Oil-immersed power transformers condition diagnosis with limited Dissolved Gas Analysis (DGA) data

For a vertically integrated utility in a developing country, the diagnosis of oil-immersed power transformers condition is not frequently performed due to limited budget and lack of past historical data. Dissolved gas analysis (DGA) for oil samples has been the most widely used diagnosis tool for transformer condition assessment for many years. However, the interpretation of DGA results becomes very difficult and uncertain when only one or two sets of data are available. The aim of this paper is to address the issue of DGA interpretation with very limited test data. This paper will present DGA tests results from 38 power transformers in a developing country and will propose a maintenance decision making procedure using the IEC 60599-2007 and Duval´s Triangle schemes. Limitation of the methodology proposed in this paper and further possible development will also be highlighted in this paper.