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The Dissipation Factor (tan δ) Monitoring of A Stator Winding Insulation of A Synchronous Machine
(2018-11-14)
Phloymuk, N.
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Nimsanong, P.
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Phumipunepon, N.
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Potivejkul, S.
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Wiangtong, T.
the aim of this paper is to describe the dielectric loss tangent (tan δ) behaviors of the stator winding insulation of the 14.5 MVA 11kV synchronous machine from 2014-2017. This machine is still operated up to now. The tan δ values at different test voltages was measured and recorded. It was found that the sharp increase in tan δ values gave the sign of a significant degree of contamination and damage on the insulation surface which was proved by inspection. From the investigation the tan δ measurements is one of the effective ways to monitor and evaluate the insulation conditions of the stator insulation. The analysis and discussion of the existed problem of the synchronous machine are also included in this paper.
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Breakdown characteristics and partial discharge phenomena of gas-insulated system under slightly nonuniform electric field with floating object
(2018-07-02)
Chuayin, C.
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Chamnong, C.
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Sontayananon, N.
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Kachachaveevong, T.
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Nganpitak, T.
The characteristics of breakdown voltage of air under slightly non uniform field with floating object was investigated experimentally. The sphere-plane electrodes with sphere diameter of 4.5 cm and plane diameter of 10 cm were used to study. The gap spacing between the sphere-plane electrodes was fixed at 3 cm. In this paper, the floating objects were divided into 2 types according to types of materials used, i.e., aluminum material represents a conductive particle and plastic material represents a nonconductive particle. The floating object position was varied between the sphere-plane electrodes in the test chamber. It was found that both types of floating objects clearly had negative effect on the breakdown voltage. Moreover, to more understand the effect of these floating objects, an ultra-high frequency sensor was used to detect partial discharge signal occurring during the experiment before breakdown occurred.
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Dielectric properties of natural ester based nanofluid
(2017-11-29)
Jariyanurat, K.
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Potivejkul, S.
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Pattanadech, N.
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Chotigo, S.
In this paper, AC breakdown and standard impulse breakdown characteristics of natural ester oil and natural ester base nano fluids are investigated. Three types of nanoparticles such as Zinc oxide (ZnO), Barium titanate (BaTiO3), and Titanium dioxide (TiO2) which have their diameter less than 100 nm are used to prepare the nanofluid samples which consist of the natural ester mixed with 0.01% volume fraction of each nanoparticle type. To measure AC breakdown voltage of the natural ester and natural ester based nanofluids, the oil breakdown tester (FOSTER OTS 60AF) is employed by sphere-sphere electrode system according to IEC 60156. The gap distance between electrodes is set at 2.5 mm. Furthermore, the needle-sphere electrode configuration with gap spacing of 40 mm is used for impulse breakdown voltage investigation of the dielectric liquids by the needle is tungsten and 40 μ m tip radius. The test circuit is set up in accordance with IEC 60897 and the test experiment is conducted at room temperature. The test results show that the AC breakdown voltages of the natural ester with nanopaticles is markedly higher than those of the unmodified natural ester. Additionally, TiO2, BaTiO3, and ZnO nanoparticles show their properties to increase impulse breakdown voltages of the nanofluids compared with those of the unmodified natural ester. From the test results, it is found that nanoparticles are good candidates to enhance the dielectric properties of natural ester for dielectric applications.
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Electrical characteristics of natural ester based nanofluid
(2017-10-19)
Potivejkul, S.
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Jariyanurat, K.
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Pattanadech, N.
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Wattakapaiboon, W.
