Oil-immersed transformers are critical components in electrical power distribution, used to increase or decrease voltage levels for efficient transmission of electricity. These transformers rely on oil for both cooling and electrical insulation, which is critical to their correct operation. However, not all oils are made equal, and the type of oil used in transformers is carefully chosen to assure safety, performance, and durability. In this article, we'll look at the several types of oil that are commonly used in oil-immersed transformers, as well as the properties that make them appropriate for this crucial job.
1. Mineral Oil
Mineral oil, a refined petroleum-based oil, is the most commonly used type of oil in oil-immersed transformers. It has been the traditional choice for decades due to its excellent insulating properties, good heat transfer characteristics, and availability.
Key Features of Mineral Oil:
- Good Electrical Insulation: Mineral oil has a high dielectric strength, making it an excellent electrical insulator. It prevents electrical arcing and breakdown between the transformer’s windings and core.
- Effective Heat Dissipation: The oil has good thermal conductivity, allowing it to absorb and dissipate the heat generated by the transformer’s operation effectively.
- Stability: Refined mineral oil is stable at a wide range of temperatures, ensuring that the transformer operates efficiently under varying conditions.
- Cost-Effective: Mineral oil is relatively inexpensive compared to other types of oils, making it a cost-effective choice for many transformer manufacturers.
Mineral oil remains the standard for most medium and small-sized transformers, as it provides a good balance of performance and affordability. However, it does have limitations, especially when it comes to environmental concerns and fire hazards, which has led to the development of alternative oils.
2. Silicone Oil
In some cases, silicone oil is used as an alternative to mineral oil, particularly in transformers where higher performance and better environmental properties are required.
Key Features of Silicone Oil:
- High Thermal Stability: Silicone oil has excellent thermal stability, with a higher boiling point than mineral oil. This makes it particularly suitable for transformers that operate at higher temperatures.
- Low Flammability: Silicone oil is less flammable than mineral oil, which reduces the risk of fires in the event of a transformer failure.
- Superior Insulation: It offers excellent dielectric properties, making it an effective insulator in high-voltage applications.
Although silicone oil offers enhanced performance, its higher cost compared to mineral oil makes it more suitable for specialized applications, such as in transformers for critical infrastructure or where safety and environmental concerns are paramount.
3. Vegetable Oil-Based (Natural Ester) Oil
Another alternative to traditional mineral oil is vegetable oil-based oil, often referred to as natural ester oil. These oils are derived from plant-based sources like rapeseed or soybean and are becoming increasingly popular due to their eco-friendly properties.
Key Features of Vegetable Oil-Based Oil:
- Biodegradable: One of the most significant advantages of natural ester oil is its biodegradability. In the event of a spill or leak, vegetable oils break down more quickly and cause less environmental damage compared to mineral oil.
- High Fire Point: Vegetable oils have a higher fire point than mineral oils, making them less flammable and safer in the event of a transformer fault.
- Excellent Cooling Properties: Natural esters have great heat transfer properties, helping dissipate the heat generated within the transformer.
- Low Toxicity: These oils are non-toxic, reducing health and safety risks to workers and the environment.
However, the cost of vegetable oil-based oils is typically higher than mineral oil, and these oils require careful management to maintain their performance. Additionally, vegetable oils may be more prone to oxidation than mineral oils, meaning they may require additional maintenance to prevent degradation.
4. Synthetic Esters
Synthetic esters are artificially engineered oils, typically made from synthetic chemicals, and are sometimes used in transformers where enhanced performance and safety are necessary.
Key Features of Synthetic Esters:
- High Fire Safety: Synthetic ester oils have a very high fire point, making them highly resistant to ignition and thus safer than mineral oil in high-risk environments.
- Environmental Friendliness: Like natural esters, synthetic esters are biodegradable, which makes them a safer choice for the environment in case of leaks or spills.
- Excellent Insulation and Cooling: They provide excellent dielectric properties, which allow for high-voltage applications, and also dissipate heat effectively.
- Longer Lifespan: Synthetic ester oils tend to have a longer operational life, and they are more stable than mineral oils, reducing the need for frequent maintenance.
Due to their higher cost, synthetic esters are typically used in specialized applications where their enhanced performance, environmental benefits, and safety features are required, such as in transformers for critical infrastructure, renewable energy installations, or areas with strict fire safety regulations.
5. Askarel (PCB-Based Oil)
Historically, askarel oil (a type of oil containing polychlorinated biphenyls or PCBs) was used in transformers. However, due to the environmental and health risks associated with PCBs, askarel oil is no longer used in modern transformers.
Why Askarel Is No Longer Used:
- Toxicity: PCBs are highly toxic and have been banned in many countries due to their potential health and environmental hazards.
- Environmental Impact: PCBs do not biodegrade and can persist in the environment, accumulating in the food chain and causing long-term ecological damage.
Due to these severe environmental and health risks, askarel oils have been phased out and replaced by safer alternatives such as mineral oils, esters, and silicone oils.
The type of oil used in an oil-immersed transformer is determined by various criteria, including performance requirements, cost, and environmental considerations. Mineral oil is the most widely used oil due to its low cost, efficient cooling, and insulating capabilities. Alternatives, such as silicone oil, vegetable oil-based oils, and synthetic esters, provide increased safety, environmental benefits, and high-temperature performance in specialized applications.
As the demand for sustainability and safety in electrical equipment develops, transformer makers are increasingly turning to biodegradable oils such as natural and synthetic esters, which provide great insulation and cooling while being more environmentally friendly.
Finally, the proper oil selection guarantees that oil-immersed transformers continue to work efficiently, safely, and dependably, powering modern electrical grids and contributing to global energy distribution.
SGOB Oil Immersed Transformers, a premium line of electrical transformers designed to meet the rigorous demands of modern power distribution systems. These transformers leverage the proven technology of oil immersion to provide superior thermal management, enhanced durability, and reliable performance in a variety of applications.Visit our website at www.sgobtransformer.com to learn more about our products. For inquiries, you can reach us at enquiry@sgobtransformer.com.
