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The propagation characteristics of lightning surges in compressed SF₆ gas insulated power substation was studied using an electromagnetic transients program. Numerical models were developed to represent the behaviour of different system components especially under lightning over-voltage conditions. The characteristics of lightning surge propagation in overhead multi-phase untransposed transmission lines was analysed first. Modal analysis, together with special rotation techniques to fit time domain solutions were then used to simulate the wave propagation in multi-phase untransposed line in an electromagnetic transients program. Non-linear voltage-dependent corona attenuation and distortion phenomena were also investigated. Available field test results could be duplicated to within 5%. The characteristics of lightning surge propagation in multi-phase single-core SF₆ cables was studied next. A program was developed to obtain the cable parameters for typical cable configurations. The amount of core current returning through its own sheath and through the earth were computed to illustrate the single phase cable representation for wave propagation in single core SF₆ cables. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Poetry collection on domestic anhedonia, the Semele myth, lightning strikes, lobotomies, mothers and wives, women from the woods, etc. / 2031-01-01T00:00:00Z

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Lightning is one of the main factors that cause Photovoltaic (PV) systems to fail. The PV modules inside PV systems, like any other electric equipment, will be degraded under electrical stress. The effect of electrical degradation of the PV modules caused by lightning induced voltage has been rarely reported. In the dissertation, the electrical properties degradation of a polycrystalline silicon module was studied. Firstly, lightning impulse voltages of positive polarity ranging from low to high are applied on different groups of the testing modules. All these lightning impulse voltage tests are conducted in the same experimental condition except for their stress voltage magnitudes. The maximum power output, I-V characteristics, and dark forward I-V curve are measured and reported periodically during the lightning impulse voltage tests. By comparing the maximum output power and changes in the internal electrical properties, it could be concluded that lightning impulse voltages, even medium voltage levels, will cause degradation to the sample. The relationship of the maximum output power and the number of applied impulses for different testing voltage levels are compared. An analysis of the electrical property changes caused by the lightning impulse voltages is presented. Secondly, a group of samples are tested with lightning impulse voltage of negative polarity. A comparison of the impulse voltage aging effects at the same voltage level with positive polarity is made. The maximum power output drop caused by positive and negative lightning impulses are compared. Laboratory results revealed that positive and negative lightning impulses will not only influence the degree of degradation, but also lead to different electrical property changes. Finally, a comparison of the effect of lightning impulses combined with other stress factors are discussed. The study simulates a field-aged sample’s behavior at lightning impulse voltage testing conditions. The result suggests that the degradation caused by lightning impulse voltage is greatly accelerated when the sample has bubbles and delamination. Electrical breakdown of the module is caused by the failure of the insulation.

The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept is characterized by through-thickness VectranTM stitching of warp-knit carbonabric prior to resin infusion. A series of novel lightning strike tests were performed on a PRSEUS panel. The panel’s lightning damage resistance was characterized as a function of peak current (50-200 kA) and strike location (mid-bay, stringer, frame). Both visual inspections and through-transmission-ultrasonic C-scans were used to investigate the damage resistance at the strike locations and to assess various damage mechanisms and morphologies. The size and severity of the damaged area depend strongly on the fiber orientation in the outermost ply, the amount of current injected into the panel, and the strike location relative to stitching lines. Increasing the current magnitude drastically increases the damaged area. Also, the presence of VectranTM structural stitches profoundly reduced the size and severity of lighting damage relative to similar strikes performed in panel regions without stitching.

