Regeneration and filtration of insulating transformer oils

Electrically insulating (transformer) oils are liquids in which their electrical insulating properties and thermo-oxidative stability are most important. If electrical insulating oils are used as insulating and cooling media of transformers, it is recommended to use liquids with low viscosity. Low-viscosity liquids fill the device space well and get into the pores of solid insulators. Electroinsulating liquids must have good thermal stability and stability of their parameters, ensuring reliable operation of transformers as a whole.
Electroinsulating liquids are used as fillings for condensers, where the oil is used to impregnate the paper dielectric or synthetic film. Condenser oils are mainly characterized by high internal resistance, small dispersion of loss factor values due to temperature, good oxidation stability and greater ability to absorb gases.

Electroinsulating oils are mostly used in switching devices, which, in addition to insulating and cooling medium, are also an extinguishing medium. With electroinsulating oils, great emphasis is placed above all on high breakdown voltage.

Liquid insulators used in electrical engineering are of three types - vegetable oils, mineral oils and synthetic insulating liquids.

Electroinsulating (transformer) oils lose their original values during operation. This happens due to the combined effect of various influences, especially temperature, solid impurities, water, metal catalysts and the electric field. These influences lead to the formation of organic acids, aldehydes, ketones, soaps and the polymerization of unsaturated hydrocarbons. All these phenomena are collectively referred to as transformer oil aging. The presence of organic acids in the insulating oil leads to massive decomposition of cellulose and oxidation of metals. Oxidation products increase the TAN (acidity number), reduce the interfacial tension (IFT), cause the formation of sludge and loss of dielectric properties.

If the transformer oil is to fulfill its function as long as possible, it must be handled very carefully from the moment of the first handling and protect it above all from influences that could cause its premature aging (excessive contact with air, high temperature, impurities). Aging products deteriorate the electrical properties of the oil and, consequently, of the solid insulation of the transformers.

By filtering electrical insulating oil through special filter elements of the TRAFO and ECOTOWER TAN types, its properties can be significantly improved or completely regenerate.

In the case of regeneration, it is necessary to assess the condition of the oil, especially its breakdown voltage, water content, TAN, loss factor, surface tension, resistance, inhibitor content and DBDS content.


Regeneration process.

Regeneration of electrical insulating (transformer) oils through ECOFIL® filtration devices regenerate electrical insulating oils to their original state, which meets the requirements of standard STN EN 60422 - Mineral insulating oils in electrical equipment (Instructions for inspection and maintenance). Electrical insulating oils after regeneration with ECOFIL® filter devices greatly exceed the recommended minimum limit values according to standard STN EN 60422. Regeneration with filtration devices also removes corrosive sulfur (DBDS), the so-called depolarization.

Regeneration of electrical insulating oils is carried out at the place of operation and is also carried out when the energy device is under power. The recommended regeneration temperature is min. 20oC. Electricity consumption energy is low. ECOFIL® filtration devices require a small volume of oil to fill and therefore regenerate electrical insulating oil from a volume of 20 liters. Regeneration is carried out by flowing through a special regeneration elements ECOTOWER TAN, which contains absorbent and coiled cellulose. ECOFIL® filtration devices integrate the process of filtration, drying, slow degassing, regeneration and replenishment of inhibitors into aged oil in one flow. Continuous flushing and cleaning of the inside of power device from solid impurities, soft sludge (deposits, sediments, resins) and residues of heat-oxidative aging of the oil is carried out by the flow of electrical insulating oil. After a certain time, the filter element becomes saturated with contaminants and is no longer able to regenerate oil, and therefore needs to be replaced. The regeneration process takes place gradually over a longer period of time. The regeneration process must be monitored using the NEURON® oms.

Time course of regeneration and filtration of electrical insulating oils:

Regeneration process