IEEE and IEC Codes to Interpret Incipient Faults in Transformers, Using Gas in Oil Analysis

The detection of incipient faults in oil immersed transformers by examination of the gases dissolved in the oil developed from the original Buchholz relay application. The gases produced during the deterioration of mineral oil and cellulose were examined and techniques were established to assist in the interpretation of the type of fault, incipient or growing, occurring within the transformer. The major technique now employed is the study of ratios of pairs of certain deterioration gases. The concepts used in the development of this technique and the modifications made to enable the technique to be established as the present method of fault interpretation, recommended by the IEC are discussed.