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Utredning av variablerna som påverkar storleken på brytspänningen i lindningskopplare / Investigation of the variables that affect the recovery voltage in tap-changersAndersson, Andreas January 2015 (has links)
Brytspänningen är den spänning som uppkommer när överkopplingsmotståndet i lindningskopplaren lämnar sitt föregående läge vid omkoppling. Storleken på brytspänningen i lindningskopplaren beror på hur stor läckinduktansen är. Är den inte känd så kan brytspänningen istället beräknas med hjälp av FEM-programmet ACE (internt ABB-program) i samband med Mathcad. I ACE beräknas först reaktanserna i p.u-enheter mellan lindningarna och hur stora de är beror på lindningslayouten. Det är tidskrävande att använda ACE och Mathcad och uppgiften är att utreda de parametrar som påverkar storleken på brytspänningen samt att ta fram en förenklad beräkning av densamma. Genom simulering i ACE av en mängd olika lindningslayouter visar det sig snart att det är alltför många parametrar som påverkar reaktanserna. De förenklingar som trots det har tagits fram är lite för grova för att det ska vara pålitligt. Mathcad är än mer komplext med tunga beräkningar som inte är lätta att förenkla. Arbetet har ändå gett mer kunskap om hur reaktanserna påverkas av geometrierna i lindningarna och kommer att vara till viss nytta, även om det inte gick att förenkla ACE- och Mathcadberäkningarna så som var tänkt. / The recovery voltage is the voltage that occur when the transition resistor in the tap-changer leaves its previous position during an operation cycle. The amplitude of the recovery voltage depends on the leakage inductance. If the leakage inductance is unknown, the recovery voltage can instead be calculated using a FEM-program called ACE (internal ABB-program) in conjunction with Mathcad. First, the reactances between the windings are calculated in per unit (p.u) using ACE and they depend on the winding layout. It is time consuming to use ACE and Mathcad and the task has been to investigate the parameters that affects the recovery voltage and to develop a simplified calculation of it. Through simulation using ACE of a number of different winding layouts one soon comes to the conclusion that there are simply too many parameters affecting the reactances. Although the simplified calculations that despite this has been developed, they soon prove to be too rough to be useful. Mathcad is even more complex with heavy calculations that are not easy to grasp. However, this thesis has given more knowledge about the way the reactances are affected by the geometry of the windings, even though it was not possible to in a reasonable way simplify the calculation of ACE and Mathcad.
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Analysis of factory test data of on-load tap-changers for power transformersStenhammar, Oscar January 2021 (has links)
On-load tap-changers (OLTC) are devices in the power grid that keeps the voltage level constant for consumers, regardless of the power demand. Hitachi ABB Power Grids, producer of the OLTC family named VUC, guarantees 30 years of lifetime. Such a pledge requires high standard devices. This thesis has analyzed data from routine tests of switching times in the diverter switch of OLTC’s, performed before devices were put in service. The correlation of part switching times for all units leaving the factory during the past year was evaluated by calculating Pearson’s correlation coefficient. A linear trend was fitted to the data, realizing that the prediction errors, as well as the part switching times, were Gaussian distributed. The time while the resistor vacuum interrupter was open could be predicted within the interval of approximately 2ms with 2 standard deviations accuracy. To classify time series from the routine test as expected or unexpected, a model-based algorithm was implemented. The average switching time for all consecutive switches was used to define expected series. A moving average was implemented to neglect outliers and remove oscillating patterns. The majority of all data was classified as expected time series. The ones who did not, still preserved a good correlation between the part switching times. Examining the relationship between part switching times could be a valuable perspective in further classification of expected time series. The possibility of incorporating measurement of part switching times on OLTC’s in normal operation, to use the knowledge gained by this thesis, was investigated. Position sensors were mounted to measure the position of the lifting yokes, opening and closing the vacuum interrupters. The time while the vacuum interrupter contacts were open could be estimated with better accuracy than the position sensor provided. Unfortunately, those sensors cannot be utilized in normal operation. If other possibilities could be found, perhaps a laser position sensor, the implemented algorithm would be valuable.
