• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.9
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• pp.24-32
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• 2020

A self-blast type gas circuit breaker has been studied in this study to improve efficiency of interrupting performance of short line fault(SLF). Hot gas flows of gas circuit breaker have been simulated to evaluate interruption performance using CFD. Design parameters such as various types of expansion chamber and nozzles are suggested by using simulation results. Simulated results and experimental ones are compared with previous (ones that of in under development and with capacitor) GCB. Modified new shape of an expansion chamber and nozzle has been suggested to improve the efficiency of gas flow and to provide guidelines for designing self-blast breaker with a higher interruption capability.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.225-233
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• 2001

Field model tests were performed to develop the grid-net landfill leachate leakage detection system using electrical resistance. Electric circuit tests were also carried out to investigate the expected electrical effects of grid-net electric circuit. The resistance of leaking point showed lower value than that of non leaking point. Grid-net leakage detection system was thought to be effective to locate the leachate leaking point. The measured electrical resistance along the wire including the leaking point was slightly reduced following the reduction of electrical resistance at the leaking point, which was explained by electric circuit test results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.7
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• pp.94-102
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• 2007

With the recent expansion of electric capacity, troubles in the electric system threatening the stable electricity supply are rapidly increasing. However, most of the current short-circuit capacity calculations have been made manually. This research focuses on the development of a program which uses the Visual Basic. We can obtain the stability in the system diagram and the reliability of the loaded facilities by calculating an exact breaking capacity for each electric facility with this method. We expect that this research can be widely used for the design and construction of the electric facilities in the future.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.1
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• pp.7-13
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• 2015

This paper presents mathematical models for high speed permanent-magnet synchronous machine. The mathematical method with two successive steps is used to estimate design parameter as well as the output power. At first, mathematical model for a linkage flux problem is employed to calculate the number of winding turns and stack length of armature core. The magnetic circuit model for an induced voltage and the electric circuit model for a current are modeled. The output powers of the electrical generator were evaluated by the mathematical techniques. The results of this mathematical methods predict the specifications of the machine and can be applied in the design stage of the electrical machine.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.908-910
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• 1998

Modern AC electric car has PWM(Pulse Width Modulation) -controlled converters, which give rise to higher harmonics. The current harmonics injected from AC electric car is propagated through power feeding circuit. As the feeding circuit is a distributed constant circuit composed of RLC, the capacitance of the feeding circuit and the inductance on the side of power system cause a parallel resonance and a magnification of current harmonics at a specific frequency. The magnified current harmonics usually brings about various problems. That is, the current harmonics makes interference in the adjacent lines of communications and the railway signalling system. Furthermore, in case it flows on the side of power system, not only overheating and vibration at the power capacitors but also wrong operation at the protective devices can occur. Therefore, the exact assessment of the harmonic current flow must be undertaken at design and planning stage for the electric traction systems. From these point of view, this study presents an approach to model and to analyse traction power feeding system focused on the amplification of harmonic current. The proposed algorithm is applied to a standard AT(Auto-transformer)-fed test system in which electric car with PWM-controlled converters is running.

• Proceedings of the KSR Conference
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• 1999.11a
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• pp.318-325
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• 1999

Modern AC electric car has PWM(Pulse Width Modulation)-controlled converters, which give rise to higher harmonics. The current harmonics injected from AC electric car is propagated through power feeding circuit, As the feeding circuit is a distributed constant circuit composed of RLC, the capacitance of the feeding circuit and the inductance on the side of power system cause a parallel resonance and a magnification of current harmonics at a specific frequency. The magnified current harmonics usually brings about various problems. That is, the current harmonics makes interference in the adjacent lines of communications and the railway signalling system. Furthermore, in case it flows on the side of power system, not only overheating and vibration at the power capacitors but also wrong operation at the protective devices can occur. Therefore, the exact assessment of the harmonic current flow must be undertaken at design and planning stage for the electric traction systems. From these point of view, this study presents an approach to model and to analyse traction power feeding system focused on the amplification of harmonic current The proposed algorithm is applied to a standard AT(Auto-transformer)-fed test system in which electric car with PWM-controlled converters is running.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.93-99
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• 2000

This paper presents a study on the assessment of electrical fire hazards by electric circuits with leakage. The hazards are evaluated with the energy supplied by earth-leakage currents which flow in the circuits simulating the actual circuit of domestic premises. Also, operating time and current of ELB are measured by an experimental approach. A common specification of ELB used in this paper has a sensitivity of 30[mA] for leakage current working on the current-balance principle. Total charges and energy of leakage currents are calculated quantitatively by a theoretical approach and compared with the results obtained from experiments.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.6
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• pp.1109-1113
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• 2010

Recently, important for the safety has been increasing together economic developments. The leakage only is measured by the voltage difference. This method is a way to contact the electric leakage area. It can cause electric shock at users. We propose a non-contact method to detect a short circuit in this paper. We investigate magnetic field at electric leakage area to present non-contact method. Simulated environment created a short circuit in the flooded areas. Voltage is supplied 50, 150 and 200[V]. Magnetic field was measured at 0, 5 and 10[cm]. Magnetic flux was reduced about $0.4[{\mu}T/cm]$ depending on the distance changes in the steady region. But we confirmed that magnetic flux is measured the same value depending on the distance changes in the electric leakage area.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.544-551
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• 2011

This paper presents the circuit arrangement and effective control method of regenerative energy storage system for an electric vehicle using super-capacitors as the braking energy storage element. A bi-directional controlled current flow of the DC-DC converters with the capacitor bank is connected in parallel with battery, and is controlled so that the whole of the braking energy is effectively absorbed into the capacitors and released back to the electric motor upon acceleration. The converter needs the series-parallel switching circuit for making the best use of the series capacitors and for limiting the step-up ratio of the boost converter. The proposed methods are verified by computer simulation and experimental set-up. They are usefully applied to the electric vehicles such as green cars, electric motorcycles, bike, etc which are power- supplied by the electric batteries.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1754-1763
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• 2017

This paper analyses the characteristics of incomplete-journey double-circuit transmission lines on the same tower formed by single-circuit lines and double-circuit lines, and then presents a fault location algorithm based on identification of fault branch. With the relationship between the three-phase system and the double-circuit line system, a phase-mode transformation matrix for double-circuit lines can be derived. Based on the derived matrix, the double-circuit lines with faults can be decoupled, and then the fault location for an incomplete-journey double-circuit line is achieved by using modal components in the mode domain. The algorithm is divided into two steps. Firstly, the fault branch is identified by comparing the relationships of voltage amplitudes at the bonding point. Then the fault location, on the basis of the identification result, is calculated by using a two-terminal method, and only the fault distance of the actual fault branch can be obtained. There is no limit on synchronization of each terminal sampling data. The results of ATP-EMTP simulation show that the proposed algorithm can be applied within the entire line and can accurately locate faults in different fault types, fault resistances, and fault distances.