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The Experiment of Partial Discharge for Cast Resin Transformer
(2024-01-01)
Aiamrungruang, Phitthaya
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Pannil, Pittaya
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Dorkmai, Kritsada
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Maneerot, Sakda
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Jeenmuang, Siwakorn
Dry-type cast resin transformers, utilizing epoxy resin insulation instead of traditional liquid insulation like mineral oil, are designed to prioritize safety, avoid fire hazards, be environmentally compatible, and endure short circuits well. Limitations of dry-type transformers are the installation area by which it should be dry, free from dust, excessive moisture, fertilizers, chemicals, and other corrosive fumes or fumes. This paper investigates the Partial Discharge (PD) phenomena occurring on a 12 kV dry-type transformer surface using HighFrequency Current Transformers (HFCT) with 100 kHz -20 MHz bandwidth as a PD detection device. The simulated PD sources were made from the conductive wire. Moreover, the scheme of winding connections in the dry-type transformer related to cross-talk phenomena between transformer coils is also reported. The recorded Phase-resolved PD (PRPD) and the PD Inception Voltage (PDIV) have been summarized and compared, as described in this paper.
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Experimental Study of the Electrical and Physiochemical Properties of Different Types of Crude Palm Oils as Dielectric Insulating Fluids in Transformers
(2023-10-01)
Muangpratoom, Pichai
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Suriyasakulpong, Chinnapat
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Maneerot, Sakda
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Vittayakorn, Wanwilai
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Pattanadech, Norasage
This paper gives information on the electrical and physiochemical characteristics of six different types of palm oil compared with traditional mineral oil. We found that natural processed crude palm oil (PO-C) had a higher resistance to AC breakdown voltage than other types of palm oil, including traditional mineral oil. The results of the positive lightning impulse voltage test for PO-C were still the highest compared to other types of palm oil, including traditional mineral oil, at 58.26%. The summarised dissipation factors of all tested crude palm oils were significantly higher than those of mineral oils, which will make the palm oil less insulating, especially in PO-A palm oil (36.197%), where the values were higher than those of other oils, while mineral oil has a slightly increased dispersion factor. For relative permittivity, all palm oils were compared, and it was found that PO-C had a lower relative permittivity than the other oils. In terms of physical and chemical properties, in the moisture content test on all oils, PO-C had the percentile with the highest moisture content decrease of 58.74%. In the case of testing the surface tension value, it was found that traditional mineral oil had the highest value (48.46 m/Nm) when compared to palm oil. On the other hand, the acidity in traditional mineral oil is the lowest (0.03 mg KOH/g) compared to all palm oils. Results from studies demonstrate the possibility of using natural processed crude palm oil, or PO-C, as a replacement for traditional mineral oil. This is consistent with the results of electrical properties that show PO-C is higher than other types of palm oil and includes traditional mineral oil.
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Physical and chemical properties’ comparison of natural ester and palm oil used in a distribution transformer
(2023-03-01)
Kittikhuntharadol, Yannaphol
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Pattanadech, Norasage
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Maneerot, Sakda
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Jongvilaikasem, Korraya
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Jariyanurat, Kittipod
Because of its low cost and suitable qualities, mineral oil (MO) has been commonly employed in transformers. Alternative liquid insulations with great characteristics have recently been presented. Natural ester (NE) and palm oil (PO) are considered alternative liquid insulations. This paper aims to study the physical and chemical properties of NE and PO which were used in a transformer for 21 months. All of the liquid insulation test specimens were sampled every 3 months. Physical properties of the liquid insulation, i.e., interfacial tension (IFT), viscosity, and particles count, were examined. Chemical properties of the liquid insulation, i.e., moisture content, acidity, corrosive sulfur, and furanic compound (2-FAL), were investigated. IFT, particles count, moisture content, acidity, and 2-FAL test results indicated deterioration of liquid insulations of the used liquid insulation; however, there is no observation change for particles amount and acidity of NE. The other test results were not found significantly change.
