Understanding Transformer Oil Types for Optimal Performance and Sustainability

This article describes various Transformer Oil Types, indicating their distinctive properties and uses. By understanding the types of oil and their regeneration processes, stakeholders can make informed decisions to protect their electrical infrastructure and contribute to sustainable power management practices.

List of Transformer Oil Types

1. Paraffinic Mineral Oils
2. Naphthenic Mineral Oils
3. Silicone Oils
4. Natural Esters
5. Synthetic Esters
6. Synthetic Hydrocarbons
7. Bio-based Oils
8. High Fire Point (HFP) Oils
9. Nanofluids
10. Hybrid Oils
11. Blended Oils
12. High-Temperature Hydrocarbon Oils

It is very important to maintain transformer oil quality as the power grid expands and adapts to new energy challenges. All oils degrade over time, the result of thermal, chemical, and electrical stresses that diminish both insulation and cooling properties. In order to address this critical need, INVEXOIL provides “Transformer Oil Regeneration Systems” that not only restore the properties of aged oils but also ensure compliance with industry-leading standards such as IEC 60296 and IEC 60422. These systems, together with specialized “Transformer Oil Regenerating Services“, demonstrate INVEXOIL’s commitment to enhancing transformer reliability while minimizing environmental impact.

Related Article: Comprehensive Guide to 17 Transformer Oil Regeneration Standards: Best Practices & Future Trends

Let’s Explore Detailed Explanation of Each Type:

1. Paraffinic Mineral Transformer Oils

These are the oils derived from crude oil by refining process. They show good oxidation stability and have a high flash point that makes them suitable for transformer applications with higher temperatures.

Paraffinic Mineral Oils Applications:

Used in transformer applications where there is a long-term requirement for stability against oxidation.

Table: Paraffinic Mineral Transformer Oils Properties

Property	Value
Density	~0.86–0.89 g/cm³
Viscosity	4–150 cSt (at 40°C)
Viscosity Index	90–120
Flash Point	160–230°C
Pour Point	-10 to -25°C
Composition	High in paraffinic hydrocarbons (straight and branched chains)
Thermal Stability	Moderate
Oxidation Stability	High

 

2. Naphthenic Mineral Transformer Oils

Naphthenic mineral oils are also derived from crude oil but are of a different chemical structure from paraffinic oils. They have a low pour point and are highly soluble, hence ideal for being used in cold regions.

Naphthenic Mineral Oils Applications:

Ideal for transformers operating in regions with low temperatures.

Table: Naphthenic  Mineral Transformer Oils Properties

Property	Value
Density	~0.89–0.92 g/cm³
Viscosity	3–100 cSt (at 40°C)
Viscosity Index	20–80
Flash Point	150–200°C
Pour Point	-20 to -40°C
Composition	High in cycloparaffins and aromatic hydrocarbons
Thermal Stability	Moderate
Oxidation Stability	Moderate

 

3. Silicone Transformer Oils

These are synthetic oils with superior thermal and oxidative stability. It has a high flashpoint and finds application in transformer applications where safety and better performance are required.

Silicone Transformer Oil Applications:

Used for transformers that require high temperatures and fire safety.

Table: Silicone Transformer Oils Properties

Property	Value
Density	~0.95–1.10 g/cm³
Viscosity	5–100,000 cSt (customizable)
Viscosity Index	>300
Flash Point	>300°C
Pour Point	-50 to -100°C
Composition	Polysiloxane-based with alternating silicon and oxygen atoms
Thermal Stability	Very high
Oxidation Stability	High

 

4. Natural Esters Transformer Oils

Natural esters are derived from vegetable oils and are biodegradable. They have a high fire point and good dielectric strength, making them environmentally friendly alternatives to mineral oils.

Natural Esters Oils Applications:

Suitable for transformers in environmentally sensitive areas.

Table: Natural Esters Transformer Oils Properties

Property	Value
Density	~0.90–0.95 g/cm³
Viscosity	30–50 cSt (at 40°C)
Viscosity Index	~200
Flash Point	>300°C
Pour Point	-10 to -30°C
Composition	Triglycerides derived from renewable sources like vegetable oils
Thermal Stability	Moderate
Oxidation Stability	Moderate

 

5. Synthetic Ester Transformer Oils

Synthetic ester derive balance properties between mineral oil and silicones. Its manufacturing processes are by chemical synthesis. They contain properties with high load-carrying capacity thermal and biodegradable.

Synthetic Ester Oils Applications:

Employed in transformers where thermal stability, safety, and environmental performance need to be balanced.

