Diagnostics of HV bushings through oil sampling and analysis: Experience with GSU transformers

Bushings are highly stressed parts of power transformers and their failures can lead to a transformer break-down. The diagnostics and predictive surveillance of bushings is essential for uninterrupted operation of transformers. Diagnostic tools applied include electrical tests, thermography and, to a minor extent, oil anal-ysis for oil-impregnated bushings. This paper gives a short review of bushing types and related applications, including procedures for in-field inspection and oil sampling. Dissolved Gas Analysis (DGA) issues in bush-ings’ mineral oil are briefly discussed and diagnostic criteria for DGA interpretation are given, comparing the experience of the authors with the available literature and standards

Diagnostics of HV bushings through oil sampling and analysis: Experience with GSU transformers

Bushings are highly stressed parts of power transformers and their failures can lead to a transformer break-down. The diagnostics and predictive surveillance of bushings is essential for uninterrupted operation of transformers. Diagnostic tools applied include electrical tests, thermography and, to a minor extent, oil anal-ysis for oil-impregnated bushings. This paper gives a short review of bushing types and related applications, including procedures for in-field inspection and oil sampling. Dissolved Gas Analysis (DGA) issues in bush-ings’ mineral oil are briefly discussed and diagnostic criteria for DGA interpretation are given, comparing the experience of the authors with the available literature and standards

On-load integrated treatment of giant power transformers in a severe scenario

The article describes the asset and risk management approach of a primary electrical company in the Middle East area. A specific maintenance strategy has been carried out for loss prevention of giant transformers, addressing mainly the corrosive sulfur. Starting from the international standards and considering the specific context, the appointed consultancy company GCC Lab selected the most efficient long-term mitigation technique: the selective depolarization. This process, developed and operated by Sea Marconi, is proven to be effective in the removal of DBDS and oil corrosive compounds, even after one year, also restoring all chemical and physical properties of the oil

Understanding the ageing performance of alternative dielectric fluids

Mineral oil has traditionally been used as a cooling fluid in power transformers, but its low biodegradability and low fire point have motivated the search of alternatives. In this work, six different dielectric fluids have been studied, including four vegetable liquids, from sunflower, rapeseed, soybean, and palm, one synthetic ester and a mineral oil used for comparison. These oils were subjected to an accelerated thermal ageing in glass vessels at 150°C for four weeks (672 hours) in presence of Kraft insulating paper. Different oils parameters were measured during the ageing, i.e. breakdown voltage, dielectric dissipation factor, permittivity, DC resistivity, density, kinematic viscosity, flash and fire points, interfacial tension, acidity, and dissolved gases; additionally, the degree of polymerisation (DP) of the paper was measured. Results showed that the changes of the natural esters properties, except for the palm oil, were similar along the ageing time. Palm oil results were similar to those of the mineral oil, whereas synthetic ester showed a behaviour similar to natural esters. The kraft paper degradation was higher in the mineral oil, followed by the synthetic ester and the palm oil. No significant differences were found in the ageing with the natural esters.This work was supported in part by the European Union’s Horizon 2020 Research and Innovation Program, through the Marie Sklodowska-Curie, under Grant 823969, and in part by the Ministry of Economy, through the National Research Project: Gestión del Ciclo de Vida de Transformadores Aislados con Fluidos Biodegradables, under Grant PID 2019-107126RBC22

The pharmacological bases for repurposing statins in depression: a review of mechanistic studies

Statins are commonly prescribed medications widely investigated for their potential actions on the brain and mental health. Pre-clinical and clinical evidence suggests that statins may play a role in the treatment of depressive disorders, but only the latter has been systematically assessed. Thus, the physiopathological mechanisms underlying statins’ putative antidepressant or depressogenic effects have not been established. This review aims to gather available evidence from mechanistic studies to strengthen the pharmacological basis for repurposing statins in depression. We used a broad, well-validated search strategy over three major databases (Pubmed/MEDLINE, Embase, PsychINFO) to retrieve any mechanistic study investigating statins’ effects on depression. The systematic search yielded 8068 records, which were narrowed down to 77 relevant papers. The selected studies (some dealing with more than one bodily system) described several neuropsychopharmacological (44 studies), endocrine-metabolic (17 studies), cardiovascular (6 studies) and immunological (15 studies) mechanisms potentially contributing to the effects of statins on mood. Numerous articles highlighted the beneficial effect of statins on depression, particularly through positive actions on serotonergic neurotransmission, neurogenesis and neuroplasticity, hypothalamic-pituitary axis regulation and modulation of inflammation. The role of other mechanisms, especially the association between statins, lipid metabolism and worsening of depressive symptoms, appears more controversial. Overall, most mechanistic evidence supports an antidepressant activity for statins, likely mediated by a variety of intertwined processes involving several bodily systems. Further research in this area can benefit from measuring relevant biomarkers to inform the selection of patients most likely to respond to statins’ antidepressant effects while also improving our understanding of the physiopathological basis of depression

Investigation of the degradation of a wood pulp-cotton presspaper in different biodegradable oils

New insulating materials, as biodegradable oils and upgraded paper, need to be investigated. In this paper, the ageing of a wood pulp - cotton presspaper is studied. Solid insulation is impregnated and aged with three different fluids: a mineral oil and two vegetable oils, from sunflower and soybean. Both oils and paper were dried before the ageing process, which was carried out at 150°C for 732 hours in iron vessels. Degradation of oils is analysed through the measurement of their breakdown voltage, dielectric dissipation factor (tan δ), resistivity, moisture content and acidity. Deterioration of presspaper is quantified by its polymerization degree (DP), moisture content and dielectric dissipation factor. Results showed that the dielectric properties of oils are negatively affected by the ageing, since the breakdown voltage and resistivity were reduced, whereas the dissipation factor increased. Also, acidity increased, especially in the vegetable oils. In the case of the solid insulation, its tanδ increased with the ageing, despite the reduction of its moisture content. DP was reduced, reaching the end-of-life criteria (DP<200) in the ageing with mineral oil (134) whereas it remained at higher values for the sunflower (206) and soybean (216) oils.This research is under BIOTRAFO project, which has received funding from the European Union’s Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie Action-Research and Innovation Staff Exchange (MSCA-RISE) grant agreement No 823969. The authors of this research wish to thank the Ministry of Economy for its financial support for the National Research Project: Gestión del Ciclo de Vida de Transformadores Aislados con Fluidos Biodegradables (PID 2019-107126RBC22). Cristina Méndez also wants to acknowledge the Spanish Ministry of Science, Innovation and Universities for the financial support for the FPU grant (FPU19/01849)