• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.45 no.1
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• pp.14-21
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• 2009

This experimental study was carried out to obtain the base data for saving the man power in the fishing operation of largehead hairtail hand line by using the continuous type hand line system with a rotary device which could make a main line move automatically. In order to solve the twists and entangling on the main line happened during operating test, the resistance board was suspended at the end of the main line at sea. As the result, there were no problems of tangling and so on due to up and down moving of a main line. According to the control of a fixed angle of guide roller, it was possible to prevent the main line to be separated from a side roller and a guide roller. In addition, PVC tube between a guide roller and a side roller enabled a main line to be moved smoothly without any entanglement.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.675-682
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• 2016

Sudden voltage drops and outages frequently disturb the operation of sensitive loads for domestic, commercial, and industrial use. In some cases, these events may even impair the functioning of relevant equipment. To maintain power under such conditions, a UPS system is usually installed. Once a disturbance happens at the grid side, the line-interactive UPS system takes over the load to prevent an interruption. But, due to magnetic saturation of the transformer, a significant inrush current may occur for the transformer-coupled loads during this transition. The generation of such transient currents may in turn decrease the line voltage and activates over-current protecting devices of the system. In this work, a cost-effective, line-interactive UPS system is proposed that eliminates the inrush current phenomenon associated with transformer-coupled loads. The strategy was implemented by connecting a standard current-regulated voltage source inverter (CRVSI) to the secondary winding of the load transformer. During any transient condition at the grid side, the load current is monitored and regulated to achieve either seamless compensation of the load current or complete transferal of load from grid to the inverter. Experimental results were obtained for a prototype under all possible operating conditions so as to validate the performance of the proposed topology.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.9
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• pp.441-448
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• 2005

On-line dynamic security assessment is becoming more and more important for the stable operation of power systems as load level increases. The necessity is getting apparent under Electricity Market environments, as operation of power system is exposed to more various operating conditions. For on-line dynamic security assessment, fast transient stability analysis tool is required for contingency selection. The TEF(Transient Energy Function) method is a good candidate for this purpose. The clustering of critical generators is crucial for the precise and fast calculation of energy margin. In this paper, we propose a new method for fast decision of mode of instability by using stability indices. Case study shows very promising results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.612-615
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• 2015

This paper proposed an high-speed superconducting fault current limiter (H-SFCL). The proposed H-SFCL functioned the initial fault current could be covered by the SFCL and the continued fault current after the one-cycle from fault occurrence could be controlled current-limiting-element of the normal conduction. To investigate the operation characteristics of the H-SFCL, a simulation power system was constructed, and a single line-to-ground fault was occurred. As a result, the H-SFCL limited the fault current by more than about 70%, and it was confirmed that the electric power burden was reduced compared to the SFCL that consisted only of superconductors.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.45-52
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• 2017

This paper deals with the operation strategy of reactive power in a multi-infeed HVDC (MIHVDC) system, in which several converters are connected to the same or nearby separate AC buses. The potential problems concerning a MIHVDC system when feeding a weak AC network are as follows: the need for coordination of the recovery control, the possibility of voltage instability or low quality of the area connected to the MIHVDC system, and the risk of mutual commutation failures. These problems in MIHVDC systems are similar to those in single-infeed HVDC (SIHVDC) systems, but the differences with the phenomenon of the SIHVDC system are the interactions between converters. The main reason for the potential problems of HVDC systems (MIHVDC or SIHVDC) is voltage variation; therefore, to mitigate the voltage variations, the performances of the HVDC system should be enhanced. Consequently, to mitigate the potential problems of MIHVDC systems, several solutions are suggested in this study, including installing STATCOM and installing a line arrester on the tower. The study results will be applied to a multi-infeed HVDC system in Korea.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.6
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• pp.298-306
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• 2002

