Dissertations / Theses on the topic 'Transient overvoltage'
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1
Laznevoy, A., Ірина Анатоліївна Башлак, Ирина Анатольевна Башлак, and Iryna Anatoliivna Bashlak. "Transient overvoltage and its effect on a substation." Thesis, Sumy State University, 2019. https://essuir.sumdu.edu.ua/handle/123456789/77004.
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We seem to have problems with power industry nowadays. It often faces
unforeseen overvoltages in the system. But what does overvoltage mean?
Overvoltage is associated with the electric field strength, namely with its
increase. Overvoltage happens when the electric field strength reaches a value that is
dangerous for the insulation state. What consequences might overvoltage cause?
Factories are losing tens of millions per year due to power interruptions.
Moreover, the cost of replacing equipments damaged because of voltage spikes is very
high. Power industry experiences huge losses of production. The effect of transient
overvoltage on substation equipment and the conforming protection against it are likely
to be the most important elements of this problem.
2
Galliano, Francois. "Propagation and mitigation of Very Fast Transient Overvoltage in Gas Insulated Substation." Thesis, KTH, Elektroteknisk teori och konstruktion, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160516.
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Very Fast Transients are surge overvoltages created for example when opening or closing a disconnector switch (DS). Because of the very high frequency stress they exert on the equipment and their magnitude (up to 3 pu), they constitute an important issue in the design of ultra-high voltage Gas Insulated Substations. This thesis offers a general understanding of Very Fast Transient Overvoltages (VFTO or VFT) and explores different mitigation techniques, mainly based on dissipation of the energy associated with it. Two solutions are mainly discussed for attenuating the VFTO: applying a semi resistive and magnetic coating or using magnetic rings. Both rely on the non-linearity of skin effect and magnetic losses and are treated in similar manners. An electromagnetic model of both systems is proposed as well as a way to model the influence of the device on the transient behaviour of the system. The performances of both systems still have to be determined by experimentation but they both should significantly reduce the impact of the VFTO.Mycket snabba transienter (eng. Very Fast Transients) är överspänningar som skapas till exempel när en frånskiljare öppnas eller stängs (DS). På grund av de mycket högfrekventa påkänningar som de utövar på utrustningen och deras storlek (upp till 3 pu), utgör de en viktig fråga i utformningen av ultrahögspännings gasisolerade ställverk. Denna avhandling ger en allmän förståelse för mycket snabba transienta överspänningar (VFTO eller VFT) och undersöker olika metoder för dämpning, främst baserade på förlust av energi. . Främst diskuteras två lösningar för dämpning av VFTO: applicering av en semi resistiv och magnetisk beläggning kring ledaren eller använda magnetiska ringar. Båda är beroende av icke-linjäritet av strömförträngningseffekt och magnetiska förluster, båda metodernabehandlas på liknande sätt. En elektromagnetisk modell av båda systemen föreslås liksom ett sätt att modellera inverkan av anordningen på transienta systemets beteende. Utförandet av båda systemen måste verifieras genom experiment, men de båda bör avsevärt minska effekterna av VFTO.
3
Khan, Md Nazmus Shakib. "Transient Voltage Distribution in Bushing." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-292753.
