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Thermal aging and ultraviolet (UV) irradiation are used as methods to prepare samples of kraft paper spanning its full lifecycle within a high-voltage transformer, from new to end of life. The mechanical break strain is correlated with the degree of polymerization (DP), representing a progressive deterioration of mechanical properties during aging. Subsequent exposure to oil flow mimicking both normal plant operation and reclamation activities shows that aged paper exposed to high rates of flow experiences noticeable surface roughening. Despite this, no measurable erosion occurs even after long-term temperature/flow cycling in used mineral oil containing a notable particulate content. This indicates that kraft paper is unlikely to be eroded by normal reclamation activities, even in a severely aged asset. This confirms the validity of using this approach to extend plant life. [ABSTRACT FROM AUTHOR]

Viscometric Degree of Polymerization (DPv or DP for short) is a well-established method used in the transformer industry to track degradation of the paper insulation used inside transformers. The DP method works well for both new, unprocessed paper, and for aged paper. But in recent years it has become an established fact that there are unclear issues related to measurements of DP on new paper after factory drying. This phenomenon has been observed for different paper types, paper dried using different drying methods, different types of pulp and measurements made at different laboratories. Cigré has recently published a reference paper on the subject [1], written by experts from different transformer manufacturers, paper manufacturers, independent laboratories and utilities. It is further noted in Cigré brochure 738 (WG D1.53) that at times, new paper after factory drying does not dissolve well in the Cuen solution used for DP measurement. This difficulty introduces tremendous uncertainties in the average DP numbers reported by laboratories for such papers. In this article we seek to shed some light on this problem and its effect on reported DP values. [ABSTRACT FROM AUTHOR]

In this study, a flexible capacitive pressure sensor based on filter paper substrate is proposed. The electric double layer (EDL) structure was constructed through the introduction of ionic liquid (IL), and the pressure-sensing was realized by using the change of ion-electron interface contact. The paper-based iontronic pressure sensor possesses a high sensitivity of 221.9 kPa−1, which is hundreds of times higher than that of the capacitive pressure sensors with conventional parallel plate structure, as well as an ultra-low detection limit of 2 Pa. The sensor exhibits an enormous application potential in healthcare wearable electronics and human-machine interface equipment. [ABSTRACT FROM AUTHOR]

The total/partial oil change treatment can affect the furfural partitioning in oil-paper-pressboard insulation, resulting in poor accuracy of furfural analysis. Moreover, due to the high cost of total oil change, partial oil change is more practical during transformer operation. This paper investigates the furfural partitioning in the oil-paper-pressboard insulation under partial oil change conditions. First, the initial furfural partitioning equation with non-oil change is proposed based on the obtained furfural content in oil, paper, and pressboard. Then, the modified furfural partitioning model under partial oil change condition is established by introducing a correction factor. Moreover, a preliminary correction scheme for the furfural partitioning model considering the influence of moisture and acid is provided. Finally, furfural content in oil-Kraft paper and oil-thermally upgraded Kraft (TUK) paper insulation are discussed, and results indicate that the proposed modified furfural partitioning model is not suitable for the oil-TUK paper insulation. This work can provide theoretical support for furfural analysis of oil-immersed transformers. [ABSTRACT FROM AUTHOR]

The intent of this work is to evaluate the influence of cellulose insulation paper on gassing tendency of transformer oil under electrical discharge conditions. For comprehensive enumeration, insulation oil was thermally stressed at 115°C as per ASTM D 1934 with a controlled thermal aging history. The thermally aged oils were considered for gassing tendency evaluation as per ASTM D 6180 (5 hours, 10 kV AC) in the presence of cellulose. Different cellulose Kraft paper proportions including 0, 10, 20, and 30% of aged oil were introduced in to discharge cell. Different cellulose proportions and aging conditions were considered to understand the impact of cellulose while understanding the decomposition aspects of insulation. Diagnostic measurements with those including dissolved gas analysis, moisture, interfacial tension, turbidity, dissolved decay contents, acidity, and dissipation factor were performed before and after gassing tendency evaluation. It was found that, cellulose paper aids significantly in increasing dissolved gases and moisture in oil during electrical discharge. Importantly, diagnostic measurements have shown the ability of paper to absorb certain decomposition products during the discharge process. [ABSTRACT FROM AUTHOR]

The thermal index for thermally upgraded Kraft paper was determined for a series of five mineral insulating liquids and two natural esters using IEEE Standard C57.100 Annex A.4.2 and compared with the values in IEEE Standard C57.91. [ABSTRACT FROM AUTHOR]

