Condition evaluation of power transformers using dissolved gas analysis and dielectric breakdown voltage test

Abstract

This paper proposes the techniques for evaluating power transformer condition based on frequently updated test results. According to planned maintenance, insulation oil is regularly sampled and analyzed in laboratory to determine problems inside main tank by dissolved gas analysis as well as dielectric breakdown voltage test to determine dielectric property of the oil. The dissolved gas analysis is firstly compared with limit values of gases in IEC standard. If values of gases exceed normal condition, the dissolved gases are analyzed by using Duval triangle while dielectric breakdown voltage criterion is reference with the IEC standard. These two methods are subsequently implemented in Microsoft Excel and Visual Basic for Application to evaluate the condition of power transformer and dielectric strength of insulating oil.