• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 하계학술대회 논문집 A
• /
• pp.409-411
• /
• 2003

As power demand increases gradually, the call for underground transmission system increases. But it is very difficult and high in cost to construct new ducts and/or tunnels for power cables in metropolitan areas. HTS (High Temperature Superconducting) cable has the several useful characteristics such as increased power density. Therefore HTS cable can allow more power to be moved in existing ducts, which means very large economical and environmental benefits. In this paper, we carried out investigation for Application of 22kV class HTS cable in Korean utility networks. The results show that the HTS cable is applicable to replace IPB in pumping-up power plant, withdrawal line in distributed generation, withdrawal line in complex power plant, and conventional under ground cable. Finally, as the cost of HTS wire and refrigeration drops, the technical and economical potential of HTS cable is evaluated positively.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1993년도 하계학술대회 논문집 A
• /
• pp.137-139
• /
• 1993

This paper details methods used to verify the adquacy of a dc traction power supply for design in Seoul matropolitain subway Line-6 system. Examples of the approach are given for a major subway presently under construction. The performance of trains operating at maximum system design capacity is modelled using a train simulation program. Using a dc network analyser program, the maximum train operating timetable, and a model of the ac and dc electrical suppy system, the electrical performance of the entire system can be modelled over a 24-hour period. The results of this analysis are used to determime: train voltage at a level sufficient to ensure train schedules: adequacy of traction transformers, rectifier, and switchgear ratings; sizes of the overhead contact systern conductors, and ac and de feeder cables: and power and energy demands at the utility company's supply points for inital and final timetable operations.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
• /
• pp.1759-1761
• /
• 2005

The exploitation of the resource wind energy is a rapidly growing area world-wide. The number of installed units is continuously increasing, and therefore, it is important to respect and to deal with the impact of wind power generation system. From the view of an electric grid utility, there is a major problem with the impact of the wind system on the voltage of the electric grid, to which a turbine in connected. The problem is rather common in the connection of a wind power system to an already existing grid, since the grid is very seldom designed for the transmission of additional power. In this paper, it is investigated the voltage impact of distribution line, to which wind power generation system is connected.

• Journal of Welding and Joining
• /
• 제13권1호
• /
• pp.78-88
• /
• 1995

This paper was performed to study the utility of the SP(small punch) test and the AE(acoustic emission) test in the evaluation of SCC(stress corrosion cracking) susceptibility for parent metal and bond line of HT80 steel-weld joint by SAW(submerged arc welding) with the various pH values. The loading rate used was 3*10$^{-4}$ mm/min and the corrosive environment used was synthetic sea water during the SP test and the AE test. According to the test results, the SCC susceptibility of the parent metal was increased in the order of pH6.0, pH8.2 and pH10.0. On the other hand, the bond line showed almost the same high SCC susceptibility in all pH concentrations. Synthetically, from the results of the SCC susceptibility, the macro- and micro-SEM observation, the microfracture behaviors by AE test and the relationship between SCC susceptibility and displacement at incipient failure, .delta.$_{i.f-AE}$, it can be concluded that the SP test and the AE test are the good test methods to evaluate the SCC susceptibility for parent metal and bond line of the weld joint with the change of environmental factors.

• 한국안전학회지
• /
• 제29권5호
• /
• pp.47-53
• /
• 2014

Despite the automatic fire alarm system, according to the national fire data system of national emergency management agency, the fires account for 40,932 incidents, 2,184 injuries and about 430 billion won in property losses in 2013. Since the conventional automatic fire alarm system has several weaknesses related to electrical signal such as noise, surge, lighting, etc. Most fires are mainly caused by electrical faults, mechanical problem, chemical, carelessness and natural. The electrical faults such as line to ground fault, line to line fault, electrical leakage and arc are one of the major problems in fire. This paper describes the development of a novel real-time fire monitoring system algorithm including fault detection function which puts the existing optic smoke and heat detectors for fire detection with current and voltage sensors in order to utility fault monitoring using high accuracy DAQ measurement system with LabVIEW program. The fire detection and electrical fault monitoring with a proposed a new detection algorithm are implemented under several test. The fire detection and monitoring system operates according to the proposed algorithm well.

