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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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Determination of water in transformer by water solubility and percent moisture by dry weight in comparison with ppm water value for justification transformer maintenance
(2020-10-25)
Wannapring, E.
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Sirisithichote, T.
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Pattanadech, N.
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Leelajindakrairerk, M.
The measure of water content is to find water content in transformers. There are many ways that water can occur in the transformers, such as residual moisture in the paper insulation and oils during the manufacturing process, generating from the degradation of transformer paper insulation and oil, ingression into the transformer, etc. The water in the transformer resides in liquid insulation approximately 1% and in the solid paper insulation of roughly 99%. The status of water in oil and water in paper insulation is not stable; water in paper insulation moves into transformer oil and vice versa, depending on loads and temperature. Both waters in oil and water in paper insulation reduce the insulation property of the transformer. This paper aims to present the observations of total water content in the transformer (water in oil and water in paper insulation) compared to the PPM value directly from laboratory testing to understand the severity and manage proper transformer maintenance decisions.
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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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Evaluation of loss factor of mineral oil and alternative fluids with temperature normalization
(2020-07-01)
Maneerot, S.
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Nimsanong, P.
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Pattanadech, N.
This paper proposes the evaluation of loss factor of mineral oil and alternative fluids the natural ester (FR3) with temperature normalization. The oil samples (i.e., mineral oil, natural ester, and palm oil) were prepared for experiments. The oil samples were dried at 70 °C under 200 mbar in the controlled temperature oven and then cooled down to ambient temperature. The moisture contents of the oil samples were measured according to ASTM D1533. The test cell, according to IEC61620, was employed in these measurements. The polarization currents, ipol(t), of such oil samples under electric field stress of 0.2 kV/mm with a temperature range from 30 to 70 °C were measured, The test results are summarized in this paper. The step response measurement results were analyzed for conductivities, permittivity, and loss factor value. It was found that increasing temperature causes increasing conductivities but decreasing permittivity of oil samples.
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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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Dielectric Response Analysis of Mineral Oil Immersed Transformer Insulation during Manufacturing Process
(2019-06-01)
Nganpitak, Tritod
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Nimsanong, Phethai
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Maneerot, Sakda
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Pattanadech, Norasage
Polarization and Depolarization current (PDC) method is one of non-destructive insulation testing methods that can be used for diagnosis the insulation conditions of high voltage equipment. This paper presents the PDC analysis of an oil immersed distribution transformer measured during the manufacturing process. A 22 kV, 30 kVA single phase transformer was designed and constructed. During manufacturing process, the polarization current and depolarization current of the transformer insulation were measured for 6 case studies as follows: 1) paper insulation between iron core and low voltage (LV) windings before dry and vacuum in the oven, 2) paper insulation between LV and high voltage (HV) windings before dry and vacuum in the oven, 3) paper insulation between iron core and LV windings after dry and vacuum in the oven, 4) paper insulation between LV and HV windings after dry and vacuum in the oven, 5) oilpaper insulation between iron core and LV windings after dry and impregnation process and 6) oil-paper insulation between LV and HV windings after dry and impregnation process. Then, PDC test results were analyzed. It was found that the moisture content in the paper insulation clearly affected the capacitance at power frequency, and PDC shapes. Besides, the impregnation process had a good effect on the capacitance ratio and dielectric dissipation factor. Moreover, the current difference of dry paper insulation between HV and LV windings presented the nonlinear characteristic both before and after impregnation process.
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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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Effect of different temperatures on AC breakdown voltage of mineral oil based nanofluids
(2018-07-02)
Muangpratoom, P.
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Kunakorn, A.
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Pattanadech, N.
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Vittayakorn, W.
This study seeks to make improvements in the dielectric properties of transformer oil through the application of nanotechnology. In particular, two nanoparticles are examined experimentally: titanium dioxide (TiO<inf>2</inf>), and barium titanate (BaTiO<inf>3</inf>). Each has a mean diameter not exceeding 100 nm. The nanofluid samples comprised the nanoparticles mixed into the mineral oil through differing procedures. In the first case, the transformer oil was combined with 0.01% volume fraction of the nanoparticle; the second sample used 0.03% volume fraction of the nanoparticle volume fraction. A magnetic stirrer was then used for sample dispersal before an ultrasonic dispersant method was used on the prepared nanofluids so that sample homogeneity could be assured. The experimental process then recorded the AC breakdown voltage characteristics for the liquids through a range of temperatures from 35°C up to 90°C. The findings indicate that the AC breakdown voltages for mineral oils containing nanoparticles exceed those for unmodified mineral oils.
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Impulse breakdown characteristic of mineral oil based nanofluid
(2017-11-29)
Muangpratoom, Pichai
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Pattanadech, Norasage
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Kunakorn, Anantawat
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Vittayakorn, Wanwilai
Mineral-oil based nanofluids are proved that the addition of suitable nanoparticles can increases the AC breakdown voltage and Partial Discharge Inception Voltage (PDIV) compared with those of the unmodified mineral oil. In this paper, a standard impulse breakdown voltage of the mineral oil and the mineral-oil based nanofluids is investigated. Three types of nanoparticle, i.e., Zinc oxide (ZnO), Barium titanate (BaTiO<inf>3</inf>) and Titanium dioxide (TiO<inf>2</inf>) with the mean diameter less than 100 nm are used to prepare the nanofluid samples. The first group of the nanofluid sample consists of the mineral oil mixed with the 0.01% volume fraction of nanoparticle. Another group of nanofluid sample comprises the mineral oil mixed with the 0.03% volume fraction of nanoparticle. Besides, the surfactant sorbitan monooleate (Span 80) is added in order to modify the surface of the nanoparticles. The needle-sphere electrode configuration with the gap spacing of 15 mm is employed for impulse breakdown voltage investigation of the dielectric liquids. The test circuit is set up in accordance with IEC 60897, and the test experiment is performed at the room temperature. The results show that the addition of ZnO and TiO2 nanoparticle leads to the change in the impulse breakdown characteristics of the mineral oil in both positive and negative impulse polarities. However, no significant change in the impulse breakdown characteristics is observed when adding BaTiO3 to the oil.

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