Thermally Accelerated Aging of Insulation Paper for Transformers with Different Insulating Liquids

The article presents issues related to the aging behavior of oil-paper insulations in transformers using different oil-and ester-based insulating fluids. Despite numerous conducted studies on the subject of oil-paper aging, the use of new insulating fluids is creating open questions. In addition, new liquids such as synthetic and natural esters, as well as oil of the newest generation, are being used. Furthermore, there is still little research on the formation of aging markers with this form of the dielectric. For this reason, in this contribution, oil-paper insulations with mineral oil-based insulating fluids, natural and synthetic esters, as well as oil from natural gas, are aged thermally accelerated at 130◦C over a duration of 15 weeks, by considering two cases of free-breathing and hermetically sealed transformers. Therefore, various aging markers are investigated to allow a condition assessment. The results show that differences exist between the fluids and design of the transformer, as in the aging rate of the paper and the formation of aging markers in the insulating liquid such as acids. These findings can be used to improve asset management strategies by a more precise determination of the aging state depending on the transformer type as well as the type of insulating fluid

Impact of Selected Small-Molecule Kinase Inhibitors on Lipid Membranes

Small-molecule protein kinase inhibitors are used for the treatment of various diseases. Although their effect(s) on the respective kinase are generally quite well understood, surprisingly, their interaction with membranes is only barely investigated; even though these drugs necessarily come into contact with the plasma and intracellular membranes. Using biophysical methods such as NMR, ESR, and fluorescence spectroscopy in combination with lipid vesicles, we studied the membrane interaction of the kinase inhibitors sunitinib, erlotinib, idelalisib, and lenvatinib; these drugs are characterized by medium log p values, a parameter reflecting the overall hydrophobicity of the molecules, which is one important parameter to predict the interaction with lipid membranes. While all four molecules tend to embed in a similar region of the lipid membrane, their presence has different impacts on membrane structure and dynamics. Most notably, sunitinib, exhibiting the lowest log p value of the four inhibitors, effectively influences membrane integrity, while the others do not. This shows that the estimation of the effect of drug molecules on lipid membranes can be rather complex. In this context, experimental studies on lipid membranes are necessary to (i) identify drugs that may disturb membranes and (ii) characterize drug–membrane interactions on a molecular level. Such knowledge is important for understanding the efficacy and potential side effects of respective drugs.Peer Reviewe

Optical sensor for determining the degree of polymerization of the insulation paper inside transformers

Effective lifetime and maintenance management of a transformer fleet requires precise monitoring of the electrical insulation conditions of each transformer. Currently, the condition assessment of the insulating paper of transformers in operation is done indirectly, by oil samples and evaluation of aging markers in the liquid with only limited accuracy. In fact, sampling of the paper for direct analysis of insulation paper quality is only possible when the transformer is under maintenance or decommissioned. In this paper, the methodology and product development of a novel patented optical sensor is presented, which provides a possibility to determine the degree of polymerization (DP) of insulating paper online and in real-time with high precision via optical spectroscopy inside operating transformers. The measurement is carried out non-destructively and within seconds by a specific evaluation of the reflection spectrum of the insulating paper inside the oil or ester filled environment. The investigation has shown that measurement under strongly aged insulating oil is possible, and the medium surrounding the paper has no influence on the determination of the DP-value. Product development involves materials and technologies to ensure long-time accuracy under mechanical, vibrational, chemical, thermal, and electromagnetic challenges of the transformer environment. This novel, innovative sensor is designed to enable online monitoring of the quality of insulating paper in the transformer at various points, like the hotspot, in order to improve operational safety and economical operation. The optical measuring method provides very high reliability and high accuracy. Deviation analysis shows higher accuracy for lower DP-values, which supports the determination of the end-of-life DP-values

Possibility of electric arc detection in power transformers by directly embedded photoconductive elements in the transformer tank

