this research vindicates benefits of IEC 61850 standard over hard wired systems. Prolonged outage times due to test set preparation using hard wires are drastically reduced. The thesis findings and deliverables will be used as a solution to industrial problems, postgraduate studies of other students and research project.

Dans le cadre de l’avion plus électrique, les avionneurs cherchent à remplacer les commandes de vol hydrauliques par des commandes de vol électriques, avec pour intérêt de diminuer le poids, et d’améliorer la flexibilité des équipements aéronautiques. Sachant que sur un A380, la distance cumulée pour les câbles peut atteindre plus de 500 km, la solution consistant à faire cohabiter les transmissions de données et de puissances au sein de mêmes câbles grâce à la technologie CPL pourrait contribuer à réduire la masse de câble dans un avion. Cependant les câbles de puissance n’ont pas été dimensionnés pour transmettre un signal informationnel, et les équipements présents sur le réseau sont source de bruits. Dans ce contexte nous souhaitons montrer la faisabilité d’une transmission CPL soumise aux contraintes avioniques tout en respectant les normes aéronautiques. La première partie des travaux a consisté à mesurer le canal de propagation sur un banc de test représentatif d’un environnement aéronautique. Le canal de propagation est composé de deux coupleurs de type inductif ou capacitif dont le but est de connecter les câbles de télécommunication au réseau de puissance et d’une paire bifilaire torsadée de puissance d’une longueur de 32 m représentative d’un réseau HVDC ±270 V. Nous avons alors testé trois architectures différentes : l’architecture point-À-Point avec coupleur capacitif, l’architecture point-À-Point avec coupleur inductif et l’architecture point-À-Multipoints avec coupleur inductif. Le but de ces mesures a été d’évaluer la fonction de transfert du canal sur la bande [1 ; 100] MHz. Nous avons alors calculé les éléments caractéristiques du canal comme la bande de cohérence et l’étalement des retards. Après la caractérisation du canal de propagation, nous avons choisi et dimensionné les algorithmes de traitement du signal au regard des spécifications aéronautiques à savoir : un débit utile de 10 Mbit/s, un temps de latence de 167-334 μs, un TEB de 10-12 et le respect du gabarit de la DO-160 en émission conduite. Au regard de la fonction de transfert du canal, nous avons choisi d’utiliser l’OFDM comme technique de transmission. Ainsi, à l’aide de la caractérisation du canal de propagation nous avons au cours d’une étude paramétrique défini les paramètres de la transmission OFDM au regard des spécifications de débit et de temps réel. Dans un second temps, nous avons implanté les paramètres OFDM ainsi que la modélisation du canal de propagation dans une chaine de transmission Matlab. Cette chaine nous a alors permis de vérifier les paramètres issues de l’étude paramétrique ainsi que de définir le système de codage de canal (Reed-Solomon et code convolutif) pour respecter les spécifications aéronautiques. La dernière partie de cette thèse a consisté en l’étude du système de synchronisation. Du fait de la stabilité du canal de propagation, nous avons considéré une synchronisation fine du système lors d’une phase d’initialisation puis nous nous somme focalisé sur le dimensionnement d’un système de suivi dans le but de corriger le décalage de fenêtre FFT dû au défaut de fréquence d’échantillonnage. Pour limiter les pertes de débit lors de la phase de suivi, nous avons proposé une estimation de l’erreur de fréquence d’échantillonnage sur la phase des données reçues sur une période de 20 symboles OFDM. / In the new aircrafts, hydraulic flight control systems are replaced by electric flight control systems. The main interests are a better flexibility of the aeronautical equipments and a decrease in maintenance costs and construction costs, but the major problem is the increasing of the wires length. In order to decrease this length, it has been proposed to use power line communications (PLC) technology for flight control systems. The decrease of wire will first decrease aircraft weight and therefore the consumption of kerosene and on the other hand will simplify maintenance and construction. The first part of this work is the measurement and the characterisation of the propagation channel on an aeronautic test bench (with HVDC supply and loads). This channel is composed of two couplers (inductive or capacitive) in order to connect the telecommunication system on the power wires with galvanic isolation and one twisted pair of 32 m longs. We have tested three architectures: the point-To-Point architecture with capacitive coupler, the point-To-Point architecture with inductive coupler and the point-To-Multipoint architecture with inductive coupler. The purpose of these measurements is to measured the transfer function on the [1 ; 100] MHz bandwidth. Then, we have computed the channel parameters like the coherence bandwidth and the delay spread. The second step was the design of the signal processing algorithm in order to satisfy the aeronautical specifications: a useful bite rate of 10 Mbit/s, a latency of 167- 334 μs, a BER of 10-12 and the respect of the DO-160 gauge in conducted emissions. For the transmissions, we have chosen the OFDM technology which has been use with success in other PLC systems. With the channel characterization, we have proposed a parametric study in order to define the OFDM parameters to satisfy the bite rate and the real time constraints. After, we compute digital simulations with Matlab to check the OFDM parameters. With these simulations, we have also defined the channel coding parameters (Reed-Solomon and convolutional coding) to satisfy the aeronautical specifications. The last part of this study was the design of the synchronisation system. Because of the channel stability, we considered a precise synchronisation after an initialisation period. Then, we focus on the estimation of the FFT shift, due to the sampling frequency shift, during a following-Up period. In order to avoid the decrease of the latency and the bitrate due to the pilot symbols or pilot sub-Carriers insertion, we proposed to correct the FFT shift with the receive data thanks to the maximal likelihood algorithm.

