Novosibirsk State Technical University (NETI) has proposed a way to extend the service life of transformers by increasing the durability of the insulation system and has also developed new methods for diagnosing the gas content in transformer oil.
"A transformer is a complex system that includes both liquid and solid insulation. Here, the liquid dielectric acts as not only a dielectric but also as a heat-dissipating agent. It is necessary to remove a large amount of heat to avoid overheating and melting of conductors. There are several factors that accelerate the aging of the insulation system. The first factor is temperature: the higher the temperature, the shorter the service life of liquid dielectrics. The second factor is oxygen. Together, these factors mutually reinforce each other and significantly accelerate the aging process. Accordingly, the service life of insulation is shortened resulting in the reliable operation of high-voltage transformers, which are key devices at substations and cost a lot of money. Therefore, there is a need to improve the chemical stability of transformer oils, which means increasing their wear resistance and even more effective use in electrical equipment," said Marina Lyutikova, senior researcher at the Scientific and Educational center "Physical and Mathematical Foundations of Electromagnetic Safety and Electric Power Transport", Associate Professor of the Department of Occupational Safety at NSTU-NETI, who successfully defended in June This year, a dissertation on the topic "Aging factors of the insulation system of high-voltage transformers and increasing its durability".
Many different brands of oil are used in electrical equipment: one has greater oxidative stability, the other is prone to sedimentation, and impurities accumulate in the third, contributing to the formation of waxy deposits. These changes affect the insulation system of the transformer and, accordingly reduce the reliability of the equipment. TKp transformer oil, which is used in many transformers, is prone to precipitation, and to prevent this process or minimize the likelihood of precipitation, synthetic esters are added. Thus, the sediment formation probability is reduced, and the transformer oil life is extended. If we talk about GK oil, which is prone to waxy deposits, two additives are proposed: ionol and a substance similar to GK oil in structure. The synergistic effect is activated, they mutually reinforce each other, and GK oil is oxidized much more slowly, thereby reducing the likelihood of the formation of waxy deposits and prolonging the life of the oil.
As Marina Lyutikova notes, synthetic esters provide fire and environmental safety, biodegradability, and high chemical resistance. They are widely used power transformers in Europe. The process of creating esters is expensive, it is expensive to change all transformer oil, but to extend its life, it is enough to add esters by 20-30% of the volume.
"We have also developed new methods for diagnosing the gas content in transformer oil. Ideally, the oil should contain as few gases as possible because bubbles contribute to the development of discharge processes. A technique for detecting polar products has been developed: acids, peroxide, and ether compounds. Their presence provides information about the mechanism and path of aging and what measures can be taken to clean the oil to extend the service life of the insulation system of high—voltage transformers," Marina Lyutikova added.
Currently, work is underway to study the physicochemical properties of mixtures of natural ether with different brands of transformer oil. Natural esters, and synthetic esters, have increased fire safety and are biodegradable liquids. The latter is critical for the preservation of the ecological situation.
NSTU-NETI scientists are cooperating with an enterprise that plans to launch synthetic esters in Russia which already produces natural esters based on rapeseed oil. There is a lot of work to be done: creation of synthetic ether, study of its chemical composition, correction of its chemical composition, physicochemical, and insulating properties, assessment of compatibility of structural materials with esters, development of methods and criteria for monitoring the state of ether during its operation in equipment, search for effective ways to regenerate liquid dielectric and, in general, maintenance.