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Studies of Electrical and Thermal Characteristics of Natural Ester Immersed Transformer Compared with Mineral Oil Immersed and Palm Oil Immersed Transformer
(2018-11-14)
Maneerot, S.
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Jariyanurat, K.
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Nimsanong, P.
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Bunlaksananusor, C.
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Kunakorn, A.
This paper represents studies of electrical and thermal characteristics of natural ester immersed transformer compared with mineral oil immersed and palm oil immersed transformer by designing and constructing three single-phase transformers with rated 400/1000V 10kVA, the first transformer used mineral oil, the second transformer used natural ester, and the last one used palm oil, for studying about electrical properties, thermal properties and chemical properties under different types of liquid insulation in each transformer. First of all, three types of liquid insulation were tested with many item such as dielectric breakdown strength according to IEC 60156, dielectric dissipation factor following to ASTM D924-99. Besides, dielectric breakdown strength of impregnated pressboard were also investigated following to IEC 60243-1. Moreover, the chemical properties of the insulations were tested for some properties such as moisture content in accordance with ASTM D1533-00, interfacial tension according to ASTM D0971-99, acidity according to ASTM D974-02. After that, transformers were operated at 100 % of designed rated with inductor load for four months by which the temperature, current, and voltage were recorded every hour. Every two months, the liquid insulation was sampling from each transformer to be investigated. From the test results, they can concluded that natural ester are the alternative liquid insulation for using instead of mineral oil. In part of palm oil, it has good properties but it has the weak points about dielectric dissipation factor and acidity which are higher than the others.
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Different Moisture Contents of Pressboard Effect on Electrical and Chemical Characteristics of Liquid Insulation
(2018-11-14)
Jongvilaikasen, K.
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Pumyoy, S.
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Jariyanurat, K.
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Maneerot, S.
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Pattanadech, N.
This paper represents electrical and chemical characteristics of mineral oil samples obtained from the test cell containing the pressboards with different moisture contents immersed in the mineral oil. The pressboards with the dimension of 100×l00 mm and the thickness of 12.8 mm were used in the experiment. The pressboards were divided into two groups. The first group contained the moisture content of 3 % while the second group contained the moisture content of 7%. Then, four pressboards of each group were inserted between plane to plane electrodes contained in the test cell by which one electrode was energized by 12 kV AC; another electrode was grounded. Three identical mineral oil samples were taken from the test cells after the pressboards and mineral oil had experienced by electric field stress for 5, 10, and 15 days respectively to investigate on the changing of electrical and chemical properties of the mineral oil. The tests were performed with each oil sample on the topics of breakdown voltage, power factor, moisture content, acid number, interfacial tension and dissolved gas analysis. From the experiments, the electrical and chemical characteristics of the mineral oil with the pressboards containing different moisture contents were clearly different.
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Dielectric properties of mineral oil compared with natural ester
(2017-11-29)
Jariyanurat, K.
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Nimsanong, P.
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Chaisiri, P.
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Maneerot, S.
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Kitcharoen, P.
In this paper, dielectric properties of the mineral oil, ELECTROL A, and the natural ester, FR3, are comparatively investigated. AC breakdown voltages, dielectric dissipation factor, relative permittivity, partial discharge inception voltage and partial discharge of the mineral oil and of the natural ester are tested. In order to verify the capability in practical use of the mineral oil and the natural ester for transformer insulation systems, the impregnation of such liquids with pressboard insulation is performed. The impregnated pressboards are tested in the laboratory to measure the AC breakdown voltages. It is found that the natural ester shows superior dielectric properties to the mineral oil except the dielectric dissipation factor.
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Dielectric properties of natural ester based nanofluid
(2017-11-29)
Jariyanurat, K.
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Potivejkul, S.
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Pattanadech, N.
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Chotigo, S.
