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Understanding Oil for Transformers : What You Should Know?

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oil immersed transformers

Oil for Transformers : What you need to know?

When most people think about oils, they imagine lubricants that help reduce friction and heat. However, that is not the case for all oils. For instance, this oil is actually designed more for insulating than for lubricating, and it is used in very different applications from other oils. Not sure what type of oil for transformers we use or how it works? We’ll explore what you need to know below.

Types of  Insulating Oil

Like some other types of oil, such as motor oil, insulating oil’s purpose can be found in its name. This type of oil is designed for use in power transformers, which play a critical role in the energy grid. It is also called insulating oil for this reason.

Power transformers

What Does It Do?

Unlike other oils, transformer insulating oil is not designed to reduce friction. However, it is designed to help reduce temperature – motor oil does this to an extent, as well. With that being said, this oil also has a second, even more important, task. That is, it is designed to insulate it. Because of this, the oil differs greatly from other types of lubricants in terms of properties. In order to be used within a transformer, an oil must:

• Have a high dielectric strength • Have high thermal conductivity • Have high chemical stability • Must be able to maintain all characteristics at very high temperatures and for long periods of time This oil is used to preserve the windings and core within a power transformer. Without this oil, transformers would quickly overheat and suffer damage from corona discharge, arcing, and more.

Types of  Oil for Transformers

Most oils are mineral oil based. The two most common options on the market are paraffin-based oil and naphtha-based oil. Of these, naphtha oil oxidizes more easily, but the sludge produced during oxidation is more soluble than what is produced within paraffin-based oil. This means that the sludge does not collect at the bottom of the transformer where it would eventually obstruct convection circulation within the oil.

Paraffin-based oil does not offer the same benefit and sludge can more easily collect at the bottom of the transformer. It also has a high pour point, which can be an issue in colder climates.

Types of transformer oil

Other Applications

Transformer insulating oil is primarily used in the world of power generation. However, it does have uses in other situations. It can be used in any situation in which insulation is necessary within an electrical component, and is well-suited to very high-voltage applications. For example, high-voltage switches and capacitors, as well as some types of circuit breakers can benefit from the cooling and insulating properties of this oil.

Transformer insulating oil -Transformer insulation system

Regular Testing :

Finally, because transformer oil is a safety precaution, it must be tested regularly and replaced when its properties have been altered. On-site inspections should be conducted twice per year, and samples should be tested for dissolved gasses annually. If a transformer has been in operation for five years, this oil should be subject to Furan testing every two years.

Furan Testing of Transformers Oil

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