Fault analysis of oil-filled power transformers using spectroscopy techniques

The condition monitoring and fault diagnosis of power transformers plays a significant role in the safe, stable and reliable operation of the whole power system. Dissolved gas analysis (DGA) methods are widely used for fault diagnosis, however, their accuracy is limited by the selection of DGA features and the performance of fault diagnosis models, for example, the classical support vector machine (SVM), is easily affected by unbalanced training samples. This paper presents a transformer fault diagnosis model based on chemical reaction optimization and a twin support vector machine. Twin support vector machines (TWSVMs) are used as classifiers for solving problems involving unbalanced and insufficient samples. Restricted Boltzmann machines (RBMs) are used for data preprocessing to ensure the effective identification of feature parameters and improve the efficiency and accuracy of fault diagnosis. The chemical reaction optimization (CRO) algorithm is used to optimize TWSVM parameters to select the optimal training parameters. The cross-validation (CV) method is used to ensure the reliability and generalization ability of the diagnostic model. Finally, the validity of the model is verified using real fault samples and random testing.

Wine authentication is vital in identifying malpractice and fraud, and various physical and chemical analytical techniques have been employed for this purpose. Besides wet chemistry, these include chromatography, isotopic ratio mass spectrometry, optical spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy, which have been applied in recent years in combination with chemometric approaches. For many years, 2 H NMR spectroscopy was the method of choice and achieved official recognition in the detection of sugar addition to grape products. Recently, 1 H NMR spectroscopy, a simpler and faster method (in terms of sample preparation), has gathered more and more attention in wine analysis, even if it still lacks official recognition. This technique makes targeted quantitative determination of wine ingredients and nontargeted detection of the metabolomic fingerprint of a wine sample possible. This review summarizes the possibilities and limitations of 1 H NMR spectroscopy in analytical wine authentication, by reviewing its applications as reported in the literature. Examples of commercial and open-source solutions combining NMR spectroscopy and chemometrics are also examined herein, together with its opportunities of becoming an official method.

The Food and Drug Administration recently approved a fixed dose combination of aspirin and omeprazole that has been introduced for the treatment of gastrointestinal disorders, as it reduces the risk of upper gastrointestinal and cardiovascular adverse events in aspirin-treated patients. Therefore, an optimized eco-friendly, simple, fast, and precise quantitative nuclear magnetic resonance spectroscopy technique was presented for the concurrent estimation of that mixture in their single and combined dosage forms. The quantitative nuclear magnetic resonance spectroscopy concurrent estimation of both drugs was achieved using phloroglucinol as the internal standard and dimethyl sulfoxide as a deuterated solvent. An ideal set of acquisition parameters was determined to be 128 scans, 10 s relaxation latency, and 90° pulse angle. The selected quantitative signal of aspirin was the doublet of doublet signal appeared at 7.945 ppm, while that of omeprazole was the singlet signal at 8.18 ppm. The singlet signal at 5.69 ppm was selected for the internal standard. The spectra were subjected to integration, baseline correction, and auto phase correction. The developed quantitative proton nuclear magnetic resonance spectroscopy method was found to be rectilinear over the range of 0.05–4.0 mg mL−1 for both drugs. The detecting and quantifying limits for both drugs were approximately 0.01 and 0.03 mg mL−1, respectively. Neither labelling nor pretreatment steps were needed to assay the studied drugs using our developed quantitative nuclear magnetic resonance spectroscopy method. The proposed nuclear magnetic resonance spectroscopy approach was effectively evaluated in terms of linearity (r = 0.9999), accuracy, and precision (%RSD < 1.08). Furthermore, the suggested technique was investigated to analyze the studied drugs in their single and combined dosages. This work enables clinicians to simultaneously monitor aspirin and omeprazole levels in both single and fixed-dose combination tablets, ensuring precise dosing and effective treatment management. For patients, it supports safer therapy by reducing the risks associated with improper dosing or drug interactions in combination therapies. After evaluating the method's greenness, whiteness and blueness, it was determined that the suggested approach was environmentally friendly. The suggested approach was compared with the previously reported methods from both an analytical and eco-friendly perspective.

A nuclear magnetic resonance advance. Imaging fluorinated anesthetics in the brain.

