Ethane Levels in Natural Esters

Over the years, customers have asked us a variety of questions about dissolved gas analysis (DGA) results that indicate elevated ethane levels in natural ester fluid. 

Natural ester-filled transformers, specifically those filled with FR3, have a tendency to generate ethane—and sometimes hydrogen—as stray gasses at temperatures normally found in a properly operated transformer.

While not typical in every case, it does happen frequently enough that we do not consider it to be abnormal. 

At SDMyers, we are both cautious and concerned with maintaining the integrity of our customers’ expensive electrical equipment and everything dependent on it. When ethane is detected, we prefer to conduct further testing of the transformer to determine if it is being generated as stray gassing or if it is an indication of an electrical fault. Our procedure ensures we are doing everything we can to protect the transformer and to safeguard uninterrupted power.

We occasionally detect increased levels of ethane in a new transformer or one that does not have a history of indicating a significant concentration of ethane. We treat this occurrence as evidence of low-level overheating and recommend a retest at a shortened interval. Even if the transformer is listed as spare or de-energized, we assume the unit is an important part of the fleet, and we will treat it accordingly.

If the unit is filled with FR3 and the ethane has stabilized at 400 ppm or less, we typically recommend our standard retest interval of one year. However, in order to confidently assert that the transformer is operating normally, the other gasses in the unit must also remain stable. 

The presence of other gases (including methane, ethylene and acetylene) usually indicates active overheating rather than stray gassing.

For more technical information on dissolved gasses in FR3 fluid, click this PDF link to FR3 Dissolved Gas Guide  from Cooper, the original producers of Envirotemp FR3.