Diagnostics of transformer with insulation oil-paper (original) (raw)
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European Transactions on Electrical Power, 2011
This paper presents a study on the characterization of aging of transformer oil-pressboard insulation. Traditional and modern diagnostic tools and techniques were used to investigate aging of oil-paper insulation under controlled laboratory conditions. Insulation condition testing includes common chemical diagnostics such as acidity tests and new chemical techniques: determination of relative content of dissolved decay products by spectrophotometry, solid suspension by turbidimetry, Fourier Transform Infrared (FTIR) spectroscopy and electrical diagnostic techniques that have gained exceptional importance for utility professionals: polarisation/depolarisation current, recovery voltage measurement and frequency domain dielectric spectroscopy measurements. From the obtained results it is found that chemical tests depicted more sensitivity to insulation degradation. Also, different oil-pressboard insulation ratios were investigated to assess the influence of the relative amount of cellulosic materials on aged mineral oil decay products and vice versa. Emphasize is laid on the potentialities/avenues offered by FTIR to assess oil insulation condition. Notable experimental results have been reported, which could be valuable to researchers and practicing engineers in this field. a number of transformers remaining in service in North America that are 60, 70 and even 80 years old, and they are still giving satisfactory service .
A review on chemical diagnosis techniques for transformer paper insulation degradation
2013 Australasian Universities Power Engineering Conference (AUPEC), 2013
Energized parts within power transformer are isolated using paper insulation and are immersed in insulating oil. Hence, transformer oil and paper insulation are essential sources to detect incipient and fast developing power transformer faults. Several chemical diagnoses techniques are developed to examine the condition of paper insulation such as degree of polymerization, carbon oxides, furanic compounds and methanol. The principle and limitation of these diagnoses are discussed and compared in this paper.
An Investigation of Insulating Paper Effect on Gas and Aging on Mineral Oil Transformer
JAREE (Journal on Advanced Research in Electrical Engineering), 2022
A transformer is an essential component in a generator, electrical equipment that works non-stop to support electricity needs. There has been a lot of thermal and electrical activity that the presence of an oil-paper insulator can suppress. The insulating ability can decrease and lead the failure due to the aging of the insulator by heating, moisture, and impurities. The aging of the paper was unavoidable, which caused the cellulose bond to break and form dissolved gases with oil, such as Carbon monoxide, Carbon dioxide, Methane, Acetylene, Ethylene, and Ethane. So, conventional dissolved gas analysis (DGA) was used to investigate further. The use of paper insulation with a certain amount affects the electrical strength of the insulator. A breakdown test on AC voltage is carried out for the following investigation. The result showed that the percentage of paper had an optimum number to get high insulator strength. By heating mineral oil for 250 hours and 500 hours, carbon monoxide and carbon dioxide are released in the different results as the DGA test. It can be concluded that cellulose paper has affected mineral oil's dissolved gas and insulator strength.
Thermal Science, 2016
The calculating of reached ageing based on the history of loading according of International Electrotechnical Commission standard algorithm is the first task. In order to verify the obtained results, measurements of polymerization index were made on 28 paper samples taken directly from low voltage terminals (winding ends) and bus connections of the transformer under test rated 380 MVA, 2?15,75 kV/420 kV. The complete procedure of paper sample locations and taking off is described, thereby providing a manner of how this should be done, determined by specific conditions of the transformer under test. Furthermore, the determination of limit viscosity and using its relationship function with polymerization index are explained together. Comparison is made with those of liquid chromatography of oil. The results of particle sort and size analysis are shown. Finally, an estimation of the transformer life remainder is made, which is of paramount importance when defining the steps that have t...
A REVIEW OF CONDITION MONITORING ASSESSMENT OF POWER TRANSFORMERS INSULATION
In regard to condition monitoring assessment of power transformers, so many techniques and researches have been carried out till date and some being under progress. The insulation of coils of a power transformer is employed by the Kraft paper and dipped in an insulating mineral oil. Both of these insulation terms demean with the passage of time as occurrence of fault so lead to decrease in efficiency of transformer. The paper is presented to show a widespread assessment of winding insulation provided by dielectric oil and paper. The intention is to present an extensive point of view on the winding insulation of power transformers which deals to find out an alternative to mineral oil in which paper degradation can be minimized and to characterize the Kraft paper. The presented references are broadly classified in the paper would provide rapid and practical relevance.