In this paper, the dielectric properties of natural ester based nanofluids were investigated. This research represents the improvement of the electrical properties, AC breakdown and negative lightning impulse breakdown strength, of the natural ester (FR3) by amalgamation with nanoparticles. Two types of nanoparticles i.e., Titanium dioxide (TiO2) and Zinc Oxide (ZnO), with a mean diameter of less than 100 nm were used in this experiment. The nanofluid samples, a natural ester merged with nanoparticles, were prepared in three steps. First, the natural ester was divided into four groups. The first group was merged with 0.01% concentration of TiO2 and the second group was merged with 0.03% concentration of TiO2. The third group was merged with 0.01% concentration of ZnO and the fourth group was merged with 0.03% concentration of ZnO. Second, the nanofluid samples were dispersed using a magnetic stirrer. Finally, the ultrasonic dispersant technique was applied to the prepared nanofluids to be homogeneity. To measure AC breakdown voltage of the natural ester based nanofluids, the oil breakdown tester was employed and the testing experiment was performed according to IEC 60156. In addition, the negative lightning impulse breakdown characteristic of the natural ester based nanofluid was investigated with the needle-sphere electrodes in accordance with IEC 60897. A tungsten needle with tip radius of 40m was utilized as the high voltage electrode and the 13 mm diameter brass sphere was used as the grounded electrode. The gap distance was fixed as 15 mm. The test results showed that the AC breakdown property of the modified liquids was clearly influenced by the type of nanoparticles added. The AC breakdown voltage of the natural ester with nanopaticles was slightly higher than that of the unmodified natural ester. Additionally, both TiO2 and ZnO nanoparticles demonstrated their ability to increase negative impulse breakdown voltage of the nanofluids. These tests indicated that such nanoparticles have good potential to be used with natural ester to improve the dielectric properties.
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Electrical characteristics of natural ester impregnated pressboards under different periods of impregnation
(2016-11-28)
Jariyanurat, K.
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Maneerot, S.
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Pattanadech, N.
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Potivejkul, S.
This paper represents electrical characteristics of natural ester impregnated pressboards under different impregnation period. Each pressboard specimen was prepared as a rectangular shape having the width of 100 mm and the length of 100 mm as well. Two thickness dimensions of the pressboard for the experiment were 1.6 mm and 3.2 mm respectively. All pressboards were dry up in the oven with temperature at 60°c for 1 hour. Next, these pressboards were divided into three groups according to the impregnation periods. The first group was impregnated with natural ester (FR3) for 3 hours with temperature at 60°c and 200 mbar pressure controlled condition. The second and third group were impregnated for 6 and 9 hours respectively with the same temperature and pressure condition. Then, the breakdown voltage characteristic of the impregnated pressboards were investigated according to IEC 60243-1. Besides, the capacitance and dielectric dissipation factor of the natural ester with various conditions were examined in accordance with IEC 60247. According to the test results, the pressboard impregnated for longer period provided higher breakdown voltage than the pressboards impregnated for shorter period by which the breakdown voltage of the pressboard impregnated for 9 hours was higher than the pressboard impregnated for 6 hours about 8-24% and the breakdown voltage of the pressboard impregnated for 6 hours was higher than the pressboard impregnated for 3 hours about 5-19%. Whereas the dielectric dissipation factor of the natural ester utilized for pressboard impregnation process for 3 hours was higher than the natural ester utilized for such process for 6 and 9 hours about 5% and 12% respectively. Moreover, the electrical characteristics of pressboard impregnated with natural ester was compared with that of the pressboard impregnated with mineral oil. The breakdown voltage of natural ester impregnated pressboard was higher than the mineral oil impregnated pressboard about 5-11% but the dielectric dissipation factor of natural ester was 30 times higher than mineral oil. It is clear that the time for impregnation significantly affects the breakdown characteristic of the natural ester impregnated pressboard. Furthermore, impregnation of the pressboard with natural ester provides better breakdown strength than the pressboard impregnated with mineral oil.
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Partial discharge classification using probabilistic neural network model
(2016-01-18)
Pattanadech, N.
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Nimsanong, P.
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Potivejkul, S.
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Yuthagowith, P.
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Polmai, S.
The aim of this paper is to propose the probabilistic neural network (PNN) model for classification partial discharge (PD) patterns, which comprised of corona discharge at high voltage side and at low voltage side in air, corona discharge at high voltage side and at low voltage side in mineral oil and surface discharge in mineral oil. Partial discharge signals were investigated by conventional method according to IEC60270. Independent parameters such as skewness, kurtosis, asymmetry, and cross correlation of the Φ-q-n PD patterns were analyzed. The PNN PD classification model was constructed. Moreover, the principal component analysis (PCA) was utilized to reduce the input dimension of the developed PD classification model. After that, 60% of the experimented data was used as a training data for the PD classification models. Another 40% experimented data was used for evaluation the performance of the designed PD classification models. Effects of spread parameters and input neuron numbers on the PD classification performance were examined. It was found that the first four score variable was appropriate to be used to construct the designed PNN model with the optimal spread value of 1.2. The proposed PD classification model can classify PD types with the accuracy of 100% of 40 tested data.
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Generalized regression networks for partial discharge classification
(2016-01-18)
Pattanadech, N.
