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Dissertations / Theses on the topic 'Impedance protection'
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1
Wang, Jing. "Marine power system protection using active impedance estimation." Thesis, University of Nottingham, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537689.
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袁綺珊 and Yee-shan Cherry Yuen. "High impedance fault detection and overvoltage protection in low voltage power systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31222146.
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Yuen, Yee-shan Cherry. "High impedance fault detection and overvoltage protection in low voltage power systems /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20735297.
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Wrinch, Michael C. "Negative sequence impedance measurement for distributed generator islanding detection." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/3418.
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This thesis presents a method of detecting electrical islands in low voltage distributed generator networks by measuring negative sequence impedance differences between islanded and utility connections. Extensive testing was conducted on a commercial building and 25 kV distributed generator fed network by measuring naturally occurring and artificially injected negative sequence components. Similarly, this technique was tested using the IEEE 399-1990 bus test case using the EMTP software. The practical measurements have been matched to simulations where further system performance characteristics of detecting power system islands has been successfully demonstrated. Measured results indicate that unbalanced load conditions are naturally occurring and readily measurable while deliberately unbalanced loads can increase the accuracy of negative sequence impedance islanding detection. The typically low negative sequence impedance of induction motors was found to have only a small effect in low voltage busses, though large machines can effect the threshold settings. Careful placement of the island detector is required in these situations. The negative sequence impedance measurement method is an improvement on previous impedance measurement techniques for islanding detection due to its accuracy, and distinctly large threshold window which have challenged previous impedance based islanding detection techniques.
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Hewett, Richard James. "Impedance algorithm for distance protection of non-homogenous 33 kv power distribution systems." Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760727.
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GANDHI, JASPREET SINGH. "ELECTRODEPOSITION OF ORGANOFUNCTIONAL SILANES FOR IMPROVED CORROSION PROTECTION OF METALS." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1097867674.
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Jeffers, Kenneth E. "Electrochemical impedance spectroscopy for the characterization of corrosion and cathodic protection of buried pipelines." [Florida] : State University System of Florida, 1999. http://etd.fcla.edu/etd/uf/1999/amj9949/jeffers.pdf.
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Thesis (M.S.)--University of Florida, 1999.Title from first page of PDF file. Document formatted into pages; contains xx, 206 p.; also contains graphics. Vita. Includes bibliographical references (p. 202-205).
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Jayaraman, Vivek Adithya. "Protection of Falling Conductors into Flammable Vegetation Faults." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/101901.
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Increasing modernization of the world has brought about a human component to natural disasters, which are exacerbated by the growing threat of climate change. The Western United States and Australia have witnessed some of the deadliest, costliest, and destructive wildfires in the recent past with downed electric power lines being a significant factor amongst the causes. The relationship between wildfires and powerlines is not a newly discovered phenomenon, however, utilities across the globe are struggling to find an optimal solution to this problem. While existing regulations allow utilities to schedule power shutdowns, they are often accompanied by massive financial losses and discomfort to consumers. Utilities also need to factor in the climatic conditions in the region of their service and the flammability of the vegetation surrounding their lines while making decisions pertaining to system planning, load shedding, and protection. This multi-faceted problem can be dealt with in multiple ways – one such technique involves detection of a falling line into sensitive vegetation before it encounters the earth. This approach essentially boils down the problem into detecting a single line open circuit fault. The open circuit is momentary and hence, speed is of the essence in such a protection scheme. In this thesis, detection of an open circuit is carried out in two different ways, viz., with and without communication support between the various elements of the system, with the latter technique being a novel proposal with the aim of achieving a secure protection scheme with minimal additional infrastructural requirements.Master of Science
The contact of a live wire with the earth is a fault. While most faults can be cleared using traditional protection techniques, there is a higher risk associated with power lines that come in contact with dry surfaces, flammable plants, and bushes, which cannot be detected that easily. These surfaces offer very high resistance to the flow of current and are hence termed high impedance faults. These high impedance faults have the potential to spark and cause a fire, which can snowball into a wildfire depending on the geography and climatic conditions of the area. For years, this has been a major problem in places like Australia and California leading to loss of lives, power, and money, but the optimal solution is evasive. While several techniques to combat this problem exist, the focus of this thesis is essentially what is known as the Open Circuit Fault. The technique revolves around the detection of the fault while the falling conductor is midair. Given the short time frame, high-speed detection is of the essence. This thesis will focus on achieving open circuit detection without the need for any communication support and is a novel contribution to this field.
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Brown, Michael Carey. "Corrosion Protection Service Life of Epoxy Coated Reinforcing Steel in Virginia Bridge Decks." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/27690.
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The corrosion protection service life extension provided by epoxy-coated reinforcement (ECR) was determined by comparing ECR and bare bar from 10 bridge decks built between 1981 and 1995. The objective was to determine the corrosion protection service life time extension provided by ECR field specimens with various degrees of coating adhesion: disbonded, partially disbonded, and wholly bonded coatings.
The size and length distributions of cracks in Virginia bridge decks were investigated to assess the frequency and severity of cracks. Correlation of cracks with chloride penetration was used to characterize the influence of cracking on deck deterioration. Cracks influence the rate of chloride penetration, but the frequency and width distributions of cracks indicate that cracks are not likely to shorten the overall service life of most bridge decks in Virginia.
Altogether, 141 drilled cores, 102 mm (4 inches) in diameter, were employed in this study. For each of the decks built with ECR, 10 to 12 cores were drilled through a top reinforcing bar adjacent to the previous study core locations. In addition, approximately 3 cores were drilled through a top reinforcing bar at a surface crack location. Laboratory testing involved nondestructive monitoring using advanced electrochemical techniques to periodically assess the corrosion state of the steel bars during cyclic exposure to chloride-rich solution over 22 months of treatment. Time of corrosion initiation and time of cracking (where applicable), as well as chloride content of the concrete before and after treatment, were used in the analysis.
Less than 25 percent of all Virginia bridge decks built under specifications in place since 1981 is projected to corrode sufficiently to require rehabilitation within 100 years, regardless of bar type. The corrosion service life extension attributable to ECR in bridge decks was found to be approximately 5 years beyond that of bare steel.Ph. D.
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Zaremski, Brian Zachary. "The Advancement of Adaptive Relaying in Power Systems Protection." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32121.
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The electrical distribution system in the United States is considered one of the most complicated machines in existence. Electrical phenomena in such a complex system can inflict serious self-harm. This requires damage prevention from protection schemes. Until recently, there was a safe gap between capacity to deliver power and the demand. Therefore, these protection schemes focused on dependability allowing the disconnection of lines, transformers, or other devices with the purpose of isolating the faulted element. On some occasions, the disconnections made were not necessary. The other extreme of reliability calls for security. This aspect of reliability calls for the operation of the protective devices only for faults within the intended area of protection. There is a tradeoff here; where a dependable protection scheme will assuredly prevent damage, it is prone to unnecessary operation which can lead to cascading outages. Where a secure scheme will not operate unnecessarily, it is prone to pieces of the system becoming damaged when relays fail to operate properly. With microprocessor based relaying schemes, a hybrid reliability focus is attainable through adaptive relaying. Adaptive relaying describes protection schemes that adjust settings and/or logic of operations based on the prevailing conditions of the system. These adjustments can help to avoid relay miss-operation. Adjustments could include, but are not limited to, the logging of data for post-mortem analysis, communication throughout the system, as well changing relay parameters. Several concepts will be discussed, one of which will be implemented to prove the value of the new tools available.Master of Science
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Hoang, Van Hung. "Electrochemical Synthesis of Novel Polyaniline-Montmorillonite Nanocomposites and Corrosion Protection of Steel." Doctoral thesis, Universitätsbibliothek Chemnitz, 2007. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200700059.
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This dissertation describes a new electrochemical synthesis of novel composite materials based on montmorillonite (MMT) clay and intrinsically conducting polyaniline (PANI). PANI was successfully incorporated into MMT galleries to form PANI−MMT nanocomposites. Electropolymerization of anilinium ions which are intercalated inside the clay layers have been carried out at a constant applied potential. The synthetic conditions have been optimized taking into account the effect of concentration of aniline, magnetic stirring and potential cycling. The resulting organic-inorganic hybrid material, PANI-MMT has been characterized by various physicochemical techniques. Results of elemental analysis show that nanocomposite contains only 10 % of conducting PANI. Formation of PANI inside the clay tactoid has been confirmed by the expansion of inter layer distance of MMT as revealed by X-ray diffraction studies. Relatively lower interlayer expansion for PANI-MMT than that of anilinium-MMT indicates the higher stereoregularity in PANI-MMT which has strong influence on electrical properties of nanocomposites. Infrared spectroscopy studies reveal the presence of physicochemical interaction, probably hydrogen bonding, between clay and polyaniline. Cyclic voltammetry studies indicate that presence of electroinactive clay does not influence the electrochemical activity of PANI. Electrochromic behaviour of PANI-MMT nanocomposites have been studied using in situ UV-Vis spectroscopy which reveals that electrochromism of PANI in the composite material has been retained. One of the main technological applications of conducting polymers, particularly PANI, is in the area of corrosion protection of active metals. PANI-MMT nanocomposites synthesized using the present method and a chemically synthesized PANI which is soluble in organic solvents have been used to protect C45 steel surface against corrosion. Corrosion studies have been performed using electrochemical impedance measurements(EIM)and anodic polarization studies. Electrochemical impedance data has been analyzed using a suitable equivalent circuit. Corrosion protection of steel offered by both PANI-MMT and organically soluble PANI is evident form the increase in the value of charge transfer resistance of the coated steel surfaces. Time dependent EIM measurements reveal that charge transfer resistance gradually decreases with time, however, the values are much higher than that of uncoated surfaces. Two capacitive loops, one at higher and another at lower frequencies, observed in the Nyquist plots have been assigned to the electrical properties of coating material (in the present case, PANI-MMT or soluble PANI) and electrochemical process at the interface, respectively. An anodic shift in the corrosion potential, a decrease in the corrosion rate and a significant increase in the polarization resistance indicate a significant anti-corrosion performance of both PANI-MMT nanocomposite and organically soluble PANI deposited on the protected steel surfaceDiese Dissertation beschreibt eine neue elektrochemische Synthese neuartiger Compositmaterialien basierend auf dem Tonmineral Montmorillonite (MMT) und intrinsisch leitfähigem Polyanilin (PANI). Die Elektropolymerisation von Aniliniumionen, welche in die Tonmineralschichten eingebaut sind, wurde bei einem konstanten Potenzial durchgeführt. Das resultierende organisch-anorganische Hybridmaterial PANI-MMT wurde mit verschiedenen physikochemischen Methoden charakterisiert. Die Ergebnisse der Elementaranalyse zeigen, dass nur 10 % des Nanocompositmaterials aus leitfähigem PANI bestehen. Die Vergrößerung des Zwischenschichtabstandes von MMT, die bei Röntgendiffraktometrieuntersuchungen beobachtet wurde, lässt auf die Bildung von PANI innerhalb der Tonmineral-Taktoide schließen. IR-spektroskopische Untersuchungen deuten auf das Vorhandensein von Wechselwirkungen physikochemischer Art, wahrscheinlich Wasserstoffbindungen zwischen dem Tonmineral und Polyanilin, hin. Untersuchungen mit zyklischer Voltammetrie zeigten, dass die Anwesenheit von elektroinaktivem Tonmineral die elektrochemische Aktivität von PANI nicht beeinflusst. Das elektrochrome Verhalten von PANI-MMT Nanocompositen wurde mit UV-Vis-Spektroskopie untersucht, wobei sich herausstellte, dass das elektrochrome Verhalten vom PANI im Compositmaterial erhalten bleibt. Eines der technologischen Hauptanwendungsgebiete von leitfähigen Polymeren, insbesondere von PANI, ist der Korrosionsschutz von aktiven Metallen. PANI-MMT Nanocomposite die mit der angegebenen Methode (elektrochemisch) synthetisiert wurden und chemisch synthetisiertes in organischen Medien lösliches PANI wurden zum Korrosionsschutz von C45 Stahl eingesetzt. Die Korrosionsuntersuchungen wurden mit Hilfe von elektrochemischen Impedanzmessungen (EIM) und anodischen Polarisationsuntersuchungen durchgeführt. Der von PANI-MMT und von in organischen Medien löslichem PANI gebotene Korrosionsschutz ist wahrscheinlich auf die Zunahme des Ladungsdurchtritts widerstandes der beschichteten Stahloberfläche zurückzuführen. Die anodische Verschiebung des Korrosionspotenzials, eine Verringerung der Korrosions-geschwindigkeit und eine deutliche Zunahme des Polarisationswiderstandes sind eindeutige Hinweise für das Antikorrosionsvermögen von PANI-MMT und auch von in organischen Medien löslichem PANI, welche auf der zu schützenden Stahloberfläche abgeschieden wurden
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Maram, Sandeep. "A New Special Protection Scheme for Power System Controlled Separation." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/31038.