We performed an safety evaluation on constructing of a common grounding system for electrical railway in view of its efficacy and technical fit. In order to compare the conventional grounding method, which has been individually conducted, with the common grounding with all ground wires connected in common to the counterpoise buried below the surface of the earth in parallel with rail, we set up scenarios with several cases of fault and load conditions in Chungbuk railway sections with the common grounding system. Based on models for railway conductors including the grounded system, line Parameters of railway power system are computed. The circuit model for power system with up and down lines, auto-transformers and railway substations is used to compute impedances of counterpoise and substation ground net. For each scenario with faults and operation conditions of railway, the induced potentials on signal and communication lines are also computed. It is shown that the common grounding for Chungbuk railway is superior experimentally to the conventional method in three respects: (1) the lower rail potentials during operation of railway in line, (2) the lower rail potentials for short-circuit faults between catenary and rail, and (3) the lower stress voltages on signal and communication lines for short-circuit or ground faults. The analysis results confirm that the grounding system for electric railway is required to be built by the common grounding and be evaluated on its safety in design.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1234-1235
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• 2007

This paper represents the generating principles of the doubly-fed induction generator (DFIG) based wind power system and developes a simulation model of DFIG by using PSCAD/EMTDC. In addition, this paper analyzes the steady state operation and the transient operation during the voltage sags in the power common coupling. The voltage sags are occurred by three phase line-to-ground faults and full-voltage startup of an induction motor in the simulation.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.1
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• pp.1-7
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• 2005

This paper proposes a novel UPQC(unified power quality conditioner) based on H-bridge modules, isolated through single-phase multi-winding transformers. The dynamic performance of proposed system was analyzed by simulation with PSCAD/EMTDC, assuming that the UPQC is connected with the 22.9kV distribution line. The proposed system can be directly connected to the transmission line without series injection transformers. It has flexibility in expanding the operation voltage by increasing the number of H-bridge modules and can compensate reactive power, harmonics, voltage sag and swell, voltage unbalance. The proposing UPQC has the ultimate capability of improving power quality at the point of installation on power distribution systems.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.315-321
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• 2009

Since the KTX start its service on April 1st of 2004, KTX increased its share up to 17.4% (2008). It's the 2nd after the passenger car share of 59.2% in the national transportation, but the gap is still wide. In addition, because of the rise of goods' and oil price, the share of intercity express bus is growing up. Nevertheless Korail is trying to improve the train schedule and develop internodal transit system, the number of passengers of KTX is remain flat. KORAIL should start and proceed the tasks below. - Analysis of the 5 year's operation of KTX since the year of 2004 to make plans for the steady growth - development of the KTX operation plan for expansion of railway - preparing the operation of additional passenger rail services on the mail line for newly introduced trains. - expansion of KTX's service area after the introduction of KTX-II - introduction of other new trains - examination for the action plans to promote marketing in main-line including refinement of the rate structure

• Journal of the Korean Society for Aviation and Aeronautics
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• v.31 no.2
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• pp.116-121
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• 2023

항공 사고는 첨단 항공 기술의 발달로 꾸준히 감소해 왔지만, 여전히 발생하고 있다. 조종사는 목적지 공항까지 안전하고 효율적으로 비행하기 위해 위협과 오류를 관리해야 한다. 조종사에게 영향을 미치는 위협은 환경적 위협과 항공사 위협으로 나눌 수 있으며, 환경사위협에는 객실 위협이 포함된다. 조종사와 객실 승무원은 정상적인 운항 중에는 협력이 필요하며, 비상시에는 안전한 비행을 위해 효과적인 협력이 절대적으로 필요하다. 조종사가 비행 중에 간섭이나 작업 흐름의 중단이 발생할 때 에러를 할 가능성이 높아진다. 항공사들은 안전 운항을 방해할 수 있는 객실위협의 종류를 적극적으로 식별하고 분석하여, 조종사들이 안전한 비행을 유지하기 위해서 위협을 관리하도록 절차 및 훈련을 개선해야 한다. 본 연구는 안전관리시스템(SMS)의 안전도구인 LOSA(Line Operation Safety Audit)를 기반으로 기내위협의 유형을 파악하고, 항공사들에게 조종실위협 관리를 체계적으로 개선하는 데 필요한 객실위협과 간섭에 대한 자료를 제공하고자 한다.