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Nimsanong, P.
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Potivejkul, S.
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Yuthagowith, P.
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Polmai, S.
This document represents a partial discharge (PD) classification by using Generalized Regression Networks (GRNN) model. Two PD classification models, GRNN1 with 11 input variables and GRNN2 with 3 selected derived statistic parameters, were investigated for classification of PD signals into 5 patterns, corona at high voltage side in air, corona at low voltage side in air, corona at high voltage side in mineral oil, corona at low voltage side in mineral oil and surface discharge in mineral oil. The conventional PD measurement was performed for measuring PD signals of the artificial PD models. The statistical parameters of the PD signals such as skewness, kurtosis, asymmetry, cross correlation and so on were calculated from the developed computer program. Then, 60% of the experimented data was used as a training data for the developed PD classification models. Another 40% experimented data was used to evaluate the performance of the designed PD classification models. It was found that the GRNN1 model can classify PD patterns better than GRNN2 model. The accuracy for PD classification of GRNN1 model was 100% while the accuracy of GRNN2 model was 97.5% of 40 testing data.
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A development design of ozone generator with a new helix coil electrode for micro bacterial disinfection in hospitals
(2015-01-26)
Potivejkul, S.
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Leejongpermpoon, S.
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Markchun, C.
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Kinnares, V.
This article presents development of a new helix coil electrode of an ozone generator for disinfection in hospital. In development of the proposed electrode, the optimal spacing between each turn of the helix coil has been investigated. The considered spaces are 1 cm, 2 cm, and 3 cm. To confirm the performance of the proposed electrode, the capability in ozone generation has been considered in an HV laboratory by comparison of ozone concentration generated by the proposed and conventional cylindrical electrodes. The helix coil electrode as an inner electrode was made from copper wire and the cylindrical electrode with radius of 1.5 cm as outer electrode was made of stainless steel. Those two electrodes are separated by air gap with gap spacing of 1 mm and glass material with thickness of 1.4 mm. The inner electrode is connected to a high voltage source and the outer one is connected to ground. In the experiment, air flow rate was set to be 20 l/hr to 150 l/hr. The applied peak high voltage with frequency of 20 kHz used in the experimental is set to be 0 to 6 kV. The experimental result show that the condition of the spacing of 2 cm, air flow rate of 50 l/hr and peak voltage of 6 kV provides the highest ozone concentration of 840 ppm. From the experimental results, it is high possibility that the developed electrode is able to use in ozone generators for micro bacterial disinfection in hospitals.
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The development of a prototype of polluted gas reducing instrument used for gasoline vehicle
(2015-01-26)
Potivejkul, S.
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Kitwattana, K.
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Udomdat, P.
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Kinnares, V.
This paper presents the development of a prototype of polluted gas reducing instrument which used for a gasoline vehicle. Effect of the electric field between electrodes in the instrument to capability in polluted gas reduction has been studied. In experiments, the electric field of 0-25 kV/cm 20kHz was varied. The revolution speed of engine was set to be 700 rpm. Electrode is wire-plan with 2 layer insulated acrylic plastic and air are 3 mm both of them. It is not necessary to use another power supply from outside the vehicle, since the battery used in the vehicle is used as a power supply of the instrument. The prototype can operate very well. The results showed that using only vehicle battery can provide energy to the electrodes to generate an electric field for reducing emission gases. Actually, it can reduce carbon monoxide, carbon dioxide and hydrocarbons by 36.3%, 21.6% and 9.1% respectively.
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Transient equivalent circuit of a horizontal grounding electrode
(2012-12-31)
Yutthagowith, P.
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Kunakorn, A.
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Potivejkul, S.
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Chaisiri, P.
This paper proposes an equivalent circuit of grounding electrode which has validity upto a frequency range of sub-sequence stroke lightning current. The equivalent circuit is modelled by lumped and distributed parameters based on quasistatic assumption. In this study, only a grounding electrode installed horizontally is in consideration. The limitation of the uniform distributed equivalent circuit of a grounding electrode is presented. The non-uniform distributed equivalent circuit is proposed. The proposed equivalent circuits are verified by comparison of the results of ground potential rise computed by the proposed circuit, the partial element equivalent circuit method, and available experimental data. The proposed equivalent circuit can be adapted for being the models for development and design of the grounding system for lightning protection system in transmission and distribution systems in an effective way. © 2012 IEEE.

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