KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 10 of 11

Some of the metrics are blocked by your
consent settings
Overload Duration Analysis of Mineral Oil and Natural Ester in Retrofilled Distribution Transformers
(2025-01-01)
Pongpitak, Siriwut
;
Pannil, Pittaya
;
Pattanadech, Norasage
Natural ester fluids such as FR3 provide higher fire safety, better biodegradability, and extended insulation life compared with mineral oil. Retrofilling existing transformers with FR3 offers a practical means to enhance safety and environmental performance without redesigning the unit. This study evaluates the thermal performance and overload endurance capability of a 160 kVA distribution transformer before and after retrofilling from mineral oil to FR3. Results show that steady-state temperature rises increased modestly after retrofilling (+1.3-4 K for top oil and windings) but remained within IEC limits. Under 1.5 p.u. normal cyclic loading, the mineral-oil unit reached its 120 °C hot-spot limit after 5 hours and 20 minutes, whereas the FR3 unit stabilized near 126 °C and did not reach its 140 °C limit within 10 hours. Under 1.8 p.u. long-time emergency loading, FR3 extended the time-to-limit to 5 hours and 20 minutes, compared with 4 hours and 30 minutes for mineral oil (18.5% increase). Overall, FR3 trades slightly higher temperature rises for a wider operational safety envelope and longer overload endurance, supporting safer peak-shaving and contingency operations in retrofilled assets. These findings provide actionable insights for utilities considering FR3 retrofilling as a cost-effective transformer upgrade strategy.
Some of the metrics are blocked by your
consent settings
Polarization and Depolarization Current of Pressboard Impregnated with Natural Ester under Thermal Stress
(2022-01-01)
Kittikhuntharadol, Yannaphol
;
Worthong, Tehneht
;
Pattanadech, Norasage
Mineral oil has long been utilized in transformers due to its low cost and suitable qualities. Alternative liquid insulations with great characteristics have recently been presented, and natural ester was considered. Pressboard is a type of cellulose insulation used for electrical insulation and mechanical support. This paper intends to study pressboard impregnated with natural ester under thermal stress. The pressboards and the natural ester were prepared for the experiment. Vacuum ovens were used for moisture elimination of materials and the impregnation process. The test specimens consisted of impregnated pressboards for 0, 8, 16, and 24 hours with thermal stress by heating at 150 degrees Celsius in a vacuum oven for 0, 30, and 90 days. Polarization and depolarization current (PDC) of the test specimens were investigated in each period by PDC-Analyser 1MOD. The test cell for PDC measurement was designed according to JIS C2111, and it was clean before the experiment. The PDC characteristics of the pressboard that had been subjected to thermal stress were discovered to be slightly different when compared with the same impregnation time of the pressboard.
Some of the metrics are blocked by your
consent settings
AC Breakdown Characteristics of Different Moisture Content Pressboards Impregnated with Natural Ester
(2021-04-01)
Pattanadech, Norasage
;
Kittikhuntharadol, Yannaphol
;
Pannil, Pittaya
Biodegradable materials are necessary for saving the environment. Natural ester is alternative liquid insulation that can be biodegraded and used in a transformer. Insulation system in a transformer, liquid insulation cooperates with solid insulation such as cellulose. Pressboard is the main kind of cellulose used in the transformers. Normally, the characteristics of solid insulation can be investigated and analyzed by diverse methods. This paper represents the study of AC breakdown voltage of non-impregnation, 8-hours, and 16-hours impregnated pressboard with natural ester with different moisture content. To vary the moisture content of the pressboards, they were heated at 100 degrees Celsius for 12 hours and 24 -hours in a vacuum oven. After that, the Coulometric Karl Fischer method was used to determine the moisture content. Before impregnation, the natural ester was heated at 100 degrees Celsius for 12-hours in another vacuum oven. To investigate AC breakdown voltage, electrode configuration and test circuit were set-ups according to IEC 60243-1. From the test result, higher' moisture content caused clearly lower AC breakdown voltage of the pressboards.
