Investigation of Low-temperature Ethylene Production of Transformer Oil Using IEC 60296-2020 Method

The dissolved gas analysis (DGA) interpreting methods detect several irregularities in power transformers using the variation in levels and ratios of gases in transformer oil. Nevertheless, proving the correlation between gases levels and actual faults is challenging. One of the significant gas production sources is thermo-oxidative stray gases that lead to errors in DGA interpretation methods. This type of gas production is due to a chemical reaction independent of the internal faults of active parts. Recently, in IEC 60296-2020, a new method has been presented to determine stray gassing characteristics. To investigate application of this method, this paper studies the DGA results of fifteen sister power transformers with excessive gas production. The most aged transformer oil and its reclaimed one are studied to show the effect of acidic by-products on stray gases production using the new IEC method. Moreover, two different new oils are studied using this method. Applying the IEC 60296-2020 method proves that ethylene should also be considered as a stray gas in addition to methane, ethane, and hydrogen.