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The development of a IGBT-based tap changerFourie, Reinhart 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Voltage regulation on distribution networks has so far been done by means of
mechanical tap changers. However, these tap changers are plagued by high
maintenance costs due to the arcing caused while switching, which degrades
both the contacts and transformer oil. The major advances made during the
last decade with regard to semiconductor technology have led to the development
of high power IGBTs. These high power IGBTs are capable of conducting
currents up to 1 000 A, while the voltage over the IGBT reaches well over 3
000 V. Using these high power IGBTs to design and build a solid-state tap
changer allows the tap changer to regulate the output voltage with higher accuracy
and speed. The supporting hardware is also discussed, while the design
is verified by the use of simulations and practical measurements conducted on
a scale-model of the IGBT-based solid-state tap changer. / AFRIKAANSE OPSOMMING: Spannings regulasie op distribusie netwerke word hedendaags verrig deur meganiese
tap geskalde spanning reguleerders. Maar hierdie tap skakelaars word
konstant beïnvloed deur oorvonking wat plaasvind tussen die kontakte wat hierdie
kontakte beskadig en die transformator olie degradeer. Die laaste dekade
het groot vordering getoon in halfgeleier navorsing wat gelei het tot die ontwikkeling
van hoë drywing halfgeleiers. Die halfgeleiers of IGBTs kan strome
so groot soos 1 000 A gelei terwyl die spanning oor die halfgeleier 3 000 V kan
oorskry. Die gebruik van die hoë drywing halfgeleiers maak die pad oop vir die
ontwerp en bou van ’n tap geskakelde reguleerder wat die uitree spanning akurater
en vinniger kan reguleer. Die aanvullende hardeware is ook bespreek en
die ontwerp is geverifieër deur middel van simulasies en deur praktiese metings
wat geneem is op ’n skaal model van die hoogspanning spannings reguleerder.
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Load flow control and optimization of Banverket’s 132 kV 16 2/3 Hz high voltage gridLindén, Annica, Ågren, Anna January 2005 (has links)
<p>The purpose of this thesis was to investigate the possibility of power flow control, on a section of a railway grid fed by rotary converters, using an extra feeding line. Two possible solutions for the power flow control were examined. The first using a series reactance in connection to each converter station and the second by changing the tap changer level of the transformer between the converter station and the feeding line.</p><p>In the two models a distance, comparable to the distance between Boden and Häggvik, in Stockholm, was used. The simulations were performed using the software SIMPOW.</p><p>The results from the performed simulations show that series reactances, under the stated conditions, can essentially improve the power flow. To implement this air coils with inductances in the approximate size of 10 to 45 mH could be used. Further, the tap changer levels of the transformer may be used, for individual converter stations, as a way to control the reactive power flow.</p>
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Load flow control and optimization of Banverket’s 132 kV 16 2/3 Hz high voltage gridLindén, Annica, Ågren, Anna January 2005 (has links)
The purpose of this thesis was to investigate the possibility of power flow control, on a section of a railway grid fed by rotary converters, using an extra feeding line. Two possible solutions for the power flow control were examined. The first using a series reactance in connection to each converter station and the second by changing the tap changer level of the transformer between the converter station and the feeding line. In the two models a distance, comparable to the distance between Boden and Häggvik, in Stockholm, was used. The simulations were performed using the software SIMPOW. The results from the performed simulations show that series reactances, under the stated conditions, can essentially improve the power flow. To implement this air coils with inductances in the approximate size of 10 to 45 mH could be used. Further, the tap changer levels of the transformer may be used, for individual converter stations, as a way to control the reactive power flow.
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A heuristic optimal approach for coordinated volt/var control in distribution networksMokgonyana, Lesiba January 2015 (has links)
This dissertation focuses on daily volt/var control in distribution networks with feeder capacitors,
substation capacitors and transformers equipped with on-load tap changers. A hybrid
approach is proposed to solve the daily volt/var control problem. To reduce the computational
requirements of the problem, this approach combines two methods, namely heuristic
and optimal scheduling for the substation and feeder sub-problems respectively.
The feeder capacitor dispatch schedule is determined based on a heuristic reactive power setpoint
method. At this stage the objective is to minimize the reactive power flow through the
substation bus in every time-interval. And as such, mathematical modeling of the distribution
network components is adapted to suit time-varying conditions. Furthermore, an optimization
model to determine a proper dispatch schedule of the substation devices is formulated.
The objective of this model is to minimize the daily total energy loss and voltage deviations.