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An electrical bushing is one of the most important elements in a power transformer. Steep front surges such as transient impulse voltage from lightning strikes is an inevitable electromagnetic transient mostly happening in power transmission and distribution system. The bushing might lead to be degraded due to such kind of surge. This project deals with overvoltage stress distribution on the transformer bushing under the effect of electromagnetic transient response such as lightning impulse. To understand the behavior of transient response on the bushing, a proper model of power transformer bushing is built-in Comsol multiphysics to authenticate the stress distribution. The electromagnetic wave of impulse propagates onto the overhead line that connects with the transformer. Some understanding of the transient behavior of a conductor bushing has been achieved through studying the influence of inductance property and the skin effect characteristics of a multi-layer coaxial cable on the wave propagation, which has been structured in this project to simplify the model. On the other hand, the skin effect analysis on the conductor of the bushing has been taken also into account in this project using real conductor simulation in the Comsol model. Thus, it will be interesting to compare the real conductor model with the perfect conductor of the bushing through analyzing the current density effect on it. In this project, multi-layer of coaxial cable and transformer bushing are simulated. The simulation is carried out for time domain and frequency domain in Comsol based on the model characteristics.En elektrisk genomföring är ett av de viktigaste elementen i en transformator. Spänningsvågor med branta fronter som impulsspänningar från blixtnedslag är ett oundvikligt elektromagnetiskt övergående fenomen som oftast sker i kraftöverförings- och distributionssystem. Genomföringen kan leda till att degraderas på grund av en sådan våg. Detta projekt handlar om fördelning av överspännings på transformatorgenomföringen under påverkan av elektromagnetisk transient respons, såsom blixtimpuls. För att förstå beteendet hos övergående respons på genomföringen är en korrekt modell av transformatorgenomföring inbyggd Comsol-flerfysik för att autentisera spänningsfördelningen. Den elektromagnetiska impulsvågen fortplantas från luftledningen som ansluter till transformatorn. Viss förståelse för det övergående beteendet hos en ledargenomföring har uppnåtts genom att studera påverkan av induktansegenskaper och hudeffektegenskaperna hos en flerskikts koaxialkabel på vågutbredningen, vilket har strukturerats i detta projekt för att förenkla modellen. Å andra sidan har hudeffektanalysen på genomföringens ledare beaktats i detta projekt med användning av verklig ledarsimulering i Comsol-modellen. Således blir det intressant att jämföra den riktiga ledarmodellen med den perfekta ledaren för genomföringen genom att analysera strömtäthetseffekten på den. I detta projekt simuleras flerskikt av koaxialkabel och transformatorgenomföring. Simuleringen utförs för tidsdomän och frekvensdomän i Comsol baserat på modellegenskaperna.
4
Bátora, Branislav. "Analýza ferorezonančního přepětí v elektrických sítích." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-233633.
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This thesis deals with the ferroresonance phenomenon and ferroresonance overvoltage in electric networks. That’s why the introduction part explains the theoretical basis of ferroresonance and its consequences in the power system. The work then focuses on the power system as a non-linear dynamic system and describes various analytical methods for solving these systems. These methods are further applied to diagnose specific systems. There are a number of various power system configurations susceptible to ferroresonance. The most frequent one is theoretically analyzed in this thesis and a number of recommendations are offered for reducing the ferroresonance phenomenon. The thesis further deals with the selection of suitable software for this computationally chal-lenging task. A number of different tools are considered and efficiently reduced to Matlab Sim-ulink and PSCAD software. Matlab Simulink and its SimPowerSystem Toolbox are used to ana-lyze the effect of hysteresis of the magnetic core of the transformer on the emergence and course of the ferroresonance phenomenon. Using PSCAD, various configurations of the power systems are compared in terms of possible emergence and course of ferroresonance and also to find the limiting conditions that increase the probability of this phenomenon. The possibility of using arti-ficial neural networks for ferroresonance diagnosis is also mentioned in this thesis. The final part provides a number of recommendations for design and operation of both new and existing power systems.
5
Ezzeddine, Kassem, and Robert Oskarsson. "Analys av kondensatorbatteriers tillkopplingsfenomen : Undersökning av de kopplingsfenomen som uppstår vid tillkoppling av kondensatorbatterier och deras påverkan på närliggande komponenter." Thesis, KTH, Data- och elektroteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-208948.
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Många elektriska apparater är i behov av reaktiv effekt för att kunna fungera. Transport av reaktiv effekt tar onödig plats av den tillgängliga kapaciteten i elnätet, därför används kondensatorbatterier nära slutanvändaren för att generera reaktiv effekt. Därmed genereras och förbrukas den reaktiva effekten i en avskild del av nätet. Tillkoppling av kondensatorbatterier ger upphov till transienter som kan skada andra närliggande komponenter. Utifrån det verkliga ställverket Stallbacka i Trollhättan har denna rapport analyserat de transienter som uppstår efter tillkoppling av ett kondensatorbatteri inom mellanspänningsområdet. Analysen har innefattat hur stora transienterna blir efter olika förutsättningar och scenarier. Resultatet visade att transienterna i detta fall aldrig nådde upp till några allvarliga nivåer, och därmed klarade komponenterna sig med god marginal. Huruvida transienterna påverkar elkvaliteten är oklart, då det inte finns några definierade krav. Slutligen skulle ett beräkningsverktyg för förutspådda transienter tas fram. Beräkningsverktyget blev aldrig fullständigt på grund av den ohanterliga lösningen som erhölls.Many electrical devices need reactive power to operate. Transmission of reactive power occupies a proportion of the available capacity in the power system and therefore capacitor banks are used near to the end user to generate reactive power. Thus, the reactive effect is generated and consumed in a separate part of the power system. Capacitor banks switching causes transients which may damage the surrounding components. Based on the real substation Stallbacka in Trollhättan, this study has analysed capacitor banks switching transients within the medium voltage level. The analysis has covered the size of these transients according to different conditions and scenarios. The result showed that the transients in this case never reached serious levels, thus there was no impact on the components. It is not clear whether the transients affect the power quality because there are no defined limits. A calculation tool to the predicted transients was supposed to be created in the process. This calculation tool was never completed due to the unmanageable solution that was obtained.