The vast majority of power transformers have an insulation system consisting of both insulating mineral oil and Kraft paper. The principal oil degradation agents are oxygen and temperature, whereas the main mechanisms of insulating Kraft paper degradation are water and acids (acidic hydrolysis degradation), temperature (pyrolytic degradation), and oxygen (oxidative degradation). [ABSTRACT FROM AUTHOR]

In this paper, a method of aging diagnosis under different oil-paper ratios is proposed by investigating the accelerated thermal aging data with different oil-paper ratios. Aged oil-paper insulation samples with oil-paper ratios of 10:1, 15:1 and 20:1 are obtained by accelerated thermal aging tests. The Raman spectra of the transformer oil samples are measured by a Raman spectrometer, and screened by random forest algorithm to extract the features. A modified model is established to correcting the features of the aged oil samples under the conditions of 15:1 and 20:1 oil-paper ratio to features under the condition of 10:1 oil-paper ratio. An grid search optimized support vector machine (SVM) classification model is established, and verified by the corrected features. The experimental results show that the proposed method can effectively identify the aging of oil-paper insulation with different oil-paper ratios. [ABSTRACT FROM AUTHOR]

Origami structures held promise for their flexibility, simultaneous responsiveness, and adaptability, yet they are vulnerable due to the hygroscopic property when exposed to the humid environments. However, the patterning of hydrophobic material along the design enhances the controllability of paper for self-folding to robotics locomotion. The capillary action of sprayed water molecules is localized through the number or sizes of hydrophilic channels defined by the printed wax patterns resulting in large deformation to form various 3D geometries. The patterned paper performed folding actuation with water and unfolding behavior with evaporation without being mechanically manipulated by external forces or moments. The paper actuators further enable the sequential self-folding along the multiple hinges for the cube and diamond structures. Advances in soft robotics for practical applications, the utilization of different swelling/shrinking properties with water and kirigami-inspired programmable structures interact with the lightweight and non-planar objects. The anisotropic properties of paper in response to water spraying combined with folding/unfolding deformations permit the fold-to-pop-up robots for biomimetic locomotion on the plane or water. Two robots deform their body to move forward through bending-relaxation gait. [2020-0083] [ABSTRACT FROM AUTHOR]

We report our recent progress in quantitative aging assessment of the oil-impregnated-paper (OIP) equipment (i.e., degree of polymerization, DP) by near infrared spectroscopy (NIRS). The NIRS database is built by incorporating 8 types of insulating paper and total 478 differently aged samples. We propose an improved PCA-RBF-NN model to address the nonlinear correlation between DP of insulating paper and spectra, and hence strengthening the prediction accuracy for field assessment. In the improved model, the principle component analysis (PCA) and the filtering layer are two essential procedures for eliminating the noises and unrelated information from the spectra. The field practices show that the improved PCA-RBF-NN model owns better performance than the classic PLS model and general RBF-NN model on the disassembled bushing (RMSE: 56 vs 109 vs 124) and transformer (RMSE: 50 vs 237 vs 244), respectively. The NIRS powered by the improved algorithm can provide a rapid solution to the aging condition assessment of the OIP power equipment in the field. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the physicochemical properties of rice oil, peanut oil, corn oil and Kraft paper immersed in these oils in the presence of antioxidants (butylated hydroxytoluene, tertiary butyl hydroquinone and Naugalube¯ 750). The experiments are performed on new and aged conditions. Ageing of oils is carried at 115 °C for 96 hours while Kraft paper is aged in oils at 130 °C for 164 hours. Both closed and open cup methods are used for ageing. The results show that ageing insignificantly affects the breakdown voltage, but markedly increases the acid number and the viscosity of the vegetable oils. The combination of tertiary butyl hydroquinone and either butylated hydroxytoluene or Naugalube¯ 750 slightly increases the breakdown voltage, but significantly raises the oxidation stability of the vegetable oils. This results in a reduction in the viscosity and the acid number of the vegetable oils. Moisture significantly affects the breakdown voltage of both vegetable and mineral oil. High moisture content results in low breakdown voltage. The results also show that ageing insignificantly affects the breakdown voltage, but markedly decreases the tensile strength of oil-impregnated paper. Although the presence of antioxidants does not increase the breakdown voltage of aged paper, these additives slow down the ageing process. This results in an increase in tensile strength of the paper. [ABSTRACT FROM AUTHOR]

