Comparison of Different DGA (Dissolved Gas Analysis) Methods for the Condition Assessment of Power Transformers

Abstract: Transformers are one of the most important and cost-intensive components of electrical energy supply networks, thus it is of special interest to prolong their life duration while reducing their maintenance expenditures. In order to reach these aims it is indispensable to gather detailed information about the operation conditions of transformers, which is usually done by various kinds of oil analyses like the standard oil test, the DGA (Dissolved Gas Analysis) and the Furan analysis. Usually electrical abnormities are shown by a DGA, which allows a detection of two different kind of failures: electrical and thermal faults, whereby each type of failure can be subdivided in three different categories according to the international standard IEC 60599 [1], thus the DGA became a well known and approved technique in the last decades, although different techniques of dissolved gas analysis and its interpretation exist. In this contribution different DGA methods are introduced and compared in order to explain the problems of DGA and its evaluation and to give recommendations concerning the questions how to analyze an oil sample and how to evaluate the results of the analysis with a focus on different equipment