Application of Duval Pentagon Compared with Other DGA Interpretation Techniques: Case Studies for Actual Transformer Inspections Including Experience from Power Plants in Thailand

The interpretation of dissolved gas analysis (DGA) is one of the most important procedure to identify the incipient fault which may occur in transformers. Various interpretation methods can be used; however, they may identify different fault types for the same investigation case. This paper aims to study the performance of DGA interpretation, i.e., IEC Ratio, Duval Triangle and Duval Pentagon, and Doernenburg Ratio. The performance of the DGA interpretation techniques is evaluated from twenty-four fault cases obtained from both academic references and problem investigated transformers utilized in an electrical power plant in Thailand. It was found that the Duval Pentagon method provided the highest consistency DGA interpretation compared with other methods. Duval Pentagon also has the capability to distinguish the normal aging of the insulation system from other fault types.