• Journal of radiological science and technology
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• v.2 no.1
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• pp.71-83
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• 1979

Not only the insulating oil used for extra high voltage and high capacity transformer has a lot of possibilites of a corona discharge in oil, but the oil is easily degraded by a response of light oxidization. This study is either to classfy, with priority given to a transformer oil produced in Korea belonging to, the insulating oil No. 2, the sample irradiated the ultraviolet rays, treated a corona discharge in oil by a high voltage DC source and done nothing, or to measure the characteristics of breakdown, V-i, I-t and electrode material. The obtained results can be summarized as followings: (1) Unless the sample is contacted with the air, on the process to irradiate the ultraviolet rays, the sample less influence on the changes of the electric characteristics. At the same time, if the sample is contacted with the air and irradiated the ultraviolet rays, the sample shows a remarkable changes of the electric characteristics, and a declined breakdown strength. This tells us that the influence of the light irradiation must be considered as a primary factor of degrading the insulating oil. (2) In the oil treated by a corona discharge, breakdown voltage is declined more than in the oil not to be treated with it. This means that the degradation of the insulating oil is getting increased by a corona discharge in oil. (3) It shows that the increase of conducting current has little to do with breakdown voltage. (4) The conducting current depending on the electrode materials can be put in order by value as Al>Cu>Fe. This is due to the differences of the work function of each metals, and an chemical reaction with the insulating oil. These result can be a great help in verifying the degradation progress of the insulating oil and furnish a new technical information to the manufacturers of the insulating oil and electrical equipment designers and operators. Besides, this study would be helpful to improve the electrical characteristics of the insulating oil produced in Korea.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1455_1456
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• 2009

$SF_6$ is the most commonly used insulating gas in electrical systems. But In these days $SF_6$ mixtures and alternative gas has been studied because of global warming. so although many studies have been carried out about binary gas mixtures with $SF_6$, few studies were presented about breakdown characteristics of $SF_6/CF_4$ mixtures. At present study the breakdown characteristics of $SF_6/CF_4$ mixtures in quasi-uniform field was performed. This experiments were carried out under AC voltages. The rod-rod electrode was used with 5 mm gap distance. The mixture of $SF_6/CF_4$ containing 20%,50%,70% of $SF_6$ were compared with pure $SF_6$ and $CF_4$ gas and gas pressure ranged from 0.1 to 0.5 MPa. The show that the breakdown voltages of gas were linearly increased according to the pressure in quasi-uniform field. For breakdown vlotage values of $(E/P)_{crit}$ are important. Because If values of (E/P) is a little more than $(E/P)_{crit}$, electrons rapidly increase and streamer discharge gernerates. Through this experiments values of $(E/P)_{crit}$ are found to vary with the ratio of $SF_6/CF_4$ mixture according to the following relationship. $V_b=(E/P)_{crit}{\cdot}p{\cdot}d$

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.8
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• pp.71-79
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• 2006

For clearing the cause of firing due to the tacking on the surface of phenolic resin, this paper describes the analysis through a couple of methods ; FT-IR; DTA; photograph analysis, etc. Phenolic resin has been widely employed as a case of low voltage appliances. In the experiment it was confirmed that its surface was carbonized and graphitized by the external fire. In the FT-IR test a graphite specimen thermally treated at $150[^{\circ}C]$ showed the 2 different IR absorption peaks at $1,730[cm^{-1}]\;and\;1,680[cm^{-1}]$. In normal phenolic resin, the exothermic peak appeared at $450[^{\circ}C]$, while in graphite specimen, it appeared at $610[^{\circ}C]$ in DTA test. From the results, the electrical fire causes could be cleared and it is expected to protect the human life and property from the electrical fire by using the important data.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.6
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• pp.44-49
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• 2013

This study investigates the surface discharge characteristics of solid insulators by varying their materials, their shapes, and the dew-point of dry-air. The methodology of this study is that a quasi-uniform field is first applied to a test chamber. Then, the chamber is filled with dry-air as an insulation gas which pressure is varied from 1 to 6atm while applying an AC voltage to the chamber. The used solid insulators are teflon, polycarbonate, and bakelite. As the dew-point is lower and the pressure of dry-air is higher, the flashover voltage of all solid insulators increases more. When each characteristic of the solid insulators is compared under the same gas pressure, the flashover voltage of teflon is the highest. Then, the flashover voltage of polycarbonate is higher than that of bakelite. Moreover, it is observed that the flashover voltage increases as the diameter and the thickness of each solid insulator become larger and thicker, respectively. However, the thickness of the solid insulators is more critical for increasing the flashover voltage than their diameter.

• Journal of the Korean Society of Safety
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• v.33 no.5
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• pp.15-20
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• 2018

This paper describes the fusing time characteristics of Light PVC Sheathed Circular Cord(VCTF) and Tray Frame Retardant(TFR) cables according to increased temperature under over current condition. The experimental equation will be used to determine the validity and reliability of the test results. The over current flowed 3, 5 and 10 times higher than the amount of allowable current using DC power supply with DAQ(Data Acquisition) measurement system. An infrared radiation heater, which was controlled by a variable AC auto transformer, was used to increase the temperature from room temperature to 50, 100 and 150 degrees Celsius. First, two type of cables were analyzed those with different cross-sectional areas with in the same structure and those with different structures with in the same cross-sectional areas. Then, it was determined how fusing time had been influenced according to the cross-sectional areas and different structures, respectively. The cable resistance was increased by joule heating according to increasing temperature. Therefore, the allowable current of cable is decreased. Finally, the fusing time of the cable was decreased due to increased temperatures at current flow, which were 3 times the amount of allowable current. The instantaneous breakdown was observed when current flow was 5 and 10 times over the amount of allowable current. The fusing time is directly affected by the structure of cable insulation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.6
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• pp.49-57
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• 2015