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The Comparison of DGA Interpretation Techniques Application for Actual Failure Transformer Inspections Including Experience from Power Plants in Thailand
(2022-03-01)
Jongvilaikasem, Korraya
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Pattanadech, Norasage
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Wattakapaiboon, Wilasinee
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Kando, Masaaki
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Maneerot, Sakda
Dissolve gas analysis (DGA) is a diagnostic test technique applied for transformer condition evaluation. The interpretation of the dissolved gas results is a significant procedure to classify the incipient fault types in transformers. A variety of dissolved gas interpretation methods utilized for the same investigation case may give different fault type results. This paper investigates the performance of dissolved gas interpretation methods, including Doernenburg Ratio, Roger Ratio, IEC Ratio, Müller-Schlliesing and Soldner Method, Duval Triangle, and Duval Pentagon. The twenty-four failure transformer cases are used to evaluate the performance of the dissolved gas interpretation methods. The test result shows that the Duval pentagon interpretation technique shows the highest consistency interpretation. Besides, the Duval pentagon method demonstrates the ability to identify a normal aging problem of the transformer insulation.
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Polarization and Conduction Characteristics of Mineral Oil and Natural Ester Mixed with Nanoparticles
(2022-01-01)
Maneerot, Sakda
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Pattanadech, Norasage
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Kittikhuntharadol, Yannaphol
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Nimsanong, Phethai
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Bunlaksananusorn, Chanin
Mineral oil (MO) has been widely used in transformers because of its reasonable price and acceptable properties. Currently, alternative liquid insulations have been proposed with some excellent properties. Therefore, the mineral oil characteristics need to be enhanced for high performance to compete with such alternative liquid insulations. This paper aims to study the power frequency dielectric dissipation factor (tanδ) along with polarization and depolarization current (PDC) characteristics of the mineral oil-based nanofluid and natural ester (NE)-based nanofluid. Besides, Fourier-transform infrared spectroscopy (FT-IR) measurement of the test specimen was performed. Titanium dioxide (TiO2) and zinc oxide (ZnO) with 0.01% and also 0.03% volume concentration were used to mix with the unmodified liquid to create liquid insulation-based nanofluid. Then, unmodified mineral oil, unmodified natural ester, mineral oil-based nanofluid, and natural ester-based nanofluid were comparatively investigated. Tanδ at power frequency and the PDC characteristics of such liquids were examined. For PDC measurement, TiO2 clearly affected the polarization current and conduction loss factor, whereas ZnO evidently impacted the depolarization current and polarization loss factor. In the case of FT-IR test results, there was no significant change when the modified insulating liquid was compared with those of the unmodified insulating liquid.
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Effect of ZnO and BaTiO3Nanoparticle on Partial Discharge Characteristics of Palm Oil Based Nanofluids
(2020-10-25)
Maneerot, Sakda
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Vittayakorn, Wanwilai
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Pattanadech, Norasage
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Soubol, Nichaya
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Yodrayub, Noppol
This paper presents the partial discharge inception voltage (PDIV) and partial discharge extinction voltage (PDEV) of palm oil based on nanofluids with different concentration of ZnO and BaTiO3. Each liquid specimen was prepared in a 2000 ml beaker. The palm oil sample was heated under vacuum in the oven with temperature at 80°C under 200 mbar for 12 hours. Next, these liquids were divided into seven groups according to the amount of ZnO and BaTiO3 nanoparticle. The first group was the unmodified palm oil. The second and third group were palm oil mixed with 0.01% of ZnO and BaTiO3 nanoparticle respectively. The fourth-the seventh group were palm oil mixed with 0.03% and 0.05% ZnO and BaTiO3 respectively. Then all specimens were heated at 80°C under 200 mbar for 12 hours. After that, the PDIV and PDEV of the liquid specimen were investigated using the test circuit according to IEC 60270 using needle-plane electrodes with the needle tip radius of 10 μm. Each group was tested in 6 times. The mean values of PDIV and PDEV were reported. From the test results, it was clear that the types and concentrations of nanoparticle obviously affected the PDIV and PDEV characteristics of the palm oil based nanofluids.
