Influence of aging byproducts on the gassing tendency of transformer oils

Dissolved Gas Analysis (DGA) has now become a standard in the utility industry throughout the world and is considered to be the most important oil test for oil-filled power transformers. This article intends to show that the gassing of oil is a more complex phenomenon. Aged oil and reclaimed aged oil samples were submitted thermal and electrical stresses (considering various scenarios) and the dissolved gasses analyzed by chromatography. This contribution provides experimental evidence that the chemical composition of hydrocarbon blend and the oil born decay products are also contributing factors to oil gassing. The influence of oil born decay products onto the diagnostics predicted by some DGA techniques is also emphasized. Although such a research is still in a preliminary stage, some very stimulating results have been obtained.