Table: Synthetic Ester Transformer Oils Properties

Property	Value
Density	~0.90–1.0 g/cm³
Viscosity	Wide range (customizable, typically 10–100 cSt at 40°C)
Viscosity Index	120–180
Flash Point	200–300°C
Pour Point	-40 to -60°C
Composition	Chemically engineered esters (monoesters, diesters, polyol esters)
Thermal Stability	High
Oxidation Stability	High

 

6. Synthetic Hydrocarbons Transformer Oils

Synthetic hydrocarbons are engineered oils that offer a balance of properties similar to mineral oils but with enhanced performance characteristics. They are known for their stability and efficiency.

Synthetic Hydrocarbons Oils Applications:

The most suitable for transformers under severe operating conditions where consistency in performance is highly desired.

Table: Synthetic Hydrocarbons Transformer Oils Properties

Property	Value
Density	~0.80–0.85 g/cm³
Viscosity	2–50 cSt (at 40°C)
Viscosity Index	120–160
Flash Point	~200–300°C
Pour Point	-50 to -70°C
Composition	Pure hydrocarbon chains (PAOs – polyalphaolefins)
Thermal Stability	High
Oxidation Stability	High

 

7. Bio-based Transformer Oils

These kind of oils are derived from renewable sources such as plants or algae. They are environmentally friendly and biodegradable, offering a sustainable alternative to traditional transformer oils.

Bio-based Oils Applicarions:

Used in transformers where environmental impact is a concern.

Table: Bio-based Transformer Oils Properties

Property	Value
Density	~0.88–0.92 g/cm³
Viscosity	30–60 cSt (at 40°C)
Viscosity Index	~180
Flash Point	>300°C
Pour Point	-10 to -30°C
Composition	Derived from plant-based sources like soy, sunflower, and palm oils
Thermal Stability	Moderate
Oxidation Stability	Moderate

 

8. High Fire Point (HFP) Transformer Oils

HFP oils are specifically designed to have enhanced fire safety properties. They are used in critical applications where fire hazards need to be minimized.

High Fire Point Oils Applications:

Suitable for transformers in high-risk environments such as industrial plants and densely populated areas.

Table: High Fire Point (HFP) Transformer Oils Properties

Property	Value
Density	~0.85–0.95 g/cm³
Viscosity	20–50 cSt (at 40°C)
Viscosity Index	100–150
Flash Point	>300°C
Pour Point	-20 to -40°C
Composition	Modified hydrocarbon or ester-based oils
Thermal Stability	High
Oxidation Stability	High

 

9. Nanofluids Transformer Oils

These oils contain nanoparticles, which enhance the thermal conductivity and dielectric properties of the oil. The performance of nanofluids is better than conventional ones.

Nanofluids Applications:

Utilized in transformers that need very high efficiency and better cooling.

Table: Nanofluids Transformer Oils Properties

Property	Value
Density	Base oil density + nanomaterial contribution
Viscosity	10–50 cSt (at 40°C), varies with nanoparticle concentration
Thermal Conductivity	Higher than base oil (~0.1–1.0 W/m·K, depending on nanoparticles)
Flash Point	Dependent on base oil (>200°C typical)
Pour Point	Dependent on base oil (-20 to -50°C typical)
Composition	Base oil (mineral/synthetic/ester) with dispersed nanoparticles
Stability	High (with proper dispersants)
Oxidation Stability	Varies with nanomaterial type

 

10. Hybrid Transformer Oils

Hybrid oils are a combination of various base oils to get customized properties. They offer the advantages of both mineral and synthetic oils.

Hybrid Transformer Oils Applications:

Best for special transformer applications where certain performance characteristics are needed.

Table: Hybrid Transformer Oils Properties

Property	Value
Density	~0.85–0.95 g/cm³
Viscosity	10–100 cSt (at 40°C)
Viscosity Index	100–200
Flash Point	>200°C
Pour Point	-20 to -40°C
Composition	Combination of different base oils (e.g., mineral and synthetic blends)
Thermal Stability	Moderate to high
Oxidation Stability	Moderate to high

 

11. Blended Transformer Oils

These are mixtures of various base stocks or oils with added additives for the enhancement of performance. They provide tailored properties for particular applications.

Blended Oils Applications:

They are used in those transformers that require particular performance enhancement.

