• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.436-444
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• 2016

Oil-paper insulation of valve-side windings in converter transformers withstand electrical stresses combining with AC, DC and strong harmonic components. This paper presents the physical mechanisms and experimental researches on partial discharge (PD) of oil-paper insulation at pulsating DC voltage. Theoretical analysis showed that the phase-resolved distributions of PDs generated from different insulated models varied as the increase of the applied voltages following a certain rule. Four artificial insulation defect models were designed to generate PD signals at pulsating DC voltages. Theoretical statements and experimental results show that the PD pulses first appear at the maximum value of the applied pulsating DC voltage, and the resolved PD phase distribution became wider as the applied voltage increased. The PD phase-resolved distributions generated from the different discharge models are also different in the phase-resolved distributions and development progress. It implies that the theoretical analysis is suitable for interpretation of PD at pulsating DC voltage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.11
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• pp.1061-1066
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• 2006

This paper presents the electrical characteristics with manufacturing process and performance evaluation of high performance zinc oxide varistors. ZnO varistors were fabricated with typical ceramic production methods with different thickness and the structural and electrical characteristics of ZnO varistors were investigated. All varistors exhibited high density, which was in the range of $5.41{\sim}5.49g/cm^3$. In the electrical properties, the reference voltage increased in the range of $4.410{\sim}5.250kV$ with increasing their thickness and the residual voltage exhibited the same trends as the reference voltage. In the long duration current impulse withstand test, E-2 and F-1 samples failed at the two and four shots of impulse current, respectively, but E-1 and F-2 samples survived 18 shots during the test. Before and after this test, the variation ratio of residual voltage of E-1 and F-2 samples were -0.34 % and 0.05 %, respectively, which were in the acceptance range of 5 %. According to the results of tests, it is thought that if the fabrication process such as insulating coating, sintering condition, and soldering method is improved, these ZnO varistors would be possible to apply to the station class arresters in the near future.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2071-2072
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• 2011

Withstand voltage characteristics of the nanocomposites, as a material with excellent abrasion resistance and water resistance, low shrinkage upon curing with moisture even in very good adhesion, workability is not lost. In this study, the fusion of nanoparticles and the high functionality epoxy nano-composite material produces the electricity. Degeneration of the unit based on this power structure and breakdown characteristics, efficiency and cross-measurement system as closely related organisms that can be applied to the power plant electrical efficiency of the nano-composite material is designed to develop skills.

• The Korean Journal of Ceramics
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• v.5 no.1
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• pp.87-90
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• 1999

It was suggested that tape casting method can be used to fabricate high-temperature electrostatic chucks(HTESC) based on a metal substrate coated with a glass-ceramic insulating layer. The adhesion of the coating was excellent such that it was able to withstand temperature cycling to over $300^{\circ}C$ without spalling. The electrostatic clamping pressure reached a very high value of about 9 torr at 600V and generally followed the theoretical voltage-squared curve. Based on these results, we believe that we successfully developed a viable technique for manufacturing low cost HTESC.

• Transactions on Electrical and Electronic Materials
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• v.10 no.6
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• pp.193-195
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• 2009

This paper aims to develop a low gate source voltage ($V_{gs}$) N-LDMOS element that is fully operational at a CMOS Logic Gate voltage (3.3 or 5 V) realized using the 0.35 μm BCDMOS process. The basic structure of the N-LDMOS element presented here has a Low $V_{gs}$ LDMOS structure to which the thickness of a logic gate oxide is applied. Additional modification has been carried out in order to obtain features of an improved breakdown voltage and a specific on resistance ($R_{sp}$). A N-LDMOS element can be developed with improved features of breakdown voltage and specific on resistance, which is an important criterion for power elements by means of using a proper structure and appropriate process modification. In this paper, the structure has been made to withstand the excessive electrical field on the drain side by applying the double gate oxide structure to the channel area, to improve the specific on resistance in addition to providing a sufficient breakdown voltage margin. It is shown that the resulting modified N-LDMOS structure with the feature of the specific on resistance is improved by 31%, and so it is expected that optimized power efficiencies and the size-effectiveness can be obtained.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.6
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• pp.91-98
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• 2014

