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.

The 5 W’s of Transformer Oil Analysis

The 5 W’s of Transformer Oil Analysis


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.


Transformer oil analysis involves obtaining oil samples from electrical equipment and having them analyzed at a certified lab. 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. General and physical tests are suggested twice a year, dissolved gas analysis once a year, and Furan testing every 2 years for transformers in operation at least 5 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. The sampled oil can then be analyzed by various labs across the country.


Transformer oil ages over time due to various conditions like load, heat, contaminants such as water or gas, and more. As the oil deteriorates, its ability to provide the required dielectric and cooling properties are diminished. Periodic oil analysis is proven to be very cost-effective maintenance to continually access the viability of the transformer oil to timely and conveniently address 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!

The transformer manufacturing plant of CTC in Vietnam

CTC specializes in providing products such as Oil TransformerAmorphous TransformerDry TransformerReactor Coiland other electrical equipment. With 15 years of experience in the field of electricity and transformer manufacturing, we are confident that we can provide you with the optimal solution