Interpretation of Dissolved Gas Analysis Using Dempster-Shafer´s Theory of Evidence

Dissolved gas analysis is a well-known technique to detect incipient faults of oil-immersed electrical equipment. Interpretation is usually difficult because there is no unique relationship between the identified gases and the type of fault. On the basis of IEC standards for the interpretation of dissolved gas analyses and Dempster-Shafer´s theory of evidence a method to automatically determine the correct diagnosis is presented. A Markov tree is used for modeling the relationship between the diagnoses and propagating evidence originating from the measured gas concentrations. Uncertainty arising from the measurement of the gas concentration is considered appropriately. The method is verified by calculating the diagnosis from authentic dissolved gas analyses of several power transformers and comparing the result to the true fault. Based on the extent of support for the calculated diagnosis necessary countermeasures are proposed