A series of accelerated aging tests of high voltage transformer oil from Karamay of China were completed. All the oil samples were processed by dehydration and degasification firstly, and added with different contents of oxygen and copper, then aged under 120degC in different periods up to 675 hours, which is equal to 30 years on service of transformer oil. Improved mini-static tester was adopted to measure the electrostatic charging tendency (ECT), meanwhile, other traditional parameters, such as dissipation factor, volume resistivity, acid number, were also measured according to standard methods. The results indicate that ECT increases with aging time obviously, addition of copper advances the process of accelerated aging and leads to saturated period occurred in the late part of the aging (450 h-675 h). It can be found from mathematic analysis that correlation between ECT and dissipation factor is positive and the highest. These results are valuable for the life evaluation and condition monitoring of large power transformers.

Detailed knowledge of the structure of bio molecules with atomic resolution is essential for the understanding of their function. Moreover the identification and quantification of their dynamic processes are important, as they are the origin of molecular functionalities. Different spectroscopic methods like X-ray crystallography (limited to structure elucidation, no dynamics), mass spectroscopy, electron spin resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopy can deliver this detailed structural information. Especially NMR spectroscopy has found its application in the identification of dynamic processes. This thesis was focused on the characterization of dynamic processes, the structure elucidation of natural products available in nanograms and the synthesis of lanthanide chelating tags for the study of protein-ligand and protein-protein interactions in solution. The thesis is divided into three chapters addressing a specific task of the mentioned topic. A: The influences of different donors and linkers on lanthanide chelating tags were investigated. A 4S-Tetramethylcyclen was used as enantiomerically pure core molecule. The side chains were based on enantiopure lactic acid derivatives. The carboxylic acids of lactic acid were transformed into different functional groups like thiols, nitrogens, and carbonyl. These different donor groups are expected to change the magnetic susceptibility tensor of the lanthanide cation in complex with the synthesized tags. Special protection protocols for the introduction of heteroatoms are presented. On this basis also two new linkers were introduced. These linkers bind in a selective way to cysteins on a protein surface as thioethers. The alpha-bromoketones are very selective for the coupling to cysteins, nevertheless they have a tendency to hydrolyse under Lewis acidic conditions. Vinylsulfones require harsher tagging conditions but they are much more stable against hydrolysis. All new tags were attached to proteins and tested as PCS reagents in protein NMR spectroscopy. B: The effects of para-substituents on the rotation barrier of 2,2«-propyl and 2,2«-butyl-bridged biphenyls were studied by dynamic NMR spectroscopy and dynamic HPLC measurements. Gibbs free activation energies of the rotation about the central biphenyl bond were estimated by variable temperature 1H-NMR experiments for the propyl bridged biphenyl. The resulting data were correlated to Hammett-parameters ?P as a measure of electron donor and acceptor strength. It was demonstrated that the electronic effects influence the activation barrier significantly, whereas sterics had only minor influence. Rate constants were calculated from line shape analysis and analysed by Eyring plots to calculate the entropic and enthalpic contributions. Thermodynamic data for the butyl-bridged biphenyls were directly obtained from dynamic HPLC chromatograms. DFT calculations delivered different transition states for the two series of biphenyls. The calculation of the activation parameters showed a similar trend and therefore the model is validated. The differences in the enthalpic and entropic contributions between HPLC, NMR and DFT calculations are method dependent, which was proven by changes of the solvent in NMR experiments that led to alteration of these contributions. C: The identification and total synthesis of a novel methylated lipid antigen (mLPA) was performed. The presented mLPA shows potent inhibition properties against human leukaemia. A combination of extraction protocols, activation essays and HPLC-MS measurements were used to identify the different antigen molecules from cell extracts. Three different candidates were identified. MS-MS experiments delivered structural insights, which were further confirmed by NMR spectroscopy and allowed the characterization of two of these structures. Total syntheses of the identified structures were performed in 6 linear steps. The high biological activity of the synthesized structures corroborated the identity of the active molecule.

