What You Need to Know about Oil-immersed Transformer

An oil-immersed transformer is a type of power transformer that uses oil as an insulating and cooling medium. These transformers are widely used in electrical power distribution systems and industrial applications because of their efficiency, reliability, and long service life. Below are the key points you need to know about oil-immersed transformers:

1. How Oil-Immersed Transformers Work

In an oil-immersed transformer, the windings and core are submerged in oil, typically mineral oil or a synthetic insulating fluid. The primary function of the oil is to:

  - Insulate the windings and prevent electrical short circuits.

  - Cool the transformer by dissipating heat generated during operation.

  - Prevent oxidation and degradation of the internal components by limiting exposure to air.

The oil circulates either naturally or through pumps, ensuring that heat is effectively transferred away from the transformer components and dispersed through radiators or cooling fins.

2. Types of Oil-Immersed Transformers

  - ONAN (Oil Natural Air Natural): This type relies on natural convection for oil circulation and air cooling. It is the most commonly used type for distribution transformers.

  - ONAF (Oil Natural Air Forced): In this type, the oil circulates naturally, but fans force air over the transformer to enhance cooling.

  - OFAF (Oil Forced Air Forced): Both the oil and air circulation are mechanically forced to provide additional cooling for larger or more heavily loaded transformers.

  - OFWF (Oil Forced Water Forced): Cooling is enhanced by using water instead of air, typically used for large industrial applications.

3. Advantages of Oil-Immersed Transformers

  - Efficient Cooling: The use of oil allows for effective heat dissipation, making oil-immersed transformers more efficient at high power levels.

  - High Reliability: These transformers have a long operational life and require minimal maintenance if operated under normal conditions.

  - High Insulation: The oil provides excellent electrical insulation, ensuring the safety and stability of the transformer even under heavy loads.

  - Cost-Effective: Oil-immersed transformers are generally more cost-effective than dry-type transformers for larger capacities.

4. Applications

Oil-immersed transformers are widely used in:

  - Power Distribution: In electrical grids to step down high voltage electricity from transmission lines for residential or commercial use.

  - Industrial Plants: For powering heavy machinery and equipment.

  - Renewable Energy Systems: Such as wind farms and solar power installations, where large amounts of energy need to be efficiently managed and distributed.

5. Maintenance

  - Oil Testing: Regular testing of the oil for moisture, acidity, and contaminants helps detect potential problems early and prevent transformer failure.

  - Visual Inspections: Checking the oil level, radiators, and bushings for leaks or signs of damage is important for safe operation.

  - Filtration and Replacement: The oil may need to be filtered or replaced if it becomes contaminated or degraded over time.

6. Potential Issues

  - Oil Leaks: If the transformer’s casing or seals are damaged, oil leaks can occur, leading to reduced insulation and cooling.

  - Overheating: If the oil or cooling system fails, the transformer may overheat, which can cause damage to the windings and reduce the lifespan of the transformer.

  - Environmental Concerns: Mineral oil is flammable, and oil leaks or spills can have environmental impacts. However, newer synthetic or biodegradable oils are available as environmentally friendly alternatives.

7. Safety Considerations

  - Fire Risk: Since mineral oil is flammable, proper safety measures should be in place, such as fire detection systems and barriers.

  - Explosion Risk: In rare cases, internal faults can lead to transformer explosions. Pressure relief devices and proper maintenance help mitigate this risk.

8. Comparison with Dry-Type Transformers

  - Cooling: Oil-immersed transformers are more efficient at cooling compared to dry-type transformers, making them ideal for higher power ratings.

  - Size: Oil-immersed transformers are typically more compact than dry-type transformers for the same power rating.

  - Maintenance: While oil-immersed transformers require more maintenance (such as oil testing), they tend to be more durable in the long run compared to dry-type transformers.

  - Safety: Dry-type transformers are generally safer in indoor environments since they don’t use flammable oil.

Conclusion

Oil-immersed transformers are a reliable and efficient solution for high-power applications. They offer superior cooling, excellent insulation, and are cost-effective for larger installations. Regular maintenance, such as oil testing and visual inspections, is essential to ensure their longevity and safe operation. For applications requiring large-scale power distribution or industrial use, oil-immersed transformers are often the best choice.

Daya Electric Group Co., Ltd. is located in the scenic area of Yongjia, Wenzhou,Zhejiang, founded in 1988, has been more than 30 years, specializing in the production of 35KV and below wire and cable,high and low voltage switchgear.Visit our website at https://www.dayaglobal.com to learn more about our products. For inquiries, you can reach us at mina@dayaeasy.com.