• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.8
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• pp.63-69
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• 2015

This paper presents the surface flashover characteristics to simulate the poor contact between an anode and a solid dielectric in a $N_2/O_2$ mixture gas (8/2) under a non-uniform field. The surface flashover voltage of the $N_2/O_2$ mixture gas revealed the irregular tendency that was not in accordance with the Paschen's law with an increasing gap of the poor contact. In addition, the insulation performance of the $N_2/O_2$ mixture gas at 0.6MPa was comparable to that of $SF_6$ gas of 0.1MPa based on the insulation performance on the poor contact. These results are able to apply the insulation design of eco-friendly gas insulation switchgear considering the internal faults.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.7
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• pp.1-7
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• 2021

Restrictions on the emissions of nitrogen oxides, sulfur oxides, carbon dioxide, and particulate matter from marine engines are being tightened. Each of these emissions requires different reduction technologies, which are costly and require many pieces of equipment to meet the requirements. Liquefied natural gas (LNG) fuel has a great advantage in reducing harmful emissions emitted from ships. Therefore, the marine engine application of LNG fuel is significantly increasing in new ship buildings. Accordingly, this study analyzed the internal support structure, insulation type, and fuel supply piping system of a 35 m3 International Maritime Organization C type pressurized storage tank of an LNG-fueled ship. Analysis of the heat transfer characteristics revealed that A304L stainless steel has a lower heat flux than A553 nickel steel, but the effect is not significant. The heat flux of pearlite insulation is much lower than that of vacuum insulation. Moreover, the analysis results of the constraint method of the support ring showed no significant difference. A553 steel containing 9% nickel has a higher strength and lower coefficient of thermal expansion than A304L, making it a suitable material for cryogenic containers.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.7
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• pp.1410-1416
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• 2011

A corrosion detecting system for 22.9 kV distribution power line insulation cable, which can travel autonomously along the live line, is proposed. Eddy current test method is employed to detect the corrosion, and the system developed here is capable of detecting internal corrosion of a ACSR-OC. Somewhat details of the electrical and mechanical mechanism of the system and traveling algorithm are introduced. Experimental results applied to the sample cables having artificial corrosion and the operating distribution lines are provided. From the result, we confirmed that the system is useful for detecting internal corrosion of a ACSR, and is expected to be a new non-destructive testing equipment in the area of diagnosis for the distribution power line.

• Journal of Electrical Engineering and Technology
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• v.7 no.6
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• pp.959-964
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• 2012

Internal pressure of vacuum interrupter (VI) is one of the most important parameters in VI operation and may increase due to the outgassing from the materials inside VI or gas permeation through metal flange or ceramic vessel. The increase of the pressure above a certain level leads to the failures of switching or insulation. Therefore, an effective pressure check of VI is essential and an analysis of partial discharge (PD) characteristics is an effective monitoring method to identify the degree of the internal pressure of VI. This paper introduces a research work on monitoring the internal pressure of VI by analyzing PDs which were measured using a capacitive PD coupler. The authors have developed cost effective capacitive coupler based on the ceramic material that has an excellent insulation properties and the main component of the capacitive coupler is made by SrTiO3. Detectable internal pressure range and distinguishability of the internal pressure of VI were investigated. From the PD tests results, the internal pressure range, from $10^{-2}$ torr to 500 torr, can be monitored by PD measurements using the capacitive coupler and PD inception voltage (PDIV) follows the Paschen's law. In addition, rise time of PD pulse at 13.2kV decreases with the increase of the internal pressure of VI.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.6
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• pp.594-602
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• 2022

Cast-resin transformers are widely installed in various electrical power systems because of their low operating cost and low influence on external environmental factors. However, when they have an internal defect during the manufacturing process or operation, a partial discharge (PD) occurs, and eventually destroys the insulation. In this paper, a Rogowski-type PD sensor was studied to replace commercial PD sensors used for the insulation diagnosis of power apparatus. The proposed PD sensor was manufactured with four different types of PCB-based winding structures, and it was analyzed in terms of the detection characteristics for standard calibration pulses and the changes of the output voltage according to the distance. The output increased linearly in accordance with the applied discharge amount. It was confirmed that the hexagon structure sensor had the highest sensitivity, because the winding cross-sectional area of the sensor was larger than others. In addition, as the distance from the defect increased, the output voltage of the sensors decreased by 7.32% on average. It was also confirmed that the attenuation rate according to the distance decreased as the input discharge amount increased. For the application of this new type sensor, PD electrode system was designed to simulate the void defect. Waveforms and PRPD patterns measured by the proposed PD sensors at DIV and 120% of DIV were the same as the results measured by MPD 600 based on IEC 60270. The proposed PD sensors can be installed on the inner wall of the transformer tank by coating its surfaces with a non-conductive material; therefore, it is possible to detect internal defects more effectively at a closer distance from the defect than the conventional sensors.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.909-911
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• 2003

The almost pole transformers are constructed with tank, cover, clamp etc., that contains the insulation oil, core, coil, terminals, bus and the other accessories. If some fault current will be flown by some trouble or accident, interior pressure of the transformer shall be very quickly rise, and mechanical components or insulation oil from the transformer enclosure shall be propelled or dropped from the tank. For the prevention of the above accident, recently the pole transformers should be done 'the Design Tests for Fault Current Capability' according to ANSI C57.12.20(1997) There are two tests method in this standard, Test Number I with a high current arcing fault, without internal fusible elements, shall be conducted on rack enclosure with its minimum designed air space. Test Number II with an internal fusible element, shall be conducted on each enclosure diameter utilizing the internal fusible elements. KEPCO recently request to be done the 'Design Tests for Fault Current Capability' for pole transformers according to KEPCO's standard ES141-$533{\sim}545$, PS141-$482{\sim}518$ and RS141-$611{\sim}628$ that is same with Test Number I of ANSI C57.12.20.