Additionally, the reference voltage of the substation secondary bus and the transformer tap
position limits are modified to adapt to given load profiles. The optimization model is solved
with a discrete particle swarm optimization algorithm, which incorporates Newton’s method
to determine the power-flow solution. The proposed method is applied to a time-varying distribution system and evaluated under
different operational scenarios. It is also compared to on-line volt/var control with various
settings. Simulation results show that the proposed approach minimizes both the voltage deviations
and the total energy loss, while on-line control prioritizes one objective over the other depending
on the specified settings. / Dissertation (MEng)--University of Pretoria, 2015. / Electrical, Electronic and Computer Engineering / Unrestricted
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Distribution On Load Tap Changer Control Using IEC61850 Client/Server ArchitectureManeikis, Andrius January 2016 (has links)
Distributed generation is transforming the power system grid to decentralized system where separate units like wind power generators or solar panel shall coexist and operate in tandem in order to supplement each other and make one extensive system as a whole so called smart grid. It is utmost important to have a control ability over such units not only on a field level but on a system level as well. To be able to communicate with numerous devices and maintain interoperability universal standard is a must. Therefore, one of the core standards relevant to smart grids is IEC 61850 – Power Utility Automation which comes into assistance and tackles aforementioned challenges. This project uses IEC61850 architecture to implement client/server windows applications for on-load tap changer remote control. The proposed solution and designed applications are tested together with a real time simulator where simple power system is modelled to emulate the system response to control signals in a real time. In this way, the implemented applications can be tried and assessed as if performing in real environment. Consequently, a user of the client application is able to remotely control voltage on the power transformer's secondary side and manipulate the switching equipment simulated in the model. / Distribuerad generation håller på att förändra transmissionsnätet till decentraliserat system där separata enheter som vindkraftverk eller solpanel skall samexistera och fungera tillsammans för att komplettera varandra och att göra ett omfattande system som helhet så kallade smarta elnät. Det är ytterst viktigt att ha en kontroll förmåga över sådana enheter inte bara på ett fältnivå utan även på systemnivå. För att kunna kommunicera med många enheter och bibehålla interoperabiliten som universell standard är ett måste. En av de grundläggande normer som är relevanta för smarta nät är IEC 61850 - Skydd & Automation, som kommer in i bistånd och möter ovan nämnda utmaningar. Detta projekt använder IEC61850-struktur för att implementera klient/server windows applikation för lindningskopplarens fjärrkontroll. Den föreslagna lösningen och utformade applikationer testas tillsammans med en realtidssimulator där enkelt kraftsystem modelleras för att emulera systemets svar på de givna styrsignalerna i realtid. På detta sätt kan de implementerade programmen prövas och bedömas hur de utföras i verklig miljö. Följaktligen kan användare av klientapplikationen fjärrstyra spänningen på transformatorns sekundärsida och manipulera ställverk som simuleras i modellen.
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Μελέτη σφαλμάτων σε μετασχηματιστές υψηλής τάσης με αυτόματο μεταγωγέα τάσης (TAP changer)Παππά, Αγγελική 19 January 2011 (has links)
Στην παρούσα διπλωματική εργασία γίνεται αναλυτική περιγραφή της λειτουργίας της διάταξης του Μεταγωγέα Τάσης Υπό Φορτίο ενός μετασχηματιστή υψηλής τάσης 150 kV/ 21 kV. Επίσης, περιγράφονται και αναλύονται σφάλματα που εμφανίζονται σε μετασχηματιστές με Μεταγωγέα Τάσης Υπό Φορτίο με χρήση εμπειρικών δεδομένων από την εταιρεία Δ.Ε.Η. Α.Ε. και τη θεωρητική ανάλυση και εξήγησή τους μέσα από βιβλιογραφική μελέτη . Συγκεκριμένα, περιγράφονται τα αίτια που δημιουργούν αυτά τα σφάλματα, τα συμπτώματα που εμφανίζονται στο μετασχηματιστή και το μεταγωγέα τάσης , οι επιπτώσεις των σφαλμάτων αυτών στο μετασχηματιστή και τη διάταξη του μεταγωγέα τάσης . Επιπλέον, γίνεται αναφορά στα συστήματα προστασίας που διαθέτει ο μετασχηματιστής και ο μεταγωγέας τάσης προκειμένου να προστατευθεί από τις επιπτώσεις αυτών των σφαλμάτων. Στη συνέχεια, μελετάται συγκεκριμένο σφάλμα, που παρουσιάστηκε στο Μ/Σ 150 kV/21 kV Νο1 του Υ/Σ 150 kV/21 kV των Ελληνικών Ναυπηγείων Σκαραμαγκά, και καταγράφεται η αντιμετώπισή του βήμα προς βήμα σε συνεργασία με την εταιρεία ΠΑΡΑΛΟΣ ΤΕΧΝΙΚΗ Α.