The long-term operation of dry-type transformer bushings at high temperatures can impact the performance of their primary insulation material. This article presents an experimental study of the effect of thermal aging time on electrical treeing in the epoxy resin-impregnated paper. The experimental results show that the electrical treeing pattern along the middle path of the electric field and the interlayer creepage along the average direction of the electric field are closely related to the aging time. Under the effect of thermal aging at 150 °C, the tree-starting voltage of epoxy resin-impregnated paper tends to increase and decrease as the aging time increases. An analysis and discussion of the test results in conjunction with scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) tests suggest that the destruction of the cross-linked network of the epoxy resin-impregnated paper at 150 °C is a fundamental reason for the significant decrease in the material’s tree-starting voltage and the change in electrical treeing morphology and interlayer creepage. Long-term operation at high temperatures can seriously impact the primary insulation performance of dry-type transformer bushings and requires attention. [ABSTRACT FROM AUTHOR]

This paper investigates the behavior of interface charges between oil and oil immersed paper insulations in unaged and aged samples. Combined accelerated thermal and electrical aging experiments of oil immersed paper insulations are conducted to obtain aged oil and aged paper samples. The interface charges between oil and paper samples with different aging status are measured with the Pulsed Electro-acoustic (PEA) method. Zeta potentials in samples with different aging status are determined. It is shown that the amount of interface charge increases with the aging duration, and does not follow the prediction of Maxwell-Wagner-Sillars (MWS) law. This is explained in terms of the increase of the interface charge barrier due to the effect of electric double layer. It is proposed that interface charge may act as an optional characterization parameter for the assessment of oil immersed paper insulations. [ABSTRACT FROM AUTHOR]

The performance of oil-impregnated paper significantly affects the safety and reliability of transformers. Previous studies on water reducing the breakdown strength of oil-impregnated paper have been mainly due to increasing charge carriers and conductivity. However, the influence of water on the cellulose crystal structure of oil-impregnated paper is still not clear; in particular, its role on breakdown strength remains ambiguous. In this study, the AC breakdown strength and crystal structure of vegetable and mineral oil-impregnated paper with different moisture contents were investigated. The results show that with increasing moisture content, the cellulose crystallinity and crystal size increases linearly, while the breakdown strength decreases. The breakdown strength of vegetable oil-impregnated paper is higher than that of mineral oil-impregnated paper and is less affected by moisture. Herein, a model is proposed on the effects of water on the crystal structure of oil-impregnated paper and the correlation of breakdown strength with crystal structure is reported. [ABSTRACT FROM AUTHOR]

Vegetal oils are considered a suitable substitute for mineral oil that is widely used in power transformers as insulation and cooling medium. Due to the fact that more and more power transformers containing this alternative insulating fluid are being constructed a mathematical ageing models is needed to help predict transformer failures. The continued performance of power transformers depends on the condition of its paper insulation mainly. In this sense, this paper analyses Kraft paper degradation through the loss of its mechanical strength. Accelerated thermal ageing test of the paper in two different vegetal oils were carried out at three temperatures during diverse periods of time, in order to obtain information on the kinetics of the ageing degradation of the paper. The evolution of the mechanical properties of paper failure are analysed as a function of temperature and ageing time. In addition, the results obtained are compared with the traditional method of degradation analysis, based on the measurement of the degree of polymerisation. [ABSTRACT FROM AUTHOR]

The life expectancy of a transformer is closely related to the ageing state of its paper insulation. This paper presents novel markers for ageing characterization of paper insulation in oil-filled transformers based on the dispersion staining colors of cellulose fibres. Accelerated thermal ageing experiments were performed for oil-paper specimens at 120 and 130 °C to obtain aged oil-paper samples of different ageing degrees. The average degree of polymerization (DP), crystallinity index, and refractive index of insulation paper were measured; the experimental results show that an increase in refractive index of insulation paper was observed with the increase of ageing degree. Meanwhile, the dispersion staining colors of cellulose fibres in oil were observed using dispersion staining method; the experimental results show that the refractive index of cellulose fibres detached from insulation paper increases with the increment of ageing degree of insulation paper. Finally, two ageing markers—that is, the primary color ratio-based ratio of blue to red and the primary color ratio-based Mahalanobis distance were presented. Their relationship with DP and ageing time of insulation paper were obtained, and were compared with the corresponding relationship with 2-furaldehyde (2-FAL) and carbon oxides. The proposed ageing markers demonstrate an advantage over 2-FAL and carbon oxides and show potential in ageing state evaluation and residual life prediction of paper insulation in transformers. [ABSTRACT FROM AUTHOR]