In this paper, AC breakdown and standard impulse breakdown characteristics of natural ester oil and natural ester base nano fluids are investigated. Three types of nanoparticles such as Zinc oxide (ZnO), Barium titanate (BaTiO3), and Titanium dioxide (TiO2) which have their diameter less than 100 nm are used to prepare the nanofluid samples which consist of the natural ester mixed with 0.01% volume fraction of each nanoparticle type. To measure AC breakdown voltage of the natural ester and natural ester based nanofluids, the oil breakdown tester (FOSTER OTS 60AF) is employed by sphere-sphere electrode system according to IEC 60156. The gap distance between electrodes is set at 2.5 mm. Furthermore, the needle-sphere electrode configuration with gap spacing of 40 mm is used for impulse breakdown voltage investigation of the dielectric liquids by the needle is tungsten and 40 μ m tip radius. The test circuit is set up in accordance with IEC 60897 and the test experiment is conducted at room temperature. The test results show that the AC breakdown voltages of the natural ester with nanopaticles is markedly higher than those of the unmodified natural ester. Additionally, TiO2, BaTiO3, and ZnO nanoparticles show their properties to increase impulse breakdown voltages of the nanofluids compared with those of the unmodified natural ester. From the test results, it is found that nanoparticles are good candidates to enhance the dielectric properties of natural ester for dielectric applications.
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Partial discharge characteristics of mineral oil compared with natural ester
(2017-10-19)
Pattanadech, N.
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Jariyanurat, K.
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Maneerot, S.
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Nimsanong, P.
In this paper, partial discharge inception voltage (PDIV) and partial discharge (PD) characteristics of mineral oil compared with natural ester were studies. Three typical PD types, corona discharge of the liquid insulations, surface discharge and internal discharge of the liquid impregnated pressboards were investigated. In case of corona discharge, both corona discharges from high voltage side and from low voltage side were simulated by using the needle-plane electrode configuration. The needle with the tip radius of 10μm, 20μm, 40μm respectively was used as high voltage electrode while the brass plane electrode with 45 mm diameter was used as the grounded electrode for simulation the corona discharge at high voltage side, and vice versa, for simulation corona discharge at low voltage side. The gap distance was fixed for 30 mm. Moreover, the mineral oil and natural ester were used to impregnate the pressboards which were 1.6 mm thick. Then, the impregnated pressboards were selected to experiment for surface discharge and internal discharge respectively. The surface discharge experiment was performed with the 40μm tip radius needle as high voltage electrode put on the ten pieces of 12 hour impregnated pressboards stuck together as a single insulation and the plane electrode with 45 mm diameter as grounded electrode. In case of the internal discharge, ten pieces of 6 hour impregnated pressboards were stuck together as a single insulation. A cylindrical void with 5 mm diameter and a height of 3.2 mm was simulated at the middle of the insulation. Then, the insulation was placed between the mentioned plane electrodes for the internal discharge experiment. PD test circuit was prepared following to IEC 60270. PDIV was examined by applying the step voltage to the high voltage electrode with the increase rate of 1 kV per step for the step duration of 1 minute until observing the PDIV. Then, PD activity was examined and recorded for 1 minute at 110% PDIV level. Form the test results, the natural ester and pressboards impregnated with natural ester provide higher PDIV than mineral oil and the mineral oil impregnated pressboards. Consequently, the PD amplitude at 1.1 PDIV of natural ester and natural ester impregnated pressboards are higher than that of mineral oil and mineral oil impregnated pressboards.
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Electrical characteristic comparison of mineral oil and natural ester for transformer applications
(2017-10-19)
Pattanadech, N.
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Jariyanurat, K.
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Maneerot, S.
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Nimsanong, P.
In this paper, the electrical characteristics of mineral oil compared with natural ester were studies. AC breakdown strength, dielectric dissipation factor, and permittivity of both liquids were investigated. Both new liquids were heated in the oven at 60°C with 200 mbar for 6 hours before starting all investigation, the water contents of mineral oil and natural ester were 18 and 178 ppm respectively. Moreover, the mineral oil and natural ester were used to impregnate the pressboards which were 1.6 mm and 3.2 mm thick respectively. These pressboards were impregnated for 3-12 hours. Then, the AC breakdown voltage of the impregnated pressboards was examined. AC breakdown strength of the liquid insulations was tested according to IEC 60156. The dielectric dissipation factor and permittivity of the liquids with the temperature of from 35°C - 100°C were investigated as well. Moreover, the breakdown voltage strength of the impregnated pressboards was examined with the electrodes in accordance with IEC 60243-1. From the test results, mineral oil sample provided lower AC breakdown voltage than natural ester sample. However, mineral oil generated approximately 77 times lower dielectric dissipation factor compared with the natural ester. Besides, natural ester impregnated pressboards had a bit higher breakdown strength than mineral oil impregnated pressboards. Furthermore, breakdown strength of the liquid impregnated pressboard depended clearly the function of time and the pressboard thickness.
