Transformer oil refining and degassing are important processes that help you maintain the high quality and efficiency of transformers, as well as other electrical machines. Oil in transformers is used for insulation and cooling, and over time, it tends to become contaminated or accumulate gas impurities that reduce its efficiency and can lead to equipment failures. Proper oil refining and degassing help you prevent these problems and extend the service life of such equipment.
Common Contaminants in Transformer Oil
Power transformers are among the most critical components of electrical grids worldwide, with an estimated global installed capacity of approximately 3,030 million kVA. Their reliable and trouble-free operation is essential to the stability of power substations, as unexpected failures can lead to considerable financial losses. Most of transformers currently in operation are oil-filled, and one of the primary causes of transformer failures is the degradation of insulation systems due to moisture ingress and contamination.
During long-term operation, transformer oil becomes contaminated with various impurities, including particulate matter, water, and chemical compounds. The most hazardous contaminants include the particulate matter smaller than 5 microns in size, which accounts for about 95% of total contaminants in oil. This particulate matter is primarily represented by oxidation byproducts of oil. Emulsified water in oil reduces its dielectric strength, while chemical substances, such as gases, acids, and hydrocarbons, adversely affect the dielectric dissipation factor, further degrading the insulating properties of oil.
Methods of transformer oil refining
In order to restore the properties of used transformer oil, several technological processes are employed to remove aging products and contaminants. These processes include:
Mechanical Filtration: this method removes free water and solids from the oil, improving its purity and performance.
Thermal-Physical Methods: the processes, such as evaporation and vacuum distillation, effectively remove moisture and dissolved gases from the oil.
Physicochemical Methods: the techniques, such as coagulation and adsorption, help you remove fine contaminants and dissolved impurities.
Periodic transformer oil refining within transformers and circuit breakers is necessary, particularly in cases where a sudden decrease in breakdown voltage, carbonization, or other abnormal phenomena occur. Typically, in such situations, transformers and circuit breakers are taken offline and disconnected from the electrical grid to undergo thorough purification.
Before transformer oil is fed into electrical equipment, it undergoes deep thermal-vacuum treatment to ensure optimal quality. The oil used in transformers with film or nitrogen protection and sealed bushings, as well as in sealed instrument transformers should not exceed the air content of 0.5% (determined by gas chromatography) and the water content of 0.001% by mass. For transformers without film protection and sealed bushings, the allowable water content of transformer oil is up to 0.0025% by mass. Additionally, the purity class of the oil should meet specific standards: it should not be worse than class 11 for the equipment operating at voltages up to 220 kV and not worse than class 9 for the equipment operating at voltages above 220 kV.
Comprehensive Transformer Oil Purification Plants (FLD D)
Unlike conventional lubricants, transformer oil is primarily valued for its dielectric rather than lubricating properties. However, the presence of moisture, gases, and contaminants compromises these properties, rendering the oil unsuitable for further use in electrical equipment. While in service, transformer oil becomes saturated with these impurities, which necessitates complete purification by means of specialized equipment.
The purification process begins with pariculate matter removal. This is achieved by filtering the oil through fine-mesh filters, which capture dust particles and metal debris. While effective in removing visible contaminants, filtration does not alter the chemical state of oil. Next, the oil undergoes degassing and dehydration, commonly performed with the use of vacuum. The vacuum process removes dissolved gases and moisture from the oil, which is crucial for maintaining its insulating properties. Vacuum treatment not only improves the oil quality, but also prevents internal corrosion of transformers.
The FLD D purification plants combine filtration and thermal vacuum treatment to achieve comprehensive transformer oil purification. These systems effectively remove impurities, restore the dielectric strength of oil, and ensure the continued reliable performance of power transformers. By employing a combination of mechanical, thermal, and physicochemical processes, the FLD D plants deliver thorough oil purification, extending the service life of both the oil and the transformers it serves.
Transformer Oil Reclamation Plants (FLD R)
When transformer oil becomes critically degraded, mechanical processing and vacuum treatment may not be sufficient. At this stage, the reclamation process is required to remove oxidation byproducts and restore the antioxidant protection of oil. The FLD R transformer oil reclamation plants involve the use of Fuller’s Earth sorbents that adsorb oxidized compounds and acids, thereby restoring the chemical properties of oil. This method not only removes acidic and oxidized compounds, but also restores the molecular structure of oil, considerably improving its physical and chemical properties.
Reclamation by means of FLD R plants not only restores the dielectric and physical properties of used transformer oil, but also provides the most efficient approach to its reuse. The development and implementation of effective transformer oil refining technologies are essential for resource conservation and environmental sustainability.
Fuller’s Earth effectively removes oxidation byproducts and impurities, restoring the oil to as good as new condition. Transformer oil refining extends the service life of oil while significantly reducing the environmental impact associated with oil disposal.
Contamination of transformer oil by moisture, gases, and solid impurities degrades its insulating properties and can lead to transformer failure. Through a combination of mechanical, thermal, and adsorption-based purification techniques, transformer oil can be effectively reclaimed and reused. Applying advanced purification and reclamation technologies, such as the FLD D and FLD R plants, ensures optimal performance, reduces maintenance costs, and supports sustainable resource management.