In recent years, the establishment of a substantial amount of academic groups on scientific social network has brought new opportunities for the collaboration among researchers. In this situation, conducting paper recommendation to these academic groups is of terrific necessity in that it can further facilitate group activities. However, when producing group recommendation, existing methods fail to make full use of the abundant group information, from which a great deal of valuable information can be inferred to facilitate the recommendation performance. In addition, those methods tend to assign an equal weight to each group member when aggregating their recommendations, which is unreasonable in practice. Although some improvements have been made to remedy this problem by assigning different weights to group members, they fail to take into account the reliabilities of group members. Therefore, a group-oriented paper recommendation method based on probabilistic matrix factorization and evidential reasoning (GPMF_ER) is proposed in this article to tackle these problems. More specifically, the group and paper content information are integrated into the probabilistic matrix factorization model to enhance the accuracy of individual recommendation. Afterward, evidential reasoning rule is introduced in the aggregation step to consider both the weights and reliabilities of group members. Extensive experiments have been conducted on the real world CiteULike dataset and the results demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The generation and distribution of furfural are significantly affected by moisture content in the insulating paper. However, the diffusion mechanism of furfural under moisture effect is not clear, hence, this study investigates the effect of moisture on the diffusion characteristics of furfural by combining macro experiment and micro molecular dynamics simulation. The simulation results demonstrate that the increased moisture content in paper accelerates the diffusion of furfural from paper to oil, which is also proved by the experimental data. Then, the results of interaction energy analysis indicate that the increase of moisture enhances the van der Waals force between oil and furfural. The present findings are expected to improve the theoretical level of furfural analysis, which will facilitate the aging evaluation of the transformer insulating paper based on furfural. [ABSTRACT FROM AUTHOR]

This paper presents an investigation of the underlying mechanism behind the interface charge barrier between oil and oil immersed paper. Two types of oils and two types of cellulose papers are selected in the study. The interface charges of the samples are measured by the pulsed electro-acoustic (PEA) method and the zeta potentials of different oil-paper combinations are also measured. The results show that the amount of interface charge changes with the type of oils and papers, and is much larger than the Maxwell-Wagner-Sillars (MWS) polarization charge. The difference in the amount of interface charges cannot be attributed to the difference in the conductivity and permittivity of the materials. It is suggested that the barrier for charge transport across the interface, which is formed due to the electric double layer, should be taken into consideration to explain the interface charge behavior in oil-paper insulation. [ABSTRACT FROM AUTHOR]

The application of vibration-based condition monitoring methods to power transformers has shown the potential for detecting mechanical transformer failures. The ageing of winding insulation paper, which is a common problem in long-serving power transformers, affects both the electrical and mechanical strength of the windings. This paper is concerned with the vibration features of winding disks with aged insulation paper. The vibration characteristics of single-layer winding disks wrapped with insulation paper are investigated. By examining the vibration frequency responses of winding disks with different degrees of ageing of insulation paper, the effects of aged paper on the vibration behaviors of winding disks are demonstrated. The experimental results show that changes in the vibration responses of winding disks can be related to the ageing of insulation paper, and thus it is possible to detect this failure mode in a power transformer using a vibration-based method. A qualitative explanation for these changes is presented, using the degradation of the mechanical strength of the insulation paper. [ABSTRACT FROM AUTHOR]

We report on investigation of the mechanical properties of paper electronics (printed and made out of paper). One key objective of such paper electronics is to achieve ultraflexibility. Therefore, it is important to understand electrical functionality and reliability of paper electronics under various physical (mechanical) deformations. Here, we show the general mechanical properties of the cellulose paper used and its electrical behavior under applied strain, tackling the main effects that need to be identified when building paper-based systems, from product performance and stability perspective. An overview of the stress–strain behavior of silver ink on paper is discussed, and then, we tackle a more specific analysis of the performance variations of paper sensors made with recyclable household materials when exposed to various mechanical conditions of tensile and compressive bending. This paper is important for developing stable wearable sensors for incorporation into Internet of Everything applications. [ABSTRACT FROM PUBLISHER]

This paper focuses on the in-depth analysis of the physical mechanism of the broadband frequency domain spectroscopy of oil-paper insulation. The complex permittivity shows two low-frequency dispersion phenomena, and the real part of the complex conductivity exhibits two slope changes under the synergistic effect of aging and moisture. The two slope changes are mainly attributed to the migration characteristics of water molecules and polar aging products with a degradation of the oil-paper insulation, resulting in the transition of the frequency dependence between the DC conductivity and AC conductivity. When the oil-paper insulation deteriorates seriously, the imaginary part of the dielectric modulus shows double relaxation peaks. Physical models of parasitic capacitance and molecular polarity interface polarization are proposed to reveal the physical mechanism of the double relaxation peaks. The left peak of the double relaxation peaks is caused by the accumulation of water molecules and polar aging products at the electrode/insulation interface, and the right peak is due to the charge disturbance of the cellulose molecular chain surface. This paper can provide theoretical support and technical guidance for the condition diagnosis and evaluation of oil-paper insulation. [ABSTRACT FROM AUTHOR]

