The duval pentagon-a new complementary tool for the interpretation of dissolved gas analysis in transformers

Several methods are available for the interpretation of dissolved gas analysis (DGA) results in oil-filled electrical equipment. These methods use ratios of the five main hydrocarbon gases formed, namely H
²
, CH
⁴
, C
²
H
⁶
, C
²
H
⁴
, and C
²
H
²
, either 2-gas ratios, e.g., in IEEE [1] and IEC [2]; 3-gas ratios, in Duval Triangles 1 to 7 [3]; or 4-gas ratios in [4]. In this article a new method is presented using 5-gas ratios in a "pentagon" representation applicable to mineral oil–filled equipment. Carbon oxides CO and CO2 are examined separately as in other methods.