What Is an Oil Immersed Transformer and Why Is It Widely Used?

An oil immersed transformer is a type of electrical transformer that uses mineral oil as an insulating and cooling medium. This design is one of the most common and reliable transformer types used in power distribution and transmission networks worldwide.

What Is an Oil Immersed Transformer?

In an oil immersed transformer, the core and windings are submerged in oil inside a sealed tank. The oil acts both as an electrical insulator and as a coolant to dissipate the heat generated during transformer operation. This helps maintain the transformer's efficiency and prolongs its service life.

How Does It Work?

When electrical current passes through the transformer windings, it induces magnetic flux in the core, enabling voltage transformation. The process generates heat, which the oil absorbs and transfers to the tank walls. The tank often has radiators or cooling fins to release the heat into the surrounding environment.

Advantages of Oil Immersed Transformers

Efficient Cooling: Oil effectively absorbs and transfers heat, allowing the transformer to handle high loads.

Superior Insulation: Mineral oil provides excellent dielectric strength, preventing electrical breakdowns.

Durability: Designed for long service life with robust construction and maintenance-friendly features.

Cost-Effective: Compared to dry-type transformers, oil immersed units often have better performance-to-cost ratios.

Wide Application Range: Suitable for outdoor and indoor use, including power plants, substations, and industrial facilities.

Types of Oil Immersed Transformers

Distribution Transformers: Used in power distribution networks for stepping down voltage to usable levels.

Power Transformers: Used in transmission networks to step up or step down high voltages.

Autotransformers: A variant with a single winding serving both primary and secondary functions, also oil immersed.

Maintenance and Safety

Regular maintenance includes oil testing for moisture and contamination, inspecting the tank and cooling system, and checking for leaks. Safety measures must address fire risks due to the flammability of mineral oil, with modern transformers incorporating fire-resistant oils or additional protective features.

Environmental Considerations

While mineral oil is effective, environmental concerns over leaks and disposal have led to the development of biodegradable and less flammable insulating fluids, which are increasingly used as alternatives.

Conclusion

Oil immersed transformers remain a backbone of electrical power infrastructure due to their efficiency, reliability, and cost-effectiveness. With proper maintenance and modern innovations, they continue to meet the demanding needs of today’s power systems.