Some of the metrics are blocked by your
consent settings
Furan Analysis of Oil Impregnated Paper Aged by Chemical Stress
(2020-10-25)
Suksawat, Dusit
;
Atthaphotpong, Kittiphot
;
Takboontam, Kriangsak
;
Satirapattanakiat, Kanin
;
Raphephat, Chiranuwat
The objective of this paper is to study the deterioration of impregnated kraft papers immersed in dielectric liquids under the chemical stress conditions by furan analysis according to ASTM D5837 and IEC 61198. Mineral oil and natural ester (FR3) were liquid used in this study. Kraft paper samples, 3 pieces per each case study, are prepared in rectangle shape with 25.4 ± 0.5 millimeters (1.00 ± 0.02 inches) wide and approximately 254 millimeters (10.0 inches) long according to the ASTM D828 standard. The paper and liquid insulation are heated to dehydrate at 80 °C for 12 hours with 200 mbar pressure, and then they are filled in 200 milliliter bottles and heated with 5 different temperatures being 60 °C, 80 °C, 100 °C, 120 °C and 140 °C respectively. In the case of 120 °C and 140 °C are only conducted with FR3 due to its thermal characteristics. After that, 98% concentration of acetic acid of 2 quantities, 0.04 and 0.08 milliliters, and oxygen (O2) at 1 psi for 1,200 ml, are used for the chemical aging process for 9 days of the test samples before being tested to find furanic compounds. According to the test result, it can be concluded that all 4 factors, temperature, acetic volume, oxygen and moisture, effect on generated furanic compounds of aging paper insulation.
Some of the metrics are blocked by your
consent settings
Dissolved Gas Behavior in Natural Ester under Corona, Surface, and Internal Discharges
(2020-10-25)
Jongvilaikasem, Korraya
;
Pattanadech, Norasage
The normal operating transformers encounter various kinds of stresses such as thermal stress, electrical stress, mechanical stress, and ambient effect that can expedite the deterioration process. Partial discharge occurs normally in high voltage equipment under high electric field. For a natural-immersed transformer, partial discharge can be detected by the dissolved gas analysis technique. This paper presents the patterns of dissolved gas generation in natural ester under partial discharge conditions. Besides, the existence of acidity number is also reported. Various types of partial discharge, including corona discharge, surface discharge, and the FR3 impregnated pressboard internal discharge, were simulated. A needle-plane electrode was used to simulate corona discharge, a needle-plane electrode with the impregnated pressboard was used to simulate surface discharge, whereas the plane electrode with pressboards was used to simulate the internal discharge. Each experiment was simulated in the test vessel under 24 kV test voltage for 3000 hours. The natural ester and the pressboards were heated at 80°C for 12 hours. before filled in the test vessel. Each test vessel was contained two identical plane electrodes with a 32 mm gap spacing. The impregnated pressboard was fit-inserted between such electrodes. The high voltage electrode was subjected to 24 kV whereas another plane electrode was grounded. Then, the natural ester were sampled from the vessel after operating for 350, 1000, and 3000 hours respectively. Dissolved gas analysis of the natural ester in this work followed ASTM D3612; the acidity number of aging natural ester was also tested according to ASTM D664. From the test results, it was found that different types of partial discharges generated various patterns of dissolved gas generation. Besides, the experiment with non-impregnated pressboards couldn't survive in this condition.
Some of the metrics are blocked by your
consent settings
The Polarization and Depolarization Current Characteristics of Natural Ester Stressed by Partial Discharge
(2020-10-25)
Maneerat, Noppadol
;
Makmork, Kawee
;
Kittikhuntharadol, Yannaphol
;
Suksai, Nattapat
;
Chusang, Thanapat
This paper represents the polarization and depolarization current (PDC) of the natural ester stressed by partial discharge (PD). The needle-plane electrode was used to simulate corona discharge in natural ester. Besides, the needle electrode as a high voltage electrode placed on the 8 hours natural ester impregnated pressboards and the plane electrode as a grounded electrode were used to simulate the surface discharge. To simulate the internal discharge, the plane-plane electrode inserted with various condition impregnated pressboards were experimented. PD phenomena were simulated in the natural ester container for 1, 3, and 6 months. Then the PD-stressed natural ester was used as the liquid specimen for polarization and depolarization current measurement. It was found that the PDC characteristics of natural ester undergone with various PD types were obviously different.
