Case studies on transformer fault diagnosis using dissolved gas analysis

In this paper the results of dissolved gas analysis (DGA) along with details of the DGA data from in-service transformers are discussed. Two case studies are given of which, first case study deals with the detection of the partial discharge and the second case study deals with the detection of thermal fault in transformers at thermal power stations in India. The interpretation of DGA data are conducted using key gas method. The interpretations are validated by the application of gas ratio method. Gas ratio method included in this study are Rogers ratio and Doernenburg ratio.