Investigations on power transformer faults based on dissolved gas analysis

Abstract

The primary function of Transformer oil are to provide insulation, cooling, and helps in extinguishing arcs in transformer. Due to electrical and thermal faults resulting from unfavorable operational conditions in transformers, the gas generation in transformer oil is induced. Along with aged conditions of transformers, operational factors like abnormal rise in temperature, vigorous electrical fields, electrical discharges, mechanical stresses, insulation deterioration and contaminants cause impending risks of wrong and irreversible harm to the transformers. All over the world the utilities employ the well proven widely used technique to estimate Dissolved Gas Analysis (DGA) to make sure timely and correct diagnostics of the electrical and thermal faults occurring within the transformers, to save time, equipment and expenditure. Doernenburg, Rogers, Duval triangle, IEC three ratio method and key gases strategies are some of the classical strategies used to interpret the kind of transformer faults. Most of the Utilities employ manual calculations of ratios to determine the fault conditions, which require more effort and time. The objective of this paper is mainly to obtain the DGA results with available data from DGA test for different methods as given in the Standards by developing user friendly software using Excel and visual basic in a simple method for diagnosing the power transformer faults. For this purpose the available DGA data/results have been obtained from the Utility.