For the purpose of designing and applying the optimum surge protection scheme, multi-stage coordinated surge protective device(SPD) system is suitable to successfully fulfill its tasks; first, to divert a large amount of the transient energy, second, to clamp the overvoltage to the level below the withstand impulse voltage of the equipment to be protected. The length of SPD connecting leads shall be as short as possible. Long connecting leads will degrade the protection effect of SPDs. In this paper, the influences of the length of connecting leads on the energy sharing in a coordinated SPD system were investigated experimentally, and the simulation of determining the energy sharing and protection voltage level of each SPD depending on the length of connecting leads was carried out by using P-spice program. It was confirmed that the protection voltage level and energy sharing in coordinated SPD systems are strongly influenced by the length of connecting leads.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.593-602
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• 2020

Power cables installed in domestic factories or underground can cause accidents depending on the manufacturing process, installation, and environmental conditions during use. When an accident occurs in a power cable, it can cause enormous economic loss and social confusion. Hence, the importance of preventive management of the cable through diagnosis is increasing to prevent it. Therefore, in this paper, a diagnostic sample cable was produced by simulating a part that could be a problem due to the installation, manufacturing defects, or deterioration of cables that can occur in the field. Dielectric loss Tangent (tan 𝛿; TD), and Partial Discharge(PD) tests were performed. Partial discharge and AC (60Hz) withstand voltage equipment using High-Frequency Current Transformer (HFCT) were applied After applying a VLF (Very Low Frequency) power supply with a frequency of 0.1Hz was applied. As a result, B and C phase defect samples at a 2.0U₀ voltage through the VLF could measure the internal partial discharge in the A-phase normal sample cable from the noise at a 0.5U₀ to 2.0U₀ voltage. In addition, the 1.5U₀ voltage was measured through the AC (60Hz) withstand voltage equipment of the commercial frequency to verify its effectiveness. Partial discharge in the run-off state was measured at a voltage of 1.0U₀, and there was a risk when installing the equipment. AC power equipment showed a difficulty of movement by volume or weight. The diagnostic method, through the VLF of the quadrant state, revealed its safety and effectiveness.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.3
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• pp.130-137
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• 2015

This study is about the controller development of the Electric Operating Cell(EOC) which will replace the Mechanical Operated Cell(MOC) of the vacuum circuit breaker which has been used in the power plant and the performance test for the developed controller. The controller developed through this study was manufactured considering the harsh installation environment and electrical condition of the power plant, and the controller performance certification test for confirming the product reliability was taken to know whether or not to withstand fully in various electrical and mechanical problems. Items for performance certification test were AC power frequency voltage withstand test, combined surge immunity test, 1 [MHz] oscillatory SWC test, fast transient SWC test, radiated electromagnetic interference test, vibration test. As a result, all tests has passed an examination without malfunction.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.551-553
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• 2002

The cubicle type GIS rated at 25.8kV has been designed and manufactured by Jinkwang E&C eacently with their own technologies and KERI's assistances. The C-GIS has been tested to check the design capability for reference before conducting the type test. The operating characteristics test, short time withstand current and peak withstand current test, basic short circuit test duty T60 for preconditioning test, cable charging current switching test, capacitor bank current switching test, basic short circuit test duty T100s and T100a, single phase earth fault test, double earth fault test has been conducted. The test results show that the design and the manufacturing of the C-GIS has an enough capability to pass through the type test except the occurrence of 2 NSDDs in the cable charging current switching test and the instability of opening time at the minimum operating voltage. The problems shown in the tests will be improved soon and the successful pass will be expected in the following type test.

• Journal of the Korean institute of surface engineering
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• v.54 no.1
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• pp.30-36
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• 2021

In this study, double-layered anodizing films were formed on Al 5052 and Al 6061 alloys consecutively first in sulfuric acid and then in oxalic acid, and hardness, withstand voltage, surface roughness and acid resistance of the anodizing films were compared with single-layered anodizing films in sulfuric acid and oxalic acid electrolytes. Hardness of the double-layered anodizing film decreased with increasing ratio of inner layer to outer layer for both Al 5052 and Al 6061 alloys, suggesting that outer anodizing film formed in sulfuric acid electrolyte is damaged during the second anodizing in oxalic acid electrolyte. Withstand voltage of the double-layered anodizing films increased with increasing the thickness ratio of inner layer to outer layer. Surface roughness of the double-layered anodizing films were comparable with that of single-layered anodizing film formed in sulfuric acid but higher than that of single layer anodizing film formed in oxalic acid electrolyte. In acid resistance test, all of the double-layered and single-layered anodizing films showed good acid resistance more than 3 h without any visible gas evolution, which is attributable to sealing of pores. Based on the experimental results obtained in this work, it is possible to design a double-layered anodizing film with cost-effectiveness and improved physical and electrical properties by combining two consecutive anodizing processes of sulfuric acid anodizing and oxalic acid anodizing methods.