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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.
;
Jariyanurat, K.
;
Nimsanong, P.
;
Bunlaksananusor, C.
;
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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Dielectric Properties of Mineral Oil-based Nanofluids using Zinc Oxide Nano-composites for Power Transformer Application
(2018-11-14)
Muangpratoom, P.
;
Kunakorn, A.
;
Pattanadech, N.
;
Vittayakorn, W.
;
Thungsook, K.
This research paper describes and analyzes various experiments designed to investigate the dielectric properties (at a series of pre-determined test temperatures and % moisture content) of mineral oil-based nanofluids produced by the incorporation of zinc oxide (ZnO) powder (of mean diameter less than 100nm) into a standard mineral oil, with the surfactant sorbitan mono-oleate (Span 80) added to modify the surface of the nanoparticles in all but the control sample. Five different nanofluid test samples (one control sample and four modified samples) based on the standard mineral oil were produced for testing: 1) a control sample containing no Span 80 and no ZnO, 2) a modified sample with Span 80, and ZnO volume fraction of 0.01 %, 3) a modified sample without Span 80, and ZnO volume fraction of 0.01 %, 4) a modified sample with Span 80, and ZnO volume fraction of 0.03%, and 5) a modified sample without Span 80, and ZnO volume fraction of 0.03 %. In addition, the five liquid samples above were tested to determine AC breakdown voltage at seven different temperatures in the range of 35°C to 90°C. The test circuit was set up in accordance with IEC 60156 using a sphere-sphere electrode configuration with gap spacing of 2.5 mm. Several significant results were obtained from the investigation. Firstly, ZnO nanoparticles had a positive effect on all the test solutions in which they were used. Second, a positive relationship was confirmed between breakdown voltages, temperature rise. Third, a negative correlation was established between higher concentration of ZnO nanoparticles and breakdown voltage. Fourth, the use of surfactant proved to have both positive and negative effects on breakdown voltages.
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Different Moisture Contents of Pressboard Effect on Electrical and Chemical Characteristics of Liquid Insulation
(2018-11-14)
Jongvilaikasen, K.
;
Pumyoy, S.
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Jariyanurat, K.
;
Maneerot, S.
;
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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Partial discharge inception voltage investigation of mineral oil: Effect of electrode configurations and oil conditions
(2016-10-01)
Pattanadech, N.
;
Muhr, M.
The aim of this paper is to describe the Partial Discharge Inception Voltage (PDIV) and Partial Discharge (PD) characteristic of mineral oil tested by various electrode configurations. Furthermore, mineral oil with different conditions was investigated under AC voltage. The PDIV and PD of the mineral oil, Nynas Nytro 4000x, with water content about 4 ppm was investigated by using various electrode configurations of needle - plane and needle - sphere electrodes under room temperature. The PDIV test circuit was set up according to IEC 60270. Then, two PDIV measurements were applied for the investigation. The first PDIV test procedure (IEC method) was performed in accordance with IEC 61294. The second PDIV test procedure so-called combined PDIV method was adapted from IEC standard. Moreover, the electric field distributions of the electrode systems were also calculated. According to the test results, PDIV depended clearly on the electric field stress of the electrode system and the test method. Compared with other electrode configurations, the 10 μm tip radius needle - 75 mm dia. plane electrode gave the highest electric field stress and inversely provided the lowest PDIV value tested by both test methods. The combined PDIV test method generated the PDIV, charge quantity, and charge repetition significantly lower than measuring by IEC method. To investigate the effect of oil conditions on PDIV and PD characteristics, the combined conditions of temperature and water content of the mineral oil were controlled as the parameters for investigation. It was found that the water content in the mineral oil influenced approximately on PDIV value when the oil temperature was at room temperature. However, at the oil temperature of 40-90 °C, the PDIV values of the mineral oil with water content 4, 20 and 40 ppm were relatively the same. From the PD pulse current test results, PD pulse current recorded at the PDIV value from both test methods was about 0.15-1.3 mA. Pulse duration was in the range of 0.7-9 μs and the rise time was between 40-570 ns.

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