Ε., στην οποία ανατέθηκε η επίλυση του σφάλματος. Τέλος, μέσα από την προσομοίωση ενός Μ/Σ υψηλής τάσης με μεταγωγέα τάσης υπό φορτίο με χρήση του λογισμικού πακέτου MatLab/SimuLink κατανοούμε σε βάθος τη λειτουργία του μεταγωγέα τάσης υπό φορτίο. Η προσομοίωση περιλαμβάνει την εφαρμογή διαταραχών της τάσης του δικτύου στο Μ/Σ στην περίπτωση ορθής και εσφαλμένης λειτουργίας του οργάνου του ρυθμιστή τάσης, καθώς η εσφαλμένη λειτουργία του ρυθμιστή τάσης ήταν και η αιτία του σφάλματος στο Μ/Σ του Υ/Σ 150 kV/21 kV των Ελληνικών Ναυπηγείων Σκαραμαγκά. / The particular project deals with the detailed description of the layout and the operation of the on load tap changer belonging to a transformer of high tension 150kV/21 kV. Furthermore, it describes and analyzes faults that occurs to transformers with on load tap changer using empirical data from DEI S.A. (Public Power Corporation) as well as theoretical analysis and explanation based on bibliography. In particular, there are described the reasons behind these faults , the symptoms that appear to the transformer and the tap changer and the consequences to the transformer and the layout of the tap changer. Moreover, there is reference to the protection systems that the transformer and the tap changer have in order to be protected from the consequences of the faults. Further on, a particular troubleshooting is studied that occurred at the transformer 150 kV/21 kV no1 of the high voltage substation 150 kV/21 kV at the Hellenic Shipyards of Skaramagas and its handling is reported step by step in association with PARALOS TECHNICAL S.A. , the company which was assigned to solve the troubleshooting. Finally, the operation of the on load tap changer is studied in depth through simulation of a high voltage transformer with on load tap changer using MatLab/SimuLink software package. The simulation includes the application of voltage variations at the transformer, occurred to the high voltage network in the case of orderly or disorderly operation of the voltage regulator, as the faulty operation of the voltage regulator was the reason behind the troubleshooting of the transformer of the substation of 150 kV/ 21 kV at the Hellenic Shipyards of Skaramagas.
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Probabilistische Modellierung dezentraler Energieanlagen und Sekundärtechnik für die VerteilnetzplanungDallmer-Zerbe, Kilian 29 January 2018 (has links) (PDF)
Der Ausbau dezentraler Energieanlagen wie fotovoltaischen Anlagen beeinflusst die Netzzustände signifikant. Dabei ist unsicher, wo und in welchem Maße deren Ausbau zukünftig erfolgt. Es ist nun an den Netzbetreibern gleichzeitig die aktuellen Herausforderungen zu meistern und die Netzplanung und -regelung für die Zukunft zu aktualisieren. Eine statistische Methode wird entwickelt, die Verteilnetzplanung unter Einsatz von quasi-stationär modellierten ”Smart Grid”-Lösungen wie Blindleistungsreglern und regelbaren Ortsnetztransformatoren ermöglicht. Durch Stichprobenverfahren werden Unsicherheiten wie Ort, Größe und Leistungsprofile der Energieanlagen in das Netzmodell eingebunden. Diese als probabilistischer Lastfluss bekannte Methode wird durch Gütemaße im Bereich geringer Kombination evaluiert. Beispiele probabilistischer Netzplanung werden an Netztopologien präsentiert. / Development of distributed energy units such as photovoltaic systems affects grid states significantly. It is uncertain, where and to what extent the development of these units is carried out in the future. It is now up to the distribution system operator to cope with todays grid challenges and to update grid planning and control for the future. A statistical method is developed, which incorporates quasi-stationary modeled ”smart grid” solutions such as reactive power controllers and on-load tap-changers. Uncertainties such as location, size and power profiles of energy systems are integrated into the grid model by sampling. This method is known as probabilistic load flow and is evaluated by quality measures at low combinations. Examples on probabilistic grid planning of different grid topologies are presented.