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A new power system controlled separation scheme is proposed to prevent the propagation of cascading failures across a transmission network should it undergoes a major disturbance, thereby reducing the possibility of a large-scale blackout. This scheme is developed based on a set of conjectures, which state the following: (i) the locations of out-of-step operations are independent of the severity and the location of the initial faults; (ii) these out-of-step operations occur sequentially over a sufficiently long duration so that relay blocking and transfer tripping can take place to minimize the load-generation imbalance in the formed islands. To verify these conjectures, extensive dynamic stability simulations are executed on a 30-bus and a 517-bus system, which exhibit characteristics suitable for this study. Furthermore, we verify that these out-of-step operations do depend on the prevailing system topology and the operating conditions.Master of Science
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Valero, Masa Alicia. "High impedance fault detection method in multi-grounded distribution networks." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209580.
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High Impedance Faults (HIFs) are undetectable by conventional protection technology under certainconditions. These faults occur when an energized conductor makes undesired contact with a
quasi-insulating object, such as a tree or a road. This contact restricts the level of the fault current to a very low value, from a few mA up to 75A. In solidly grounded distribution networks where the value of the residual current under normal conditions is considerable, overcurrent devices do not protect against HIFs. However, such a protection is essential for guaranteeing public security, because of the possibility of reaching the fallen conductor and the risk of fire.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Persson, Björn, and johanna Svensk. "Corrosion protection of powder coatings : Testing the barrier properties and adhesion of powder coating on aluminum for predicting corrosion protection by Electrochemical Impedance Spectroscopy." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Produktutveckling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-36772.
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The choice of corrosion protection system depends on the environment and needed lifetime for the product. The right corrosion protection should be selected in a sustainable point of view, since a well-selected coating system can reduce the environmental and economical impact, by using less and better material. The systems used for classifying corrosion protection often give a passed/not passed result for the number of years it is expected to last in a specific corrosive environment. In the last decades, Electrochemical Impedance Spectroscopy (EIS) has become a popular method for evaluating corrosion protection for organic coatings. EIS can collect quantitative data by monitoring the coatings electrochemical behavior over time, which can be used for optimizing the coating system. The purpose of this thesis was to try to predict how different combinations of coating layers and substrates will perform as a corrosion protection, which could provide information that can optimize the coating process. In this thesis, EIS has been used as a test method to evaluate organic coating systems for corrosion protection, by looking at barrier properties and adhesion for powder coatings on aluminum substrates. The main part of the coatings were applied in the coating plant at Fagerhult AB, but an external supplier has been used as a reference. The powders used in the coating process were based on polyester resins and the substrates were different aluminum alloys. The EIS measurements were performed in the chemistry lab at the School of Engineering at Jönköping University and depending on the sample setup was each sample evaluated for two or four weeks of testing. Two groups of samples had intact coatings and a third group had samples with an applied defect in the coating. The analysis of sample setups with intact coatings showed that the topcoat absorbed water faster than the primer. The samples showed no significant degradation in corrosion protection for the evaluated period and could thereby not provide enough information to be able to conclude which setup give the best corrosion protection over time. The samples with a defect in the coating indicated that two of the substrates provided similar adhesion in the coating-substrate interface. The coating from the external supplier was also included in the test and it showed the best adhesion of the tested samples. The main conclusion is that the coating system used at Fagerhult AB provides a very good corrosion protection. Longer testing time with EIS measurements on intact coatings is needed to be able to rank the different sample setups by failure of corrosion protection.
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Jardy, Alain. "Equilibres en solution des diphosphates metalliques : depot et proprietes de films de diphosphates en protection contre la corrosion." Paris 6, 1987. http://www.theses.fr/1987PA066107.
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Determination des constantes des complexes formes entre les ions diphosphate et differents cations metalliques permettant un choix raisonne des conditions optimales de formation d'un depot adherent de diphosphate metallique pour la protection contre la corrosion. Application a la protection d'un acier galvanise au contact des eaux de distribution
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Manna, Tapan K. "Impulse impedance of grounding systems and its effect on tower crossarm voltage : a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online version, 2006. http://proquest.umi.com/pqdweb?index=97&did=1208141981&SrchMode=1&sid=1&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1256323226&clientId=28564.
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Hassan, Abdi Mohamed. "Corrosion protection of aluminum coated with a polymer matrix in presence and absence of conductive polymer." Thesis, KTH, Ytbehandlingsteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-289175.
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Aluminium och aluminiumlegeringar har ganska bra korrosionsbeständighet, men dessa material kan fortfarande korrodera. Metallkorrosion är aldrig önskvärt och det kan leda till katastrofala resultat i olika branscher och applikationer. Det finns olika metoder för att skydda aluminium och dess legeringar från korrosion, såsom anodisering och användning av olika beläggningstekniker. Inte mycket forskning har gjorts på aluminium belagd med en organisk beläggning innehållande ledande polymer. Ännu mindre är känt om aluminium belagt med en vattenbaserad polymer matris innehållande ledande polymer. Tre system undersöktes i mitt examensarbete om deras korrosionsskyddande egenskaper. För detta ändamål användes elektrokemisk impedansspektroskopi, öppen kretspotential och potentiodynamisk polarisering, samt gjordes även en del atomkraftsmikroskopi, AFM, mätningar. Aluminium belagt med en vattenbaserad polymer matris i frånvaro av PANI hade ett bra korrosionsskydd först men reducerade barriäregenskaper över tiden i 1 M NaCl. Hållbarheten för den vattenbaserade polymer matrisen i frånvaro av PANI undersöktes också kort. Det visades att en nygjord vattenbaserad polymer matris uppvisade bättre korrosionsskydd än en 2 år gammal vattenbaserad polymer matris lagrad vid rumstemperatur. Aluminium belagt med den vattenbaserade polymer matrisen i närvaro av PANI visade initialt tecken på aktivt korrosionsskydd men övergick till passivt korrosionsskydd med tiden. Atomkraftmikroskop användes i olika lägen för att få insikt om den vattenbaserade polymer matrisen i närvaro av PANI. Ett ledande nätverk observerades i AFM-mätningarna och konfokalt ljusmikroskop antydde verkligen att detta skulle vara fallet. Det ledande nätverket i den vattenbaserade polymer matrisen kan förklara det aktiva korrosionsskyddet som observerades initialt. Fler studier behövs för att få insikt om de kemiska processerna vid gränssnittet mellan aluminiumlegeringen och den vattenbaserade polymer matrisen i närvaro av PANI.Aluminum and aluminum alloys have rather good corrosion resistance, but these materials can still corrode. Metal corrosion is never wanted, and it can lead to disastrous outcomes in various industries and applications. There are different methods to protects aluminum and its alloys from corrosion, such as anodization and the use of various coatings techniques. Not a lot of research have been done on aluminum coated with an organic coating containing conductive polymer. Even less is known about aluminum coated with a waterborne polymer matrix containing conductive polymer. Three systems were investigated in my diploma thesis work regarding their anti-corrosion properties. To this end electrochemical impedance spectroscopy, open circuit potential and potentiodynamic polarization were utilized, and also some atomic force microscopy, AFM, measurements were done. Aluminum coated with a waterborne polymer matrix in the absence of PANI had a good corrosion protection at first but reduced barrier properties over time in 1 M NaCl. The shelf-life of the waterborne polymer matrix in the absence of PANI was also briefly investigated. It was shown that a freshly made waterborne polymer matrix exhibited better corrosion protection than a 2 years old waterborne polymer matrix stored at room temperature. Aluminum coated with the waterborne polymer matrix in the presence of PANI showed signs of active corrosion protection initially, but it transitioned to passive corrosion protection with time. Atomic force microscopy was used in various modes to gain insight on the waterborne polymer matrix in the presence of PANI. A conducting network was observed in the AFM measurements and confocal light optical microscopy indeed suggested that this would be the case. The conducting network in the waterborne polymer matrix could explain the active corrosion protection observed initially. More studies are needed to gain insight on the chemical processes at the interface of the aluminum alloy and the waterborne polymer matrix in presence of PANI.
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Lamont, Lafras. "Development of a new pole-slip protection function for synchronous machines / Lafras Lamont." Thesis, North-West University, 2011. http://hdl.handle.net/10394/9730.
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The rotor shaft of a synchronous machine can experience severe mechanical stress due to torque
pulsations during a pole-slip condition. All pole-slip protection relays currently on the market use the
impedance pole-slip protection method to detect a pole-slip.