Lightning damage resistance of unstitched carbon/epoxy laminates and a Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) panel were characterized by laboratory-scale lightning strike tests and multiphysics-based lightning strike finite element (FE) models. This dissertation combines three related research topics: (1) a three-dimensional (3D) heat transfer problem, (2) lightning damage resistance assessments of carbon/epoxy laminates, and (3) lightning damage resistance of PRSEUS panel. The first project deals with a 3D analytical heat transfer problem as a solid foundation for understanding the steady-state temperature distribution in an anisotropic composite heat spreader. The second project characterizes lightning damage to unprotected carbon/epoxy laminates and laminates with either copper mesh (CM) or pitch carbon fiber paper (PCFP) protection layers subjected to standard impulse current waveforms, consistent with actual lightning waveforms, with 50, 125, and 200 kA nominal peak currents. Multiphysics-based FE models were developed to predict matrix thermal decomposition (a primary form of lightning damage) in unprotected, CM-protected, and PCFP-protected carbon/epoxy laminates. The predicted matrix decomposition domains in the damaged laminates showed good agreement with experimental results available in the literature. Both the CM and the PCFP lightning protection layers successfully mitigated lightning damage development in the underlying composites. The third project includes lightning damage characterization of a PRSEUS panel. Laboratory-scale lightning strike tests with nominal 50, 125, and 200 kA peak currents were performed at the mid-bay, stringer, frame, and frame/stringer intersection locations of the PRSEUS panel. The elliptical regions of intense local damage were elongated along the outermost lamina’s carbon fiber direction, consistent with observations from the unstitched carbon/epoxy laminates. However, the damaged PRSEUS panel exhibited unique damage features due to use of warp-knitted fabrics and through-thickness VectranTM stitches. The polyester threads used to weave the warp-knitted laminates locally confined small-scale fiber damage. This resulted in somewhat periodic and scattered small tufts of carbon fibers near the lightning attachments. Through-thickness VectranTM stitches also confined intense local damage development at the stringer and frame locations. The polyester warp-knit fabric skins and through-thickness VectranTMstitches have a significant beneficial effect on lightning damage development on a PRSEUS panel.

This work contributes toward research in the field of lightning performance of High Voltage Direct Current (HVDC) transmission lines, focusing on the impact of the line polarity on the incidence of line faults. Although there has been some recent research into the influence of polarity, there appears to be no confirmed effect that might influence the design of new lines. The research presents an investigation into the lightning performance of the two poles of the Cahora-Bassa HVDC transmission line. In order to compare the performance of the two polarities, the average lightning exposure over an 8-year period was confirmed to be very similar for both lines. Lightning stroke data from the South African Lightning Detection Network was correlated with fault times from the transmission-line protection scheme. The classification of the lightning related faults was used to determine the relative performance of the two poles, particularly in relation to polarity, and to infer if there was any influence of polarity on the lightning attachment process. This investigation for the Cahora-Bassa scheme shows that twenty-three out of twenty-five lightning related faults occurred on the positive pole. The results concur with performance experience on several HVDC lines from China and Canada, which indicate that lightning related faults favour the positive pole by a ratio of between 8:1 and 10:1. This represents a valuable contribution, which substantiates that HVDC line polarity has an influence on the lightning attachment process, and indicates that there is a need to re-examine the lightning shielding design for HVDC transmission lines. / GS2016

Este trabalho apresenta alguns aspectos específicos sobre o tema “proteção de estruturas contra descargas atmosféricas”, principalmente no que se refere ao uso de partes estruturais das edificações como integrantes do sistema de proteção. São discutidos neste trabalho diversos pontos polêmicos referentes ao tema, tais como: captores especiais, o sistema dissipativo e o uso das ferragens das colunas de concreto armado como parte dos subsistemas de descida e de aterramento. São abordados, também, os principais danos que podem ocorrer nas edificações devido às descargas atmosféricas, principalmente quando a proteção utilizar partes naturais da estrutura, tais como: os telhados metálicos e as emendas das ferragens das colunas de concreto armado. Após uma verificação do estado da arte no assunto, onde são estudados diversos trabalhos, normas e livros sobre as características das descargas, sobre os danos oriundos das descargas, blindagens, medições de campos eletromagnéticos, distribuição de correntes e sobre a normalização e ensaios referentes à proteção de estruturas contra descargas atmosféricas, o assunto foi estudado em três partes que compõem os subsistemas do SPDA. No subsistema de captação, os danos em telhas metálicas e de concreto protendido foram estudados através de ensaios e verificações teóricas e, principalmente, experimentais. No subsistema de descida, o estudo experimental deu enfoque às emendas das ferragens e ao uso destas como descidas naturais. Finalmente, no subsistema de aterramento, as fundações das edificações foram estudadas através de verificações experimentais como parte do aterramento. Este trabalho acrescenta ao conhecimento atual sobre o assunto, diversas particularidades não contempladas nas normas e nas publicações mais recentes no que tange à proteção de estruturas contra as descargas atmosféricas utilizando partes naturais das edificações. / This work presents some specific aspects on the subject “lightning protection of structures“, mainly when the use of structural parts of the buildings as part of the protection systems is concerned. Several polemical issues are discussed, such as: special air-termination, the dissipation array system and the use of steel-reinforcing rods of the reinforced concrete columns as part of the down-conductor system and of the earth-termination system. Also treated is the main damage that can occur to the buildings due to lightning, mainly when the protection system uses the natural components of the structures, such as: the metallic rooftops and the joints of the steel-reinforcing rods of the reinforced concrete columns. After examining the state-of-the-art in the subject, which analyses several papers, standards and books about lightning characteristics, damage resulting from lightning, shieldings, measurements of electromagnetic fields, distribution of currents and about standardisation and tests related to the protection of structures against lightning, the subject was studied in the three parts that compose the lightning protection systems. In the air-termination system, the damage to metallic rooftops and to pre-stressed concrete rooftop tiles was studied by means of tests and theoretical and mainly experimental analyses. In the down-conductor system, the experimental study focused on the joints of the steel-reinforcing rods and on the use of these as natural down-conductors. Finally, in the earth-termination system, the foundations of the buildings were studied (as part of the grounding) through experimental analyses. This work adds to the current knowledge about the subject several particularities which are not observed in the standards or in the most recent publications concerning the lightning protection systems in buildings that use their natural components for this purpose.