In this article, an application of potential light-sensitive semiconductive elements, including photoresistors and photodiodes as electric arc detection sensors in the transformer tank, is comprehensively investigated. Conventionally, a Buchholz relay (BHR) is implemented for arc fault detection in power transformers. Unfortunately, in some cases, the tripping of the transformer is not fast enough in order to prevent a tank rupture and catastrophic collateral damages. Therefore, an application of light-sensitive elements as optical sensors is investigated for detecting an arc inside a transformer tank faster under various operational conditions. This contribution focuses on the performance of sensors, which are inserted in the transformer tank. Apart from consideration of different factors such as stochastic nature of light in the arc, thermal cycling, the distance effect on the light sensitivity and possibility of light reflection by the tank, challenges and limitations of arc sensing with light sensors in the mentioned approach are comprehensively discussed. The deficiencies and limitations of the arc sensors are revealed through the experimental investigations conducted

Possibility of electric arc detection in power transformers by directly embedded photoconductive elements in the transformer tank

In this article, an application of potential light-sensitive semiconductive elements, including photoresistors and photodiodes as electric arc detection sensors in the transformer tank, is comprehensively investigated. Conventionally, a Buchholz relay (BHR) is implemented for arc fault detection in power transformers. Unfortunately, in some cases, the tripping of the transformer is not fast enough in order to prevent a tank rupture and catastrophic collateral damages. Therefore, an application of light-sensitive elements as optical sensors is investigated for detecting an arc inside a transformer tank faster under various operational conditions. This contribution focuses on the performance of sensors, which are inserted in the transformer tank. Apart from consideration of different factors such as stochastic nature of light in the arc, thermal cycling, the distance effect on the light sensitivity and possibility of light reflection by the tank, challenges and limitations of arc sensing with light sensors in the mentioned approach are comprehensively discussed. The deficiencies and limitations of the arc sensors are revealed through the experimental investigations conducted

Movement of Xylosandrus germanus (Coleoptera: Curculionidae) in Ornamental Nurseries and Surrounding Habitats

Some exotic ambrosia beetles are damaging pests in ornamental nurseries. Xylosandrus germanus (Blandford) is the most problematic ambrosia beetle in Ohio nurseries. Movement of X. germanus in nurseries has not been characterized, and knowledge is lacking on whether infestations originate from within nurseries or surrounding habitats. Flight activity of X. germanus was monitored in nurseries and adjacent wooded areas to determine the source of beetles infesting nurseries, and characterize their movement within nurseries. Ethanol-baited bottle traps were positioned within wooded areas adjacent to commercial nurseries and within nurseries at various distances from the nursery woodlot interface. Flight activity of overwintered X. germanus occurred in wooded areas adjacent to nurseries before occurrence within nurseries. There was a direct relationship between degree-days and the distance from woodlots when X. germanus were first found in traps in spring, with earlier captures closest to wooded areas and latest ones furthest away into the nursery. X. germanus appeared to move into nurseries from adjacent wooded areas, with numbers trapped within nurseries decreasing with distance away from wooded areas. Trees in the interior of nurseries would appear to be subjected to less attack pressure than trees near the nursery border. Intercepting beetles as they move into nurseries might be an effective strategy to reduce attack pressure on valuable trees

Maghemite nanofluid based on natural ester: cooling and insulation properties assessment

The objective of this work is to study the effect that the addition of magnetic nanoparticles to a natural ester has on its properties and its cooling capacity. Some samples of ferrofluid (natural ester with maghemite) have been prepared using different concentrations. These have been characterized by measuring their thermo-hydraulic and dielectric properties, to find an optimal concentration. Then, the cooling capacities of the optimal nanofluid and the base fluid have been tested in a transformer immersed in these liquids. The experimental platform allowed the measurement of temperatures in different locations at different load levels. Parallel simulations of these tests have been carried out with a Computational Fluid Dynamics model of the experimental platform. The results show an improvement of the insulating capacity of the base fluid with the addition of maghemite nanoparticles, and an enhanced cooling capacity.This work was supported in part by the European Union’s Horizon 2020 Research and Innovation Programme through the Marie Sklodowska-Curie under Grant 823969, and in part by the Ministry of Economy through the National Research Project: Improvement of Insulation Systems of Transformers through Dielectric Nanofluids under Grant DPI2015-71219-C2 1-R. The work of C. Olmo was supported by the University of Cantabria and the Government of Cantabria through Ph.D. Scholarship under Grant CVE-2016-6626

Keine Angst vor dem Blackout : Ein dezentral organisierter Schwarzstart ist machbar!

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