Insulating oils cool, lubricate - what else? Insulating oil properties

Insulating oil is used in transformers primarily to insulate the winding and to cool the system. The insulating oil also ensures efficient heat transfer and insulates the transformer from its surroundings. Th oil also helps prevent corona discharges adn arcing. Read more about the properties of insulating oils in this blog article.

Transformer oil or insulating oil is a highly refined mineral oil or a low-viscosity silicone oil that remains stable at high temperatures. They are ideal for use as insulating and cooling fluids in transformers, reactors, chokes, converters, switches and other high-voltage devices that operate under high thermal loads.

Transformer oils and insulating oils are true all-rounders

Transformer oil not only insulates, it also cools, lubricates, maintains stability, has dielectric properties and a medium to low viscosity:

1. Insulation: 
Insulating oils are often used in electrical transformers and switchgear to ensure efficient electrical insulation. They have a high dielectric strength, which prevents current from flowing through the oil and causing short circuits.

2. Cooling:
Transformer oils have good thermal conductivity, which allows them to effectively dissipate heat from electrical components. This helps to reduce the operating temperature of the equipment and
extend its service life.

3. Lubrication: 
Insulating oils also have lubricating properties that help reduce wear on moving parts in transformers and switchgears. This helps to extend the operating life of the equipment and maintain its performance.

4. Stability: 
Transformer oils must be chemically stable to withstand the demands of operation in electrical equipment. They should not cause corrosion or degrade under normal operating conditions.

5. Dielectric properties: 
Insulating oils must have high dielectric strength to reliably insulate electrical voltages. That means they must be able to withstand high voltages without breaking down.

6. Viscosity: 
The viscosity of transformer oils is important to ensure that they can spread evenly over the electrical components. A suitable viscosity also ensures good lubrication and heat dissipation.

The properties of insulating oils ensure good transformer performance

The insulating oil should have good resistance to ageing and oxidation to ensure a long service life for the transformer.

The following properties are important for transformer oils:

• Good ageing stability (depending on operating time, temperature, load-cycle and ambient conditions)
• High flash point (compatible with the high temperatures in the transformer)
• Good water separation (even small traces of water reduce the breakdown voltage)

It is important that the insulating oil is regularly checked for its properties and maintained to ensure optimum transformer performance.

Read more in these blog articles:

• Laboratory services for insulating oils: what to look out for
• Transformer maintenance: When to change the oil in transformers?
• Valuable tips when you have the insulating oil in the transformer changed
  
  
  

Conclusion

Insulating oils are true all-rounders - they insulate, cool, lubricate, maintain stability, have excellent  dielectric properties. Specialised oil maintenance companies are available in the market to maintain and regularly check these properties. They help electrical plant operators to extend the service life of their transformers by checking the quality and condition of the transformer oils with a simple insulating oil sample, which can be reliably analysed to identify potential adverse properties which may affect their performance.

You can find more tips in this blog article:

• How companies can extend the service life of transformers

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