No commercial relay currently available can predict accurately when a generator is about to experience a
damaging pole-slip. All the relays will only trip a generator after it has pole-slipped one or more times.
Severe mechanical damage could be caused to a machine after only one pole-slip. It is therefore essential
to enhance pole-slip protection relays to such an extent that it can trip a generator before it pole slips.
The proposed pole-slip protection function must predict when a generator will become unstable during a
network fault. As soon as instability is predicted, the generator must be tripped before the fault is cleared
to avoid damaging post-fault torque effects. Conventional impedance pole-slip protection methods are
are also discussed and the shortcomings of impedance pole-slip protection are investigated.
The new pole-slip protection function was designed by using PSCAD. Detailed PSCAD simulations on
different network configurations proved that the new pole-slip protection function will trip a generator
before a damaging pole-slip occurs. The new pole-slip protection function was also implemented on an
ABB REM543 multifunctional protection relay and tested on a RTDS. The concept of the new pole-slip
function was successfully demonstrated on the protection relay.
The operation of conventional impedance scheme relays was compared with the proposed pole-slip
function for different fault conditions. Although the new pole-slip protection function is more complex
than the existing impedance functions, it was concluded that similar skills are required to test and
commission the new protection function. The new pole-slip function outperforms the impedance
protection methods, since the new protection function can trip the generator before it pole-slips.PhD (Electrical Engineering), North-West University, Potchefstroom Campus, 2011
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Tamilselvan, Karthi. "The Impacts of Ultra High Voltage AC line characteristics on line distance protection." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-194315.
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With the growing load demand, Ultra high Voltage (UHV) transmission lines are utilized in many countries around the world for bulk power transmission from remote locations over long distance. UHV transmission lines have typical features and it poses a challenge to the power system design with respect to protection, insulation and reactive power compensation, etc. Protection is a key issue in UHV transmission since a relay failure can interrupt and damage the power system. There are distance and differential protection schemes in the transmission line which account for security of the power system. This thesis report is based on analysis carried out to find out the typical features associated with the UHV transmission systems. Also the impacts of the UHV transmission line characteristics on line distance protection scheme are observed. The traditional distance relays based on the lumped line parameters are not suited for the UHV transmission lines of very long distances. In this case a simulation is carried out for a 765 kV transmission system modeled in PSCAD. In such a case the non-linearity is even more prominent and the relay is less dependable. In line with the simulation and the analysis for the challenges in UHV transmission system, it is observed that the fault impedance of the line is non-linear and this non-linearity causes the failure of relay operation for a fault location at the boundary of the zone of protection. The fault simulation was carried out in PSCAD and the quadrilateral distance relay characteristics were plotted using MATLAB. From the simulation and results, it is finally concluded that traditional distance protection relays with lumped parameter line modeling is not suitable for UHV transmission liens due to non-linearity in fault impedance and it leads to relay failure.Ultra high voltage (UHV) transmissionsledningar används i många länder till följd av ett växande behov av överföra hög effekt från avlägset belägna produktionsanläggningar till konsumenter. UHV-transmissionsledningar har speciella egenskaper som innebär utmaningar vid designandet av kraftsystem. Några utmaningar är systemskydd, isolation, och reaktiv effektkompensering. Systemskydd är en viktig aspekt för UHV-transmission eftersom haveri av reläskydd kan orsaka driftstopp och även skada ett kraftsystem. Det finns distans- och differentialskydd i transmissionsledningar som utgör skydd för kraftsystemet. Denna avhandling är baserad på analyser som har utförts för att åskådliggöra de typiska egenskaperna som är sammankopplade med UHV-transmissionssystem. Även inverkan på distansskydd orsakad av karaktäristiken av UHV-transmissionsledningar utvärderas. De traditionella distansreläskydden som baseras på de sammanslagna ledningsparametrarna är inte lämpade för UHV-transmissionsledningar som stäcker sig över långa avstånd. I detta fall har en simulering utförts i PSCAD för ett transmissionssystem med spänningen 765 kV. I ett sådant fall är karaktäristiken ännu mer olinjär och reläskydden ännu mindre pålitliga. Det observeras att felimpedansen för ledningen är olinjär och till följd av detta orsakas problem med reläskydden då ett fel uppkommer vid utkanten av den skyddade zonen. Denna observation överensstämmer med simuleringarna och de förväntade utmaningarna kopplade till UHV. Simuleringar av felfall utfördes i PSCAD och karaktäristiken av reläskydden plottades med hjälp av MATLAB. Från resultat presenteras i rapporten, konkluderas det att konventionella distansskyddsreläer med modellering av sammanslagna ledningsparametrar inte är lämpliga för UHV-transmissionsledningar på grund av att den olinjära felimpedansen leder till att reläskydden havererar.
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Holmes, Steven. "An investigation into the practical and theoretical aspects of hybrid cathodic protection." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/12280.
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Galvanic anode technology has in recent years come to the fore as a cost-effective method of successfully mitigating the corrosion of reinforcing steel in concrete structures. Developments in the field of cathodic protection have included the introduction of a novel Hybrid anode system, which uses the same sacrificial anode to pass a short-term impressed current before being connected to the steel directly to provide a long-term galvanic current. Galvanic and hybrid technologies are often seen as less powerful solutions in the treatment of reinforcement corrosion, and the test methodologies which determine the efficacy of cathodic protection systems favour impressed current technologies. The work completed has investigated the application of traditional and novel corrosion assessment techniques to laboratory samples to assess the protection offered by the hybrid treatment methodology in both treatment phases. In addition, the response of both galvanic and hybrid anodes to environmental conditions has been recorded and assessed before being discussed in the context of steel protection criteria. Finally, an investigation is presented into the on-site deterioration of commercially pure titanium feeder wire installed as part of the hybrid anode system and potential solutions to the problem have been documented. The research undertaken found that the hybrid anode system is capable of protecting steel in challenging, aggressive environments. This was confirmed by steel corrosion rate and indicative steel potential measurements. The responsive behaviour investigation showed that the current output of galvanic and hybrid anodes responds rapidly to changes in the corrosion risk posed to the steel and that this has a direct effect on anode system lifetimes. An assessment of the polarisation-based protection criteria applied to steel in concrete has found that the standard inhibits the use of responsive behaviour, and that revisions which consider the present risk of steel corrosion by considering the corrosion current resulting from the relative aggressivity of the concrete environment would be more valid in their application. A cathodic protection system based on the concepts of pit re-alkalisation and pH maintenance can fully utilise galvanic anode responsive behaviour. It was discovered that the deterioration of commercially pure titanium feeder wire seen on site installations was due to anodising in the presence of chloride media which had the potential to lead to pitting corrosion. The pitting risk varied depending on the duration of the treatment and proximity to the installed anode. An anodically grown oxide delayed the onset of corrosion in aqueous KBr solution, but did not significantly increase the pitting potential.
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Li, Ximing. "Damage Evolution of Pipeline API X52 Steel with Different Coating Conditions under Cathodic Protection in Soil and NS4 Solutions." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1406291563.
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MARTINS, EMERSON A. "Avaliacao do efeito de tratamentos superficiais na resistencia a corrosao de magnetos de Nd-Fe-B." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9404.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Loison, Pierre. "Development of a smart coating based on hollow nanoparticles for corrosion detection and protection." Thesis, La Rochelle, 2019. http://www.theses.fr/2019LAROS009.
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Dans de nombreux domaines, et particulièrement dans le secteur aérospatial, la corrosion est un problème majeur qui engendre d’importants coûts de maintenance et de réparation. Il est donc crucial de protéger les pièces soumises à des environnements agressifs. Dans ce but, une solution originale et prometteuse consiste à détecter et ralentir la corrosion dès ses prémices, en utilisant des revêtements capables de réagir dès son initiation. Récemment, de nombreuses études ont été réalisées en ce sens, développant des revêtements sensibles aux processus électrochimiques liés à la corrosion, faisant partie de la catégorie des revêtements dits « intelligents ». Les travaux présentés, financés par ArianeGroup, visent à développer des nanocapsules contenant un inhibiteur de corrosion. Ces capsules, formées suivant un procédé de mini-émulsion, sont ensuite intégrées à un revêtement organique, appliqué sur un substrat d’acier ou d’alliage d’aluminium. Lors d’une élévation locale de pH, observée lors de la corrosion des substrats métalliques, ces capsules sont capables de relarguer leur contenu. Les travaux présentés décrivent la synthèse et la caractérisation des nanocapsules, ainsi que leur incorporation dans une matrice organique à base aqueuse. Des capsules à cœur hydrophile et hydrophobe ont été envisagées avant de concentrer les recherches sur des capsules de silice à cœur hydrophobe dont le diamètre moyen est d’environ 180 nm. L’encapsulation et le relargage d’un inhibiteur de corrosion, le 2-mercaptobenzothiazole, sont décrits et les propriétés inhibitrices mises en évidence. Dans un deuxième temps, l‘impact de l’addition de capsules sur les propriétés du polymère est étudié, principalement par spectroscopie d’impédance électrochimique. Le système présenté peut potentiellement être adapté à la détection de la corrosion en remplaçant l’agent inhibiteur par un capteur de corrosionIn various domains, but especially in the space industry, protection of metallic structures against corrosion is a foremost objective because of maintenance and fixing costs in harsh environments. In order to preserve their integrity, a promising and original solution consists in detecting and slowing down corrosion as soon as it appears by developing a corrosion-sensitive and reactive coating. Recently, numerous studies have searched for the development of functional surfaces able to locally react to corrosion-related stimuli, belonging to the category of smart coatings. This PhD project, granted by ArianeGroup, is focused on this objective and deals with the development of nanocapsules containing corrosion inhibitors. These nanocapsules, formed through a miniemulsion process, are incorporated within an organic coating, applied on top of either steel of aluminum alloy substrates. The formed nanocapsules are then able to release their payload using a pH increase as a trigger. A pH change is indeed expected during cathodic activity, appearing at the early stages of the substrate degradation. This work describes the synthesis and characterization of nanocapsules, as well as their incorporation within an organic waterborne matrix. Both hydrophilic and hydrophobic-core capsules have been investigated before focusing on oil-core silica nanocapsules with diameter ca. 180 nm. In the first part, the release of a model inhibitor, namely 2-mercaptobenzothiazole (MBT) has been investigated and the inhibiting properties demonstrated. Then, the impact of capsules addition on coating integrity and properties has been studied using mainly electrochemical impedance spectroscopy. Potential enhancements of the proposed system are discussed. This system could be adapted and used for early detection of corrosion, using a corrosion sensor instead of the encapsulated inhibitor
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YAMAGUTI, ROSELE C. de L. "Avaliação de alternativas ao usi de níquel e cromatos no processo de fosfatização tricatiônico aplicado ao aço carbono." reponame:Repositório Institucional do IPEN, 2012. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10122.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Holmér, Camilla. "Study of green film-forming corrosion inhibitor based on mussel adhesive protein." Thesis, KTH, Skolan för kemivetenskap (CHE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-143553.
