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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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Biological Insulating Liquids: New Insulating Liquids for High Voltage Engineering
(2023-01-01)
Pagger, Ernst Peter
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Pattanadech, Norasage
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Uhlig, Frank
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Muhr, Michael
This book describes the state-of-the-art use of biological insulating liquids in detail. In recent years, more and more transformers filled with esters have been put into operation. This is because people recognize the benefits of ester liquids in terms of their fire safety (high flash and fire points) and environmental characteristics, judging from their biodegradability, their low CO2 footprint (only valid for natural ester) and their beneficial interactions with solid insulation, etc. One of the main reasons is that the water adsorption and absorption characteristics of these liquids are excellent and very different compared to mineral oil. The today’s discussion about climate change and global warming is an additional driver for using natural ester. Another advantage is that transformers filled with biological insulating liquids can operate with an overload of up to 150%. This is advantageous in the case of volatile energy generation from wind and solar power and in the supply of electrical energy for electromobility. Liquid inside electrical equipment is the lifeblood that serves both as a dielectric and a cooling medium. Some properties of these liquids differ from mineral oil, which had to be considered in the transformer design. The dielectric liquid is always in direct contact with transformer materials; therefore, the interaction should be very well understood, especially when retrofilling an existing mineral oil filled device. There are several natural ester fluids derived from various seeds and fruits on the market, and their properties may differ more or less. In the book, the most important properties of the different biological insulating fluids and mineral oil are compared. Ester fluids have already found their way into various standards. The condition of the device can be verified very well from the contents of the insulating liquids. For analysis and testing, the same equipment and devices that are commonly used for mineral oil are used for ester liquid. The chemical and physical behaviors of ester fluids compared to mineral oil are different. This must always be considered when interpreting test results stemming from ester fluids. The book is a guideline for students, original equipment manufacturers, users, laboratories and authorities in the use of biological insulating liquids.
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Ac and lightning impulse breakdown voltage of natural ester impregnated pressboards
(2020-10-25)
Siriworachanyadee, Jompatara
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Pattanadech, Norasage
The paper represents AC and lightning impulse (positive and negative impulse) breakdown voltage characteristics of natural ester impregnated pressboards with different impregnation period. The pressboard specimen was 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-group according to the impregnation periods. The 1st group, the pressboards were impregnated with natural ester at 60°C for 8 hours under 200 mbar pressure. The 2nd and 3rd group, the pressboards were impregnated at 60°C for 16 and 24 hours, respectively, under 200 mbar pressure-controlled conditions. 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 AC breakdown voltage and impulse breakdown voltage characteristics of the impregnated pressboard were investigated in accordance with IEC 60243-1 and IEC 60243-3, respectively. At the end of the third month, another half of the pressboard samples was token from the test cells to perform AC and lightning impulse breakdown voltage test also. From the test results, all pressboards which are impregnated for a long period provided higher AC breakdown voltage than the pressboard which are impregnated for a short period. In the other hand, the impulse breakdown voltage values of each condition are not very different. Obviously, the period for impregnation significantly affects the AC breakdown characteristic of the natural ester impregnated pressboard. On the otherwise, it is not affecting the impulse breakdown characteristic of the natural ester impregnated pressboard.
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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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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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Dissolved gas analysis of liquid insulation under ac and impulse breakdown voltage tests
(2019-07-01)
Pattanadech, Norasage
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Lukin, Kanchanaporn
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Samerpak, Chantapapa
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Chumninuan, Nattakrit
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Piyapatamin, Nadpakul
This paper represents the study of dissolved gas analysis in mineral oil compared with natural ester (FR3) under AC and impulse breakdown voltage tests. Liquid insulation was heated at 60°C with 200 mbar for 12 hours. Liquid test samples were divided into three groups. The first group was tested with AC voltage using the spherical electrodes with the gap distance of 1.0, 1.5, and 2.0 mm. The AC test procedure was in accordant with IEC 60156. The second and the third group of liquid samples was tested with standard positive lightning impulse and standard negative lightning impulse voltage using the needle - sphere electrode with the distance of 10, 15, and 20 mm. The impulse test procedure was according to IEC 60897. Testing experiments were performed 5, 10, and 15 times consecutively for each test sample. Then dissolved gas analysis of each test sample was performed. From the test results, the type of breakdown voltage and the number of breakdowns effected on the quantity of the dissolved gas in the liquid insulation.