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The comparative study of physical and chemical properties of palm oil and mineral oil used in a distribution transformer
(2020-10-25)
Maneerot, Sakda
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Pattanadech, Norasage
This paper represents the physical and chemical characteristics of palm oil compared with mineral oil as insulating liquid. Two identical single-phase transformers with rated 22000/230V 30kVA were designed and constructed. The first transformer used palm oil and the second transformer used mineral oil as dielectric liquid. The physical and chemical properties of new liquids were investigated before and during transformer operation. The physical properties and chemical properties such as interfacial tension, viscosity, moisture content, acidity, and corrosive sulfur of the liquid specimen were tested according to international standards. Then these liquids were filled in the transformer. After that, transformers were operated at 80 % of designed rated with inductor load for two years by which the temperature, current, and voltage were recorded every hour. Every three months, the liquid insulation was sampling from each transformer to be investigated as the same mentioned items. From the preliminary test results (six months after transformer operation), it can be concluded that palm oil is the potentially alternative liquid insulation for using in the transformer.
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How Water Affects the Properties of Insulating Liquids
(2020-10-25)
Pagger, Ernst
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Muhr, Michael
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Pattanadech, Norasage
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Kongdang, Peeraphong
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Tieber, Michael
Water has a great influence on the properties of insulating liquids, but this influence does not always have the same impact on the insulation system. Depending on what kind of insulating liquid is used the influence can be more or less. Liquids with a higher water absorption and adsorption capacity are less susceptible to changing liquid properties compared to insulating liquids like mineral oil. This paper provides results of how properties of viscosity, refractive index, breakdown voltage and moisture equilibrium in transformer paper-liquid systems change in relation to the water content.
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Polarization and Depolarization Current Characteristics of Natural Ester Impregnated Pressboards with Different Periods of Impregnation
(2020-10-25)
Maneerot, Sakda
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Siriworachanyadee, Jompatara
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Likhitsupin, Wit
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Likhitsupin, Suwapich
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Srinangyam, Chissanupong
This paper represents the polarization and depolarization current (PDC) characteristics of natural ester impregnated pressboards with different impregnation period. The pressboard specimen were prepared as a rectangular shape (the length and the width are 120 mm as well) and thickness dimension of the pressboard in the experiment was approximately 1.6 mm. The pressboards were dried up in the vacuum oven with temperature at 80°C for 12 hours under 200 mbar pressure. In addition, these pressboards were divided into 3 groups according to the impregnation periods. The 1st group, the pressboard was non-impregnated with natural ester. The 2nd and 3rd group, the pressboards were impregnated at 60°C for 8 and 16 hours, respectively, under 200 mbar pressure-controlled condition. The plane-plane electrodes inserted with the specified number of the pressboard specimens were prepared. These electrodes were installed in the test cell filled with the natural ester. A 24 kV AC Voltage was applied to the test cell for 3 months. At the end of the first month, half of the pressboard samples was token from the test cells. Then, the PDC characteristics of these natural ester impregnated pressboards were investigated. At the end of the third month, another half of the pressboard samples was token from the test cells to perform PDC measurement also. It was found that the PDC values of the pressboards with longer period impregnation process were lower than these of the pressboards with longer period impregnation process. Besides, the PDC values of the pressboards experienced with longer electric field stress period (3 months) were higher than these of the pressboards experienced with shorter electric field stress period (1 month).
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Partial discharge characteristics of mineral oil immersed transformer compared with natural ester and palm oil immersed transformer under different periods of impregnation
(2020-09-13)
Maneerot, Sakda
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Pattanadech, Norasage
This paper represents the partial discharge (PD) characteristics of mineral oil immersed transformer compared with natural ester, and palm oil immersed transformer under different periods of impregnation. Three identical three-phase transformers with 22kV/400V 50 kVA rated were designed and constructed. The first transformer was fully filled with mineral oil. The second transformer was fully filled with natural ester (FR3), and the third transformer was fully filled with palm oil. The partial discharge at 1.1Urated of these transformers with various conditions, i.e., non-impregnated paper, impregnated paper with 3 hours, and 6 hours was investigated. The impregnation process was done with 65 <sup>o</sup>C liquid temperature and 5 mmbar pressure. From the test results, it can be concluded that PD characteristics of the mineral oil immersed transformer was obviously different compared with these of the natural oil (FR3) immersed transformer and the palm oil immersed transformer. Moreover, the impregnation impacted PD characteristics of the tested transformers, which were analyzed and reported in this paper.

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