Function of transformer oil

What is the Purpose of Transformer Oil?

Transformer oil plays a pivotal role in the operation and longevity of electrical transformers, serving four vital functions:

1. Heat Dissipation: The primary function of transformer oil is to disperse heat from the core and coil. As the oil heats up, it rises to the top and flows out into the tops of the radiator's tubes. It cools as it works its way down the tubes and returns to the transformer at the bottom. This process, known as thermal siphoning, ensures that the transformer components remain at optimal temperatures.

2. Dielectric Capabilities: Transformer oil must possess dielectric properties to insulate and protect the transformer's components from electrical discharges.

3. Protection of Solid Insulation: The oil safeguards the solid insulation (typically paper) within the transformer. Damage to this paper can weaken its tensile strength, shortening the transformer's lifespan.

4. Monitoring and Maintenance: Transformer oil facilitates easy monitoring. By taking representative samples and sending them to a lab, various tests (such as oil aging, dissolved gas analysis, and moisture content) can be conducted to assess the transformer's health.

What Types of Fluid?

Manufacturers produce a variety of transformer fluids, with mineral oil being the most prevalent. There are two main types of transformer oil:

• Type 1: Uninhibited oil.
• Type 2: Inhibited oil with an oxidation inhibitor added to prevent aging caused by oxygen ingress. Type 2 oil is generally recommended due to its enhanced longevity.

Transformer oil also has a breakdown voltage (BDV) which indicates its ability to withstand electrical stress without failure. Contaminants such as water, dirt, and fibers can lower the dielectric strength of the oil. Regular testing and maintenance are essential to ensure the oil's effectiveness.

What is the Color of Transformer Fluids?

The color of transformer fluids varies depending on their type and age:

• New Mineral Oil: Typically water-white (clear).
• Aged Mineral Oil: Changes from water-white to dark brown or even black due to carbon buildup.
• Natural Esters: Newer fluids have a light green tint.

The color of the oil can indicate its condition and whether it requires cleaning or replacement. When fluids are no longer in production, finding compatible replacements is crucial for maintaining transformer performance.

Why is Transformer Oil Testing Important?

Transformer oil testing is critical for several reasons:

• Electrical Property Assessment: Determines the essential electrical properties of the transformer oil.
• Suitability for Future Use: Identifies if the oil is suitable for continued use or needs replacement.
• Maintenance Needs: Detects whether oil regeneration or filtration is required.
• Cost Reduction and Lifespan Enhancement: Helps reduce oil costs and enhance the life of transformer components.
• Failure Prevention and Safety Maximization: Prevents untimely failures and maximizes operational safety.

Oil Processing (Hot Oil Cleaning)

Hot oil cleaning, or oil processing, is a method used to remove oxidation decay products, including sludges from mineral oil-immersed transformers. The dirty oil is removed from the bottom of the transformer, cleaned through an oil processor, and returned to the transformer. This process may need to be repeated several times, depending on test results and the volume of oil in the transformer. Additionally, reinhibiting can be performed to restore the oxidation inhibitor levels, further extending the oil's usefulness.

Advantages of Regular Transformer Oil Maintenance

Regular maintenance of transformer oil offers several benefits:

• Improved Transformer Efficiency: Clean oil ensures better heat dissipation and dielectric performance.
• Extended Transformer Life: Regular oil testing and maintenance prevent damage to the solid insulation and other critical components.
• Saving Costs: By maintaining oil quality, transformers can operate more efficiently and with fewer interruptions.
• Enhanced Safety: Properly maintained oil reduces the risk of electrical discharges and potential transformer failures.

Conclusion

Transformer oil is essential for the efficient and reliable operation of electrical transformers. It serves crucial functions such as heat dissipation, dielectric insulation, and protection of solid insulation. Regular testing and maintenance of transformer oil are vital for ensuring the longevity and safety of transformers. By understanding the types of transformer fluids, their color indications, and the importance of oil testing, operators can better manage their equipment and prevent costly failures.