M.Sc. / The need for a fire-induced flashover (power line arcing to the ground) probability index for Eskom transmission (high voltage power) lines became evident soon after the installation the Advanced Fire Information System (AFIS) in 2004. AFIS is a satellite based fire detection system that utilizes polar and geostationary satellite sensors to detect fires as small as 50 m x 50 m in size. As soon as a fire is detected by either, the Terra, and Aqua Moderate Resolution Imaging Spectro-radiometer (MODIS) or Meteosat Second Generation (MSG) geostationary satellites close to any of the 28 000 km of Eskom transmission lines, a cell phone and email text warning is sent out to line managers responsible for the management of the particular section of line affected. Between 3000 - 6000 fires are recorded annually close to Eskom transmission lines with a fire-induced flashover rate of 100 - 150 transmission line trips per year. Fire-induced flashovers occur when the air around high voltage transmission lines are ionised due to a hot flame (> 500° C). As the air becomes conductive, electricity can move from the line to the ground in the form of a lightning flash. Studies have shown that one flashover can cause an average of three voltage depressions (dips) on the electrical transmission system, and each voltage depression can cause damage to a customer’s production ranging between R5000 and R150000 per dip. The aim of this study was to develop a prediction model with the ability to accurately predict fire-induced flashover occurrences on Eskom transmission lines in order to reduce the large amount of false alarms (SMS and email messages) produced annually by AFIS. The prediction model in the form of a probability index was derived from a combination of remote sensing satellite products as well as weather forecast variables. With the MODIS active fire product as base layer, weather forecast variables in the form of air temperature, relative humidity, wind speed and wind direction, as well as topographical elevation and a satellite derived vegetation condition product served as input to the predictor data set of the model, while flashover statistics for 2007 provided the target data set within a Classification and Regression Tree (CART) analysis. iii The prediction capabilities for each of the variables were evaluated based on their prediction accuracy and Receiver Operation Characteristic (ROC) value in terms of the validation data set. Wind speed, relative humidity, wind direction and air temperature were shown to have the highest predictor importance and were used to develop the probability index calculated from a logistic regression analysis. The Fire-induced Flashover Probability Index (FIFPI) was tested through simulations of predictor variables and was also compared to existing Fire Danger Indices (Willis et al. 2001). The FIFPI was able to outperform most of the standard Fire Danger Indices (FDI’s) with only the McArthur Grassland Index (MK 4) which demonstrated some prediction capability. The importance of wind direction as an environmental component in the prediction of flashovers became clear as it tended to decrease the misclassification rate from 4.45% when only wind speed, relative humidity and temperature were used to 3.87% when wind direction was added. The research has shown that wind speed, wind direction, relative humidity and temperature can be used as an indicator of possible fire-induced flashovers underneath Eskom transmission lines. However, additional research is needed to verify the results from 2007. Ideally at least 3 years of data should be used.

With the attempt to achieve the optimum in analysis and design, the technological global knowledge base grows more and more. Engineers all over the world continuously modify and innovate existing analysis methods and design procedures to perform the same task more efficiently and with better results. In the field of complex structural analysis many researchers pursue this challenging task. The complexity of a lattice type structure is caused by numerous parameters: the nonlinear member performance of the material, the statistical variation of member load capacities, the highly indeterminate structural composition, etc. In order to achieve a simulation approach which represents the real world problem more accurately, it is necessary to develop technologies which include these parameters in the analysis. One of the new technologies is the first order nonlinear analysis of lattice type structures including the after failure response of individual members. Such an analysis is able to predict the failure behavior of a structural system under ultimate loads more accurately than the traditionally used linear elastic analysis or a classical first order nonlinear analysis. It is an analysis procedure which can more accurately evaluate the limit-state of a structural system. The Probability Based Analysis (PBA) is a new technology. It provides the user with a tool to analyze structural systems based on statistical variations in member capacities. Current analysis techniques have shown that structural failure is sensitive to member capacity. The combination of probability based analysis and the limit-state analysis will give the engineer the capability to establish a failure load distribution based on the limit-state capacity of the structure. This failure load distribution which gives statistical properties such as mean and variance improves the engineering judgment. The mean shows the expected value or the mathematical expectation of the failure load. The variance is a tool to measure the variability of the failure load distribution. Based on a certain load case, a small variance will indicate that a few members cause the tower failure over and over again; the design is unbalanced. A large variance will indicate that many different members caused the tower failure. The failure load distribution helps in comparing and evaluating actual test results versus analytical results by locating an actual test among the possible failure loads of a tower series. Additionally, the failure load distribution allows the engineer to calculate exclusion limits which are a measure of the probability of success, or conversely the probability of failure for a given load condition. The exclusion limit allows engineers to redefine their judgement on safety and usability of transmission towers. Existing transmission towers can be reanalyzed using this PBA and upgraded based on a given exclusion limit for a chosen tower capacity increase according to the elastic analysis from which the tower was designed. New transmission towers can be analyzed based on the actual yield strength data and their nonlinear member performances. Based on this innovative analysis the engineer is able to improve tower design by using a tool which represents the real world behavior of steel transmission towers more accurately. Consequently it will improve structural safety and reduce cost.

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.