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

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

Pintura à base de cal como alternativa de revestimento frio

Os centros urbanos vêm sofrendo alterações climáticas oriundas do fenômeno das ilhas de calor. Como consequência, há o aumento na demanda de energia para condicionamento térmico, além de causar desconforto em habitações que não fazem uso de ar-condicionado. Revestimento frio é uma alternativa que pode minimizar os efeitos da ilha de calor, pois possui capacidade de refletir a luz solar incidente, bem como reemitir parte do calor absorvido pela superfície para o ambiente. Tradicionalmente, superfícies brancas são responsáveis por alto poder de reflexão. Partindo desse conceito, o presente trabalho mediu as propriedades de refletância e emissividade térmica de superfícies pintadas com tinta à base de cal, em diferentes números de demãos, sobre substratos distintos. Além dessas propriedades, foi feita uma análise da capacidade de cobertura das amostras nas condições úmida e seca. Os resultados de refletância variaram de 0,56 a 0,83, dependendo do número de demãos e do tipo de substrato. A emissividade térmica manteve-se com índice de, em média, 0,97, independentemente do tipo de substrato e demãos de pintura. Por fim, percebeu-se um contraste expressivo entre as superfícies sob as condições úmida e seca. Os resultados demonstram que a pintura de cal atende aos requisitos de refletância e emissividade térmica para um revestimento frio

A method to assess the relevance of nanomaterial dissolution during reactivity testing

The reactivity of particle surfaces can be used as a criterion to group nanoforms (NFs) based on similar potential hazard. Since NFs may partially or completely dissolve over the duration of the assays, with the ions themselves inducing a response, reactivity assays commonly measure the additive reactivity of the particles and ions combined. Here, we determine the concentration of ions released over the course of particle testing, and determine the relative contributions of the released ions to the total reactivity measured. We differentiate three classes of reactivity, defined as being A) dominated by particles, B) additive of particles and ions, or C) dominated by ions. We provide examples for each class by analyzing the NF reactivity of Fe2O3, ZnO, CuO, Ag using the ferric reduction ability of serum (FRAS) assay. Furthermore, another two reactivity tests were performed: Dichlorodihydrofluorescin diacetate (DCFH2‑DA) assay and electron paramagnetic resonance (EPR) spectroscopy. We compare assays and demonstrate that the dose‑response may be almost entirely assigned to ions in one assay (CuO in DCFH2‑DA), but to particles in others (CuO in EPR and FRAS). When considering this data, we conclude that one cannot specify the contribution of ions to NF toxicity for a certain NF, but only for a certain NF in a specific assay, medium and dose. The extent of dissolution depends on the buffer used, particle concentration applied, and duration of exposure. This culminates in the DCFH2‑DA, EPR, FRAS assays being performed under different ion‑to‑particle ratios, and differing in their sensitivity towards reactions induced by either ions or particles. If applied for grouping, read‑across, or other concepts based on the similarity of partially soluble NFs, results on reactivity should only be compared if measured by the same assay, incubation time, and dose range

Pintura à base de cal como alternativa de revestimento frio

Os centros urbanos vêm sofrendo alterações climáticas oriundas do fenômeno das ilhas de calor. Como consequência, há o aumento na demanda de energia para condicionamento térmico, além de causar desconforto em habitações que não fazem uso de ar-condicionado. Revestimento frio é uma alternativa que pode minimizar os efeitos da ilha de calor, pois possui capacidade de refletir a luz solar incidente, bem como reemitir parte do calor absorvido pela superfície para o ambiente. Tradicionalmente, superfícies brancas são responsáveis por alto poder de reflexão. Partindo desse conceito, o presente trabalho mediu as propriedades de refletância e emissividade térmica de superfícies pintadas com tinta à base de cal, em diferentes números de demãos, sobre substratos distintos. Além dessas propriedades, foi feita uma análise da capacidade de cobertura das amostras nas condições úmida e seca. Os resultados de refletância variaram de 0,56 a 0,83, dependendo do número de demãos e do tipo de substrato. A emissividade térmica manteve-se com índice de, em média, 0,97, independentemente do tipo de substrato e demãos de pintura. Por fim, percebeu-se um contraste expressivo entre as superfícies sob as condições úmida e seca. Os resultados demonstram que a pintura de cal atende aos requisitos de refletância e emissividade térmica para um revestimento frio

Understanding Dissolution Rates via Continuous Flow Systems with Physiologically Relevant Metal Ion Saturation in Lysosome.