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Dissolved gas analysis caused by electrical breakdown of liquid impregnated pressboards
(2019-07-01)
Pattanadech, Norasage
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Luk-In, Kanchanaporn
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Samerpak, Chantapapa
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Chumninuan, Nattakrit
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Piyapatamin, Nadpakul
The aim of this paper is to analyze the dissolved gases in dielectric liquid caused by electrical breakdown of liquid-impregnated pressboards. The pressboards were prepared with dimension of 100 x 100 x 3.2 mm (W x L x H). First of all, each liquid insulation, mineral oil and natural ester (FR3), was heated at 60°C with 200 mbar for 12 hours. Second, pressboards were heated at 80°C with 200 mbar for 12 hours. Then the heated pressboards were impregnated with the dielectric liquid at 60°C with 200 mbar for 12 hours. The impregnated pressboards were divided into three groups. The first group was tested with AC voltage. The second and third group was tested with positive and negative lightning impulse voltages respectively. From the test results, the type and quantity of generated gases caused by breakdown phenomena is dependent on the type and the number of breakdowns.
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Comparison of dissolved gases in natural ester under partial discharges
(2019-06-01)
Jongvilaikasem, Korraya
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Maneerot, Sakda
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Jariyanurat, Kittipod
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Pattanadech, Norasage
Currently, natural ester is alternative liquid insulation applied for both distribution and power transformers. Generally, transformers are expected to operate stably and reliably. However, their functions may fail during operation. Dissolved gases analysis is one of the worldwide accepted diagnostic techniques to examine the insulation integrity of the transformers. This paper presents the analysis of dissolved gases generated from partial discharge (PD) experiments i.e. corona discharge, surface discharge and internal discharge which were conducted in the test cell filled with natural ester (FR3). To simulate corona discharge, a needle electrode with a tip radius of 10, 20, and 40 micrometers was used as high voltage electrode and the plane electrode with a diameter of 45 mm was used as a grounded electrode. The gap distance was fixed at 32 mm. The corona discharge experiment was performed for 2 hours at the test voltage level of 35, 40, 45 kV respectively. In case of surface discharge, the pressboard samples i.e. non-impregnated pressboards, 8-hour impregnated pressboards, and 16-hour impregnated pressboards were inserted between the 20-micrometer tip radius needle and grounded plane. Then, the test voltage of 25 kV was applied to the electrode system for 1 hour. Besides, the surface discharge was tested at 35 and 45 kV respectively. For internal discharge, the pressboard samples i.e. non-impregnated pressboards, 8-hour impregnated pressboards, and 16-hour impregnated pressboards were inserted between the plane-plane electrodes. Then the test voltage of 25 kV was applied to the electrode system for 1 hour. Moreover, the internal discharge was tested also at 35 and 45 kV. Their natural ester samples were sampling from the test cell for each experiment and the dissolved gases were measured and analyzed. From the test results, it was found that the types and quantity of dissolved gases depended strongly on the type of discharge and material samples.
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Dielectric response analysis of mineral oil immersed transformer, Natural Ester(FR3) immersed transformer, and palm oil immersed transformer
(2019-06-01)
Maneerot, Sakda
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Nimsanong, Phethai
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Siriworachanyadee, Jompatara
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Leelajindakrairerk, Monthon
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Jariyanurat, Kittipod
Currently alternative liquid insulation such as natural ester (FR3) is widely used as distribution transformer insulation because it provides outstandingly dielectric characteristics and natural friendly including highly affordable fire safety. Besides, palm oil is interesting liquid insulation for such transformers because of its distinguish dielectric properties. To analyze the dielectric properties of insulating material, polarization and depolarization current (PDC) measurement is one of the widely accepted non-destructive test technique. This paper presents the dielectric response analysis for the insulation system of a mineral oil immersed transformer, a natural ester (FR3) immersed transformer, and a palm oil immersed transformer by analyzing PDC test results. Three identical single phase transformers with 22kV/460V 30 kVA rated were designed and constructed. The first transformer was fully filled with mineral oil. The second and the third transformer was fully filled with natural ester (FR3) and palm oil respectively. After finishing the construction process, PDC measurement technique was applied for these transformers. The PDC measurement were performed for three case studies as follows: 1) dielectric response for the insulation between high voltage winding and low voltage winding, 2) dielectric response of high voltage winding insulation and low voltage connected to ground 3) dielectric response of high voltage and low voltage winding insulation by which the high voltage lead was connected to the low voltage lead. From the test results, it can be concluded that the dielectric response of the insulation system of the mineral oil immersed transformer was obviously different compared with that of the natural oil (FR3) immersed transformer and the palm oil immersed transformer. Moreover, the PDCs obtained from the tests were also analyzed and reported in this paper.

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