Transformer Oil Treatment

Transformer oil treatment should be carried out on a regular basis during the operation of high-voltage power equipment. Over time, water, oxidation products, and mechanical impurities accumulate in transformer oil.

The process sequence is typically as follows:

• Mechanical filtration (removal of water and solids from oil)
• Thermophysical purification (vacuum treatment)

Causes and Consequences of Oil Contamination

One of the primary causes of oil contamination is oxidation. When oil is exposed to oxygen, it undergoes chemical reactions that lead to the formation of acids, aldehydes, and ketones. These compounds degrade the chemical stability of oil and accelerate its aging. Moisture is another significant contaminant, often entering the system through microcracks or due to temperature and humidity fluctuations. Dissolved water reduces the dielectric strength of oil, increasing the risk of dielectric breakdown. Furthermore, transformer oil can become contaminated with solid particles such as metal shavings, insulation debris, and dust, which may enter during manufacturing, transportation, or routine operation. If left untreated, contaminated oil can cause overheating, increased energy losses, and major transformer faults.

Methods of Transformer Oil Treatment

Several methods are used to purify transformer oil and restore its performance:

• Removal of solid particles: which involves removing large particles of contaminants with the use of filters. Mechanical cleaning is usually the first step in oil treatment, as it allows for effective removal of mechanical impurities without altering the chemical properties of oil. For this purpose, strainers or cartridge filters are used to capture impurities without allowing them to enter the transformer oil circuit.
• Adsorptive Purification: sorbents can be of natural origin (e.g. activated carbon), or of synthetic type (silica gel, zeolites). The advantage of adsorptive purification is its ability to remove not only mechanical impurities, but also dissolved compounds in the oil, such as acids and oxides that develop during the oil oxidation process. However, adsorptive purification can be quite expensive due to the need to change sorbents after each treatment.
• Vacuum treatment: vacuum degassing reduces oxygen and carbon dioxide in oil, which significantly slows down oxidation processes and extends the service life of oil. This method is often used in combination with other cleaning methods to maximize the effect.

Periodic transformer oil treatment significantly extends the service life of a transformer and enhances its operational reliability. By removing impurities and moisture, the probability of short circuits is reduced and the risk of overheating is mitigated.

Comprehensive Transformer Oil Treatment with the use of FLD D Fluidex

The FLD D Fluidex Vacuum Oil Purifier is designed for high-performance transformer oil treatment, which involves degassing, dehydration, mechanical filtration, and heating. This system is suitable for transformers with voltage ratings up to 1,150 kV and can be utilized for multiple applications, including hot oil circulation, vacuum drying, and transformer evacuation. The FLD D Fluidex system can be used for heating of oil-filled electrical units with hot transformer oil, for vacuum drying and evacuation of transformers. The system is used by installation, repair, and maintenance organizations engaged in transformer oil treatment.  It supports multiple operating modes, including:

• Evacuation
• Heating and Filtration
• Degassing
• Vacuum Treatment

In Heating and Filtration mode, untreated oil is run by a pump through a pre-filter, flows through a shut-off valve, a heater, and a fine cartridge filter before exiting the system. This process filters out solid impurities and prepares the oil for further treatment.

For vacuum degassing, the purifier is connected to an oil tank. The oil is first heated and filtered, then fed into a vacuum chamber through a sprayer system. As the oil passes through the sprayers, dissolved gases and moisture are efficiently removed under vacuum. The vacuum level is maintained by high-performance vacuum pumps, ensuring that the oil meets the required dielectric strength and purity standards.