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Today there are numerous methods to slow down a corrosion process of metallic materials. However, due to environmental effects and health risk issues, several traditional corrosion inhibitors have to be phased out. Hence, it is of great importance to develop new corrosion inhibitors that are “green”, safe, smart and multifunctional. In this essay, the focus is on mussel adhesive protein (MAP) and its possibility to reduce the rate of the corrosion process. The protein exhibit great adhesive strength and protective properties, allowing it to adhere to a multitude of different surfaces and is therefore of great interest of corrosion science. The protein Mefp-1, derived from the blue mussel´s foot, had been pre-adsorbed on the carbon steel surface and provided good corrosion inhibition in a basic chloride solution for a short exposure time. The protection was further improved with the assist of iron and ceria ions by formation of protein/ions complexes within the surface films and thus enhanced the corrosion protection for longer exposure time. Ceria nanoparticles were used in order to create a multi-layer composite film with an even higher corrosion protection. The results suggest a denser film compared to previous samples and a more uniform surface.
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Grisso, Benjamin Luke. "Advancing Autonomous Structural Health Monitoring." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/29960.
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The focus of this dissertation is aimed at advancing autonomous structural health monitoring. All the research is based on developing the impedance method for monitoring structural health. The impedance technique utilizes piezoelectric patches to interrogate structures of interested with high frequency excitations. These patches are bonded directly to the structure, so information about the health of the structure can be seen in the electrical impedance of the piezoelectric patch. However, traditional impedance techniques require the use of a bulky and expensive impedance analyzer. Research presented here describes efforts to miniaturize the hardware necessary for damage detection. A prototype impedance-based structural health monitoring system, incorporating wireless based communications, is fabricated and validated with experimental testing. The first steps towards a completely autonomous structural health monitoring sensor are also presented. Power harvesting from ambient energy allows a prototype to be operable from a rechargeable power source.
Aerospace vehicles are equipped with thermal protection systems to isolate internal components from harsh reentry conditions. While the thermal protection systems are critical to the safety of the vehicle, finding damage in these structures presents a unique challenge. Impedance techniques will be used to detect the standard damage mechanism for one type of thermal protection system. The sensitivity of the impedance method at elevated temperatures is also investigated.
Sensors are often affixed to structures as a means of identifying structural defects. However, these sensors are susceptible to damage themselves. Sensor diagnostics is a field of study directed at identifying faulty sensors. The influence of temperature on these techniques is largely unstudied. In this dissertation, a model is generated to identify damaged sensors at any temperature. A sensor diagnostics method is also adapted for use in developed hardware. The prototype used is completely digital, so standard sensor diagnostics techniques are inapplicable. A new method is developed to work with the digital hardware.Ph. D.
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van, Rensburg Karel Jensen. "Analysis of arcing faults on distribution lines for protection and monitoring." Queensland University of Technology, 2003. http://eprints.qut.edu.au/15800/.
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This thesis describes an investigation into the influences of arcing and conductor deflection due to magnetic forces on the accuracy of fault locator algorithms in electrical distribution networks. The work also explores the possibilities of using the properties of an arc to identify two specific types of faults that may occur on an overhead distribution line. A new technique using the convolution operator is introduced for deriving differential equation algorithms. The first algorithm was derived by estimating the voltage as an array of impulse functions while the second algorithm was derived using a piecewise linear voltage signal. These algorithms were tested on a simulated single-phase circuit using a PI-model line. It was shown that the second algorithm gave identical results as the existing dynamic integration operator type algorithm. The first algorithm used a transformation to a three-phase circuit that did not require any matrix calculations as an equivalent sequence component circuit is utilised for a single-phase to ground fault. A simulated arc was used to test the influence of the non-linearity of an arc on the accuracy of this algorithm. The simulations showed that the variation in the resistance due to arcing causes large oscillations of the algorithm output and a 40th order mean filter was used to increase the accuracy and stability of the algorithm. The same tests were performed on a previously developed fault locator algorithm that includes a square-wave power frequency proximation of the fault arc. This algorithm gave more accurate and stable results even with large arc length variations. During phase-to-phase fault conditions, two opposing magnetic fields force the conductors outwards away from each other and this movement causes a change in the total inductance of the line. A three dimensional finite element line model based on standard wave equations but incorporating magnetic forces was used to evaluate this phenomenon. The results show that appreciable errors in the distance estimations can be expected especially on poorly tensioned di stribution lines.New techniques were also explored that are based on identification of the fault arc. Two methods were successfully tested on simulated networks to identify a breakingconductor. The methods are based on the rate of increase in arc length during the breaking of the conductor. The first method uses arc voltage increase as the basis of the detection while the second method make use of the increase in the non-linearity of the network resistance to identify a breaking conductor. An unsuccessful attempt was made to identifying conductor clashing caused by high winds: it was found that too many parameters influence the separation speed of the two conductors. No unique characteristic could be found to identify the conductor clashing using the speed of conductor separation. The existing algorithm was also used to estimate the voltage in a distribution network during a fault for power quality monitoring purposes.
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Amand, Sylvain. "Etude par spectroscopies d'impédance électrochimique globale et locale d'une monocouche hybride organique-inorganique respectueuse de l'environnement pour la protection contre la corrosion de l'alliage d'aluminium 2024." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0025/document.
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L'utilisation de revêtements sol-gel pour la protection contre la corrosion des métaux est une alternative aux traitements à base de chromates, proscrits du fait de leur forte toxicité. Ces travaux de thèse ont porté sur la caractérisation de revêtements sol-gel hybrides organique-inorganique contenant des pigments inhibiteurs de corrosion non toxiques, pour la protection contre la corrosion de l'alliage d'aluminium 2024. Tout d'abord, la caractérisation par spectroscopie d'impédance électrochimique de différents revêtements relativement poreux a permis d'analyser l'influence de l'épaisseur, de la température de séchage, de l'hydrolyse de la partie silane et du ratio silane/amine sur les performances du revêtement, en particulier des propriétés barrière. Puis, l'ajout d'un époxy dans la formulation a permis d'augmenter de façon significative les propriétés barrière du film. Les diagrammes d'impédance présentent une dispersion en fréquence, exprimée en termes de « constant phase element (CPE) », en haute et basse fréquence. En haute fréquence, ce comportement a été analysé à l'aide d'un modèle qui permet d'obtenir des profils de résistivité dans l'épaisseur du revêtement et au cours du temps d'immersion. Ce modèle est appliqué pour la première fois à l'étude de revêtements. Différents pigments inhibiteurs de corrosion ont ensuite été incorporés dans des revêtements de porosité différente. L'action des inhibiteurs est exacerbée lorsqu'ils sont incorporés dans un revêtement poreux. Néanmoins, lorsqu'ils sont incorporés dans un film dense, les performances vis-à-vis de la résistance à la corrosion sont élevéesThe use of sol-gel coatings for the protection against the corrosion of metals is an alternative to chrome-based treatments, banned for the industry for their high toxicity. This work is based on the characterisation of hybrid organic-inorganic coatings, filled with non-toxic corrosion inhibitors, for the protection against the corrosion of aluminium alloy 2024. First, the characterisation by electrochemical impedance spectroscopy of different, relatively porous coatings, allowed the investigation of the influence of thickness, drying temperature, silane hydrolysis, and the silane/amine ratio on the coating performances, in particular the barrier properties. Then, the addition of an epoxy compound in the formulation allowed a significant increase in the film barrier properties. The impedance diagrams show a frequency dispersion, expressed in terms of a constant phase element (CPE), both in the high and low frequency range. In the high frequency range, this behaviour was analyzed using a model that allows obtaining resistivity profiles in the thickness of the coating and with immersion time. This model is applied for the first time to study coatings. Different corrosion inhibitors were then incorporated in coatings of different porosity. The action of the inhibitors was heightened when they are incorporated in a porous coating. Nevertheless, in a dense coating, the performances towards corrosion are high
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Shreepathi, Subrahmanya, Hung Van Hoang, and Rudolf Holze. "Corrosion Protection Performance and Spectroscopic Investigations of Soluble Conducting Polyaniline-Dodecylbenzenesulfonate Synthesized via Inverse Emulsion Procedure." Universitätsbibliothek Chemnitz, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200900775.
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Corrosion protection performance of a completely soluble polyaniline-dodecylbenzenesulfonic acid salt (PANI-DBSA) on C45 steel has been studied with electrochemical impedance and potentiodynamic measurements. Chloroform is the most suitable solvent to process the pristine PANI-DBSA because of negligible interaction of the solvent with the polyaniline (PANI) backbone. An anodic shift in the corrosion potential (
E=~70 mV), a decrease in the corrosion current and a significant increase in the charge transfer resistance indicate a significant anti-corrosion performance of the soluble PANI deposited on the protected steel surface. Corrosion protection follows the mechanism of formation of a passive oxide layer on the surface of C45 steel. In situ UV-Vis spectroscopy was used to investigate the differences in permeability of aqueous anions into PANI-DBSA. Preliminary results of electron diffraction studies show that PANI-DBSA possesses an orthorhombic type of crystal structure. An increase in the feed ratio of DBSA to aniline increases the tendency of aggregation of spherical particles of PANI obvious in transmission electron microscopy. PANI-DBSA slowly loses its electrochemical activity in acid free electrolyte without undergoing degradation.
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Baux, Jordan. "Utilisation d'une amine filmante pour la protection des aciers au carbone dans l'industrie nucléaire : apport de la spectroscopie d'impédance électrochimique." Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0128/document.