Some of the metrics are blocked by your
consent settings
How Water Affects the Properties of Insulating Liquids
(2020-10-25)
Pagger, Ernst
;
Muhr, Michael
;
Pattanadech, Norasage
;
Kongdang, Peeraphong
;
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.
Some of the metrics are blocked by your
consent settings
Dielectric Properties of Natural Ester Mixed with Nanoparticles under Thermal Stress
(2020-10-25)
Kittikhuntharadol, Yannaphol
;
Vittayakorn, Wanwilai
;
Pattanadech, Norasage
This paper aim to study of the dielectric properties of thermal stressed natural ester mixed with TiO2, and ZnO. Polarization and depolarization current (PDC) along with dielectric loss factor (tanδ) of the test specimens were investigated. The test specimens comprised of unmodified natural ester and natural ester mixed with different volume concentration, i.e., 0.01%, and 0.03% of TiO2, and ZnO. After preparing the natural ester and the natural ester nanofluid specimen, such specimens were undergone with thermal stress at 110 degree Celsius for 72 hours in vacuum oven. Then, a PDC-Analyser-1MOD was utilized for PDC measurement of the test samples. For tanδ measurement, test circuit was set-up according to IEC 60247 and the C and tanδ meter with the liquid electrode were used. From the test result, thermal stress strongly affects the PDC and tanδ characteristics of the liquid samples. Besides, natural ester mixed with 0.01% of TiO2 concentration shows the high potential dielectric liquids compared with other specimens.
Some of the metrics are blocked by your
consent settings
Polarization and Depolarization Current Characteristics of Natural Ester Impregnated Pressboards with Different Periods of Impregnation
(2020-10-25)
Maneerot, Sakda
;
Siriworachanyadee, Jompatara
;
Likhitsupin, Wit
;
Likhitsupin, Suwapich
;
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).
Some of the metrics are blocked by your
consent settings
AC Breakdown and Resistivity of Natural Ester Based Nanofluids
(2020-10-25)
Maneerat, Noppadol
;
Makmork, Kawee
;
Kittikhuntharadol, Yannaphol
;
Suksai, Nattapat
;
Chusang, Thanapat
In this paper, AC breakdown including resistivity of natural ester and natural ester mixed with nanoparticles were studied. Two types of nanoparticles i.e. Barium titanate (BaTiO3) and Titanium dioxide (TiO2) which have their diameter less than 100 nm were used in experiment. For the nanofluid samples, three concentration of nanoparticles including 0.01%, 0.03% and 0.05% were prepared in five processes. Firstly, the natural ester mixed was with 0.01%, 0.03% and 0.05% of volume fraction of nanoparticles. Second, a magnetic stirrer was used to diffuse them evenly over the liquid later, ultrasonic dispersion was also used to ensure that the prepared nanofluids were homogeneous. Then, the nanofluid liquid was heated at 80 degree Celsius in vacuum oven for 15 hours. Finally, this liquid was dispersed by using magnetic stirrer again. Besides, the mixed liquid sample was heated at 110, and 130 degree Celsius for 72 hours to simulated thermal stress. To measure the AC breakdown voltage, a dielectric breakdown testing device was used. The test circuit was set up according to ASTM D1816. The gap distance between electrode was set at 2.0 mm. Furthermore, the test cell for liquid insulation testing (Model DAC-OBE-2: SOKEN) was used for polarization and depolarization current (PDC) experiment. The PDC test result was then used to calculated the resistivity of the liquid samples. The test results show that the AC breakdown voltages of the natural ester mixed with nanoparticles is higher than unmodified natural ester. Additionally, Barium titanate nanoparticles and Titanium dioxide nanoparticles enhance the breakdown strength and the resistivity of the ester nanofluid tested. According to the results, it concluded that nanoparticles were an good alternative to enhance the dielectric properties of natural ester for dielectric application.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results