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Electrical characteristics of natural ester based nanofluid
(2017-10-19)
Potivejkul, S.
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Jariyanurat, K.
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Pattanadech, N.
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Wattakapaiboon, W.
In this paper, the dielectric properties of natural ester based nanofluids were investigated. This research represents the improvement of the electrical properties, AC breakdown and negative lightning impulse breakdown strength, of the natural ester (FR3) by amalgamation with nanoparticles. Two types of nanoparticles i.e., Titanium dioxide (TiO2) and Zinc Oxide (ZnO), with a mean diameter of less than 100 nm were used in this experiment. The nanofluid samples, a natural ester merged with nanoparticles, were prepared in three steps. First, the natural ester was divided into four groups. The first group was merged with 0.01% concentration of TiO2 and the second group was merged with 0.03% concentration of TiO2. The third group was merged with 0.01% concentration of ZnO and the fourth group was merged with 0.03% concentration of ZnO. Second, the nanofluid samples were dispersed using a magnetic stirrer. Finally, the ultrasonic dispersant technique was applied to the prepared nanofluids to be homogeneity. To measure AC breakdown voltage of the natural ester based nanofluids, the oil breakdown tester was employed and the testing experiment was performed according to IEC 60156. In addition, the negative lightning impulse breakdown characteristic of the natural ester based nanofluid was investigated with the needle-sphere electrodes in accordance with IEC 60897. A tungsten needle with tip radius of 40m was utilized as the high voltage electrode and the 13 mm diameter brass sphere was used as the grounded electrode. The gap distance was fixed as 15 mm. The test results showed that the AC breakdown property of the modified liquids was clearly influenced by the type of nanoparticles added. The AC breakdown voltage of the natural ester with nanopaticles was slightly higher than that of the unmodified natural ester. Additionally, both TiO2 and ZnO nanoparticles demonstrated their ability to increase negative impulse breakdown voltage of the nanofluids. These tests indicated that such nanoparticles have good potential to be used with natural ester to improve the dielectric properties.
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Electrical characteristics of natural ester impregnated pressboards under different periods of impregnation
(2016-11-28)
Jariyanurat, K.
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Maneerot, S.
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Pattanadech, N.
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Potivejkul, S.
This paper represents electrical characteristics of natural ester impregnated pressboards under different impregnation period. Each pressboard specimen was prepared as a rectangular shape having the width of 100 mm and the length of 100 mm as well. Two thickness dimensions of the pressboard for the experiment were 1.6 mm and 3.2 mm respectively. All pressboards were dry up in the oven with temperature at 60°c for 1 hour. Next, these pressboards were divided into three groups according to the impregnation periods. The first group was impregnated with natural ester (FR3) for 3 hours with temperature at 60°c and 200 mbar pressure controlled condition. The second and third group were impregnated for 6 and 9 hours respectively with the same temperature and pressure condition. Then, the breakdown voltage characteristic of the impregnated pressboards were investigated according to IEC 60243-1. Besides, the capacitance and dielectric dissipation factor of the natural ester with various conditions were examined in accordance with IEC 60247. According to the test results, the pressboard impregnated for longer period provided higher breakdown voltage than the pressboards impregnated for shorter period by which the breakdown voltage of the pressboard impregnated for 9 hours was higher than the pressboard impregnated for 6 hours about 8-24% and the breakdown voltage of the pressboard impregnated for 6 hours was higher than the pressboard impregnated for 3 hours about 5-19%. Whereas the dielectric dissipation factor of the natural ester utilized for pressboard impregnation process for 3 hours was higher than the natural ester utilized for such process for 6 and 9 hours about 5% and 12% respectively. Moreover, the electrical characteristics of pressboard impregnated with natural ester was compared with that of the pressboard impregnated with mineral oil. The breakdown voltage of natural ester impregnated pressboard was higher than the mineral oil impregnated pressboard about 5-11% but the dielectric dissipation factor of natural ester was 30 times higher than mineral oil. It is clear that the time for impregnation significantly affects the breakdown characteristic of the natural ester impregnated pressboard. Furthermore, impregnation of the pressboard with natural ester provides better breakdown strength than the pressboard impregnated with mineral oil.

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