6
Haddad, Abderrahmane. "Attenuation and limitation of transient overvoltages on transmission systems." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427994.
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Qureshi, Suhail Aftab. "Calculation of fast transients in gas insulated substations." Thesis, University of Manchester, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363514.
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Gregory, Raquel Cristina Filiagi. "Análise computacional do desempenho de estratégia para o religamento controlado de linhas de transmissão." Universidade Federal de Uberlândia, 2016. https://repositorio.ufu.br/handle/123456789/17617.
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Conselho Nacional de Desenvolvimento Científico e TecnológicoA busca por soluções mitigatórias, no que tange aos efeitos das sobretensões transitórias atreladas às manobras de energizações e religamentos das linhas de transmissão, contemplam um tema desafiador e com fortes impactos sobre a coordenação de isolamento dos sistemas elétricos. Muito embora o reconhecimento de propostas clássicas e comerciais para a atenuação destes fenômenos, outras possibilidades, certamente, ainda são meritórias de destaque e investigações. Neste contexto, a presente dissertação encontra-se alicerçada na exposição dos fundamentos físicos e matemáticos de uma estratégia baseada em chaveamentos controlados, cujos instantes para o religamento da linha são pré-programados. A avaliação computacional da eficácia da metodologia é realizada utilizando o simulador ATP, no qual são efetuados estudos em um sistema elétrico típico submetido à curtos-circuitos sucedidos por desligamentos e subsequentes religamentos, sob a ação da tecnologia aqui focada e na ausência da mesma.
The search for mitigation solutions, with respect to the effects of overvoltages linked to the energization and reclosing maneuvers of transmission lines include a challenging subject with strong impact on the insulation coordination of electrical systems. Although the recognition of classical and commercial proposals to mitigate these phenomena, other possibilities are certainly still worthwhile highlighting and investigations. In this context, the present work is grounded in the exposure of the physical and mathematical foundations of a strategy based on controlled switchings, whose moments to the line reclosing are pre-programmed. The computational evaluation of the effectiveness of the methodology is made using the ATP simulator, which are studies in a typical electrical system subjected to the action of short-circuits fallowed by shutdowns and subsequent reclosing, under the action of technology here focused and lack thereof.
Dissertação (Mestrado)
9
Kunakorn, Anantawat. "A study of transient overvoltages from power electronic converters and their distribution in random-wound electrical machines." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/565.
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Gercek, Cem Ozgur. "Optimizing Transient And Filtering Performance Of A C-type 2nd Harmonic Power Filter By The Use Of Solid-state Switches." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608836/index.pdf.
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In this research work, the performance of a C-type, 2nd harmonic power filter is
optimized by the use of a thyristor switched damping resistor. In the design of
conventional C-type, 2nd harmonic filtersthe resistance of permanently connected damping resistor is to be optimized for minimization of voltage stresses on filter elements arising from switchings in transient state and for maximization of filtering effectiveness in the steady-state. Transformer inrush current during energization of power transformers and connection of filter bank to the supply are the major causes of voltage stresses arising on filter elements in transient state. These can be minimized by designing a highly damped C-type filter (low damping resistor) at the expense of inadequate filtering performance and high losses in the steady-state. On the other hand, higher damping resistance (high quality factor) is to be chosen in the design of C-type filter for satisfactory filtering of 2nd harmonic current component at the expense of higher voltage rating for capacitor bank and hence a more costly filter bank design. This drawback of conventional C-type 2nd harmonic filter circuit can be eliminated by subdividing damping resistor into two parallel parts
one is permanently connected while the other is connected to and disconnected from the circuit by back-to-back connected thyristor assemblies. The use of light triggered thyristors provides isolation between power stage and control circuit, and hence allows outdoor installation.
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Mestas, Valero Patricia. "Controle adaptativo para religamento tripolar aplicado a linhas de transmissão com compensação reativa em derivação." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260992.