For extra-high-voltage high-temperature superconducting (HTS) cables, not only high electrical insulation performance but also low dielectric loss is required. Therefore, we focus on a porous synthetic paper with lower dielectric loss, e.g., Tyvek polyethylene nonwoven fabric, than that of polypropylene laminated paper (PPLP), which has been used for a conventional HTS cable insulation system. In this paper, we compare partial discharge inception characteristics for different liquid nitrogen/synthetic paper composite insulation systems. The partial discharge inception electric field strength in the composite insulation system depends on the electric field strength in the porous area of synthetic paper. [ABSTRACT FROM AUTHOR]

Numbers of citations of outstanding conference papers (OCPs) of IEEE Nuclear and Space Radiation Effects Conferences (NSRECs) from 1966 to 2017 are compared with citations of the most highly cited papers (HCPs) of the corresponding special issues of the IEEE TRANSACTIONS ON NUCLEAR SCIENCE (TNS), as well as average numbers of citations and cumulative $h$ index, $h_{\mathrm {cum}}$ , for all TNS papers published in the same year. 85% of NSREC OCPs are cited at a higher rate than the average for all TNS articles in that year. 55% of NSREC OCP citation totals are higher than $h_{\mathrm {cum}}$ for TNS in that year; these rank among the ~8% most highly cited TNS papers for that year. In ~10% of cases, the NSREC OCP is also the most HCP. Similarly high citation impact is found for papers nominated as candidates for OCPs. Radiation effects papers published in annual NSREC special issues comprise a significant fraction of all TNS articles cited $h_{\mathrm {cum}}$ times or more. These results support the use of $h_{\mathrm {cum}}$ as a metric of citation impact in this work and show that the NSREC OCP process generally meets awards criteria guidelines for impact. Potential reasons for variations in citation rates are discussed, and recommendations are provided to enhance the awards process. [ABSTRACT FROM AUTHOR]

Background: Although some have noted that combining technical and marketing content is precarious, technical communication professionals are increasingly involved in content marketing, which includes the creation of white papers. Literature review: The little existing literature on white papers provides conflicting guidance about managing the combination of technical and marketing content. Both soft-sell and hard-sell marketing approaches have been recommended. One source of such inconsistent guidance may be the lack of agreement about definitions. Research on print advertisements has described hard and soft selling as multidimensional rather than binary aspects of persuasive appeals. Research question: Which dimensions of hard- and soft-sell appeals are predominant in white papers? Research methodology: To complete our descriptive study, we collected a corpus of documents labeled as white papers in TechRepublic, and then selected and trained three raters to complete a series of judgments about dimensions of persuasive appeals in the corpus. We aggregated those ratings, calculating the mean and standard deviation for the dimensions to describe their distribution across the corpus. Results/discussion: Overall, hard-sell dimensions were more prevalent than soft-sell dimensions. However, the soft-sell category of “implicitness” was also dominant. Conclusion: Our results demonstrate the value of treating hard and soft selling as multidimensional, complementary, and combinatory marketing appeals that allow, for example, a single white paper to be both “subjective” (soft sell), and “precise” (hard sell), or both “creative” (soft sell) and “informative” (hard sell). [ABSTRACT FROM AUTHOR]

The mechanical performance of two commercial papers used as solid insulation in power transformers, namely standard Kraft and a thermally upgraded Kraft paper, were studied during accelerated aging in Luminol oil at 170 ?C. The results show a relationship between the degree of polymerization and the mechanical properties measured by tensile testing. A linear relationship was found between the mechanical properties of paper, the tensile index (Tidx), and the concentration of methanol present in the oil. The methanol chemical marker has been proven to be an accurate assessment tool for the aging of cellulosic paper. The results show a promising tool for correlating the methanol concentration in oil, as an indirect indicator, with the mechanical performance of the paper. This approach can be used to monitor the real state of the cellulose chains in the power transformer insulation paper. [ABSTRACT FROM AUTHOR]

Furfural content in oil is widely accepted as an effective parameter to mirror aging of insulation paper. However, pressboards are also abundant in transformers, which are always neglected in furfural analysis. Different masses of insulation paper and pressboard produce different amounts of furfural during the aging process. Thus, the furfural content in oil may differ in systems with different oil-paper-pressboard mass ratios. To address this problem, accelerated thermal aging experiments and furfural equilibrium experiments with different oil-paper-pressboard mass ratio systems were conducted under laboratory conditions. Furfural contents in oil, paper, and pressboard were measured. In a simplified oil-paper system, the furfural content in oil differs in systems with different oil-paper mass ratios. Further analysis shows the furfural amount produced by 1 g insulation paper is the same with good repeatability in groups with different mass ratios. Different oil-paper mass ratios change the distribution coefficient of furfural between oil and paper, and an increase in the mass of insulation paper leads to more furfural remaining in the insulation paper. The pressboards in field transformers produce little furfural during the aging process, but absorb part of the furfural from oil, which decreases the furfural content in oil. Therefore, more pressboard in an oil-paper-pressboard system indicates lower furfural content in oil. An increase in insulation paper in the oil-paper-pressboard system causes a decrease in the effect of pressboard on furfural content in oil. [ABSTRACT FROM AUTHOR]