Este trabalho apresenta alguns aspectos específicos sobre o tema “proteção de estruturas contra descargas atmosféricas", principalmente no que se refere ao uso de partes estruturais das edificações como integrantes do sistema de proteção. São discutidos neste trabalho diversos pontos polêmicos referentes ao tema, tais como: captores especiais, o sistema dissipativo e o uso das ferragens das colunas de concreto armado como parte dos subsistemas de descida e de aterramento. São abordados, também, os principais danos que podem ocorrer nas edificações devido às descargas atmosféricas, principalmente quando a proteção utilizar partes naturais da estrutura, tais como: os telhados metálicos e as emendas das ferragens das colunas de concreto armado. Após uma verificação do estado da arte no assunto, onde são estudados diversos trabalhos, normas e livros sobre as características das descargas, sobre os danos oriundos das descargas, blindagens, medições de campos eletromagnéticos, distribuição de correntes e sobre a normalização e ensaios referentes à proteção de estruturas contra descargas atmosféricas, o assunto foi estudado em três partes que compõem os subsistemas do SPDA. No subsistema de captação, os danos em telhas metálicas e de concreto protendido foram estudados através de ensaios e verificações teóricas e, principalmente, experimentais. No subsistema de descida, o estudo experimental deu enfoque às emendas das ferragens e ao uso destas como descidas naturais. Finalmente, no subsistema de aterramento, as fundações das edificações foram estudadas através de verificações experimentais como parte do aterramento. Este trabalho acrescenta ao conhecimento atual sobre o assunto, diversas particularidades não contempladas nas normas e nas publicações mais recentes no que tange à proteção de estruturas contra as descargas atmosféricas utilizando partes naturais das edificações. / This work presents some specific aspects on the subject “lightning protection of structures“, mainly when the use of structural parts of the buildings as part of the protection systems is concerned. Several polemical issues are discussed, such as: special air-termination, the dissipation array system and the use of steel-reinforcing rods of the reinforced concrete columns as part of the down-conductor system and of the earth-termination system. Also treated is the main damage that can occur to the buildings due to lightning, mainly when the protection system uses the natural components of the structures, such as: the metallic rooftops and the joints of the steel-reinforcing rods of the reinforced concrete columns. After examining the state-of-the-art in the subject, which analyses several papers, standards and books about lightning characteristics, damage resulting from lightning, shieldings, measurements of electromagnetic fields, distribution of currents and about standardisation and tests related to the protection of structures against lightning, the subject was studied in the three parts that compose the lightning protection systems. In the air-termination system, the damage to metallic rooftops and to pre-stressed concrete rooftop tiles was studied by means of tests and theoretical and mainly experimental analyses. In the down-conductor system, the experimental study focused on the joints of the steel-reinforcing rods and on the use of these as natural down-conductors. Finally, in the earth-termination system, the foundations of the buildings were studied (as part of the grounding) through experimental analyses. This work adds to the current knowledge about the subject several particularities which are not observed in the standards or in the most recent publications concerning the lightning protection systems in buildings that use their natural components for this purpose.