Table: Blended Transformer Oils Properties

Property	Value
Density	~0.85–0.92 g/cm³
Viscosity	5–100 cSt (at 40°C)
Viscosity Index	90–150
Flash Point	~150–300°C
Pour Point	-10 to -50°C
Composition	Mixture of mineral, synthetic, or natural ester oils
Thermal Stability	Varies (dependent on blend ratio)
Oxidation Stability	Moderate

 

12. High-Temperture Hydrocarbon Transformer Oils

These oils are specifically designed to operate at higher temperatures without compromising their dielectric properties. They provide stability and reliability under severe conditions.

High-Temperture Hydrocarbon Oils Applications:

Ideal for transformers operating in high-temperature environments, such as those in industrial plants or desert regions.

Table: High-Temperture Hydrocarbon Oils Properties

Property	Value
Density	~0.80–0.85 g/cm³
Viscosity	5–50 cSt (at 40°C)
Viscosity Index	>150
Flash Point	>200°C
Pour Point	-40 to -60°C
Composition	High-purity hydrocarbon chains (polyalphaolefins or other synthetics)
Thermal Stability	Very high
Oxidation Stability	Very high

 

Classification of Transformer Oils Based on Different Aspects

By classifying transformer oils based on these different aspects, we gain a comprehensive understanding of their unique properties, applications, and environmental impacts. This detailed analysis helps in selecting the appropriate transformer oil for specific requirements, ensuring optimal performance and safety. Let’s explore them:

1. Transformer Oil Types Based on Chemical Composition

• • Mineral Oils

    • Paraffinic Mineral Oils
    • Naphthenic Mineral Oils

  • Synthetic Oils

    • Silicone Oils
    • Synthetic Esters
    • Synthetic Hydrocarbons

  • Ester Oils

    • Natural Esters
    • Synthetic Esters

  • Bio-based Oils

    • Bio-based Oils

  • Other Types

    • Nanofluids
    • Hybrid Oils
    • Blended Oils
    • High-Temperature Hydrocarbon Oils

2. Transformer Oil Types Based on Source

1. • Petroleum-Based Oils

     • Paraffinic Mineral Oils
     • Naphthenic Mineral Oils

   • Bio-Based Oils

     • Natural Esters
     • Bio-based Oils

   • Synthetic Oils

     • Silicone Oils
     • Synthetic Esters
     • Synthetic Hydrocarbons

3. Transformer Oil Types Based on Environmental Impact

1. • Biodegradable Oils

     • Natural Esters
     • Synthetic Esters
     • Bio-based Oils

   • Non-Biodegradable Oils

     • Paraffinic Mineral Oils
     • Naphthenic Mineral Oils
     • Silicone Oils
     • Synthetic Hydrocarbons

4. Transformer Oil Types Based on Performance Characteristics

1. • High Fire Point (HFP) Oils

     • Natural Esters
     • Silicone Oils

   • Low-Temperature Performance Oils

     • Naphthenic Mineral Oils
     • Synthetic Esters

   • High-Temperature Performance Oils

     • High-Temperature Hydrocarbon Oils
     • Silicone Oils

   • Enhanced Dielectric Properties

     • Nanofluids
     • Blended Oils

5. Transformer Oil Types Based on Application

1. • General Purpose Oils

     • Paraffinic Mineral Oils
     • Naphthenic Mineral Oils

   • High-Performance and Specialized Oils

     • Silicone Oils
     • Natural Esters
     • Nanofluids

6. Transformer Oil Types Based on Processing and Additives

1. • Pure Oils

     • Paraffinic Mineral Oils
     • Naphthenic Mineral Oils

   • Modified Oils

     • Hybrid Oils
     • Blended Oils

7. Transformer Oil Types Based on Inhibited and Uninhibited 

• Inhibited Oils:

  • Paraffinic Mineral Oils
  • Naphthenic Mineral Oils
  • Synthetic Esters
  • Synthetic Hydrocarbons
  • High Fire Point (HFP) Oils
  • High-Temperature Hydrocarbon Oils

• Uninhibited Oils:

  • Silicone Oils
  • Natural Esters
  • Bio-based Oils
  • Nanofluids
  • Hybrid Oils
  • Blended Oils

 

Conclusion

Understanding the type of transformer oil such as Paraffinic Mineral Oils, Naphthenic Mineral Oils, Silicone Oils, Natural Esters, Synthetic Estersand, and etc. where they are used can facilitate well-informed decisions among stakeholders for maximizing performance and securing the future in constantly changing electrical infrastructure. The innovative INVEXOIL Transformer Oil Regeneration Systems and Transformer Oil Regenerating services based on IEC 60296 and IEC 60422 standards show just how important sustaining the quality of the oil can be to environmental sustainability and operational excellence.