Recent studies have reported that thermal aging of insulation paper affects its moisture absorption property, which can affect moisture equilibrium in oil-paper insulation. In engineering practice, Fessler's model is one of the most widely used methods to estimate the moisture content of paper through measurement of moisture content of oil. However, this model lacks consideration of the thermal aging effect on equilibrium moisture. This study comprehensively investigated the effect of thermal aging on moisture equilibrium in oil-paper insulation. Based on the accelerated ageing and moisture measurements, the equilibrium moisture content of insulation paper with different aging and temperatures were obtained. The effects of aging condition and the temperature on equilibrium moisture are discussed and Fessler's model was modified accordingly. The results show that: 1) the decreasing of specific surface area is the dominant factor that affects the moisture equilibrium in oil-paper insulation, which is caused by thermal aging; 2) the modified Fessler model is reasonable and suitable to estimate the equilibrium moisture content of insulation paper with different aging. [ABSTRACT FROM AUTHOR]

Methanol is considered to be a new chemical marker to estimate the aging state of transformer cellulose insulation paper. The key to improve the assessment accuracy is to establish the precise relationship between the concentration of methanol in oil and degree of polymerization (DP) of insulation paper. The previous research in this area has shortcomings and needs to be further improved. In this article, first, an aging assessment basic model (temperature 20 °C, moisture content of insulation paper 0.637%) is established based on the theoretical derivation of cellulose degradation kinetics, and is calculated by 130 °C thermal aging experiment. Furthermore, the effects of different temperatures (20 °C–90 °C) and moisture contents of insulation paper (0.6%–3.4%) on methanol in oil are studied by diffusion experiment. Based on the above effects, the temperature and moisture correction factors are established by mathematical reduction. What is more, a modified model is proposed by integrating the basic model and the correction factors. Eventually, the verification experiment is randomly prepared to test the accuracy of modified model and the result shows that the relative error of DP is within 7%. The physical meaning and accuracy of aging assessment are improved by model derivation and modification of influencing factors. [ABSTRACT FROM AUTHOR]

The space charge effect of transformer insulating paper will distort its internal electric field, and its space charge effect will be more prominent under extremely complex working conditions. At present, the micromechanism of charge transport and electric field distortion characteristics of paperboard are not clear under complex working conditions. So in this article, based on the bipolar carrier transport (BCT) model and the dynamic carrier balance model, the effects of high temperature, aging degree, moisture content, and bent degree on charges accumulation in paperboard are studied under dc high voltage by numerical simulation and the measured data needed for simulation. The results show that the higher temperature strengthens the carrier migration, deepens the injection depth of the charge, and aggravates the distortion of electric field intensity in paperboard. The more extended the aging time of paperboard, the greater the internal trap density and the deeper the trap depth, which lead to charges migration difficultly. Increasing water content in the paperboard will accelerate space charges to reach a steady state, while further increasing it will slow down this process, which is related to the shallow trap getting deeper. When the critical part of paperboard is extruded, many traps are introduced, resulting in charges accumulation seriously. The research results can reference the design of paperboard and the maintenance of transformer insulation system. [ABSTRACT FROM AUTHOR]

A growing body of evidence suggests that the ethanol dissolved in the oil can be used as an indicator to effectively monitor the aging behavior of insulating paper. In this study, thermal aging experiments are performed on oil-paper systems with different initial moisture contents and aging temperatures, and then a gas chromatography-mass spectrometer equipped with an automatic headspace sampler is used to test the ethanol contents of the oil samples. The variations and correlations of ethanol contents with temperature, moisture and aging degree are analyzed. The experimental results show that the ethanol contents in oil had a strong correlation with temperature, and is also affected by the cellulose hydrolysis. In addition, a preliminary lifespan assessment of the oil-paper systems under laboratory conditions is conducted by establishing the relationship between ethanol and the degree of polymerization. Then, the time-temperature superposition method is applied to the relationship, and a lifespan model with any temperature is determined according to the ethanol kinetic equation. Based on the model, further observation of the fitting parameters in the case of the two moisture contents (0.8%, 2.3%), the goodness of fit reached higher values of 0.961 and 0.973, respectively. The results of this promising model can help us to a better understanding of ethanol indicator to condition assessment for the transformer paper insulation. [ABSTRACT FROM AUTHOR]