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La conservation du circuit secondaire des réacteurs à eau sous pression pendant les périodes d’arrêts nécessite la mise en oeuvre de conditions spécifiques afin de limiter les phénomènes de corrosion des aciers au carbone, qui composent en grande majorité ce circuit. Les méthodes de conservation impliquent une mise en oeuvre contraignante et couteuse lors des arrêts de tranche. L’injection d’amines filmantes (AF), en fonctionnement avant les phases d’arrêt, constitue une voie d’étude intéressante afin de protéger les composants en acier au carbone tout en simplifiant la mise en oeuvre de la conservation à l’arrêt. Le but de ce travail de thèse est d’étudier le comportement et l’efficacité d’une AF pour la protection des aciers au carbone dans les conditions représentatives des centrales REP. Pour mener à bien ces travaux, la spectroscopie d’impédance électrochimique a été utilisée en appui à des observations de surface par microscopie optique et microscopie électronique à balayage et à des analyses de surface par spectroscopie de photoelectrons X. Tout d’abord, des films d’AF formés sur un acier au carbone à basse température (80 °C) dans des conditions de dépôts optimisées ont été caractérisés (épaisseur, permittivité) et leurs propriétés inhibitrices de corrosion évaluées en milieu Na2SO4 à pH proche de 10. Cette première étude a permis de valider une méthode de caractérisation des films à travers l’analyse des données d’impédance à haute fréquence. Puis, cette méthode a été utilisée pour suivre et caractériser la formation de films d’AF d’une part, sur de la magnétite électrodéposée dans les conditions de dépôt optimisées, et d’autre part, sur des coupons d’acier au carbone polis dans les conditions thermo-chimiques du circuit secondaire à 120 °C, 220 °C et 275 °C en fixant la concentration en AF en solution à 2 ppm. Les suivis par impédance au cours du temps de l’acier au carbone traité avec l’AF ont permis de tester l’efficacité des films pendant une phase de conservation humide. Les résultats mettent en évidence l’influence des conditions de formation des films d’AF (température, concentration en AF, temps de traitement et nature du substrat) sur leur efficacité contre la corrosion en conservation. D’après nos résultats, seul le traitement réalisé à 120 °C a abouti à la formation d’un film d’AF pour lequel la protection de l’acier au carbone a été confirmé à l’issu d’une conservation humide de 30 jours. Les films formés sur l’acier au carbone nu à basse température ont montré une forte susceptibilité à la désorption au cours du temps, de même que pour les films d’AF déposés à 220 °C, et ce même avec une forte concentration en AF de 25 ppm. Enfin, pour les dépôts effectués à 275 °C, la cause la plus probable de la diminution de l’efficacité contre la corrosion observée entre 2 h et 24 h de traitement viendrait de la dégradation thermique de l’AF, détectée en solution au-delà de 2 h d’exposition à cette températureThe preservation of the secondary circuit of pressurized water reactors during layup periods requires the implementation of specific conditions in order to limit the corrosion phenomena of carbon steels, which constitute the major part of this circuit. These conservation methods are costly and very demanding for the operating. The injection of film-forming amines (FFA), in operation in before shutdown phases, is an interesting route of study to protect carbon steel components while simplifying the conservations. The aim of this thesis work is to study the behavior and the efficiency of an FFA for the protection of carbon steels in the representative conditions of PWRs. To carry out this work, electrochemical impedance spectroscopy was used with surface observations by optical microscopy and scanning electron microscopy and surface analysis by X-ray photoelectron spectroscopy. First, FFA films formed on a carbon steel at low temperature (80 ° C) under optimized deposition conditions were characterized (thickness and permittivity) and their corrosion inhibiting properties evaluated in an Na2SO4 medium at pH close to 10. This study allowed to validate a method for the film characterization through the analysis of the high frequency part of the impedance data. Then, this method was used to follow and characterize the FFA film formation on electrodeposited magnetite in optimized deposition conditions in one hand, and on a carbon steel under the thermo-chemical conditions of the secondary circuit at 120 °C, 220 ° C and 275 °C using FFA concentrations fixed at 2 ppm on the other hand. Impedance monitoring over time of the FFA-treated carbon steel allowed the effectiveness of the films to be followed during humid conservation. The results highlight the influence of FFA film formation conditions (temperature, FFA concentration, treatment time and nature of the substrate) on their efficiency against corrosion during conservation. According to our results, only the treatment at 120 °C resulted in the formation of an FFA film that could protect the carbon steel from corrosion in humid conservation during 30 days. The films formed on bare carbon steel at low temperature showed a high susceptibility to desorption over time, as well as for FFA films deposited at 220 °C, even with a high FFA concentration of 25 ppm. Finally, for FFA deposition made at 275 °C, the decrease of the efficiency against corrosion observed over time would come from the thermal degradation of the FFA, detected in solution beyond 2 hours of exposure to this temperature
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Rodríguez, Paz Martín Cruz. "Contribuição para proteção de distância em linhas compensadas com dispositivos UPFC." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/118882.
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Dispositivos baseados em eletrônica de potência, conhecidos na literatura como Dispositivos FACTS (Flexible AC Transmission Systems) permitem aumentar a capacidade de transmissão diminuindo a margem de segurança necessária para uma operação segura do sistema elétrico de potência (SEP) sem construir novas linhas, permitindo controlar os fluxos nas linhas e assim permitindo que os contratos entre as empresas de transmissão sejam respeitados. Entre os dispositivos FACTS, o de maior versatilidade é o Unified Power Flow Controller (UPFC), capaz de controlar três variáveis do sistema. No entanto, a inclusão desses dispositivos traz outros problemas ao SEP, um deles, a proteção das linhas. Este trabalho apresenta uma contribuição para uma nova formulação matemática, adaptativa e compensada para a proteção de distância baseada na impedância aparente para a proteção de linhas compensadas com dispositivos UPFC. A formulação proposta se baseia em uma modelagem trifásica do sistema e na compensação da impedância aparente calculada através dos parâmetros controlados do UPFC e da estimação da impedância da falta. Resultados obtidos através da simulação exaustiva de faltas, mostram que esta formulação apresenta um excelente desempenho para a proteção de distância de linhas compensadas por dispositivos UPFC.Power electronics-based devices, known as FACTS devices (Flexible Alternating current Transmission Systems) allow to increase transmission capacity by decreasing the safety margin required for a secure operation of the Electric Power System (EPS). It is possible without need to build new lines, allowing to control the flows in lines and thus allowing contracts between the transmission companies are respected. Among the FACTS devices, the most versatile is the Unified Power Flow Controller (UPFC) capable of controlling three variables of the system. However, the inclusion of these devices brings other problems to the EPS, one of them, the transmission lines protection. This Thesis presents a contribution to a new mathematical formulation, adaptive and compensated for the distance protection based on the apparent impedance to protect transmission lines compensated by UPFC devices. The proposed formulation is based on a three-phase frame reference and the compensation of apparent impedance by the UPFC controlled parameters and the estimation of the fault impedance. Results obtained, through the comprehensive simulation of faults, show that it formulation present excellent performance for distance protection of transmission lines compensated by UPFC devices.
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Nguyen, Anh Son. "Avancées récentes sur l'analyse des données d'impédance globale et développement de l'impédance électrochimique locale : application aux revêtements utilisés pour la protection contre la corrosion de l'alliage d'aluminium 2024." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30326/document.
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Ces travaux de thèse ont pour but d'obtenir une meilleure connaissance des mécanismes de dégradation, lors de l'exposition à un milieu agressif, de primaires de peinture en phase aqueuse (époxy-polyamino amide) utilisés dans l'industrie aéronautique pour la protection contre la corrosion de l'alliage d'aluminium 2024 à l'aide des techniques d'impédances globale et locale. Deux revêtements formulés soit avec du chromate de strontium soit avec un mélange de pigments non-chromatés ont été comparés. Les diagrammes d'impédance des deux revêtements, mesurés dans des conditions sèches (en contact avec Hg), présentent un comportement proche de celui d'une capacité pure, et ont été analysés à l'aide du modèle en loi de puissance, qui correspond à un comportement CPE (Constant Phase Element). Lors de l'immersion dans une solution chlorurée, le comportement des revêtements s'écarte progressivement de l'idéalité. Les données d'impédance électrochimique obtenues pour différents temps d'immersion ont été analysées avec un modèle qui suppose une variation exponentielle de la résistivité le long de l'épaisseur du revêtement (modèle de Young). Cette analyse a confirmé que la pénétration de l'eau et des ions dans le revêtement ne se fait pas de façon identique. La vitesse de pénétration de l'eau est plus rapide et celle-ci affecte plus fortement la permittivité que la résistivité, alors que la diffusion des ions Na+ et Cl- est plus lente et affecte exclusivement la résistivité du revêtement. L'utilisation de ces modèles permet non seulement d'expliquer les comportements CPE et pseudo CPE observés sur les diagrammes d'impédance mais aussi de déterminer la prise en eau des revêtements durant le test. Celle-ci est en accord avec des mesures gravimétriques. L'effet d'auto-cicatrisation des deux revêtements en présence de blessures artificielles a ensuite été étudié par spectroscopie d'impédance électrochimique locale. Les diagrammes locaux et les cartographies (2D ou 3D) ont permis de suivre les phénomènes d'auto-cicatrisation pour le système chromaté ou bien le développement de la corrosion pour le système non-chromaté. Ce travail de thèse propose une méthodologie qui servira de référence pour développer et caractériser les performances de peintures contenant des inhibiteurs écologiques et en particulier leur processus d'auto-cicatrisationThe aim of this work is to obtain a better understanding of the degradation mechanisms, as a function of exposition time in an aggressive environment, of commercial coatings (epoxy-polyaminoamide waterborne paint) used in aeronautical industry for corrosion protection of 2024 aluminium alloy by global and local impedance techniques. The coatings formulated with either strontium chromate (SrCrO4) or Cr(VI)-free pigments were compared. The behavior of dry coatings (in contact with Hg) was close to that of an ideal capacitor and could be accurately modelled with the power-law model corresponding to a CPE (Constant Phase Element). Upon immersion in NaCl solution, the behavior of the wet coatings became progressively less ideal, i.e. farther from a capacitive behavior. The impedance data was analyzed with the Young model that take into account the exponential variation of the coating resistivity along its thickness. This analysis confirmed that penetration of water and ions occurs on different time scales. The former process is faster and affects permittivity more strongly than resistivity; the latter is slower and affects almost exclusively resistivity. The models allows to explain not only the CPE or pseudo-CPE behaviors observed on impedance diagrams but also to determine the coatings water uptake during the test which is in good agreement with gravimetric measurements. Then, the self-healing properties of artificially damaged coatings were studied by local electrochemical impedance spectroscopy (LEIS). The local diagrams and the mappings (2D or 3D) allowed self-healing processes for the chromated system or corrosion developments for the unchromated system to be observed. The present work proposed a methodology to develop and to characterize coatings containing environmentally friendly inhibitors, and particularly the self-healing process
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Ziolkowski, Valmir. "Estratégias experimentais para ensaios de faltas fase-terra com alta impedância em sistemas de distribuição de energia elétrica." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-07052007-134218/.
