Oil Testing & Oil Analysis for Transformers

Essential to Every Power Systems’ Health

Transformer oil has excellent electrical insulation and is stable at high temperatures. The oil is used for the purpose of insulation, discharge stoppage and it acts as a cooling agent for the transformer itself. With the critical use of oil, it is important to do ongoing analysis and oil testing as your transformer is deserving of the best upkeep and servicing!

On your site or in our shop, RESA’s NETA certified technicians will work to ensure the reliability and integrity of your transformers and electrical equipment through ongoing testing and analysis. Our laboratory offers a full range of transformer oil tests in accordance with ASTM Standard Test Procedures and diagnostic recommendations that are based on IEEE Standard guidelines.


  • Oil Quality
  • Water Content
  • Dissolved Gas Analysis (DGA)
  • Inhibitor Content
  • Furan Test
  • Resistivity Test
  • Corrosive Sulfur
  • Particle Count
  • PCB Analysis of Insulating Fluid
  • Dissolved Metals Test
  • Liquid Power Factor at 25°C & 100°C


  • On-Site Fluid Sampling & Inspection Services
  • Repairs: Tap Changers, Gauges, Radiators
  • Valves, Bushings, Etc.
  • Minor Internal Repairs
  • Electrical Testing
  • De-energized Insulator Cleaning
  • Leak Repairs & Clean-up
  • Painting / Repainting
  • Nitrogen Pressurizing Service
  • Safe-TTR™ Sampling Enclosure
  • NFPA 70E Solutions
  • Load Tap Changer Services


  • Hot Oil Reconditioning
  • De-gasification of Oil
  • Dehydration of Oil
  • Standard Oil Filtering
  • Vacuum Filling
  • Retrofill with New Oil
  • Inhibi-TTR™ Inhibitor Injection
  • Passiv8-TTR™ – Corrosive Sulfur
  • Other Fluid Services

At RESA Power, we offer transformer maintenance services that include:

  • Dissolved Gas Analysis (DGA)
  • Testing for Dielectric Fluid Quality
  • Oil Processing

These quality assurance services ensure elevated service and ongoing reliability of your energy and power needs.

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Dissolved Gas Analysis (DGA)

Every transformer needs periodic maintenance, oil testing, and analysis to determine any potential problems, before a transformer’s performance is compromised. Dissolved Gas Analysis (DGA) is considered to be the best method for determining a transformer’s overall condition. RESA Power’s highly skilled technicians have expertise in the DGA universal standard of oil testing.

Benefits of DGA

Knowing the importance of oil in a transformer, it is even more critical to ongoing maintenance and support of a transformer’s health. Advantages of DGA testing include the following:

  • advanced warning of developing faults;
  • status checks on news and repaired units;
  • convenient scheduling of repairs;
  • and monitoring of units under potential overload conditions.
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Leave it to the Professionals

DGAs should be conducted by a trained professional, like RESA Power’s NETA Certified technicians. Our experts will assist in recognizing issues on both new and older power components and systems, that include for example (but not limited to):

  • Rate of gas production – A sudden increase in key gases (such as hydrogen or Acetylene). Note: the rate of increased gas production is more important in evaluating a transformer than the amount of gas
  • Thermal fault – The generation of any amount of gas in ppm indicates high energy arcing and can possibly generate a very hot thermal fault (1000 degrees Celsius)
  • Acetylene levels – Determination of the level of acetylene in the transformer. For example, if acetylene is generated by internal arcing, sampling should be taken weekly to determine if there is an additional generation of If no additional acetylene is found and the level is within the accepted IEEE standard, the transformer may continue in service. If, however, there is an increase of acetylene levels, the transformer has an internal arc and should be taken out of service. This is because operating a transformer with a high amount of acetylene is extremely hazardous.

The delicate balances of systems and supportive testing are respected by RESA Power. With safety and reliability of services at stake it is important to work with the experts at RESA Power on all your critical transformer preventative maintenance needs.

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Physical, Chemical, and Electrical Dielectric Fluid Quality

RESA Power is uniquely capable at addressing the most critical requirements of power systems’ reliability, operability and efficiency. Part of this holistic approach to power maintenance includes the consideration of specific properties or parameters of insulating oil in order to determine the serviceability of the oil. These properties of transformer oil include electrical, chemical and physical aspects. All need to be analyzed and tested for quality.

Electrical properties include: dielectric strength, gassing tendency, and dielectric dissipation factor (or power factor).

Chemical properties include: water content, acidity, and sludge content.

Physical properties include: interfacial tension, viscosity, flash point, and pour point.

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Diagnostic Testing for Transformer Fitness

Customers that incorporate RESA Power’s electrical, chemical and physical testing avoid unscheduled maintenance and repair costs. Let RESA Power ensure your transformers are fit for compliance standards and meet safety guidelines that will provide you with a peace of mind.

Electrical Dielectric Diagnosis

When testing electrical properties RESA Power NETA technicians utilize diagnostic methods that measure dielectric levels. These tests provide crucial evidence of changes in the condition of the insulation. The results and tracking of this critical data increase the longevity of the transformer and prevents system failures.

RESA Power utilizes dielectric testing to test a transformer’s reaction, duration and breakdown during an analysis using voltage rates. We test the durability of the insulating barrier materials in transformers while analyzing the resistance to various harmful voltage levels. Results are not only important to safeguarding material damage, but also important to reducing injuries due to faulty equipment.

Chemical Testing

Water, gas and particles in the transformer’s insulation system will negatively impact the transformer’s longevity. These are tested thoroughly by RESA Power to reduce damage and limit equipment downtime.

Moisture or water content in transformer oil is highly undesirable affecting the dielectric properties of the oil adversely. Water content in oil also affects the paper insulation of the core and winding of a transformer. Another chemical property that can affect transformer performance is acidity: if oil becomes acidic, the water content in the oil becomes more soluble, deteriorating the insulation properties of the paper as it is winding. Acidity can also accelerate the oxidation process and the rusting of iron in the presence of moisture

Physical Fitness Analysis

The physical properties of transformer oil are analyzed by RESA Power with the focus on the following elements: interfacial tension, flash point, pour point, and viscosity.

In general, good new oil generally exhibits high interfacial tension. It is also desirable to have a very high flash point: over 145 degrees is considered acceptable. The best pour point is the minimum temperature at which oil starts to flow under standard test conditions. Therefore, higher pour points are desirable in colder temperatures, but it also depends upon the type of oil being used (e.g. Paraffin-based oil necessitates higher pouring temperatures than Naphtha-based oils).

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