29Tashkent State Transport University Volume 3 | TSTU Conference 1 | 2022
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TRANSFORMER OIL CLEANING TECHNOLOGY
Bobomurod Kurbonovich Avazov O'tkir Bahodirovich Sulaymonov Karimberdi Tavbayevich Qarshiyev
Tashkent state transport university assistant avazovbk88@gmail.com
During the operation of powerful power transformers, it is necessary to regularly clean the transformer oil. During operation, water, oxidation products, and mechanical impurities accumulate in the oil.
Transformer oils are obtained by deep purification of petroleum oils in various ways. Oil, as a rule, is extracted from different fields, therefore, transformer oil obtained from oil has different physico-chemical parameters and hydrocarbon composition. With the development of modern technologies, the requirements for transformer oils have become stricter. The service life of the transformer directly depends on the life of the transformer oil. Regeneration or purification of transformer oil is carried out in order to fully or partially restore operational properties.
Transformer oil purification is the process of extracting moisture, mechanical impurities, nitrogen and sulfur compounds, asphalt-resinous substances from it. Various technological operations are used to regenerate or purify transformer oil. They are based on chemical, physical or chemical-physical processes [1].
In the technological operations carried out, the following sequence of actions is usually followed:
- mechanical cleaning of transformer oil (water and solid impurities are removed from the oil);
- thermophysical purification of transformer oil (vacuum treatment);
- physico-chemical purification of transformer oil (adsorption, coagulation);
- chemical cleaning of transformer oil (if the first three are not enough, then the cleaning method is associated with more complex equipment and high financial costs).
The aging process of transformer oil. Aging or damage to the cooling insulation oil usually occurs due to oxidation of the tank walls. When oxygen and water react in the oil, the cooling insulating oil is oxidized under ideal conditions. The condition of the cooling insulating oil is also affected by contamination with oil-soluble solid transformer
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materials. Reactions with unstable hydrocarbons in the oil, other catalysts such as oxygen and moisture, and accelerators such as heat can cause decomposition (oxidation) of the oil [1].
Heat and humidity, along with oxidation, which act as a primary accelerator, are the main enemies of solid insulation. With proper maintenance of the cooling and insulation systems, the service life of the insulation system can be extended from 40 to 60 years. Unfortunately, the oxidation of the oil cannot be prevented, but it can be controlled (slowed down) by the cleaning process. One of the basic rules of transformer maintenance is to check the oils once a year. Oil analysis shows the condition of the transformer insulation system. Moisture in oil consists of pure water, water dissolved in petroleum products, and water having a chemical bond (part of the chemical structure in glucose molecules and necessary to maintain the mechanical strength of cellulose). It is impossible to completely remove moisture from the insulating cellulose.
Transformer oil dissolves more moisture at higher temperatures than at lower temperatures. When the mixture of oil and water cools down, water is released separately. The removed water is produced by absorption from insulation or is drawn into decomposition products in oil (water mixed with oil). Moisture is disproportionately distributed between paper and oil. The insulating paper absorbs water from the oil and holds it inside, at the points with the highest voltage [2].
Oil contamination as a result of long-term operation of the transformer. Acids formed during the oxidation process affect cellulose and metals with the formation of soap metals, aldehydes, alcohols, which in the form of acidic contaminants (heavy substances) get into the insulation, side walls of the oil tank, oil circulation system, cooling system, etc. At high loads, hot and improperly operated transformers will fail faster. Waste increases the viscosity of the oil and thereby reduces its cooling capacity, which shortens the service life of the transformer. Damage also leads to a decrease in insulation, which, in turn, leads to damage to paint and cellulose materials [4]. They are also hygroscopic with respect to conductive and discharge conductors, absorbing moisture and causing overheating of the insulation system. Waste accumulates in the core with stockings, which leads to an increase in the temperature of the working transformer [6].
Basically, what factors affect the service life of the transformer. Cellulose materials are the weakest links in the insulation system. The service life of the transformer is the service life of the cellulose cooling insulation, which cannot be restored in case of failure of
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the cellulose, and it is recommended to destroy small particles to prevent direct damage to the cellulose. With strict insulation care, insulation can have a long service life. The normal service life of a power transformer should be from 50 to 75 years. However, the storage conditions of the insulation system determine the difference in actual operation between the service life of the transformer and 20-50 years. Experience has shown that the most common causes of transformer failure are, as a rule, negligence in the maintenance and operation of the transformer. Transformer oil can be completely refined, i.e. prepared as fresh oil, and with complete refining, the service life of the insulating oil can be extended for a long time.
The costs of recycling used oil should be taken into account due to the high cost of new oil. It is important to lose moisture and maintain a low level of insulation. The presence of moisture increases the rate of oil wear. Insulating clay with a humidity of 1% accelerates the decomposition of oil ten times faster than the humidity of 0.1%
[7].
Considering the above, we would like to offer a mobile device of a combined type for cleaning transformer oil (pic.1). The cost-effectiveness of this device is to reduce additional costs, such as transporting the transformer from the place of work to the service point and calling a special machine, additional broaching, the presence of a machine (crane) for disassembling the transformer.
Pic 1. The process of preparing transformer oil on site.
With the help of a mobile device, it is possible to achieve the greatest efficiency and low cost of water purification from mechanical impurities. With this device, the oil can be applied on
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the spot without moving the transformer. The advantage of this device is that it is possible to clean the oil by circulating it during operation of the transformer. We will provide information about this device in our previous and next releases [3].
REFERENCES
1. Ковальский Б.И., Безбородов Ю.Н., Фельдман Л.А., Юдин А.В., Петров О.Н. Современные методы очистки и регенерации отработанных смазочных масел. Препринт. — Красноярск: Сибирский федеральный университет, 2011. — 104 с
2. Богачков И.М., Савиных Ю.А. Способ очистки трансформаторного масла// Журнал «Нефть и газ», 2011 г., №1, - С.87-91.
3. Avazov B.K., Yusupov D.T. Cleaning of used transformer oil. Journal NX - A Multidisciplinary Peer Reviewed Journal, 2021, p. 719-724.
4. Кан В.В. Юсупов Д.Т. Очистка масляных трансформаторов с использованием мобильных установок на базе керамических мембран // Журнал Проблемы информатики и энергетики. 2014 г., №6, С.85-89.
5. Горбунов Н.И. и др. Повышение эффективности регенерации отработанного масла//Вюник СевНТУ: зб, наук. пр. Вип. 122/2011. -С. 159-162.
6. Д. В. Шуварин. Новые технологии очистки и регенерации энергетических масел. Сборник докладов научно-практической конференции «Экологическая безопасность энергетики: опыт, проблемы, инновационные решения» - М., НП «Московский учебный центр ЕЭС»,: 2015 - с. 49-57.
7. Валиуллина Д.М., Загустина И.Д., Козлов В.К., Определение качественного состава примесей в отработанном трансформаторном масле. Казанский государственный энергетический университет, г. Казань, Россия. 18 июня 2018 г.
8. Гайнуллина Л.Р., Тутубалина В.П., Осушка трансформаторного масла цеолитом САА на электрических станциях. Казанский государственный энергетический университет, г. Казань, Россия. 22.03.2016 г.
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