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This article presents an innovative methodological development for the hot spot temperature estimation in mineral oil immersed power transformers by using the support vector regression (SVR). The SVR algorithm is based on the statistical learning theory and is part of the machine learning tools. It was used through a six stage implementation where an SVR model capable of estimating the variable under study is obtained. The method was applied to a real 30 MVA transformer with ONAN/ONAF cooling at 70/100% of load using a database for a 10 year period. The developed SVR model was validated by comparison to the results obtained with the Dejan Susa model using statistical performance metrics. In conclusion, the results obtained indicate that the implemented SVR model allows estimating the hot spot temperature with high accuracy. [ABSTRACT FROM AUTHOR]

The kinetics of thermal inactivation of pectinmethylesterase (PME; EC3.1.1.11) was performed on tree tomato juice (Solanum betaceum Cav.). The behavior of the enzyme at temperatures between 50 and 80 ° C and times between 5 and 60 s was evaluated. The residual enzyme activity (AR) was measured by spectrophotometry. The content of total carotenoids (CT) at temperatures-time AR ≤ 10% was determined. The kinetics was studied under a two-phase model of first order. The calculated constants KR were 0.077 min-1 at 50 °C, 0.623 min-1 at 60 °C, 15.34 min-1 at 70 °C, y 19.88 min-1 at 80 °C. The constants KL were 0.778 min-1 at 50°C y 2.783 min-1 at 60 °C. Arrhenius representation yielded a value of 189.6 kJ/mol for EaR. No significant difference in total carotenoids was found at 70 and 80 °C × 10 and 7 s. It is conclude that AR ≤ 10% are obtained at temperatures ≥ 70 ° C × 10 s, showing losses of carotenoids of the order of 11.2%. [ABSTRACT FROM AUTHOR]

Water absorption kinetics in pea seeds (Pisum sativum L.), varieties San Isidro and Sureña, were determined. Rehydration was conducted at three temperatures (6, 18 and 30 °C), using a seed/water ratio 1: 4 (w/v), and measurements at 0, 3, 6, 9, 12 and 24 hours were taken. The effect of temperature was evaluated by the water adsorption capacity, whereas the water adsorption kinetics was studied in two models (Exponential and Peleg). The water adsorption capacity increased with increasing water temperature. The models adequately describe the kinetics of adsorption of water. Both diffusivity and kinetic parameters show dependence on temperature and when are evaluated by the Arrhenius activation energy of 17.24 kJ/mol for San Isidro and 9.25 kJ/mol for Sureña were obtained. [ABSTRACT FROM AUTHOR]

This article presents an overview of the conceptual framework related to the asset management of power transformers, and to the assessment of risks associated with transformer failures. The risk index is an essential tool for developing the management of this asset, especially because it supports the asset manager in the decision-making process. The risk index is composed by two indicators: i) consequence factor, which assesses the impacts that could arise in the event of equipment failure, and ii) the probability of failure, which is determined from the results of tests for transformer functioning, operating history, and failure history, among others. General aspects of asset management according to international standards are presented, to then deal with specific aspects related to evaluation of the transformer risk index, found in the literature. [ABSTRACT FROM AUTHOR]

This article provides a methodology for calculating the health index for oil-paper insulation system in power transformers with rated voltage between 69kV and 230kV, using fuzzy logic. The article also provides a detailed review of the existing limits of acceptance, according to the present standards and for each of the six input variables: moisture content, acidity, dielectric strength, dissipation factor oil, dissolved gas and furan content. With this information, the membership functions are obtained and the six input values are related to the output value, which represents the health index of the transformer. Using data provided by a company of the Colombian electricity sector for 18 power transformers the health index is calculated and the results are analyzed. The health index could be useful for establishing a ranking of the state of power transformers with the aim of better assigning resources and maintenance activities. [ABSTRACT FROM AUTHOR]