• KIEE International Transactions on Power Engineering
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• v.5A no.4
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• pp.366-370
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• 2005

To meet increasing power demand, 500 kV power systems are under consideration in the regions of some Middle Asian countries. As the power system voltage becomes higher, the cost for the power system insulation increases significantly. 500 kV transmission systems will become the basis of a region's power system and they require much higher system reliability. Consequently, by the methods of limiting overvoltages effectively, a reasonable insulation design and coordination must be accomplished. In particular, the Substations must be constructed to be of outdoor type. In order to determine the various factors for the insulation design, the EMTP (Electro-magnetic transient program) is used for the magnification of transient phenomena of the 500 kV systems in the planned network. In this paper, we will explain the calculation results of lightning overvoltages by the EMTP for lightning protection design for the 500 kV substations. To obtain reliable results, the multi-story tower model and EMTP/TACS model are introduced for the simulation of dynamic arc characteristics.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.767-775
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• 2005

Power Supply System for electric railways is diversified with technical development and is required high technologies. especially, recently there is required many research and development for earthing to ensure safety of people and protection of installations. Generally, leakage resistance is high between rail and ground at tunnel section of subway. because of short circuit of feeding line, earthing interference by transient overvoltage between signals and communication system, and insulation failure, it can damage to human and equipments To minimize these obstacles, earthing equipment is installed at underground section of railway, but it brings about problems in accordance with operate each earthing system to be not enough required protection provisions for electrified railways. This paper proposes effective earthing method to be concerned about installation cost and maintenance. The validity of the proposed earth method is verified by simulation results at underground section of railways.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.380-382
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• 2001

This paper describes the protection of insulation joint box in combined transmission line which is connected with the 154kV underground power cables. An actual power cable system was selected to establish modeling and to analyze. Modeling was established in EMTP and ATPDraw. Simulation was carried out according to the buried method of cable and connection method of CCPU. Results presented in this paper will be applied to another power cable systems.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.8
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• pp.454-460
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• 2004

The effects of surge arresters for protection of transmission systems against direct lightning strokes have already been reviewed using Electromagnetic Transients Program(EMTP). Distribution lines are spanned in much larger area than transmission lines, and therefore, are more susceptible to lightning strokes. We have modelled the 22.9kV underground distribution cable systems that have arresters and grounding wires. And this paper analyzes the overvoltages on underground distribution cable systems when direct lightning strokes strike on the overhead grounding wire using EMTP. Then we investigated that (1) the effects of lightning stroke according to underground distribution cable length (2) voltages at the riser pole and at the cable terminal according to installation of arrester. This study will provide insulation coordination methods for reasonable systems design in 22.9kV underground distribution cable systems.

• Proceedings of the KIEE Conference
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• 2005.11c
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• pp.80-82
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• 2005

Lightning surge damages of low voltage equipments in building are increasing due to increase in electrical and communication networks in the information-oriented society. And electrical circuits with semiconductor are very weak against lightning surge. To achieve effective method of surge protection on low voltage lines, there are needs for the relationship between propagation aspects of lightning surge and arrangement of indoor wire. This paper describes the experimental study on the relationship between them. This result may be raw data for establishment of surge protection system.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1220-1222
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• 2003

An analysis of thyristor firing and protection circuit applied to SFC(static Frequency Converter) is presented. This consists of firing circuit when thyristor is connected in series, one of overvoltage protection and monitor databack circuit of thyristor states etc. Also, each characteristic of foreign products was studied in this paper.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.558-560
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• 2003

The effects of surge arresters for protection of transmission systems against direct lightning strokes have already been investigated using the digital simulation program EMTP. Distribution lines are spanned on a much large area as compared to transmission lines, and therefore, are more often susceptible to lightning strokes. This paper analyzes the overvoltages on underground cable system against direct lightning strokes to the overhead ground wire using the digital simulation. The effects of lightning protection methods, such as lowering the grounding resistance and installing the surge arrester, for preventing overvoltages on underground cable system caused by direct lightning strokes to the overhead ground wire is investigated. Several schemes have been proposed to protect underground cables. This paper summarizes the main results of a study aimed at analysis of lightning overvoltages in variety underground feeders protected by metal-oxide arresters. This study will provide insulation coordination methods for reasonable system design in 22.9kV underground cable system.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.824-831
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• 2013

Lightning electromagnetic fields are important issues for the evaluation of lightning induced overvoltage on power lines and for setting the appropriate protection level for power networks. Such electromagnetic fields are strongly dependent on lightning return stroke currents at different heights along the lightning channel. On the other hand, the ground reflection factor due to the difference between the return stroke channel impedance and the equivalent ground impedance at channel base can have an effect on the shape of the return stroke currents by entering additional reflected currents into the channel. In this paper, the effect of the ground reflection factor on the return stroke currents at different heights along a channel and the electromagnetic fields associated with the lightning channel at close distances are considered. Moreover, the behavior of the electromagnetic fields versus the reflection factor changes and the radial distance changes are considered and the results are discussed accordingly. The results illustrate that the reflection factor has a direct relationship with the values of the electromagnetic fields while this is usually ignored in earlier studies.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.5
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• pp.641-644
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• 2021

Wearable devices and IoT are being utilized in various fields, where all systems are developing in the direction of multi-functionality, low power consumption, and high speed. In this paper, we propose a DC -DC Step-down C onverter for IoT smart devices. The proposed DC -DC Step-down converter is composed of a control block of the power supply stage. It also consists of an overheat protection circuit, under-voltage protection circuit, an overvoltage protection circuit, a soft start circuit, a reference voltage circuit, a lamp generator, an error amplifier, and a hysteresis comparator. The proposed DC-DC converter was designed and fabricated using a Magnachip / Hynix 180nm CMOS process, 1-poly 6-metal, the measured results showed a good match with the simulation results.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.501-503
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• 2000

Since an arrester has been generally used at the distribution line and abroad for the protection of electrical equipments against overvoltage (or abnormal surge) taking place in or from an electrical system, a fault, especially, in the distribution line is very likely to result in the destruction of insulation of other protection devices to cause an overall paralysis of a power system, a chaos. Considering the importance of arresters, its earlier replacement than its proposed life cycle causes an economical loss, and a negligence not to replace or repair it in time gives rise to a crucial accidence. The purpose of this paper is to invent an electric leakage current detector and to solve such problems by the continuous and regular inspection of an arrester.