— Transformer oil is very important because it functions as a coolant and also as an insulator. In transformer oil there are dissolved gases that can cause failure of the transformer due to gas failure (fault gas). This research was conducted to determine the condition of transformer oil by analyzing the results of the Dissolved Gas Analysis (DGA) test. The DGA (Dissolved Gas Analysis) test is used to determine the type of failure in a transformer that has been operating for years. The DGA test is carried out by monitoring fault gases such as H2, CH4, CO, CO2, C2H4, C2H6, C2H2, O2, N2 and O2N2 which generally cannot be detected in testing the characteristics of transformer oil. Based on the test results using the Total Dissolve Gas Analysis (TDCG) method condition 1 with the amount of flammable gas 202.845 ppm with the interpretation that the transformer can operate normally. The test results using the Roger's Ratio method on the Power Transformer 1 GI Kotabumi obtained codes 0 0 0. From the combination of the 3 codes above, it shows that the transformer oil is in good condition. The results of the test using the Key Gas method on Power Transformer 1 GI Kotabumi obtained a CO value of 56% caused by overheating of cellulose or overheating of solid insulation in the transformer but that value is still far from the threshold&#x0D; Keywords— Dissolved Gas Analysis (DGA),Transformer oil, Roger'r ratio method, KeyGas

A power transformer outage has a dramatic financial consequence not only for electric power systems utilities but also for interconnected customers. The service reliability of this important asset largely depends upon the condition of the oil-paper insulation. Therefore, by keeping the qualities of oil-paper insulation system in pristine condition, the maintenance planners can reduce the decline rate of internal faults. Accurate diagnostic methods for analyzing the condition of transformers are therefore essential. Currently, there are various electrical and physicochemical diagnostic techniques available for insulation condition monitoring of power transformers. This paper is aimed at the description, analysis and interpretation of modern physicochemical diagnostics techniques for assessing insulation condition in aged transformers. Since fields and laboratory experiences have shown that transformer oil contains about 70% of diagnostic information, the physicochemical analyses of oil samples can therefore be extremely useful in monitoring the condition of power transformers.

This article presents evolving neural nets (ENNs) for protection and condition monitoring of power transformer. Based on the proposed evolutionary algorithm, the ENNs automatically tune the network parameters (connection weights and bias terms) of the neural nets to achieve the best model. The ENNs can identify, classify and detect the fault and issue the trip signal in the case of internal fault only, using the global search capabilities of the evolutionary algorithm and the highly nonlinear mapping nature of the neural nets. The proposed protection scheme has been realized through two different structures using ENNs algorithm. This scheme has been evaluated using simulated data obtained through EMTP/ATP package. The results amply demonstrate the capabilities of fault detector (FD) and condition monitoring (CM) in terms of accuracy and speed with respect to detection of fault, classification and pattern recognition of different event of power transformer.

Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful analytical techniques available to biology. This review is an introduction to the potential of this method and is aimed at readers who have little or no experience in acquiring or analyzing NMR spectra. We focus on spectroscopic applications of the magnetic resonance effect, rather than imaging ones, and explain how various aspects of the NMR phenomenon make it a versatile tool with which to address a number of biological problems. Using detailed examples, we discuss the use of (1) H NMR spectroscopy in mixture analysis and metabolomics, the use of (13) C NMR spectroscopy in tracking isotopomers and determining the flux through metabolic pathways ('fluxomics') and the use of (31) P NMR spectroscopy in monitoring ATP generation and intracellular pH homeotasis in vivo. Further examples demonstrate how NMR spectroscopy can be used to probe the physical environment of a cell by measuring diffusion and the tumbling rates of individual metabolites and how it can determine macromolecular structures by measuring the bonds and distances which separate individual atoms. We finish by outlining some of the key challenges which remain in NMR spectroscopy and we highlight how recent advances-such as increased magnet field strengths, cryogenic cooling, microprobes and hyperpolarisation-are opening new avenues for today's biological NMR spectroscopists.

A nuclear magnetic resonance spectroscopic method is presented for the determination of hydroxyl values in mixtures of organic compounds. A nine-fold enhancement of sensitivity is obtained by the formation of trimethylsilyl derivatives, which makes the method especially useful for the determination of low hydroxyl values. The method can be applied to the rapid determination of the hydroxyl values of fatty acids, esters, polymerised fatty acids, polyesters, tertiary alcohols and certain phenols. O-Nitrophenols and highly hindered phenols fail to give correct results, as do hydroxy-compounds of low relative molecular mass, which give volatile trimethylsilyl derivatives. Epoxides and non-enolised ketones do not interfere in the determination. Certain shortcomings of methods for the determination of hydroxyl values based on acetylation and differential titration are discussed.