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O conhecimento das características experimentais das faltas de alta impedância é de suma importância para o desenvolvimento de sistemas e equipamentos voltados a detecção eficiente das mesmas em sistemas de distribuição de energia elétrica. Este trabalho apresenta um conjunto de estratégias experimentais que visam orientar passo a passo a realização de ensaios de faltas fase-terra com alta impedância, contemplando-se desde os dispositivos de proteção usados na viabilização dos experimentos até os equipamentos de oscilografias utilizados para registrar as grandezas elétricas advindas dessas situações de faltas. São ainda apresentados os resultados obtidos pelos ensaios realizados de queda de condutor energizado (lado fonte) em solo seco, queda de condutor energizado (lado fonte) em brita seca, queda de condutor energizado sobre a cruzeta e queda de condutor energizado (lado carga) em solo seco.The knowledge of experimental characteristics of high-impedance fault is of highest importance for developing both systems and equipments addressed to its efficient detection in electric power distribution systems. This work presents a set of practical strategies to guide step by step the accomplishment of experiments involving phase-ground faults with high impedance, being also contemplated from protection devices used in the experiments to oscillograph equipments dedicated to register the electric signals produced in those situations. It is still presented the results produced by fault experiments involving drop of energized cable (source side) in dry soil, drop of energized cable (source side) in dry broken stones, drop of energized cable on crossarm and drop of energized cable (load side) in dry soil.
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Wright, J. D. "Impedance studies of water based protective coatings." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386702.
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Trondoli, Luiz Henrique Pessôa da Costa. "Modelo estocástico parametrizável para o estudo de faltas de alta impedância em sistemas de distribuição de energia elétrica." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-22032018-144926/.
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As Faltas de Alta Impedância (FAI) causadas pelo rompimento de um condutor da rede primária podem trazer risco à segurança pessoal e ao patrimônio. A detecção deste defeito se faz, portanto, necessária. Não há na literatura um método que estabeleça a solução definitiva para este problema. Ainda, os estudos, quando não baseados em sinais reais, utilizam, por vezes, modelos determinísticos ou que não representam por completo as características geradas pelo defeito. Por este motivo, este trabalho propõe um modelo de falta de alta impedância que visa representar, com elevado detalhamento, a natureza do evento. O modelo desenvolvido é parametrizável para que possa representar as características dos sinais de falta e suas variações, inclusive as não determinísticas, as quais se referenciam na literatura, reproduzindo o comportamento típico de uma falta de alta impedância. O programa de simulação computacional empregado para este fim foi o ATPDraw. Para a validação do sinal gerado pelo modelo, além da comparação visual com sinais de falta reais, foi elaborado um algoritmo de detecção de FAI, o qual busca por características do fenômeno já conceituadas na literatura, com o propósito de analisar o sinal da corrente de falta gerado pelo modelo quando inserido em um sistema de distribuição de energia elétrica. Foi observada a progressão temporal do fenômeno, desde o rompimento do condutor até a formação dos arcos voltaicos. Do sinal de falta, em síntese, foram observadas características como: assimetria, variação de assimetria, ocorrência de buildup, presença e variação dos componentes harmônicos e inter-harmônicos. A observação dessa variedade de características é necessária na detecção de FAI e é coerente com o modelo proposto, já que este é o único presente na literatura capaz de reproduzi-las simultaneamente. Dos casos de falta simulados, todos foram detectados pelo algoritmo de detecção, indicando que os sinais de falta de alta impedância produzidos pelo modelo possuem as características que ele foi projetado para gerar.High Impedance Faults (HIF) caused by primary conductor rupture can pose personal safety risk and danger to property. Detection of this event is, therefore, required. There is no proposed method in the literature that establishes a decisive solution to this problem. Studies, when not based on real signals, sometimes use deterministic models or models that do not entirely represent the event\'s characteristics. For this reason, this research proposes a high impedance fault model that intend to represent, with high level of details, the nature of this event. The developed model is parametrizable so it can represent fault signal characteristic and its variations, reproducing the typical high impedance fault behavior. The software ATPDraw was used for this purpose. For model\'s behavior and signal validation, in addition to visual comparison with real HIF signals, a detection algorithm was developed, which searches for HIF characteristics presented on literature, with the intent of analyzing the fault current signal generated by the model when inserted on an electrical distribution system. The temporal progression of the event was observed from the conductor rupture until electric arc ignition. From the fault current, characteristics such as: asymmetry, asymmetry variation, buildup, presence and variation of harmonic and inter-harmonic frequencies were analyzed. The evaluation of this variety of characteristics is needed for HIF detection and it only makes sense because the proposed model is the only one presented in literature capable of reproducing of all them simultaneously. All detection tests resulted in positive identification, confirming that the proposed HIF model possesses the intended characteristics.
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Yu, Ronghua. "Impedance-Based Wireless Sensor Network for Metal-Protective Coating Evaluation." Thesis, North Dakota State University, 2011. https://hdl.handle.net/10365/28837.
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Research has focused on the influences of flowing fluid on the corrosion of bare metals, but there is little emphasis on the degradation of metal-protective coating. Evaluating the metal-protective coating usually uses the Electrochemical Impedance Spectroscopy (EIS) method. This paper presents a new impedance-based wireless sensor network for metal-protective coating evaluation. This wireless sensor network consists of two parts: impedance-based wireless sensor nodes and a wireless data base that are equipped with a network analyzer (AD5933) and a RF transceiver (CC1111/CC1110). In the experiment, three coating panels are immersed in flowing deionized water (DI water) and one coating panel immersed in stationary DI water. Experimental results demonstrate that this wireless sensor network is capable of evaluating the coating degradation.
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Ferraz, Rafael da Silva. "Dispositivo para medição de impedância em sistemas de aterramento elétricos em alta frequência." Universidade Federal de Goiás, 2016. http://repositorio.bc.ufg.br/tede/handle/tede/6615.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
This work presents the project and the implementation of a device that is capable of measuring the electrical effects, especially the impedance, in grounding meshes when subjected to atmospherical discharges. An analysis on the influence of the atmospheric discharges in electrical protection systems is performed and also a comparison between current and voltage impulsive circuits. The device is built of electronic circuits controlled by a microcontroller, with the possibility of parameter adjusting for shaping the generated impulse wave. The device was conceived such that it can be used for tests of soil impedance measurement and for verification of the behavior of electrical grounding systems under high frequencies. The results are presented for tests in different types of systems and there was satisfactory performance for the developed equipment when compared with a commercial device
Este trabalho apresenta o projeto e a implementação do dispositivo capaz de medir os efeitos elétricos, em especial, as impedâncias, em malha de aterramento, sujeito a descargas atmosféricas. Analisa-se as influências das descargas atmosféricas nos sistemas de proteção elétricos e desenvolve-se análise comparativa dos circuitos impulsivos de corrente e de tensão. Constrói-se o dispositivo que consiste de circuitos eletrônicos controlados por microcontrolador, com possibilidade de ajuste de parâmetros da onda gerada. O dispositivo produzido é utilizado para medição da impedância do solo e verificação do comportamento de sistemas de aterramento elétrico em baixas e altas frequências. São apresentados os resultados dos testes em diferentes tipos de sistemas, demonstrando o satisfatório desempenho quando comparado com instrumento comercial.
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Fanucchi, Rodrigo Zempulski. "A detecção e a localização de faltas de alta impedância em sistemas de distribuição utilizando transformadas wavelets e redes neurais artificiais." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-14102014-092706/.
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A ocorrência de faltas em sistemas elétricos de distribuição de energia é algo indesejável, porém, inerente ao mesmo devido a sua topologia normalmente aérea. Entre essas faltas, destacam-se as de alta impedância devido às características de corrente de baixa magnitude que surgem quando de sua ocorrência. No presente trabalho, um método baseado em três módulos é apresentado para a detecção e localização de faltas de alta impedância (FAI). No Módulo 1, é realizado um monitoramento contínuo dos sinais de corrente de forma a detectar a ocorrência de uma descontinuidade que pode estar vinculada a ocorrência de uma FAI. Caso haja essa detecção, o Módulo 2 é ativado de forma a analisar se o evento é realmente uma FAI. Por último, depois de detectada a FAI, o Módulo 3 é inicializado e a localização da falta, estimada. Para possibilitar a análise do método proposto e validar os resultados obtidos, um sistema de distribuição real, em conjunto com todas as etapas do sistema de aquisição de dados, foi modelado no software ATP/EMTP. Essa modelagem foi validada a partir de dados reais obtidos quando da ocorrência em campo de um curto-circuito bifásico. Vale ressaltar que um estudo de caso referente à importância da detecção e localização de um evento relacionado a uma FAI em uma concessionária de energia foi também analisado no início do trabalho de forma a mostrar o possível impacto da localização de FAIs nos indicadores de qualidade de serviço na mesma. Pelos resultados observados, a abordagem como um todo se mostra promissora e passível de aplicação no sistema real simulado e avaliado.The occurrence of faults in overhead distribution networks is undesirable but common based on its topology. Among these events, High Impedance Faults (HIF) is one of the most important due to the fact that it has a small magnitude current. In this dissertation, a modular three-phase method is presented to enable HIF´s detection and location in a distribution system. In the Module 1, the phase currents are monitored in order to detect a discontinuity that can be associated with a HIF´s occurrence. If the Module 1 detected a discontinuity, the Module 2 is initiated and it analyses if the event can be classified as a HIF. Finally, if the Module 2 returns the event as a HIF, the Module 3 is initiated and the possible location of the HIF is estimated. To enable analysis of the proposed method and to validate the results, a real-based distribution system and the acquisition system of a digital relay were modeled in ATP/EMTP software. In order to validate the model, a simulated twophase fault were compared with the data obtained in a real event occurred in the analyzed distribution system. In order to present the importance of detecting and locating a HIF to a distribution utility, a case study was developed in the beginning of its work. Its importance is based on the improvement of the service quality indicators. Based on the results, the proposed method seems to be promising and applicable in a real distribution system.
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Gazen, Yuri Neves. "Proteção contra perda de excitação em geradores síncronos: uma nova proposta utilizando o método do cálculo contínuo da impedância aparente." Universidade Federal de Santa Maria, 2015. http://repositorio.ufsm.br/handle/1/8573.
