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Ac and lightning impulse breakdown voltage of natural ester impregnated pressboards
(2020-10-25)
Siriworachanyadee, Jompatara
;
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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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).
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Dissolved gas analysis caused by electrical breakdown of liquid impregnated pressboards
(2019-07-01)
Pattanadech, Norasage
;
Luk-In, Kanchanaporn
;
Samerpak, Chantapapa
;
Chumninuan, Nattakrit
;
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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The Polarization and Depolarization Current Characteristics of Mineral Oil, Natural Ester (FR3), Palm Oil, and Liquid Impregnated Pressboard
(2019-06-01)
Siriworachanyadee, Jompatara
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Maneerot, Sakda
;
Nimsanong, Phethai
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Kitchaiya, Prakob
;
Pattanadech, Norasage
Polarization and Depolarization Current (PDC) measurement is a non-destructive dielectric testing method used to determine the electrical properties of transformer insulation. Nowadays, natural ester has been used as alternative liquid insulation in transformers because it can be easily decomposed, highly flammable, resistant to moisture, and prolong of pressboard (solid insulation in a transformer) compared with mineral oil. Furthermore, palm oil is also an interestingly alternative insulating liquid. This paper presents the PDC characteristics of mineral oil, natural ester (FR3), and palm oil under various temperatures. All received liquid specimen were dry in the controlled temperature oven at 70°C under 200 mbar and then they were cooled down to ambient temperature around 25-30°C. The liquid samples were investigated for three cases as follows: 1) moisture content measurement according to ASTM D1533, 2) dielectric dissipation factor measurement as per ASTM D924, and 3) polarization current and depolarization current measurement at liquid temperature of 30°C, 50°C, and 70°C respectively. The PDC characteristics of mineral oil impregnated pressboards and natural ester impregnated pressboards were also investigated. The PDC test results were analyzed. It was found that the dielectric response of mineral oil was significantly different from natural ester (FR3) and palm oil. Besides, it was clearly that the conduction current of liquid insulation increased with increasing liquid temperature. Moreover, the pressboard impregnated with natural ester provided better insulation characteristics such as lower conduction current than that of the pressboard impregnated with mineral oil.
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The conformity of DGA interpretation techniques: Experience from transformer 132 units
(2019-06-01)
Pattanadech, Norasage
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Sasomponsawatline, Kantitat
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Siriworachanyadee, Jompatara
;
Angsusatra, Worawich
Dissolved gas analysis (DGA) is an important method and widely used for assessment the conditions of transformer insulations. The dissolved gas interpretation is one of the most significant procedures to identify the failure causes. The objective of this paper is to represent diagnosis of the dissolved gas techniques i.e. IEC ratio, Duval Triangle and Duval Pentagon for interpretation. The data of dissolved gas is received from Metropolitan Electricity Authority (MEA), Thailand during 2016. The DGA test results obtained from 132 transformer units. Due to the transformers have various rated power so providers have made a classification of results by rated transformer power rated of 40, 60, 250 and 300 MVA respectively. Overheating at high temperature is generally found. The results of the data analysis by using Duval Triangle method is the most similar result from observation work. Moreover, the Duval Pentagon method is interested for gas interpretation. However, it needs more research work to guarantee and support this method.
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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
;
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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