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Orientador: Maria Cristina Dias TavaresTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: O presente trabalho descreve um novo método de controle adaptativo para chaveamento sincronizado de disjuntores durante a manobra de religamento tripolar de linhas de transmissão com compensação reativa em derivação. O objetivo principal do método desenvolvido é controlar as sobretensões transitórias e reduzir o tempo morto antes do religamento. Diferentes estratégias para controlar sobretensões decorrentes do religamento tripolar são descritas com a finalidade de diferenciar as vantagens do chaveamento sincronizado. Os benefícios potenciais a serem obtidos a partir do religamento tripolar rápido são expostos. O método de controle adaptativo desenvolvido consiste em identificar com antecedência a região ótima para o religamento, permitindo fechar o disjuntor já no primeiro mínimo do batimento da tensão entre os contatos do disjuntor após o tempo morto de atuação da proteção. Após os testes realizados utilizando um programa para simulação de transitórios eletromagnéticos (PSCAD/EMTDC), o método proposto foi implementado em protótipo (controlador). Este protótipo foi testado utilizando o Simulador Digital em Tempo Real (RTDS). As simulações em tempo real demonstraram a eficiência do método no controle das sobretensões e na redução do tempo morto. Finalmente, o método foi avaliado parametricamente para uma série de condições simuladas, incluindo diferentes níveis de compensação reativa em derivação, a influência da compensação série, a influência da transposição da linha de transmissão e os efeitos da variação do comprimento da linha. Além disto, outras simulações foram realizadas para comparar o desempenho dos métodos de controle existentes e do método proposto
Abstract: The present thesis describes a new adaptive control method for synchronous switching of circuit breakers during three-phase reclosing of shunt compensated transmission lines. The main objective of the developed method is to control the overvoltages and to reduce the dead time prior of reclosing. Several strategies to control overvoltages resulting from three-phase reclosing are described in order to differentiate the benefits of the proposed method. The potential benefits obtained from the developed controlled reclosing method are exposed. The proposed algorithm identified, in advance, the optimal region for reclosing of transmission line, allowing closing the circuit breaker at the first minimum voltage beat across circuit breaker, after protection dead time. After off-line testing using electromagnetic transients simulation program (PSCAD/EMTDC), the proposed method was also implemented in physical hardware. This hardware was then tested on a real-time transients simulator (RTDS). The real time simulations demonstrate the method efficiency to control overvoltages and to reduce the dead time. Finally, the method has been parametrically evaluated for a range of simulated conditions, including different shunt compensation levels, influence of series compensation, influence of transmission line transposition, effect of line lengths. In addition, simulations have been conducted to compare the performance of existing control method and the proposed method
Doutorado
Energia Eletrica
Doutor em Engenharia Elétrica
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Ramli, Mohd Shamir. "Investigation of circuit breaker switching transients for shunt reactors and shunt capacitors." Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/17822/1/Mohd_Shamir_Ramli_Thesis.pdf.
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Switching of shunt reactors and capacitor banks is known to cause a very high rate of rise of transient recovery voltage across the circuit breaker contacts. With improvements in circuit breaker technology, modern SF6 puffer circuits have been designed with less interrupter per pole than previous generations of SF6 circuit breakers. This has caused modern circuit breakers to operate with higher voltage stress in the dielectric recovery region after current interruption. Catastrophic failures of modern SF6 circuit breakers have been reported during shunt reactor and capacitor bank de-energisation. In those cases, evidence of cumulative re-strikes has been found to be the main cause of interrupter failure.
Monitoring of voltage waveforms during switching would provide information about the magnitude and frequency of small re-ignitions and re-strikes. However, measuring waveforms at a moderately high frequency require plant outages to connect equipment. In recent years, there have been increasing interests in using RF measurements in condition monitoring of switchgear. The RF measurement technique used for measuring circuit breaker inter-pole switching time during capacitor bank closing is of particular interest.
In this thesis, research has been carried out to investigate switching transients produced during circuit breaker switching capacitor banks and shunt reactors using a non-intrusive measurement technique. The proposed technique measures the high frequency and low frequency voltage waveforms during switching operations without the need of an outage. The principles of this measurement technique are discussed and field measurements were carried out at shunt rector and capacitor bank installation in two 275 kV air insulated substations. Results of the measurements are presented and discussed in this thesis.
The proposed technique shows that it is relatively easy to monitor circuit breaker switching transients and useful information on switching instances can be extracted from the measured waveforms. Further research works are discussed to realise the full potential of the measuring technique.
