Alex Barberá

The grade name of transformer oil used in power transformers is typically referred to as mineral oil. This mineral oil is specifically refined to meet the electrical and thermal properties required for effective insulation and cooling in power transformers. It is crucial for maintaining the operational efficiency and longevity of the transformer while also providing protection against electrical breakdown.

An oil immersed transformer is a type of transformer that uses oil as an insulating and cooling medium. The oil provides electrical insulation between the internal components and helps dissipate heat generated during operation. This design enhances the transformer’s efficiency and longevity, as the oil also protects against moisture and contaminants, ensuring reliable performance in various electrical applications.

Nynas transformer oils are formulated to provide stable dielectric and cooling performance in high voltage equipment, with controlled viscosity, low acidity, and strong oxidation stability depending on grade. Suitability is validated through compliance to relevant insulating oil standards and utility specifications, plus consistent quality control and test certificates. Nynas is known for naphthenic base oils in many markets, which can offer good low temperature flow and stable viscosity behavior. In practice, suitability also depends on correct handling, moisture control, and ongoing condition monitoring through BDV, moisture, tan delta, and DGA trending.

Oil cooling is used in some welding transformers to remove heat more effectively when duty cycles are high or when compact design is needed. Oil has higher heat capacity and better heat transfer than air around windings, reducing hotspot temperatures and improving reliability. However, many welding transformers are dry type for simplicity, so oil cooled designs are typically chosen for heavy duty industrial applications where thermal margins matter.

Viscosity determines how easily oil circulates through windings and radiators. Lower viscosity improves convection and heat transfer, reducing operating temperatures. High viscosity restricts oil flow, decreases cooling efficiency, and accelerates insulation aging under load.

Oil leakage reduces insulation and cooling effectiveness and can expose internal components to moisture and air. Externally, leaks create fire hazards, environmental contamination, and regulatory compliance risks. Even small leaks can worsen over time. Prompt detection, containment, and repair are critical to prevent equipment damage, environmental penalties, and unplanned outages.

Acidity measures the concentration of acidic oxidation byproducts formed as oil ages. Rising acidity indicates oxidation and degradation that can accelerate sludge formation, reduce interfacial tension, increase dielectric losses, and attack solid insulation. Higher acidity can also correlate with increased corrosion risk and reduced cooling performance due to deposits on heat transfer surfaces. Monitoring acidity helps determine when oil needs inhibitor replenishment, regeneration, or replacement. Trending acidity alongside interfacial tension and tan delta provides a strong picture of oil aging severity.

„PPM“ in transformer oil testing usually refers to concentration measured in parts per million, most commonly moisture content (water) in ppm, and sometimes contamination such as PCBs or specific inhibitors. Moisture ppm is critical because even small increases can sharply reduce dielectric strength and accelerate paper aging. Depending on the lab program, ppm can also be used for dissolved gases, metals, or sulfur compounds, but moisture is the most common meaning.