• Journal of the Korean Society of Propulsion Engineers
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• v.27 no.1
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• pp.9-16
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• 2023

This paper investigated the method to predict a thermal response of internal insulation in a solid rocket motor considering both thermal decomposition and ablation. Changes in properties due to the thermal decomposition, swelling of char layer and movement of decomposition gases inside the material were considered during a modeling. And radiative/convective heat flux from the exhaust gas were applied as boundary conditions, while the chemical ablation of the material surface is modeled with algebraic equations. Test SRM with thermocouples was solved for a validation purpose. The results showed that predicted temperatures have identical trends and values compared to the experimental values. And an error of predicted thermal destruction depth was around 0.1 mm.

• Journal of Electrical Engineering and Technology
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• v.6 no.3
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• pp.384-390
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• 2011

To evaluate the condition of stator winding insulation in generators that have been operated for a long period of time, diagnostic tests were performed on the stator bars of a 500 MW, 22 kV generator under accelerated thermal and electrical aging procedures. The tests included measurements of AC current (${\Delta}I$), dissipation factor ($tan{\delta}$), partial discharge (PD) magnitude, and capacitance (C). In addition, the AC current test was performed on the stator winding of a 350 MW, 24 kV generator under operation to confirm insulation deterioration. The values of ${\Delta}I$, ${\Delta}tan{\delta}$, and PD magnitude in one stator bar indicated serious insulation deterioration. In another stator bar, the ${\Delta}I$ measurements showed that the insulation was in good condition, whereas the values of ${\Delta}tan{\delta}$ and PD magnitude indicated an incipient stage of insulation deterioration. Measurements of ${\Delta}I$ and PD magnitude in all three phases (A, B, C) of the remaining generator stator windings showed that they were in good condition, although the ${\Delta}tan{\delta}$ measurements suggested that the condition of the insulation should be monitored carefully. Overall analysis of the results suggested that the generator stator windings were in good condition. The patterns of PD magnitude in all three phases (A, B, C) were attributed to internal discharge.

• Journal of Internet of Things and Convergence
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• v.8 no.2
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• pp.7-12
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• 2022

The main cause of cable accidents is the accelerated deterioration of the cable itself or internal and external electrical, mechanical, chemical, thermal, moisture intrusion, etc., which reduces insulation performance and causes insulation breakdown, leading to cable accidents. Insulation deterioration can occur even when there is no change in the appearance of the cable, so there is a difficulty in preventing cable accidents due to insulation deterioration. Since cable accidents can occur in areas with poor insulation due to the effects of overvoltage and overcurrent, it is necessary to comprehensively analyze transformers and circuit breakers, and ground faults caused by phase-to-phase imbalance. Ground fault accidents due to insulation breakdown of cables can occur due to defects in the cable itself and poor cable construction, as well as operational influences, arcs during operation of electrical equipment (switchers, circuit breakers, etc.). analysis is needed. This study intends to examine the causes of cable accidents through analysis of cable accidents that occurred in a manufacturing factory.

• International conference on construction engineering and project management
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• 2017.10a
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• pp.89-98
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• 2017

The floor heating method generally uses a wet construction method including the installation of resilient material, lightweight foam concrete, heating piping, and finishing mortar. Such a wet construction method not only delays other internal finishing processes during curing period for two mortar pouring process, but also has a disadvantage that it is difficult to replace the floor heating layer when it deteriorated because it is integrated with the frame. Dry floor heating construction method can be a good alternative in that it can solve these defects. Conversely, when it applied to the wall structure that is vulnerable to the interlayer noise compared with the column-beam structure, the question about the heavy-impact sound(HIS) insulation performance is raised. Therefore, conventional dry floor heating method is hard to apply to the wall structure apartments. Therefore, for the purpose to improve the applicability of dry floor heating method in wall structure apartments, this study investigated the change of floor impact sound, especially HIS insulation performance which is one of the required performance for the floor structure. This study tried to examine whether the change of heavy-impact sound pressure level(SPL) shows a tendency at the significant level according to the shape and mass of the floor structure. Through filed experiments on wall structure apartment, this study confirmed that the form of the raised floor shows better HIS insulation performance than the fully-supported form. In addition, it was also confirmed that the HIS insulation performance increases with the mass on the upper part. Moreover, this study found the fact that a mass of about 30 kg/m² or more should be placed on the upper structure to reduce the heavy-impact SPL according to the bang machine measuring method. Although this study has a limit due to insufficient experiment samples, if the accuracy of this study is increased, it will contribute to the diffusion of dry floor heating by setting the HIS insulation performance target and designing the dry floor heating structure that meets the target.