Breakdown Strength Analysis of the Transformer Insulation Oil Due to Different Standards
There are many equipment such as transformers, high voltage cables, insulators, breakers, etc., work in power systems under high voltages. The insulation oils are used in such systems to provide the insulation and cooling respectively for high voltages and temperature rises in conductors. These kinds of oils should be qualified in terms of insulation and should have some certain features for power system stability. Therefore, suitability of the physical, chemical and electrical properties of the insulation oils is specified with standard tests. These tests are performed according to the IEC 60156, ASTM D1816 and ASTM D877 .In this study, breakdown voltage variation of insulation oil which is used for high voltage equipment is investigated for particular working conditions. In experimental study, there are two types of insulation oils which are non-aged and aged insulating oils. Breakdown voltages of these insulation oils are measured for different voltage rising speed mentioned in t...
2021
Transformers are generally considered to be the costliest assets in a power network. The lifetime of a transformer is mainly attributable to the condition of its solid insulation, which in turn is measured and described according to the degree of polymerization (DP) of the cellulose. Since the determination of the DP index is complex and time-consuming and requires the transformer to be taken out of service, utilities prefer indirect and non-invasive methods of determining the DP based on the byproduct of cellulose aging. This paper analyzes solid insulation degradation by measuring the furan concentration, recently introduced methanol, and dissolved gases like carbon oxides and hydrogen, in the insulating oil. A group of service-aged distribution transformers were selected for practical investigation based on oil samples and different kinds of tests. Based on the maintenance and planning strategy of the power utility and a weighted combination of measured chemical indicators, a neu...
Performance Evaluation of Power Transformer under Different Diagnostic Techniques
—In an electrical power system, the transformer is one of the most important and efficient machines, and to ensure the continuity of power supply utmost care should be taken for its safe operation. Transformers are robust device but they may fail over time due to old age, poor insulation, deterioration of cellulose as well as oil insulation. In addition, there are several elements that may lead to insulation's premature aging and damages; these may include oxygen, heat and moisture contents. transformer oil provides insulation and cooling inside a machine, however there are various factors which affect the insulation strength and smooth flow of the transformer oil over the period of time, so it is therefore very important to observe some of the specific parameters like electrical (specific resistance, dielectric strength, dielectric dissipation factor or tan delta), chemical (Water content, sludge content, acidity) and physical (viscosity, flash point, pour point) to check the effectiveness of the transformer oil Therefore by keeping in mind the factor of reliability, this work presents three field transformers along with application of different diagnostic methods on their oil sample. At the end of this work, the detailed analysis carried out on the basis of effects of temperature, humidity, and loading. Tests are performed to check the appearance, breakdown voltage, water content, acidity, dielectric dissipation or tan delta Dissolved gas analysis (DGA) and kinematic viscosity of the oil samples, results obtained from these tests are then compared to IEC standards to check the effectiveness of the oil samples.
Analysis of insulating parameters of oil transformer by time and frequency methods
Diagnostyka, 2020
In the paper is presented experimental analysis and diagnostics of insulating system oil-paper for power transformers. In the first part of the paper is described base theory about measurement and diagnostics insulating part (oil and paper) of transformers. In the other two parts of the paper is presented experimental results of the diagnostic measurement for the transformer 22/0.4 kV at constant temperature. Specifically, in the second part is described measuring time method of insulating diagnostics-return voltage measurement (RVM). This method is used for analysis of condition of paper moisture of high-voltage equipment. In the third part is described measuring method of insulating frequency diagnostics-frequency domain spectroscopy (FDS). This method is used for analysis insulating condition of high-voltage equipment with insulating oil-paper. The both measuring methods are unique in terms of analysis of insulating system of oil power transformers. In comparison with other methods, the RVM and FDS methods it is possible comparison and evaluate the moisture state of the dielectric paper of the power transformer with high reliability and accurate. Their reliability in determining moisture in paper was shown by determining the same result (3.5%) on the same measured transformer.