Evaluating transformer condition using DGA oil analysis

Abstract

Early detection of incipient faults in transformers reduces costly unplanned outages. The most sensitive and reliable technique for evaluating the health of transformer is dissolved gas analysis (DGA). This paper uses dissolved gas analysis to study the history of different transformers in service, from which dissolved combustible gases (DCG) in oil are used as a diagnostic tool for evaluating the condition of the transformer. Oil quality and dissolved gasses tests are comparatively used for this purpose. The effect of transformer aging on dissolved combustible gasses is also examined. It is noted that the oil quality tests for transformer oil are inconclusive and that the DGA test is then necessary for complete evaluation of transformer condition.