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Ramli, Mohd Shamir. "Investigation of circuit breaker switching transients for shunt reactors and shunt capacitors." Queensland University of Technology, 2008. http://eprints.qut.edu.au/17822/.
Full textAbstract:
Switching of shunt reactors and capacitor banks is known to cause a very high rate of rise of transient recovery voltage across the circuit breaker contacts. With improvements in circuit breaker technology, modern SF6 puffer circuits have been designed with less interrupter per pole than previous generations of SF6 circuit breakers. This has caused modern circuit breakers to operate with higher voltage stress in the dielectric recovery region after current interruption. Catastrophic failures of modern SF6 circuit breakers have been reported during shunt reactor and capacitor bank de-energisation. In those cases, evidence of cumulative re-strikes has been found to be the main cause of interrupter failure.
Monitoring of voltage waveforms during switching would provide information about the magnitude and frequency of small re-ignitions and re-strikes. However, measuring waveforms at a moderately high frequency require plant outages to connect equipment. In recent years, there have been increasing interests in using RF measurements in condition monitoring of switchgear. The RF measurement technique used for measuring circuit breaker inter-pole switching time during capacitor bank closing is of particular interest.
In this thesis, research has been carried out to investigate switching transients produced during circuit breaker switching capacitor banks and shunt reactors using a non-intrusive measurement technique. The proposed technique measures the high frequency and low frequency voltage waveforms during switching operations without the need of an outage. The principles of this measurement technique are discussed and field measurements were carried out at shunt rector and capacitor bank installation in two 275 kV air insulated substations. Results of the measurements are presented and discussed in this thesis.
The proposed technique shows that it is relatively easy to monitor circuit breaker switching transients and useful information on switching instances can be extracted from the measured waveforms. Further research works are discussed to realise the full potential of the measuring technique.
14
Thomazella, Rogério [UNESP]. "Implementação computacional para avaliar os níveis de sobretensões atmosféricas induzidas em linhas de distribuição." Universidade Estadual Paulista (UNESP), 2004. http://hdl.handle.net/11449/90810.
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O presente trabalho visa o desenvolvimento de uma ferramenta computacional confiável na análise e estimação dos níveis de tensões induzidas em linhas de distribuição. Neste contexto, utilizam-se ferramentas computacionais consolidadas, como o ATP (Alternative Transients Program), que combinado a um software desenvolvido em Visual Basic, permitem quantificar e avaliar o nível de sobretensões nas linhas de distribuição. Por meio de modificações nas técnicas clássicas de modelagem das descargas atmosféricas, foi possível a construção de um software em Visual Basic capaz de quantificar os valores das tensões induzidas em linhas de distribuição finitas. A avaliação dos níveis de sobretensões induzidas nas mesmas foi implementada pela associação deste software a um programa de simulação (ATP), a fim de se obter resultados fidedignos deste transitório. Tais resultados foram utilizados para se avaliar o desempenho das...
The present work aims at the development of a trustworthy computacional tool in the analysis and estimate of the levels of induced overvoltage in distribution network. In this context, consolidated computacional tools are used, as ATP (Alternative Transients Program), that combined with a software developed in Visual Basic (beginner's all-purpose symbolic instruction code), they allow to quantify and to evaluate the level of overvoltage in the distribution network. By the means of modifications in the classic techniques of modeling of the atmospheric discharges, the construction of a software in Visual Basic was possible to quantify the values of the induced overvoltage in a finite... (Complete abstract click electronic access below)
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Felicetti, Roberto. "Voltage Transients in the Field Winding of Salient Pole Wound Synchronous Machines : Implications from fast switching power electronics." Licentiate thesis, Uppsala universitet, Elektricitetslära, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-434652.
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Wound Field Synchronous Generators provide more than 95% of the electricity need worldwide. Their primacy in electricity production is due to ease of voltage regulation, performed by simply adjusting the direct current intensity in their rotor winding. Nevertheless, the rapid progress of power electronics devices enables new possibilities for alternating current add-ins in a more than a century long DC dominated technology. Damping the rotor oscillations with less energy loss than before, reducing the wear of the bearings by actively compensating for the mechanic unbalance of the rotating parts, speeding up the generator with no need for additional means, these are just few of the new applications which imply partial or total alternated current supplying of the rotor winding. This thesis explores what happens in a winding traditionally designed for the direct current supply when an alternated current is injected into it by an inverter. The research focuses on wound field salient pole synchronous machines and investigates the changes in the field winding parameters under AC conditions. Particular attention is dedicated to the potentially harmful voltage surges and voltage gradients triggered by voltage-edges with large slew rate. For this study a wide frequency band simplified electromagnetic model of the field winding has been carried out, experimentally determined and validated. Within the specific application of the fast field current control, the research provides some references for the design of the rotor magnetic circuit and of the field winding. Finally the coordination between the power electronics and the field winding properties is addressed, when the current control is done by means of a long cable or busbars, in order to prevent or reduce the ringing.