It is well established that copper sulfide is formed due to reaction of sulfur with copper conductors in transformers and reactors. However, there is very little experimental evidence to demonstrate copper sulfide diffusion into bulk of paper. Diffusion experiments have been carried out on three samples of kraft paper having different thickness. Positron Annihilation Lifetime Spectroscopy has been used to investigate the possibilities of copper sulfide diffusion into bulk of paper. This study has demonstrated that copper sulfide can diffuse into the bulk of paper leading to either increase or decrease in free volume of paper. The reasons for changes in free volume of paper due to copper sulfide deposits are explained. The consequences of copper sulfide diffusion on PD, voltage-current characteristics under ac and volume resistivity are discussed. Electric field simulation has been used to explain the effects of Cu ions and copper sulfide formation on electric stress distribution across paper. [ABSTRACT FROM AUTHOR]

Measuring the furan concentration in transformer oil is one of the most common methods of monitoring and evaluating insulation paper and estimating its degree of polymerization (DP). Here, methods for measuring furan concentration, especially ultraviolet-visible (UV-Vis) spectroscopy method, are reviewed on the old transformers oil. The results show that the excessive turbidity of old oils and noise at low wavelengths are the main disadvantages of this method, which reduce the measurements accuracy. The following solutions are proposed to overcome these disadvantages: 1) diluting insulation oil with hexane to reduce absorption intensity and 2) using average absorption at a given wavelength to reduce noise impact. These solutions are applied to the oil samples of ten old distribution transformer. It is observed that the correlation between 2-furaldehyde (2-FAL) concentration and average absorption intensity in 190–600 nm wavelength range is equal to ${R}^{{2}} =0.98$. A mathematical equation for calculating 2-FAL concentration based on average absorption is presented. It has been shown that to reduce the test time, a 190–400 nm range is the optimal measurement wavelength range. The results show that the average difference between the values of DP in the proposed method and the direct measurement method is equal to 77.5. [ABSTRACT FROM AUTHOR]

The ecological environment is increasingly damaged due to the impact of mineral oil extraction and leakage. As a kind of sustainable resource, a vegetable oil transformer has bright application prospects in future. However, the stability of vegetable oil has always been a problem to be solved. In addition, the metallic copper inside the transformer has a certain catalytic effect on the deterioration of vegetable oil. In this article, a copper–oil–paper insulation model is established. Based on the molecular dynamics simulation method, the catalytic mechanism of copper on the deterioration of oil-paper insulation is revealed from the microscopic level. Then, the effects of temperature, contact area, and oxygen on the catalytic effect of copper are discussed. The results show that copper could accelerate the decomposition of oil-paper insulation by attracting H atoms and O atoms in oil-paper. The increase in temperature accelerates the progress of the catalytic reaction and aggravates the deterioration of oil-paper insulation. The oxygen concentration has an important influence on the catalytic reaction of copper. As the oxygen concentration increases, the catalytic effect of copper is weakened. The abovementioned research could provide some theoretical reference for further exploration of effective oil-paper insulation deterioration protection technology. [ABSTRACT FROM AUTHOR]

A Midwestern pulp and paper mill had arc-flash ratings around 100 cal/cm2 on 50 480-V unit substations. New relays were installed to replace the existing protection and add light detection to improve arc-flash detection times. During a couple of one-day outages, sample installations took place. During the cold mill outage, 44 installations were completed over 12 days by working around the clock. Old relays were removed, new plates were mounted and wired in, and fiber sensors were routed through the buswork and into the breaker cubicles. Updated arc-flash studies show an average arc-flash rating reduction of 90%. [ABSTRACT FROM AUTHOR]

It is now possible to detect dangerous arcing faults in the paper insulation of transformers and distinguish them from arcing faults in oil, using new sub-zones of Duval Pentagons 1 and 2. [ABSTRACT FROM AUTHOR]

Presents the recipients of the ITS 2018-2020 George N. Saridis Best Transactions Paper Award and the 2010-2019 Top 10 Research Papers and Top 5 Survey Papers of IEEE Transactions on Intelligent Transportation Systems. [ABSTRACT FROM AUTHOR]

