Recognition of Overheating with Temperatures of 150-300°C by Analysis of Dissolved Gases in Oil

Recognition of Discharges That Are Accompanied by Low-Temperature Overheating Based on the Analysis of Gases Dissolved in the Oil of High-Voltage Transformers

“…One way to eliminate this problem is to evaluate and analyze the values of all diagnostic criteria simultaneously in the same type of equipment with defects of the same type, with subsequent training of the diagnostic model. The use of such an approach makes it possible, on the one hand, to eliminate contradictions between different diagnostic criteria when recognizing defects of the same type [26], and, on the other hand, to determine characteristic ranges of diagnostic criteria values for defects for which such ranges are not regulated [27][28].…”

“…The raw data were first divided into several separate arrays depending on the type of defect detected. Then, by analogy with [26][27][28], the percentage content values for each of the five gases were determined, the values of characteristic gas ratios were calculated, and defect nomograms were constructed for each of the transformers analyses. The obtained values were compared with each other and if the value of at least one of the criteria differed significantly from those obtained earlier, the DGA results for the analyzed transformer were transferred to another array.…”

“…The studies performed in [29] showed that the defect nomograms constructed by the DGA results of the same type of equipment, with a defect of the same nature can differ significantly. In order to account for drift in the coordinate values of defect nomograms (values of ratios of gas concentrations to the gas with the maximum content), defect nomograms, by analogy with [26][27][28], were represented in the form of graphical areas instead of defect nomograms. Graphical areas based on the DGA results of transformers where electrical discharges with different intensity, which were accompanied by overheating with temperature of 150-300°C were detected, are shown in Fig.…”

“…However, despite this, it would be desirable to be able to determine the defect type of equipment without the presence of a similar reference nomogram or a nomogram obtained by other researchers. As shown in [27], the nomograms obtained from the DGA results for transformers with combined defects are the sum of the nomogram corresponding to the electric discharge of a certain intensity and the nomogram corresponding to the thermal defect with a certain temperature. Figure 2 illustrates this fact.…”

“…It is therefore of practical interest to assess the reliability of the recognition of discharges which are accompanied by low-temperature overheating, using the best known standards and techniques. Using the approach given in [26][27][28], in the process of analysis it was determined the statistics of correct diagnoses, partially correct diagnoses (the type of defect was determined correctly, but its intensity -temperature of heating or energy density of discharge -was estimated incorrectly). The statistics of incorrect diagnoses and failures of recognition (that is cases where the analyzed method does not allow to establish a diagnosis) were also recorded.…”