Dissolved Gas Analysis for Transformer Oil

Abstract

Transformer oil is one of the most common materials used for transformers. The oil has two important functions. The oil need to provide cooling and electrical insulation for the transformer. Any deterioration in the oil can lead to the premature failure of the transformer. When the mineral oil is subjected to high thermal and electrical stress, gases are generated from the decomposition of the mineral oil. Different type of faults will generate different gases, and the analysis of these gases will provide useful information about the condition of the oil and the identification of the type of fault in the transformer. The chemical analysis of these gases is called dissolved gas analysis or DGA. The DGA will require the removal of an oil sample from the transformer and this can be done without de-energized of the transformer. The oil sample is analyzed in the laboratory using gas chromatography technique. Many standards were established for assessing conditions of mineral oil filled transformers, such as IEC 60599 and IEEE C57.104 Among all kinds of, Dissolved Gas Analysis (DGA) interpretation methods listed in the above guide, the most comprehensive one is Duval triangle which was established by Michal Duval offering graphical interpretation.