How a Transformer Oil filtration System Works and Its Basics

by Michael M.

Oil filtration systems are necessary to purify the oil, such as the transformer oil filtration system. A vacuum is used to remove water, moisture, sludge, and chemicals from the oil. Transformers run efficiently on filtered and dried oil and keeps them in good condition for a long time. Most transformers fail due to contaminated oil; hence the filtration process has significant benefits to them. In this write-up, we discuss the basics of a transformer oil filtration system

How Does the Transformer Oil Filtration System Work?

The process involves three steps from start to finish to produce purified oil for use. In the transformer oil purifier machine, the first step is raising the temperature of the oil to 65 degrees Celcius. It becomes less dense when hot, and the latent heat can separate the moisture and other impurities like gases easily.

The second step involves removing dirt and sludge from the hot oil in two ways, i.e., centrifuging and the use of filter candles. Centrifuging makes the dust settle at the bottom of the machine while the oil remains at the top. It not 100 percent efficient as not all dust is removed. However, you can change filters often using this method. Filter candles are categorized into two: depth type filter and classical edge type. Over recent years, advancements have been made where the oil filtration equipment uses filter cartridges more than the edge paper filters.

The final step involves dehydration and degassing of the oil. The oil is taken to the degassing chamber. The difference is caused by the varying water and oil boiling points, they are separated through centrifuging, and the oil is filtered.

Advantages of the Transformer Oil Filtration System

The system has several benefits, including;

It improves the insulation capacity of the oil. The transformer oil provides insulation within the coils to prevent damages like arcing, corona discharges, overheating, and short circuits.

Make the oil a better coolant for the transformer when its voltage fluctuates and produces too much heat. It enhances heat dissipation through the radiators.

Purified and dried oil prevents the breakdown and failure of the transformer hence increasing its lifespan.

When Does the Oil Require Filtering?

The condition of the oil must be determined through tests to know whether filtration is needed. If the test results are unsafe and unacceptable, rapid filtration is done to purify the oil. Some include;

a. Visual Examination

It’s done in the lab by passing a beam of light through the oil. Contaminated oil appears cloudy with inadequate transparency and has foreign matter.

b. Dielectric Breakdown Voltage Test

DBVtest is used to measure the voltage at which the oil fails electrically. It indicates the amount of oil or moisture present.

c. Flash Point

It is used to check the oil’s volatility

d. Dissolved Gas Analysis

The oil is put in a glass syringe and taken to the lab to identify the dissolved gases.

e. Moisture Content

The oil moisture is measured by calculating the moisture weight by that of oil. Moisture should be low for the oil to be termed as good.


A transformer oil filtration system is very beneficial and shouldn’t be overlooked. Maintaining the oil helps the transformer function and perform effectively. Get a good oil purification machine that’s high quality, considering that where the process begins.

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