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Comutador eletrônico de taps aplicado a um transformador de distribuição monofásico / Electronic on load tap changer applied to a singlephase distribution transformerQuevedo, Josemar de Oliveira 27 February 2014 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Voltage regulation still is a problem faced by power utilities currently. In addition to the series
impedance and the significant load variation of the distribution grids, the main causes of voltage
regulation problems, the requirements for the enhancement of power quality by the electricity
regulatory agencies, increasing energy consumption, the inclusion of distributed generation and the
development of the smart grids tends to increase the complexity of the distribution systems. One of the
most used methods for voltage regulation in alternating current systems is the employment of tap
changer on transformers, this method allows voltage regulation by varying the transformation ratio,
modifying the value of the secondary voltage. The application of these devices is primarily performed
by manual commutation mechanical devices in distribution systems, and by automatic
electromechanical on load tap changers in substations. In the case of manual devices, operating costs
and the impossibility of automatic voltage regulation are limiting factors, while in the case of
electromechanical devices the limitations are mainly related to the costs of employment and
maintenance. Currently, the increase of voltage and current operating levels of semiconductor devices
has allowed envision the application of semiconductor switches instead of the mechanical switches
employed nowadays. However, due to the operating characteristics of these devices, a detailed
analysis of the commutation process is necessary, in order to allow the proper design of the devices
involved in the commutation and protection process of the electronic tap changer. In this context, this
work presents the analysis, design and implementation of an electronic on load tap changer applied to
a single-phase distribution transformer, proposed as an alternative to the existing mechanical and
electromechanical tap changers. Such a system enables the automatic voltage regulation, avoiding the
insulation oil degradation, resulting from the commutation process, and also the elimination of
movable parts, the main cause of defects in current automatic commutation devices. In addition to
allowing steady state voltage regulation, the system allows the regulation for momentary voltage sags,
since they occur in the transformer operating range. The analysis of the commutation process is
presented, allowing the design of the electronic switches, as well as the protection system to be
employed. Experimental results show the correct voltage regulation for different kinds of load,
demonstrating the potential application of electronic on load tap changers in the current distribution
systems and in future smart grids. / A regulação dos níveis de tensão é um problema ainda enfrentado pelas companhias
concessionárias de energia elétrica atualmente. Além da impedância série e da significativa variação
de carga das linhas de distribuição, principais causas dos problemas de regulação, a maior exigência
dos agentes reguladores do sistema elétrico para a melhoria da qualidade de energia, o aumento do
consumo de energia, a inclusão de geração distribuída e o desenvolvimento das redes inteligentes
(smart grids), tendem a aumentar a complexidade dos sistemas de distribuição. Um dos métodos mais
empregados na regulação de tensão em sistemas de corrente alternada é a aplicação de comutadores de
taps em transformadores. Este método permite a regulação da tensão através da variação da relação de
transformação, modificando o valor da tensão secundária. A aplicação desta solução é feita,
majoritariamente, através de dispositivos mecânicos de comutação manual nos sistemas de
distribuição e de dispositivos automáticos eletromecânicos de comutação sob carga em subestações.
No caso dos dispositivos manuais, os custos operacionais e a impossibilidade da regulação automática
de tensão são fatores limitantes, enquanto que no caso dos dispositivos eletromecânicos, os limitantes
estão relacionados principalmente aos custos de implantação e de manutenção. Atualmente, o aumento
dos níveis de tensão e corrente de operação dos dispositivos semicondutores tem permitido vislumbrar
a aplicação de chaves semicondutoras em substituição às chaves mecânicas empregadas. Entretanto,
devido às características de funcionamento destes dispositivos, uma análise detalhada do processo de
comutação do sistema é necessária, de modo a permitir um adequado projeto dos dispositivos
envolvidos no processo de comutação e proteção dos comutadores eletrônicos de taps. Neste contexto,
o presente trabalho apresenta a análise, projeto e implementação de um comutador eletrônico de taps
aplicado a um transformador de distribuição monofásico, proposto como alternativa aos comutadores
mecânicos ou eletromecânicos existentes. Tal sistema permite a regulação automática da tensão,
eliminando o desgaste do óleo isolante, resultante do processo de comutação sob carga e também a
eliminação de partes móveis, principal causa de defeitos nos comutadores automáticos atuais. Além de
permitir a regulação da tensão em regime permanente, o sistema possibilita a regulação para
afundamentos de tensão momentâneos, desde que estejam na faixa de operação do transformador. A
análise do processo de comutação do dispositivo estudado é apresentada, permitindo o projeto das
chaves eletrônicas, bem como do sistema de proteção a ser empregado. Resultados experimentais
demonstram a correta regulação de tensão do sistema desenvolvido, dentro dos limites de operação do
transformador, para diferentes tipos de carga, evidenciando a potencialidade dos comutadores
eletrônicos de taps em aplicações nas atuais redes de distribuição e nas futuras redes inteligentes.
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