Protein-ligand interactions lie at the heart of most biological and medical processes. To lay the groundwork for a mechanistic understanding of complex biological networks, a detailed description of the associated proteins, their roles, and their interaction partners is essential. Furthermore, a detailed description of protein-ligand interactions is of pharmaceutical interest, as small molecules targeting proteins constitute the basis for the treatment of numerous medical conditions. In this thesis, we used nuclear magnetic resonance (NMR) spectroscopy to probe the conformational properties of biologically and pharmaceutically essential proteins, either alone or complexed with small molecules, to reveal the mechanistic grounds of these interactions. The first chapter entails the structural investigation of Tumor necrosis factor-alpha (TNFα) by NMR spectroscopy. TNFα is a homotrimeric protein that enjoys tremendous scientific and pharmaceutical interest due to its pivotal role in the human immune response. However, its overexpression leads to numerous chronic inflammatory diseases. Studying the interaction between TNFα and small molecular inhibitors is thus of utmost importance if better cures for these diseases are to be found. Here, we investigated active and inhibited forms of TNFα in solution by NMR spectroscopy and showed that TNFα exhibits significant conformational exchange, especially in the receptor binding site and the trimer interface, which is crucial for its biological activity. Inhibition of TNFα by perturbing the trimer interface, either by mutagenesis or by targeting it with small molecules, does not lead to disruption of the postulated trimer in solution. Instead, it induces a significant increase in the conformational dynamics of TNFα propagating from the trimer interface to the receptor-binding site. Therefore, we propose that an allosteric dynamic coupling between the trimer interface and the active site mediates inhibition. This provides novel insights into the mechanisms of TNFα inhibition, which in turn may lead to the development of better-suited drug assays against this highly important molecule. The second chapter presents the study of alpha acid glycoprotein-1 (AGP1) by NMR. The heavily glycosylated AGP1 is one of the two most abundant human serum proteins and binds various metabolites as well as, perhaps most interestingly from a pharmaceutical perspective, many administered drugs. Understanding the interaction between AGP1 and small molecules on a molecular level in addition to revealing the yet unclear impact of the appended glycans in this process is thus of great importance - as drug binding to plasma proteins modulates their pharmacokinetics and pharmacodynamics. In this thesis, efficient protocols were developed which enabled us to shed light on the influence of glycosylation on the structure of AGP1 and to characterize its ligand binding at a level of detail which had not yet been achieved. We showed that glycosylation affects the protein conformation in the vicinity of the glycosylation site, and provide evidence for a conformational rearrangement upon binding of small molecules. By giving these novel insights, our results contribute to the functional understanding of AGP1 and more broadly to the relatively unexplored class of glycoproteins. The third chapter discusses the combination of our measured NMR data (presented in chapters one and two) with DNA-encoded chemical libraries (DECL) in drug discovery. DECL allows for the efficient identification of potential small molecule binders, while our concomitant NMR data provide the framework for assisting both the validation of ‘hits’ and the optimization process. We could confirm interactions between TNFα or AGP1 and binders identified by DECL. Here, the first application of this approach for drug discovery for TNFα and AGP1 is presented. In summary, our study contributes to a better understanding of two highly relevant proteins: AGP1 and TNFα. The data presented provides original insights into the inhibition mechanisms of small molecules and revealed the importance of conformational dynamics in these processes. Finally, our results will add a new aspect to the complex process of rational drug development, which will ultimately benefit many patients affected by diverse medical conditions.

An important part of Lyocell fibers production is solvent recycling. Determining the content of the degradation products in the solvent will be helpful to select a reasonable solvent recovery process. However, a suitable method to simultaneously measure N-methylmorpholine-N-oxide and its main degradation products N-methylmorpholine and morpholine has not yet been reported, hence in this paper, a nuclear magnetic resonance spectroscopy method for quantitative analysis of N-methylmorpholine-N-oxide and its major degradation products was established. The feasibility of this nuclear magnetic resonance method was verified by using it to determine the contents of N-methyl morpholine-N-oxide, N-methylmorpholine, and morpholine in analytical samples and actual sample.