Objective: Early stage diagnosis of sepsis without overburdening health services is essential to improving patient outcomes. Methods: A fast and simple-to-use platform that combines an integrated circuit with paper microfluidics for simultaneous detection of multiple-metabolites appropriate for diagnostics was presented. Paper based sensors are a primary candidate for widespread deployment of diagnostic or test devices. However, the majority of devices today use a simple paper strip to detect a single marker using the reflectance of light. However, for many diseases such as sepsis, one biomarker is not sufficient to make a unique diagnosis. In this work multiple measurements are made on patterned paper simultaneously. Using laser ablation to fabricate microfluidic channels on paper provides a flexible and direct approach for mass manufacture of disposable paper strips. A reusable photodiode array on a complementary metal oxide semiconductor chip is used as the transducer. Results: The system measures changes in optical absorbance in the paper to achieve a cost-effective and easily implemented system that is capable of multiple simultaneous assays. Potential sepsis metabolite biomarkers glucose and lactate have been studied and quantified with the platform, achieving sensitivity within the physiological range in human serum. Conclusion: We have detailed a disposable paper-based CMOS photodiode sensor platform for real-time simultaneous detection of metabolites for diseases such as sepsis. Significance: A combination of a low-cost paper strip with microfluidic channels and a sensitive CMOS photodiode sensor array makes our platform a robust portable and inexpensive biosensing device for multiple diagnostic tests in many different applications. [ABSTRACT FROM AUTHOR]

This paper investigates the aging properties of oil-paper insulation under thermocorona discharge. The oil-paper insulation samples were heated and kept at 140°C, and a corona discharge was generated with a needle-plate at a frequency of 15 times/day, with each discharge lasting 5 minutes. The aging properties of oil-paper insulation were investigated by measuring the degree of polymerization (DP) of insulation paper samples along with the furfural content and acid value of the transformer oil samples. The results show that corona discharge at 140°C in oil rapidly decreased the insulation paper DP and increased the furfural content and acid value of the oil compared with thermal aging and corona discharge aging at 20°C. The DP of the insulation paper was reduced to 392.12, the furfural content in oil rose to 33.75 mg/L, and the acid value grew to 4.41 mgKOH/g after 15 days under the combined thermal stress and corona discharge. Both electric and thermal stress accelerated the aging of oil-paper insulation. This research has practical significance for understanding the process of insulation failure caused by the accelerated aging of oil-paper insulation. [ABSTRACT FROM AUTHOR]

It is known that 1,2,3 benzotriazole (BTA) can effectively limit the oil flow electrification in oil–paper insulation used in HVAC transformers, but it is still unclear whether BTA is applicable to converter transformers. Thus, the effects of BTA on interface charge behaviors and charge migration in oil–paper system under dc stress are investigated in this article. The experimental results show that BTA reduces the interface barrier between oil and oil-immersed paper by altering the charge distribution of the electric double layer (EDL) at the oil–paper interface, which is beneficial to the operation stability of converter transformers in the condition of polarity inversion. However, it is also found that the BTA additive promotes the charge accumulation at oil–paper interface and enhances the local electric field by increasing the carrier mobility of oil–paper insulation. The experimental results in this article provide references for the selection of insulating oil additives for converter transformers. [ABSTRACT FROM AUTHOR]

Diagnosis of aging of the paper insulation in transformers has long been of interest to transformer manufacturers and utilities [1]-[3]. Such insulation is irreversibly aged during long-term operation, losing its mechanical strength and becoming brittle. The loss of mechanical strength is an important factor limiting the life expectancy of the transformer [4], [5]. Consequently diagnosis of aging and evaluation of residual life of paper insulation is important for the safe operation, condition-based maintenance, and replacement of power transformers [6]-[9]. [ABSTRACT FROM AUTHOR]

Furfural content in oil has been shown to be a powerful indicator of the deterioration of cellulose paper. The furfural content in oil may increase greatly when the moisture content increases in transformers. The increase of furfural content in oil can be attributed to various factors, such as aging of cellulose paper with the increase of moisture content and the difference in furfural production mechanism. In this research, thermal aging tests of oil-paper system with different moisture contents are conducted under laboratory conditions to determine the cause of such increase. Furfural content, both in insulation oil and in insulation paper, and the degree of polymerization values of insulation paper were regularly measured. Results show that the moisture content plays a significant role on the production of furfural, and the high initial moisture content in insulation paper leads to large amount of furfural produced when DP decreases to the same values. The difference in the moisture content apparently affects the distribution of furfural between oil and paper, and the increase in the moisture content in oil-paper system increases the diffusion of furfural from the insulation paper to the oil. [ABSTRACT FROM AUTHOR]

The paper presents the results of investigations on the thermal properties of cellulose and aramid paper impregnated with various liquid insulations. The liquid insulations investigated were mineral oil, synthetic ester, and natural ester. The heat transfer coefficient of the liquid was calculated on the basis of measurements of the thermal expansion, specific heat, density, thermal conductivity and kinematic viscosity of the liquid insulations. Temperatures in the paper and liquid insulations were calculated. The results allow to select the best paper and liquid insulations which provide the most effective cooling in transformers. [ABSTRACT FROM AUTHOR]