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This work presents a new Loss-of-Excitation in synchronous generators protection scheme based on the Continuous Apparent Impedance Calculation. This methodology aiming to improve security and dependability to the ANSI 40 function in order to distinguish cases of loss of excitation from other external disturbances such as stable power swings caused by the elimination of short circuits, for instance. Traditional loss of excitation protection methods may operate incorrectly in the occurrence of this kind of disturbance. Since the proposed methodology have settings related to the reactance parameters of the protected generator (Xd e X d), tests have been carried out considering two different machines with distinct parameters of the WSCC 9-bus system. Aiming to test the proposed technique and compare it with other widely used methods Mason, Berdy and Positive Offset, three kinds of events were simulated, namely, total loss of excitation, partial loss of excitation and stable power swing, for different initial generator loading. The computer simulation results demonstrate that the proposed method correctly identifies the occurrence of loss-of-excitation and does not operate in situations of stable power swings, regardless of the parameters of generators and their operating condition. Its alarm function allows taking the underexcited machine out faster by using manual intervention, which is especially useful when the initial loading is light or when it‟s a partial loss of excitation case. Another highlight is the ease adjustment of the method, which is related only with the generator‟s reactances data.Este trabalho apresenta um novo método de proteção contra perda de excitação de geradores síncronos fundamentado no Cálculo Contínuo da Impedância Aparente. Este novo conceito visa garantir segurança e disponibilidade para a função de proteção ANSI 40 através da distinção de casos de perda de excitação e outros distúrbios externos ao gerador, tais quais as oscilações estáveis de potência ocorridas após a eliminação de curto-circuitos. As técnicas tradicionais de proteção contra perda de excitação podem apresentar operações indevidas quando da ocorrência de tais distúrbios. Considerando que a metodologia desenvolvida possui ajustes em função dos parâmetros das reatâncias do gerador protegido (Xd e X d), são feitos testes com duas máquinas de parâmetros distintos do sistema WSCC 9-barras. Visando testar a técnica proposta e compará-la com métodos amplamente utilizados Mason, Berdy e Offset Positivo, foram simulados três tipos de eventos, ou seja, perda de excitação total, perda de excitação parcial e oscilação estável de potência, para diferentes pontos operacionais do gerador. Os resultados das simulações computacionais demonstraram que o método proposto identifica corretamente a ocorrência de perda de excitação e não opera em situações de oscilação estável de potência, independentemente dos parâmetros do gerador e de sua condição de operação. A função de alarme permite desligar a máquina subexcitada mais rapidamente através de intervenção manual, o que é especialmente útil quando o carregamento inicial é baixo ou a perda de excitação é parcial. Destaca-se ainda a facilidade de ajuste do método, o qual depende apenas dos dados das reatâncias do gerador.
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Amani, Bouzekri. "Contribution a l'etude des revetements electrodeposes de ni, de zn et d'alliages zn-ni : preparation, porosite, comportement a la corrosion." Caen, 1988. http://www.theses.fr/1988CAEN2031.
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Etude de la porosite des revetements electrolytiques de zn, ni et zn-12% ni par une methode basee sur les mesures du potentiel et de la vitesse de corrosion et par une methode basee sur les mesures d'impedance electrochimique. Comparaison du comportement des differents revetements en milieu neutre et en milieu acide
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Vianna, João Tito Almeida. "Métodos determinísticos para detecção e localização por área de faltas monofásicas de alta impedância sustentadas nos circuitos primários de sistemas de distribuição desequilibrados." Universidade Federal de Juiz de Fora (UFJF), 2016. https://repositorio.ufjf.br/jspui/handle/ufjf/4039.
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O presente trabalho tem por objetivo o desenvolvimento de alternativas para detecção de faltas de alta impedância (HIFs) sustentadas em sistemas de distribuição. Como a maioria destas faltas é monofásica, enfoque foi dado para este tipo de falta no desenvolvimento do trabalho. Devido ao desequilíbrio e a variação da carga dos sistemas de distribuição, a proteção tradicional dos mesmos apresenta dificuldades na detecção destas faltas, que acabam se sustentando no sistema. Isso acarreta um risco de segurança pública, na medida em que estruturas externas ao sistema elétrico são mantidas energizadas representando risco a vidas que entrem em contato com elas. Características da topologia típica de sistemas de distribuição brasileiros (conhecida como do “tipo europeu”) foram exploradas de forma a se elaborar duas propostas de métodos de detecção e localização de HIFs. Ambos os métodos se baseiam na alocação de medidores alocados ao longo do sistema de distribuição, cujas medidas são integradas a uma central de dados via rede de comunicação. Nesta central, as medidas recebidas são analisadas de forma a diagnosticar a presença e localização de faltas monofásicas de alta impedância no sistema e emitir alarmes que descrevam a situação atual do mesmo. O primeiro método, o PDSZ, baseia-se em medições fasoriais sincronizadas e, além da detecção e localização, conta com um algoritmo de classificação das fases envolvidas na falta. Já o segundo (PQDSZ) baseia-se em medições não fasoriais e não possui esta última funcionalidade. Ambos os métodos são implementados em laboratório e simulados com o uso de um Simulador Digital de Tempo Real (RTDS), o que permite uma validação bem próxima da aplicação dos métodos em um sistema real. Tais simulações comprovam a aplicabilidade dos métodos propostos e todos os resultados são analisados de forma a confirmar este fato.
This work aims to develop alternatives for the detection of sustained high impedance faults (HIFs) on distribution power systems. As the majority of these faults are single phase ones, the development was focused on this kind of fault. Due to load unbalance and variation of the distribution systems, the traditional protectiontechniques presents problems on detecting these faults, which are kept sustained on the system. This situation represents a serious public hazard, because the external electrical system structure remains energized, representing a risk to lives that eventually get in touch with it. There is also the risk of starting a fire from this fault point. Topologycal features of Brasilian distribution systems (known as “european type”) were exploited in order to elaborate two methods for detection and localization of HIFs. Both methods are based on the use of meters alocated along the distribution system, whose measurements are sent to a central data concentrator, through a network communication. Then, the received measurements are analysed in order to diagnose the ocurrence of single phase high impedance faults on the system and send alarms that describe the current system situation. The first method, named PDSZ, is based on Phasor Measurement Units (PMUs) and besides detecting and locating the fault, can also classify it, showing which phaseis involved. The second one, the PQDSZ, is based on non-synchronized measurements and can not classify the fault. Both methods were implemented on laboratory and tested using real equipament and a Real Time Digital Simulator (RTDS), which allows a very precise evaluation of the proposed methods, emulating conditions very similar the real ones. The simulations prove the aplicability of the proposed methods and the results are analysed in order to show the effectiveness of the proposed methods.
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Hosbein, Kathryn Nicole. "The Application of Electrochemical Impedance Spectroscopy to Immediately Diagnose the Protective Quality of Coatings on Artistic and Architectural Metalwork." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/3324.
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Corrosion is a spontaneous process that causes irreversible damage to nearly all metals, which has world-wide implications for architectural and artistic metalwork, such as bridges, buildings, airplanes and sculptures. Protective coatings such as wax, paint, or polymeric clear coatings are used to prolong the lifetime of metals such as steel and bronze. Unfortunately, these coatings fail over time due to oxidative damage by UV rays and by failure to exclude water that can carry salts and pollutants that cause corrosion of the underlying substrate. The current method of coating assessment is visual inspection but when coating failure is detected at this stage, irreversible damage has already occurred to the metal substrate. Diagnosing coating quality on artistic metalwork is a unique challenge as it requires a method that is non-destructive as to not alter the aesthetic of the piece. A non-destructive technique or device that can detect early signs of coating failure in the field (such as at a sculpture park) does not currently exist. The aim of this thesis is to develop a method that can be readily used in the field by a conservator to quickly diagnose the protective state of a coating on a sculpture in order to provide localized treatment.
Electrochemical impedance spectroscopy (EIS) is a method currently used to study protective coatings in the lab. The technique itself is non-destructive but the most common electrochemical cell used with it must be used on a planar substrate and requires that a portion of coating be removed. Not only is the current method destructive, but the data produced by EIS is complicated and time consuming to analyze. These issues provide the foundation for this project.
This thesis first proposes multiple methods to quickly analyze the complicated data traditionally collected through EIS. Three quick analysis methods, including the estimation of the derivative at one single frequency in EIS spectra, was successfully used to categorize coating quality of five different coating types. Using this quick analysis can aid conservators in assessing coating condition without the need for extensive training in EIS data interpretation.
This thesis also proposes a method to measure early warning signs of coating degradation through a co-planar hydrogel electrochemical cell paired with EIS. The configuration of this co-planar hydrogel cell negates the need for the removal of the coating and can be used on multiple types of surfaces because of its flexibility, therefore overcoming the drawbacks of the traditional EIS electrochemical cell. Data provided demonstrates that this co-planar hydrogel provides similar information, when compared to the standard electrochemical cell, about the bulk of the protective coating. Unique to the co-planar hydrogel cell, information about surface degradation is provided during EIS measurements. This provides a warning sign before bulk degradation of the coating and therefore before any damage to the underlying substrate has occurred.
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Stimpfling, Thomas. "Modified layered double hydroxide (LDH) platelets as corrosion inhibitors reservoirs dispersed into coating for aluminun alloy 2024." Thesis, Clermont-Ferrand 2, 2011. http://www.theses.fr/2011CLF22169.
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L’alliage d’aluminium 2024 est très répandu dans l’industrie aéronautique et automobile. Le processus de corrosion peut entrainer des dommages irréversibles pouvant engendrer des issues fatales dans le domaine aéronautique. Ainsi plusieurs couches de revêtements sont déposées à la surface du métal à protéger pour prévenir le processus de corrosion. Depuis le début du 20ième siècle, le chrome hexavalent (CrVI) a été largement utilisé comme inhibiteur de corrosion dans les différentes couches du revêtement (prétraitement, primer et top-coat). La toxicité de ce composé envers l’homme et l’environnement a entrainé son interdiction et donc son remplacement comme agent de protection. Le confinement d’agent anticorrosif dans des nano-conteneurs a ainsi été reporté puisqu’un effet auto-réparant, en relargant sur demande, peut-être apporté : l’inhibiteur de corrosion agit quand le dommage apparait. Cette étude est focalisée sur l’utilisation de matériaux de type Hydroxydes Doubles Lamellaires (HDL) comme réservoir d’inhibiteurs de corrosion en raison leur propriété d’échange. Dans ce travail, plusieurs molécules ont été étudiées comme potentiel inhibiteur de corrosion. Celles-ci ont été tout d’abord caractérisées par DC-polarisation afin de déterminer la nature de leur comportement inhibiteur (anodique, cathodique ou les deux). Ensuite, ces agents anticorrosifs ont été intercalés dans des matrices HDL et leur capacité de relargage ainsi que leur comportement face au processus de corrosion ont été étudiés. Les particules HDL ainsi obtenues ont été dispersées dans la formulation d’un revêtement primaire et déposé directement sur l’alliage aluminium 2024. La résistance à la corrosion a été suivie par spectroscopie d’impédance complexe. Les propriétés d’auto-protection de notre revêtement (relargage d’agent anticorrosive encas de dommage) et leur propriété barrière, apportée par la morphologie lamellaire des nano-conteneurs, entrainant une diminution de la perméabilité aux espèces agressives (ex. eau, O2, électrolyte) responsable de l’apparition de cloques sur les revêtements, ont ainsi été caractériséesAluminum alloy 2024 is widely used in aircraft and automotive industry. Corrosion processes can provide irreversible damage on the metal substrate which could have a tragic issue in the aircraft domain. Thus, several coating layers have been applied on the metal substrate to prevent corrosion process. Since the beginning of the 20th century, hexavalent chromate compounds have been extensively used as corrosion inhibitor agents for paint, primer and conversion coating. The toxicity for human health and environment has led to replace such compounds. The literature has reported different possibilities to replace such unfriendly compounds. Moreover, the entrapment of corrosion inhibitors in nanocontainer provides a self-healing effect by releasing, on demand, the active species when damage occurs. This study focuses on Layered Double Hydroxide (LDH) material as reservoir due to its exchange properties. This study has characterized several potential corrosion inhibitor molecules by DC-Polarization to determine the nature of the inhibitor compound (i.e. anodic, cathodic or both of them). Further, active anticorrosive species have been intercalated into LDH framework. Then, the release of inhibitor agents and their subsequent behaviour toward corrosion inhibition have been evaluated. Modified LDH materials have been further dispersed in the primer coating formulation and applied on aluminum alloys 2024 substrate. Corrosion inhibition has been followed by electrochemical impedance spectroscopy experiments on scratched and unscratched panel which have permitted to evaluate the self-healing property of these modified LDH materials when damage occurs and the barrier property provided by the lamellar morphology of the inorganic reservoir that is found to decrease the permeation by enhancing the tortuosity of the coating layer towards aggressive species (i.e. water, O2, electrolyte) responsible of the blistering phenomenon
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Mahajanam, Sudhakar P. V. "Application of hydrotalcites as corrosion-inhibiting pigments in organic coatings." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1123787459.
