Transformer Oil Testing: The Importance of Analysis - Southwest Electric

The 5 W’s of Transformer Oil Analysis

The 5 W’s of Transformer Oil Analysis

Transformer oil testing and analysis is often overlooked yet is an integral part of keeping your transformers maintained. The process is very similar to a blood test you might have performed by a doctor. The results tell us what is going on inside and give us the chance to perform needed maintenance, avoid emergencies, save money, and prolong life. This article will explain the who, what, when, where, and why of oil analysis and illustrate its importance.


Choosing an oil analysis lab that provides routine oil sampling and analysis services is typically the most cost-effective method of oil analysis. Another option is to pull your own samples and send them off to a transformer oil testing and analysis company. In emergencies (or if you prefer), any company providing oil processing services such as Southwest Electric should be available to assist.


Obtaining oil samples from electrical equipment and analyzing them at a certified lab constitute transformer oil analysis. The lab will run various tests to determine the breakdown voltage of the oil as well as other physical and chemical properties. Generally, the results will include measurements for color, dielectric breakdown voltage, dissolved gas analysis, dissolved metals, flash point, furan, inhibitor content, interfacial tension, moisture, PCB’s, power factor and specific gravity. With these test results, you can become aware of likely problems and work towards solutions before there is an emergency.


Routine testing of transformer oils and insulating oils on a regular schedule is an accepted industry practice. For transformers in operation for at least 5 years, experts recommend conducting general and physical tests twice a year, dissolved gas analysis annually, and Furan testing every 2 years.

Southwest Electric has extensive industry expertise of performing oil sampling, oil testing and (equally as important) interpreting the data. We also will always recommend getting a second opinion on any oil analysis before spending money to correct a perceived problem, similarly to how you would get a second opinion from a doctor on a serious health issue.

A common mistake to avoid is making a knee-jerk reaction at first look and potentially spending money on unneeded maintenance.


The oil sampling is done directly from the equipment at your site. This can be performed while your equipment is energized if one can safely access a sample port valve on the equipment. Various labs across the country can analyze the sampled oil.

Transformer Oil Analysis



Transformer oil ages over time due to various conditions like load, heat, contaminants such as water or gas, and more. As the oil degrades, it loses its ability to deliver the necessary dielectric and cooling properties. Regular oil analysis demonstrates that maintaining the viability of transformer oil is cost-effective, allowing timely and convenient addressing of any deteriorating conditions. This not only extends the life of your transformers, but it helps avoid unplanned shutdowns and potentially even the catastrophic loss of a transformer!

Southwest Electric offers free advice. Simply email us your reports and we will give you an evaluation as to the health of your transformers at no cost. We can then schedule a time to troubleshoot any concerns you may have as a result of your analysis. In the end, we will recommend actions to minimize cost and reduce unplanned outages. We can provide any necessary oil processing to restore the oil to its best possible condition when the results indicate poor quality.

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