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Bukvišová, Zuzana. "Modelování rychlých přechodných dějů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-316921.
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This thesis deals with the high speed transient modelling in the electrical networks. The introduction of this work discusses mathematical models of the individual devices used in the system and focuses on the line representation. It also contains a more detailed description of Bergeron and frequency dependent line model. The objective of this thesis is to design a network model using ATP-EMTP simulation program. In this model, the switching overvoltage caused by shunt reactor switching and lightning overvoltage are simulated. The thesis thoroughly describes the settings of the components used in the model of analysed network and in conclusion evaluates obtained simulation results in a relation to the insulation coordination.
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Thomazella, Rogério. "Implementação computacional para avaliar os níveis de sobretensões atmosféricas induzidas em linhas de distribuição /." Bauru : [s.n.], 2004. http://hdl.handle.net/11449/90810.
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Orientador: André Nunes de SouzaBanca: Ivan Nunes da Silva
Banca: Luiz Gonzaga Campos Porto
Resumo: O presente trabalho visa o desenvolvimento de uma ferramenta computacional confiável na análise e estimação dos níveis de tensões induzidas em linhas de distribuição. Neste contexto, utilizam-se ferramentas computacionais consolidadas, como o ATP (Alternative Transients Program), que combinado a um software desenvolvido em Visual Basic, permitem quantificar e avaliar o nível de sobretensões nas linhas de distribuição. Por meio de modificações nas técnicas clássicas de modelagem das descargas atmosféricas, foi possível a construção de um software em Visual Basic capaz de quantificar os valores das tensões induzidas em linhas de distribuição finitas. A avaliação dos níveis de sobretensões induzidas nas mesmas foi implementada pela associação deste software a um programa de simulação (ATP), a fim de se obter resultados fidedignos deste transitório. Tais resultados foram utilizados para se avaliar o desempenho das... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The present work aims at the development of a trustworthy computacional tool in the analysis and estimate of the levels of induced overvoltage in distribution network. In this context, consolidated computacional tools are used, as ATP (Alternative Transients Program), that combined with a software developed in Visual Basic (beginner's all-purpose symbolic instruction code), they allow to quantify and to evaluate the level of overvoltage in the distribution network. By the means of modifications in the classic techniques of modeling of the atmospheric discharges, the construction of a software in Visual Basic was possible to quantify the values of the induced overvoltage in a finite... (Complete abstract click electronic access below)
Mestre
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Chen, Wei-Hsiang, and 陳韋翔. "Transient Overvoltage Suppression Strategys of Power Capacitors." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/53381838054331982405.
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碩士國立勤益科技大學
電機工程系
98
This paper aims to reduce the transient overvoltages problem occurred in switching shunt capacitor banks. Capacitor banks installed in power system are used to compensate the reactive power demand for improving the network’s voltage profile and decreasing the network’s losses. Capacitor banks may be switched on and off frequently during a typical day according to certain load curves. The switching actions will produce large transient overvoltages. These transients may cause serious power quality problems. This paper uses Alternative Transients Program (ATP) to compare the responses of several typical switching strategies such as voltage zero closing, voltage peak closing, installing current-limiting reactors and pre-installed resistors, then suggestions for reducing transients are proposed. According to the result, the method of pre-installed resistors has a greater tolerance for time deviation of switch closing than other methods; it also can effectively inhibit the three-phase transient overvoltages.
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Khandelwal, Sulabh. "Artificial Neural Networks Approach For Estimation Of Line Energization Peak Transient Overvoltages During Restoration." Thesis, 2005. http://etd.iisc.ernet.in/handle/2005/1433.
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Lee, Chang-Hsing, and 李長興. "Simulation and Analysis of the Very Fast Transient Overvoltage in Medium Voltage Systems." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/00471785969251281818.