• 한국안광학회지
• /
• 제13권1호
• /
• pp.31-35
• /
• 2008

목적: 본 논문은 CCTV 카메라용 렌즈 설계를 triplet형으로 광학 설계를 하였다. 방법: 초점거리를 56 mm, 유효경을 20 mm 그리고 화각을 $5^{\circ}$로 한 망원 렌즈 형태이고, 설계하고자 하는 카메라의 CCD array detector의 크기를 2/3인치로 하였다. 결과: 광학계의 성능은 ray-fan과 spot diagram 그리고 회절 광학적인 MTF를 계산하여 평가하였고, 파장은 Fraunhofer C, d 및 F-line에 대해 achromat 되었으며 MTF 값도 tangential과 sagittal MTF 모두 50 line pairs/mm의 공간 주파수에 70% 정도가 나왔다. 결론: triplet형으로 비교적 저가 보급형 감시용 목적 CCTV 카메라를 설계하였고 충분히 실용적이라 생각된다.

• 한국의류산업학회지
• /
• 제10권2호
• /
• pp.164-172
• /
• 2008

This study explores the attributes of the on-line shopping products and prices, and their effects on the customer satisfaction. In doing so, the sample population has been segmented according to their shopping propensity of consumption on clothing to understand the group differences. Based on the previous researches, the researcher have chosen four important characteristics of the customer's shopping propensity. The number of iteration on factor analysis revealed that the sample population can be classified into three different groups; the convenience/pleasure-seeking group, the fashion/utility-seeking group, and the unconcerned group. The significant group differences resulted on the following study variables; the product assortment, the price rationality, and the value of the price. Also, from the product aspect, the characteristic, the assortment, and the expression in order, explained the significant portion of the Y variance. While, on the aspect of price, the rationality, and information in order, significantly contributed on the customer satisfaction.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
• /
• pp.1275-1282
• /
• 2009

The tunnel excavations are used for construction of common utility tunnel, electric tunnel, communication line tunnel, water supply and public sewerage pile line in urban area. The trench cut methods were mainly used in the past, but now, tunneling method is more being used. The tunnel excavation method like as NATM, Messer-Shield, Semi-Shield Methods are being applied to small section tunnel in Korea. The actual construction results of seme-shield method are increasing due to simplified construction process and reduced noise and vibration. And also this method is being used frequently in waterway tunnel and construction of prevention flooding recently. The seme-shield method design guideline is absence except for electric line tunnel construction in Korea, because of the semi-shield method was developed in Europe and Japan. In the prescriptive design, engineer's subjects are tending to intervene, because of absence of standard and specification for details. Therefore, Design and Construction Problems of Semi-Shield Method were described and construction trouble was introduced for exam. These problem and construction troubles have to be examined thoroughly in advance.

• 전기학회논문지
• /
• 제64권12호
• /
• pp.1673-1678
• /
• 2015

This paper describes magnetic field on power cable in underground transmission systems. Based on specification which is being used in domestic power utility, magnetic field was analyzed in accordance with line arrangement, line burial depth and phase spacing. Magnetic field magnitude and its trend were understood in each circuit type such as double circuits, triple circuits and quadruple circuits of underground transmission systems. In addition, magnetic field was analyzed according to phase arrangement changing in each circuit. Finally, the proper phase arrangement configuration type was suggested by the evaluation of analysis result. Magnetic field was calculated by using Biot-Savart's law. According to the evaluated magnetic fields based on phase layout configuration in each circuit, it figured out that each of magnetic fields was different. As a result, this paper proposes a proper phase layout configuration for generating minimum magnetic field. It is evaluated that the phase layout configuration in each circuit proposed in this paper can be used at actual underground transmission systems.

• 전력전자학회논문지
• /
• 제26권2호
• /
• pp.150-157
• /
• 2021

Nowadays, a DC microgrid that can link various distributed power sources is gaining much attention. Accordingly, research on fault situations, such as line-to-line and line-to-ground faults of the DC microgrid, has been conducted to improve grid reliability. However, the blackout of an AC system and the oscillation of a DC bus voltage have not been reported or have not been sufficiently verified by previous research. In this study, a 20 kW DC microgrid testbed using a power HIL simulation technique is proposed. This testbed can simulate various fault conditions without any additional grid facilities and dangerous experiments. It includes the blackout of the DC microgrid caused by the AC utility grid's blackout, a drastic load increment, and the DC bus voltage oscillation caused by the LCL filter of the voltage source converter. The effectiveness of the proposed testbed is verified by using Opal-RT's OP5707 real-time simulator with a 3 kW prototype three-port dual-active-bridge converter.