This paper presents the discharge characteristics and economic feasibility of a Dry $Air/O_2$ and a $N_2/O_2$ mixture gas in order to review $SF_6$ alternative. From AC discharge experiment in an quasi-uniform field, it was found that the optimal $N_2/O_2$ mixing ratio which breakdown voltage and surface flashover voltage were the highest was 70/30 and that the pressure dependence on the breakdown voltage was higher than that of the surface flashover voltage in the Dry $Air/O_2$ and the $N_2/O_2$ mixture gas. The mixing ratio (70/30) and the tendency of the pressure dependence were described in detail based on physical factors (impact ionization coefficient, electron attachment coefficient, secondary electron emission coefficient) involved in discharge mechanism and a electron source, respectively. In addition, the performance insulation and the economic feasibility of the Dry $Air/O_2$ and the $N_2/O_2$ mixture gas were discussed so that Dry $Air/O_2$ mixture gaswas more suitable than $N_2/O_2$ mixture gas to the $SF_6$ alternative.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.5
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• pp.481-487
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• 2005

Proposed induction-heated system is innovative system which applied special high-frequency power circuit technique for thermal converse technique and IH(Induction-Heating) magnetic induction heating generated from induction-heated metallic package that is for distillation unit. In this occurs not burning, so that the working environment can be improved. This electromagnetic induction heating technique is used high frequency inverter, By using high frequency inverter high frequency alternative current in the range of [kHz] can be made with conventional alternative current. In this contribution IGBT module is used for high frequency inverter. This paper proposes new fluid heating method. Which is operated as follows. Working coil, which is wrapped outside of pipeline, makes the eddy current. Inside of heating vessel in isolated pipeline the specially designed stainless metallic package is inserted, which can be heated by eddy current losses. And then In this paper are discussed action analysis and characteristics analysis of 5[kW] class full-bridge resonant inverter system and resonant metallic package. In addition, by using this system, how high-efficiency heater is developed and application of system are also discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.593-596
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• 2001

In the previous work, the effect of blending with two kinds of low density polyethylene (LDPE) on physical and electrical properties have been investigated. From the results, blending with two kinds of LDPE was effective method on changing the morphology of LDPE and improving the high-field characteristics in high temperature region. Especially, it suggested that the F$\_$BImp/ was associated with the changes of the crystal size. In this work, the relationship between the morphology and the high-field characteristics of blended LDPE was discussed. In addition, the physical and electrical properties of blended LDPE with extrusion treatment were investigated. The two groups of specimen were prepared; Group 1 was prepared by passing 1 time through the extruder included in the film-blowing process, and Group 2 was prepared by passing 2 times through the extruder. From the relation between the crystal size which was perpendicular to the (020) plane and the F$\_$BImp/ of blended LDPE, it was confirmed that the F$\_$BImp/ was associated with the changes of crystal size due to the blending. Moreover, the F$\_$BImp/ of blended LDPE in Group 2 was higher than that of blended LDPE in Group 1. The crystal size of the (020) plane became smaller according to the extrusion treatment. These results suggest that the uniform distribution and dispersion of crystalline occurred due to the extrusion treatment and the morphological change due to the extrusion treatment influenced on the electrical properties of blended LDPE.

• Electrical & Electronic Materials
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• v.9 no.5
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• pp.463-469
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• 1996

The double insulating layer consisting of anodic oxide and ZnS was formed for HgCdTe metal insulator semiconductor(MIS) structure. ZnS was evaporated on the anodic oxide grown in H$_{2}$O$_{2}$ electrolyte. Recently, this insulating mechanism for HgCdTe MIS has been deeply studied for improving HgCdTe surface passivation. It was found through TEM observation that an interface layer is formed between ZnS and anodic oxide layers for the first time in the study of this area. EDS analysis of chemical compositions using by electron beam of 20.angs. in diameter and XPS depth composition profile indicated strongly that the new interface is composed of ZnO. Also TEM high resolution image showed that the structure of oxide layer has been changed from the amorphous state to the microsrystalline structure of 100.angs. in diameter after the evaporation of ZnS. The double insulating layer with the resistivity of 10$^{10}$ .ohm.cm was estimated to be proper insulating layer of HgCdTe MIS device. The optical reflectance of about 7% in the region of 5.mu.m showed anti-reflection effect of the insulating layer. The measured C-V curve showed the large shoft of flat band voltage due to the high density of fixed oxide charges about 1.2*10$^{12}$ /cm$^{2}$. The oxygen vacancies and possible cationic state of Zn in the anodic oxide layer are estimated to cause this high density of fixed oxide charges.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.657-663
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• 2018

In this study, shape optimization was performed to improve the vibration isolation capability of an anti-vibration rubber assembly, which is used in the field option cabin of agricultural tractors. A uniaxial tension test and biaxial tension test were performed to characterize the hyper-elastic material properties of rubber, and the data were used to calibrate the material model used in the finite element analyses. A field test was performed to quantify the input excitation from the tractor and the output response at the cabin frame. To account for the nonlinear behavior of rubber, static analyses were performed and the load-displacement curve of rubber was derived. The stiffness of the rubber was calculated from this curve and input to the harmonic analyses of the cabin. The results were verified using the test data. Taguchi's parameter design method was used to find the optimal shape of the anti-vibration rubber assembly, which indicated a shape with reduced stiffness. The vibration of the cabin frame was reduced by the optimization by as much as 35% compared to the initial design.