Gas Production Characteristics of Mixed Insulation Oil and Oil-immersed Paper Under Overheating Faults

Mixed oil has been widely studied recently due to its dominant comprehensive performance. To date, mixed insulation oil has already been applied to field transformers, including 10 ∼ 110 kV transformers. With the application of the mixed oil, there is a lack of state monitoring and fault diagnosis methods. Dissolved gas analysis (DGA) is a valid method for mineral oil transformers; however, existed method is not suitable for the mixed insulation oil due to its different molecular components. This paper discusses the DGA of mixed insulation oil and oil-immersed paper under overheating fault. Results indicate that the mixed oil produces more CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, C<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> and H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> than mineral oil, and the proportion of H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and hydrocarbon gases can be used to judging different types of overheating. Oil-paper overheating produces more CO and CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> compared with oil overheating, which can be used to distinguish oil overheating and oil-paper overheating. The results provide a theoretical basis for DGA of mixed oil transformers.