Unusual ethylene production of in-service transformer oil at low temperature

The study sponsored by the CEATI Life Cycle Management of Station Equipment & Apparatus Interest Group deals with an unusual gassing trend of dissolved gas-in-oil in power transformers. The history of gas generation development in these free-breathing transformers shows that ethylene and carbon dioxide gases were produced progressively under normal operating conditions without the simultaneous generation of hydrogen and other hydrocarbon gases. Thermal aging experiments performed in the laboratory on inservice oil in closed air-saturated glass ampoules revealed a dominant influence of oxygen and temperature on the oil´s chemical stability. The results suggest that the degradation of the in-service oil is governed by an oxidation process in an oxygen-rich environment at unexpectedly low temperatures. The possible raisons explaining the unusual gassing trend of dissolved gas-in-oil in power transformers were not elucidated in this study.