Analysis of gas content in oil-filled equipment with defects for which ethane is the key gas

Abstract

The article presents results of a comprehensive analysis of the gas content in oil of 252 pieces of high-voltage equipment with defects, for which ethane is the key gas. There are 14 types of defects with maximum ethane content, which correspond both to overheating with temperature 150-300°C and low temperature overheating accompanied by discharges with different energy density (partial discharges, spark discharges, discharges with low and high energy density, arc discharges). The most typical defects are analysed and examples of their recognition by different researchers are given. For each type of defect, ranges of gas percentage values and gas ratio values are obtained. This is particularly important for the recognition of combined defects (overheating that is accompanied by discharges), because for such defects the values of these criteria are not regulated in any known standard for the interpretation of the results of the analysis of gases dissolved in oil. For the first time, 14 nomograms and graphic areas of defects for which ethane is the key gas have been obtained, which makes it possible to significantly expand the range of reference nomograms, as the regulatory document in force in Ukraine does not contain reference nomograms for defects with the maximum content of ethane. For all 252 pieces of equipment, a comparative analysis of known diagnoses with diagnoses made using the Duval triangle was made. It has been determined that diagnoses made using different methods may differ significantly from each other as well as from real diagnoses. The ranges of gas percentage and gas ratio values obtained in the work, together with the defect nomograms, make it possible to use three of these criteria simultaneously to recognise the type of defect with a maximum ethane content, which in turn will improve the reliability of defect type recognition based on the analysis of gases dissolved in oil.