The aldol condensation reaction is one of the many synthesis reactions carried out in second semester organic chemistry laboratories. This reaction was integrated into a novel experiment requiring students to synthesize dibenzalacetone derivatives using the crossed-aldol condensation by reacting different types of benzaldehyde derivatives with acetone, followed by analyzing those products using spectrometric and spectroscopic methods, especially gas chromatography–mass spectrometry (GC–MS). The main objective of this 2 week lab experiment compared to other procedures in the literature was the analysis of the final aldol product using GC–MS methods rather than solely nuclear magnetic resonance (NMR) spectroscopic methods. During the first week’s 3 h laboratory period, students completed the reaction with a known benzaldehyde derivative and acetone to synthesize their aldol product. In the second week, students calculated the percent yield of their product, determined the product’s melting point range, and analyzed the product by thin-layer chromatography, NMR, and GC–MS methods. Students also strengthened their skills of spectral interpretation using NMR spectroscopy, especially distortionless enhancement by polarization transfer NMR, an NMR technique rarely covered in undergraduate organic laboratory sections. Students spent more classroom time during week two, analyzing GC–MS data. Students were shown how to use molecular model kits to understand the fragmentation of compounds in the mass spectrum. As a result, the students who performed this experiment increased their general knowledge of GC–MS spectrometric techniques, including identification of compounds based on their fragmentation pattern.

Chapter 1 of this thesis provides an overview of the structure and function of proteins as well as their investigation via NMR spectroscopy. Proteins are one of the most important building blocks of life. They are part of every organism and fulfill a variety of functions including, for example, the catalysis of many chemical reactions, which is the reason various processes in an organism become possible in the first place. Proteins are made up of amino acids, which are linked together via peptide bonds during the protein biosynthesis. The 22 proteinogenic amino acids result in an almost unlimited number of sequential combinations that give proteins their versatility. The sequence of amino acids in a protein is also called the primary structure. From this, locally limited structural motifs such as α-helices and β-sheets are formed, representing the secondary structure. Further intramolecular interactions create the tertiary structure of a protein, which can be seen as the overall three-dimensional structure of the protein. Furthermore, several individual proteins can assemble into a larger complex to form a quaternary structure. There are various methods for investigating the structure of proteins, including nuclear magnetic resonance (NMR) spectroscopy. In NMR spectroscopy, atomic nuclei with a non-zero nuclear spin are polarized by a constant magnetic field and then excited using radio frequency pulses. The emitted resonance frequencies are detected in the form of a free induction decay (FID) and converted into an NMR spectrum by a Fourier transformation. Many NMR experiments are available for researching proteins. By default, a two-dimensional 1H15N-HSQC spectrum is measured, which provides signals for each N-H bond in a protein meaning that one signal is obtained for each N-H in the backbone of the amino acids. Using 3D NMR experiments, these signals can then be assigned to the respective amino acids in the protein sequence. This makes it possible to investigate the dynamics of proteins as well as the formation of complexes with a ligand or another biomacromolecule if they interact. Further 3D NMR experiments also make it possible to assign the side-chains of the protein. With the help of the determined resonance assignments and spatial information from various NOESY spectra, a protein structure can then be calculated using a suitable computer program. Recently, the prediction of protein structures using AI (artificial intelligence)-supported programs has also become more prevalent. In particular, the artificial neural network AlphaFold has been extremely successful in predicting correct structures without any experimental data provided by the user. Chapter 2 of this thesis introduces the research field of small proteins. These are proteins with a length of usually less than 100 amino acids, although definitions in literature vary and upper limits of, for example, 50 or 200 amino acids exist as well. Various other names are also used to describe small proteins, such as μ-proteins or sORF-encoded peptides. The field of small proteins is still relatively new, as they were overlooked in research for many years. One reason for this was the lower limit of 100 codons that was set for the identification of open reading frames (ORFs) in genome projects. This served to exclude numerous biologically irrelevant ORFs from genome annotation. However, this meant that functional ORFs coding for small proteins were also ignored. Another reason was that experimental methods were not designed for the analysis of small proteins, meaning they could often not be detected at all. However, new analytical methods such as ribosome profiling and a generally increased focus on the detection of small proteins have led to their detection in all domains of life. In the research group of Prof. Dr. Schwalbe, small proteins of various prokaryotes were structurally characterized as part of a special priority program by the DFG. NMR spectroscopy was primarily used for this purpose, as it is the method of choice for the investigation of small proteins. The results of this research were published in several articles, two of which are part of this dissertation.