Influence of Oil Quality on the Interpretation of Dissolved Gas Analysis Data

Abstract

Dissolved gas analysis (DGA) is being used for many years as a diagnostic tool for the condition monitoring of power transformers. However, field experiences reveal that the interpretation of these dissolved gas data is not an easy task due to the complexity of the gassing phenomenon. This is due to a number of factors. One of those contributing factors namely, the impact of oil quality is investigated in this contribution. The measurement of the dissolved and undissolved (non-gaseous decomposition) aging by-products respectively assessed by UV / VIS spectrophotometry and turbidity allowed assessing the oil’s quality and its relationships with gas generation under electrical or thermal faults. The obtained results indicated that the degraded oils release more CO along with some small amounts of combustible gases under thermal stress. The volume of gases in the case of an electrical fault is almost the same regardless the oil’s condition.