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博士國立清華大學
電機工程學系
99
The very fast transient overvoltage (VFTO) is a common transient phenomenon caused by the switching operation in the extra-high-voltage (EHV) gas insulated substation (GIS), and is characterized by its fast rising wavefront within nanoseconds. Besides the peak of VFTO higher than the breakdown voltage of insulation material, the main affection of VFTO on the equipments is the fast rising wavefront, causing the non-uniform electric field inside the insulation material, then leading the partial overvoltage inside the insulation material, and resulting in the accelerating aging of the insulation material. Furthermore, the very fast transient may cause electromagnetic interference and result in the malfunction of control instruments. As for the equipments in the secondary side of power transformer, the VFTO is thought to be small and less dangerous due to the mismatch of impedance. Therefore, most researches involving VFTO usually focus on the affection of VFTO on the GIS itself, and the equipments adjacent GIS or directly connected to GIS. Hence, there are few researches dealing with the VFTO in the secondary side of power transformer. However, a few field experiments showed that some root causes of medium voltage events were suspected to be the switching surge of GIS operation. Moreover, the authors measured the VFTO in 4.16 kV system in the 3rd nuclear power plant of Taipower at 2002, and the VFTO was, hence, confirmed to be able to transmit into medium voltage system. Therefore, this thesis takes the analysis of VFTO in medium voltage system as the major topic by simulating and measuring the VFTO in medium voltage system. Limited by the capabilities of software, ElectroMagnetic Transient Program (EMTP), it is impossible to simulate the transient phenomena of whole process of switching operation by the 1 ns time step. Therefore, most literatures estimated the affection of VFTO by the single strike simulation with the most series situation, such as 2.0 PU inter-contact breakdown voltage. However, according to the field measurement results in the 3rd nuclear power plant and the study of this thesis, the characteristics of VFTO in medium voltage system are not only affected by the inter-contact breakdown voltage, but also affected by the properties of whole process. Hence, this thesis is devoted to develop simulation method to simulate the whole process phenomena of disconnect switch (DS). This thesis gets the following results: 1. By the analysis of components’ characteristics, the notice is addressed for the simulation, and the simulation method for whole process phenomena of switching operation is proposed, which includes the proposition of an adequate simulation timestep and the high frequency recovery factor (HFRF) to adjust the maximum peak of VFTO simulated at this timestep; 2. By analysis of the simulation results, the properties of the VFTO transmitting into medium voltage system are characterized: the capacitive transfer of high turn-ratio transformer, the superposition effect of the oscillation caused by former restike superimposing into the following restrike, the three phases coupling caused by three-phase system, the duration of arcing time, and the properties of DS opening/closing; 3. By simulating the DS operating at different operation angle, the property of VFTO in medium voltage system is discussed including aforementioned factors; 4. By the several field measurement results, the recommendation is made for the measuring of VFTO in the medium voltage system.
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(9826433), Rodney Peters. "Transient overvoltages in mine power systems." Thesis, 1998. https://figshare.com/articles/thesis/Transient_overvoltages_in_mine_power_systems/20341575.
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This thesis investigates the nature and magnitude of switching transient overvoltages that can be expected in inductively grounded underground coal mines. Computer models of power system equipment have been developed to analyse single-phase fault isolations; motor starts (including prestriking) and motor turn offs. The computer models that were developed have been validated against field recordings. The "Alternative Transients Program" (ATP) software was used to conduct the computer simulation studies.
The underground substations used in Central Queensland coal mines are grounded through a Neutral Earthing Reactor (NER). The primary purpose of a NER is to limit earth fault currents. However, when a single -phase -to -ground fault occurs, energy is stored in the NER. Consequent to the isolation of such a fault, the energy stored in the NER is released. The release of this energy manifests itself as a transient overvoltage. This thesis investigates the effect of the rating of the NER and the value of the electric current at the instant of earth fault isolation on transient overvoltages.
Two alternate earthing schemes were investigated in an attempt to reduce the severity of the transient overvoltages consequent to the isolation of earth faults. The first alternative that was investigated was the addition of a Resistor -Capacitor Snubber in parallel with a NER. Computer simulations indicate that the proper choice of Snubber parameters is very effective in reducing transient overvoltages following the isolation of earth faults. Consequently, a decision was made to manufacture a R -C Snubber and conduct field tests on the same. A summary of the field tests results has been included in the thesis.
The other alternate grounding scheme that was investigated was the substitution of a Neutral Earthing Reactor with a Neutral Earthing Resistor. Computer simulations indicate that transient overvoltages following the isolation of earth faults are virtually eliminated if a Neutral Earthing Resistor is used.