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Hlaváč, Štěpán. "Vysokofrekvenční měřič výkonu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220258.
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This master’s thesis describes various principles of measurement of electromagnetic waves in a free space and on a line. Used sensors and their real parameters are given for every method. The analysis of protections of high-frequency inputs of measuring instruments is done here and the most suitable method and protections of input for realization are chosen. The analysis of design of secondary protection of high-frequency input is done in this project. The protection of input is realized and measured. The suitable method of measurement is chosen as well as the sensor for measurement of power. The block diagram and circuit diagram of the meter of power are designed. According to designed conception the measuring instrument for measurement of power is realized and its single qualities are measured during the realization. In the final part its precision is measured and the evaluation of results is done.
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Gregores, Guilherme Buzon. "Efeitos hemodinâmicos de duas estratégias de ventilação mecânica protetora em um modelo suíno de Síndrome do Desconforto Respiratório Agudo." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/10/10132/tde-03042012-154729/.
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A Síndrome do Desconforto Respiratório Agudo (SDRA) cursa com insuficiência respiratória e necessidade de ventilação mecânica invasiva (VMI). A mortalidade desta síndrome é elevada, mas pode ser reduzida com o uso de estratégias protetoras de ventilação mecânica que usam baixo de volume corrente (VC), geralmente 6ml/Kg ou menos, para minimizar a lesão causada pelo ventilador. Algumas destas estratégias de ventilação protetora utilizam valores elevados de PEEP que podem produzir instabilidade hemodinâmica. O objetivo deste estudo foi comparar, em um modelo experimental suíno de SDRA, os efeitos hemodinâmicos causados por duas estratégias de ventilação mecânica protetora: uma que utiliza PEEP ajustado pela Tomografia de Impedância Elétrica (OLA) e a outra, a mais comumente utilizada na prática clínica (ARDSNET), em que a PEEP é ajustada através de uma tabela. Foram utilizados 17 animais após randomização (8 no grupo OLA; 9 no grupo ARDSNET) que foram ventilados por 42 horas. As variáveis foram analisadas utilizando ANOVA de medidas repetidas. Antes da radomização, os grupos não apresentavam diferenças nos parâmetros hemodinâmicos e respiratórios. Considerando o período de 42 horas de estudo: 1) o grupo OLA utilizou valores maiores de PEEP, obteve uma melhor oxigenação, mas com valores de PaCO2 mais elevado; não houve diferença entre os grupos para o platô de pressão, mas o delta de pressão foi menor no grupo OLA o que pode minimizar o risco de lesão pulmonar induzida pelo ventilador; 2) o grupo OLA apresentou valores de índice cardíaco (IC) menores durante o estudo, mas não houve um comprometimento aos órgãos alvos conforme pode ser constatado pelos valores normais do lactato arterial e pelos valores de saturação do sangue venoso misto maiores do que no grupo ARDSNET; 3) pela análise de regressão múltipla pode se observar que o aumento da PEEP esteve associado com aumento da pressão média de artéria pulmonar (PMAP), mas redução do IC e da pressão arterial média, enquanto que o aumento da PaCO2 esteve associado com um aumento da PMAP e do IC. Concluímos que uma estratégia ventilatória protetora para SDRA cujo ajuste de PEEP é guiado por TIE, quando comparada com outra estratégia protetora comumente utilizada na prática clínica por um período de 42 horas, determina uso de valores maiores de PEEP, o que melhora a oxigenação e minimiza o delta de pressão, mas causa redução do IC que não resulta em isquemia tecidual.The Acute Respiratory Distress Syndrome (ARDS) is associated with respiratory failure and need for invasive mechanical ventilation (IMV). The mortality of this syndrome is high, but can be reduced with the use of protective strategies of mechanical ventilation using low tidal volume (VT), usually 6ml/Kg or less, to minimize the damage caused by the ventilator. Some of these strategies of protective ventilation use high levels of PEEP that can produce hemodynamic instability. The aim of this study was to compare, in an experimental pig model of ARDS, the hemodynamic effects caused by two strategies of protective ventilation: one strategy adjusts PEEP values using Electrical Impedance Tomography (EIT-OLA) and the other, the most commonly used in clinical practice (ARDSNET), in which PEEP is adjusted through a table. Seventeen animals were randomized (8 in OLA group; 9 in ARDSNET group) that were ventilated for 42 hours. The variables were analyzed using repeated measures ANOVA. Before randomization, the groups had no difference in hemodynamic and respiratory parameters. Considering the period of 42 hours of study: 1) OLA group used higher values of PEEP, had a better oxygenation but with higher values of PaCO2; there was no difference between groups for the plateau pressure, but the delta pressure was lower in OLA group which can minimize the risk for ventilator-induced lung injury; 2) the OLA group showed lower values of cardiac index (CI) during the study, but there was no damage to target organs as showed by normal blood lactate values and values of mixed venous blood saturation greater than in ARDSNET; 3) multiple regression analysis revealed that, increasing PEEP was associated with increasing in mean pulmonary artery pressure (MPAP), but reduction CI and mean arterial pressure, while increasing in PaCO2 was associated with an increase in MPAP and CI. We conclude that a protective ventilatory strategy for ARDS whose setting of PEEP is guided by EIT, when compared with other protective strategy commonly used in clinical practice for a period of 42 hours requires the use of higher values of PEEP, which improves oxygenation and minimizes delta pressure, but causes reduction of CI that does not result in tissue ischemia.
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Rodriguez, Alvaro A. "Corrosion inhibition mechanism of a surfactant admixture on carbon steel alloy ASTM A36 [UNS K02600] coated with a high performance UV-cured coating." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1460564870.
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Chen, Chun-Kai, and 陳俊凱. "Application of High Impedance Surface Structures in Electromagnetic Protection." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/80241647440337479028.
Full textAbstract:
碩士國立雲林科技大學
電機工程系碩士班
100
In recent years, wireless products have been vigorously developed. Mobile internet is more and more popular, and smartphones are ubiquitous. To avoid complex wired networking, more and more wireless local area networks (WLANs) are being devised in metropolitan areas. However, when wireless products are used, the associated EM radiation could seriously damage human bodies. Avoiding EM radiation hazard is hence an important research topic in the area of electromagnetic compatibility (EMC). This thesis investigates how an electromagnetic protection sheet, which is a high-impedance surface (HIS) structure, is combined with a cellphone antenna to reduce the EM radiation toward the user holding the cellphone. The electromagnetic simulator Ansoft HFSS was used to explore the characteristics of a standalone HIS and the HIS combined with a cellphone antenna. The properties of the HIS were also verified using an in-house arch horn antenna measurement system. We designed an HIS to be combined with a monopole antenna for the GSM (1.8 GHz) system. Various characteristics, such as the reflection coefficient, radiation pattern, total radiated power (TRP), horizon radiated power (HRP), and near-horizon partial radiated power (NHPRP), of the antenna backed by the HIS have been explored. We hope that electromagnetic protection sheets can improve the quality of mobile communications and reduce the impact of electromagnetic damage to human bodies. In addition, we established a human head model to investigate whether an HIS-added antenna can meet the regulated specific absorption rate (SAR) limit. Also, we used this human head model to analyze the effect of the human head on the antenna performance. Finally, in order to demonstrate the usefulness of the HIS, we compared the performance of the HIS-added antenna with that of the antenna backed by a different protection sheet, such as the M71 RF absorber, 5-Ohm R-card, and 131-Ohm R-card.
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Wu, Lixuan. "Adaptive impedance relay for the protection of series compensated lines." 1995. http://hdl.handle.net/1993/19045.
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CHEN, YEN-LI, and 陳彥禮. "Development of anti-islanding protection method based on impedance measurement." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/e8jkf8.
Full textAbstract:
碩士明志科技大學
電機工程系碩士班
106
Most of distributed generations (DG) are intermittent energy sources. DG can provide the stable electrical energy when it is connected to a grid. DG must be able to detect the islanding event while connecting to the grid. The circuit breaker of DG side must immediately trip to prevent the damage to workers or equipments when DG is subject to islanding event. An anti-islanding protection method of the intermittent-disturbance hybrid impedance estimation is developed for the islanding protection scheme in this thesis. The DG output terminal voltage and current signals were measured to estimate the impedance of a frequency based on Fourier transform. A running sum DFT, RS-DFT, method has been published in the literature for reducing the calculating time. A moving window DFT, MW-DFT, is developed in this thesis to further improve the calculating time of RS-DFT. The non-detection zone, NDZ, of passive method is derived with the DG and the grid currents, and the constraint on the 0.5Ω impedance variation in EN 50330-1. When the system falls into the NDZ, the intermittent-disturbance active method will be used to detecte the islanding. An 80Hz noncharacteristic harmonic of the active method is added to the system at the abc frame in place of 0dq frame to overcome the disadvantage of derivating another disturbance frequency. The simulations and experiments are carried out by Matlab/Simulink and actual circuit to alternately verify the accuracy of the results. The NDZ of passive method under various quality factor of local loads were found out in this thesis, and both continuous and intermittent noncharacteristic harmonic frequency are added to the power system to evaluate the influence on power quality. Final, the proposed method compares with reactive power variation (RPV) method in the performances by following the islanding operation part of IEEE 1547.1. The experiential results show that the proposed method can quickly trip circuit breaker of inverter side comparison with RPV, which comfirms the superior of the proposed method.