The gassing tendency of oil under corona discharge

Even though insulating oils are very carefully refined by the petroleum industry, the impact of electric and thermal stress as well as the chemical aggressiveness of dissolved oxygen generates a variety of decay products in service conditions. In order to emphasize the role played by contaminants in the gassing of oil, fundamental investigations were undertaken. The amount of gases evolved under the impact of electrical stress (ASTM D6180) by a sample of new and aged oil was accurately measured along with some physicochemical properties, to assess the relationship between the cause and the symptoms of oil deterioration. This contribution intends to show that the gassing of oil is a more complex phenomenon. It provides experimental evidence that the chemical composition of hydrocarbon blend and the oil born decay products are also contributing factors to oil gassing. Besides the testing on new samples, testing was also performed on aged samples too. The influence of decay product was highlighted.