Consequent to this research work, the use of R -C Snubbers has become a recommended practice at various coal mine sites in Australia which use NER grounded, container type substations. The R -C Snubber is the preferred alternative at such installations as it is very compact and also eliminates the heating/reliability problems associated with resistance grounding.
Vacuum contactors are used throughout the Central Queensland mines to frequently turn motors on and off. One of the most significant characteristics of vacuum contactors is their ability to interrupt high frequency currents. The consequence of this is that a considerable number of high frequency prestriking transients can be generated whenever a motor is turned on. These high frequency transients can lead to the premature aging of insulation. This thesis presents a computer model that was developed to simulate prestriking transients using the TACS (Transient Analysis of Control Systems) programming feature of the ATP software. Further investigation of prestriking transients was considered to be beyond the scope of the present research project. However, the unique TACS based prestriking model of a vacuum contactor that has been developed will be a useful tool for conducting further research.
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"Investigating Transient Overvoltage Produced by Switching Action on Long Transmission Lines and Its Effect on Substations." Master's thesis, 2018. http://hdl.handle.net/2286/R.I.51756.
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abstract: Switching surges are a common type of phenomenon that occur on any sort of power system network. These are more pronounced on long transmission lines and in high voltage substations. The problem with switching surges is encountered when a lot of power is transmitted across a transmission line/network, typically from a concentrated generation node to a concentrated load. The problem becomes significantly worse when the transmission line is long and when the voltage levels are high, typically above 400 kV. These overvoltage transients occur following any type of switching action such as breaker operation, fault occurrence/clearance and energization, and they pose a very real danger to weakly interconnected systems. At EHV levels, the insulation coordination of such lines is mainly dictated by the peak level of switching surges, the most dangerous of which include three phase line energization and single-phase reclosing. Switching surges can depend on a number of independent and inter-dependent factors like voltage level, line length, tower construction, location along the line, and presence of other equipment like shunt/series reactors and capacitors.
This project discusses the approaches taken and methods applied to observe and tackle the problems associated with switching surges on a long transmission line. A detailed discussion pertaining to different aspects of switching surges and their effects is presented with results from various studies published in IEEE journals and conference papers. Then a series of simulations are presented to determine an arrangement of substation equipment with respect to incoming transmission lines; that correspond to the lowest surge levels at that substation.Dissertation/Thesis
Masters Thesis Electrical Engineering 2018
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Gumede, Makhosonke. "In-service condition monitoring of polymer housed surge arrester within eThekwini Electricity." Thesis, 2015. http://hdl.handle.net/10321/1677.
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Submitted in fulfillment of the requirements for the degree of Master in Technology, Durban University of Technology, Durban, South Africa, 2015.The primary objective of this research was to investigate the failures occurring in the family of surge arresters used within EThekwini Electricity, making use of different diagnostic methods, such as leakage current testing (LC), infrared scanning (IR), and partial discharge (PD) measurements. The different diagnostic tests were used to assess the degradation process of the polymer housed surge arresters and their failure. The measurements were used for diagnosis of 120 kV/65 kA surge arresters of different brands. Tests were performed on surge arresters that were still in the system and these test results were compared with results from tests performed on failed units. Results obtained from the different tests were compared to the test results for different families or designs. An imperfect arrester will exhibit excessive heating when an electrical surge is discharged. The aforementioned tenets are the primary factors influencing degradation and causing failure of Metal Oxide Surge Arrester (MOSA) in a system. These factors can decrease creepage and flashover distance on insulation, which could result in a substantial increase in resistive leakage current, (which is a few microamperes in ideal condition), overheating, and PD formation on the zinc oxide varistor element. Therefore, it is extremely important to assess the status of the surge arresters whilst they are in service, firstly so that they can be removed from the system before they fail and, and secondly, to verify their condition, and their ability to effectively protect the substation apparatus. Using infrared inspection, valuable information of condition of surge arresters was obtained, heat inside the surge arresters was detected and this shows that IR analysis can therefore be considered as an additional method to assess the condition of polymer housed surge arresters. It was observed that partial discharge activity is an indication of degradation in arrester varistor. LC test, IR, and PD measurement were valuable in obtaining sufficient information for failure of surge arresters. In additional, during the visual internal inspection of arresters, evidence of punctures, treeing, tracking, and moisture masks were noted on ZnO blocks and seals. These results indicate that the moisture ingress through the sealing collar can cause unnecessary outages.
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