Dissolution rates of nanomaterials can be decisive for acute in vivo toxicity (via the released ions) and for biopersistence (of the remaining particles). Continuous flow systems (CFSs) can screen for both aspects, but operational parameters need to be adjusted to the specific physiological compartment, including local metal ion saturation. CFSs have two adjustable parameters: the volume flow-rate and the initial particle loading. Here we explore the pulmonary lysosomal dissolution of nanomaterials containing the metals Al, Ba, Zn, Cu over a wide range of volume flow-rates in a single experiment. We identify the ratio of particle surface area (SA) per volume flow-rate (SA/V) as critical parameter that superimposes all dissolution rates of the same material. Three complementary benchmark materials-ZnO (quick dissolution), TiO2 (very slow dissolution), and BaSO4 (partial dissolution)-consistently identify the SA/V range of 0.01 to 0.03 h/cm as predictive for lysosomal pulmonary biodissolution. We then apply the identified method to compare against non-nanoforms of the same substances and test aluminosilicates. For BaSO4 and TiO2, we find high similarity of the dissolution rates of their respective nanoform and non-nanoform, governed by the local ion solubility limit at relevant SA/V ranges. For aluminosilicates, we find high similarity of the dissolution rates of two Kaolin nanoforms but significant dissimilarity against Bentonite despite the similar composition

Behaviour of advanced materials in environmental aquatic media – dissolution kinetics and dispersion stability of perovskite automotive catalysts

Tighter regulations on exhaust emission limits require more effective catalysts and here advanced materials (AdMa) play an increasingly important role. Perovskite-based catalysts are among the promising candidates. However, like other automotive catalysts, they contain metal elements of potential concern like nickel, cobalt and noble metals; hence, their likelihood to be released and their fate under environmentally relevant conditions must be assessed at the early stages of material development, so as to align with the goals of the EU Chemical Strategy for Sustainability. The aim of this study is to provide insights into the dissolution and agglomeration behaviour of perovskites in aqueous media with different ionic strengths and salt contents, as well as the influence of the presence of natural organic matter (NOM). The current OECD guidance document and testing guidelines (GD 318 and TG 318, respectively) for nanomaterial testing were applied to three different perovskite AdMa with a lanthanum–cobalt–nickel (LaCoNi) structure with and without doping with palladium or platinum. These tests resulted in a range of practical insights into the feasibility of this methodological cross-over as well as evidence on transferability and applicability to other case studies. Our findings rank the dissolution kinetics of these perovskites to lie between the two reference nanomaterials ZnO and BaSO4. Dissolution rates were found to be, respectively, for ZnO NM110, LaCoNi, and BaSO4 NM220: 0.13, 0.041, and 0.013 μg m−2 s. The ionic strength of the media used in this study did not seem to impact the overall leachable amount of metals (% w/w); however, we found that metal release was mostly incongruent and metal specific i.e., a lower lanthanum ratio with respect to either cobalt or nickel. The presence of NOM increased the dissolution of both benchmark materials; however, no strong influence on dissolution was observed for the perovskite materials. The dispersion stability of perovskites in solution was substantially increased by the presence of NOM and decreased by increased hardness in the test media. Finally, this study provides methodological insights and practical recommendations for testing the dissolution and dispersion stability in different media relevant for ecotoxicological testing and environmental risk assessment

Composition, Respirable Fraction and Dissolution Rate of 24 Stone Wool MMVF with their Binder

Abstract Background Man-made vitreous fibres (MMVF) are produced on a large scale for thermal insulation purposes. After extensive studies of fibre effects in the 1980ies and 1990ies, the composition of MMVF was modified to reduce the fibrotic and cancerogenic potential via reduced biopersistence. However, occupational risks by handling, applying, disposing modern MMVF may be underestimated as the conventional regulatory classification -combining composition, in-vivo clearance and effects- seems to be based entirely on MMVF after removal of the binder. Results Here we report the oxide composition of 23 modern MMVF from Germany, Finland, UK, Denmark, Russia, China (five different producers) and one pre-1995 MMVF. We find that most of the investigated modern MMVF can be classified as “High-alumina, low-silica wool”, but several were on or beyond the borderline to “pre-1995 Rock (Stone) wool”. We then used well-established flow-through dissolution testing at pH 4.5 and pH 7.4, with and without binder, at various flow rates, to screen the biosolubility of 14 MMVF over 32 days. At the flow rate and acidic pH of reports that found 47 ng/cm2/h dissolution rate for reference biopersistent MMVF21 (without binder), we find rates from 17 to 90 ng/cm2/h for modern MMVF as customary in trade (with binder). Removing the binder accelerates the dissolution significantly, but not to the level of reference biosoluble MMVF34. We finally simulated handling or disposing of MMVF and measured size fractions in the aerosol. The respirable fraction of modern MMVF is low, but not less than pre-1995 MMVF. Conclusions The average composition of modern stone wool MMVF is different from historic biopersistent MMVF, but to a lesser extent than expected. The dissolution rates measured by abiotic methods indicate that the binder has a significant influence on dissolution via gel formation. Considering the content of respirable fibres, these findings imply that the risk assessment of modern stone wool may need to be revisited based on in-vivo studies of MMFV as marketed (with binder)