• 수산해양기술연구
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• 제30권3호
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• pp.142-149
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• 1994

In order to investigate the environmental properties of set net grounds located in the coastal waters of Yeosu. The current in the vicinity of set net grounds was observed by drogue and current meter in 1990 and 1992. The results obtained are summarized as follows: The direction of tidal current at the north enterance of Yeosu bay was southerly in ebb and northwesterly in flood without the distiction of the neap tide and the spring tide. In spring tide the maximum Velocity of the tidal current was 68 cm/sec in ebb and 66 cm/sec in flood. In neap tide the maximum velocity of the tidal current was 37 cm/sec in ebb and 35 cm/sec in flood. And so the direction of residual current was the south ward mainly and 21 cm/sec. The direction of tidal current at set net fishing grounds was southwesterly in ebb and westerly or northwesterly in flood. Regardless of the distinction of neap and spring. The maximum velocity of the current in spring tide was 50 cm/sec in ebb and 40 cm/sec in flood and that in neap was 28 cm/sec in ebb and 25 cm/sec in flood. In spring tide the speed vector along the major axis of semidiurnal tide component was three times as large as diurnal tide. In neap tide, however, the speed vector was about 50% less then that in spring tide, and the semidiurnal tide and diurnal tide were equal in the size of current ellipse and the direction of major axis. The sea area had a southwesterly residual current. 11 cm/sec in spring tide and 7 cm/sec in neap tide. According to the result of drogue tracking, the vicinity of set net fishing ground had a southerly residual current which formed in Yeosu Bay and a weak westerly residual current toward Dolsando from Namhedo. Therefore, set net fishing ground in coastal water of Yeosu was distributed in boundary of inner water which formed from Seamjin river and offshore water supplied from the vicinity of Sorido and Yochido.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1159_1160
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• 2009

본 논문에서는 초고속 자기부상열차의 유력한 후보가 될 수 있는 초전도 반발식 자기부상의 특성을 연구하기 위한 반발력을 3차원 유한요소 자기 해석을 통하여 계산하고 분석하였다. 본 해석의 결과에 따르면 움직이는 부분이 없는 정지형 시험기는 반발식 자기부상시험기로써 적용될 수 있다.

• Journal of Electrical Engineering and Technology
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• 제1권1호
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• pp.16-22
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• 2006

Selective ground relays (SGRs) are useful fur distinguishing a faulted feeder from the sound feeders in ungrounded systems. However, they sometimes mis-operate due to human or device errors. Particularly, the reversed polarity of zero-sequence current transducers (ZCTs) is the most frequent cause of mis-operation. This paper presents a modified SGR for reducing the probability of mis-operations caused by the reversed polarity of ZCTs. The modification is achieved by introducing an adaptive time delay, which depends on the magnitude of the zero-sequence current and the phase angle deviation from the reference. The modified SGR was successfully demonstrated on a sample ungrounded system without mis-operation.

• 전기학회논문지
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• 제57권7호
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• pp.1141-1149
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• 2008

Most faults are single-phase-to-ground fault in ungrounded system. The fault currents of single-phase-to-ground are much smaller than detection thresholds of measurement devices, so detecting single-phase-to-ground faults is difficult and important in ungrounded system. This paper proposed to a FI(Fault Indicator) generation algorithm in ungrounded system. The algorithm just using line-to-line voltage and zero-sequence current detects fault line, fault phase, fault section and FI(Fault Indicator) at terminal device, This paper also proposed to application plan for this algorithm. In the case study, the proposed algorithm has been testified in demo system by Matlab/Simulink simulations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 E
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• pp.1773-1775
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• 1998

This paper deals with the pulse generator using PFN(Pulse Forming Network), and its operation characteristics and application. Two kinds of pulse generator were composed of the best appropriate condition circuit. The output current of the one pulse generator has the rise time of 28 ns and the pulse duration of $7{\mu}s$. The other pulse generator has high current of about 2kA. By use of the former generator with rapid rise time, the impulse impedance characteristic of ground electrodes was investigated with measuring the ground potential rise when the pulse current was injected into the ground electrode.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1874-1876
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• 2000

In this paper, the effects of the positions of the current probe on the measurements of the ground resistanc, and potential gradients with fall-of-potential method are described, and the testing techniques to minimize the measuring errors are proposed. The fall-of-potential method is theoretically based on the potential and current measuring principle and the measuring error is primarily caused by the position of the measuring auxiliary probes. The ground resistance is calculated by applying the 61.8% lute using fall-of-potential method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.417-420
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• 2003

In this paper, we have designed the ground faults detection and disconnection algorithm at normal rendition of AC 120V to 240V rating voltage. Ground faults in electrical network have the characteristics of low current, 60Hz frequency to 2kHz frequency. The load rendition are no load and 20A load. The controller have the trip level are 6mA with ground faults. Conventional controller does not have the miswiring condition. The Controller algorithm using pic16c71 microprotessor.

• 한국군사과학기술학회지
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• 제24권5호
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• pp.511-518
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• 2021

To accelerate a launch mass with a low level of pressure as possible in a railgun, it is required to hold supplied current nearly constant during launch phase. We obtained the discharging conditions for required current shaping by modeling and analysis of circuit equations coupled to acceleration equation of the launch mass. The acceleration characteristics of the railgun in the conditions were analyzed by comparing experimental and theoretical results.

• Structural Engineering and Mechanics
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• 제25권3호
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• pp.291-310
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• 2007

Current seismic design guidelines in Japan are diverse in the seismic ground strain estimates, because the concepts on a horizontally propagating wave model are not consistent in various seismic design guidelines including gas, water and other underground structures. The purpose of this study is (a) to derive the analytical methods to estimate the ground strains for incident seismic waves, (b) to develop a statistical estimation technique of the ground strains, and finally (c) to compare the theoretical estimation with the observed data which was measured at 441 sites in the 1999 Chi-Chi Earthquake in Taiwan.

• 조명전기설비학회논문지
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• 제27권3호
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• pp.36-42
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• 2013

This paper deals with the frequency-dependent ground impedance of ground grids combined with the carbon ground electrodes. Ground grids are generally valid for multipurpose grounding systems as well as lightning protection systems. The carbon ground electrodes may be supplementarily used to reduce the high frequency ground impedance and to improve the transient response to surge currents. The frequency-dependent ground impedances of ground grids combined with or without the carbon ground electrodes were measured and their simulations with due regard to frequency-dependent soil resistivity were implemented by using EMTP program and Matlab modeling. As a consequence, the ground impedance of ground grids combined with the carbon ground electrodes is significantly reduced when the test current is injected at the terminal of the carbon ground electrode. The measured and simulated data for the test ground grids fairly agree with each other. It was found that the proposed method of simulating the frequency-dependent ground impedance is distinguished. The simulation techniques of predicting accurately the ground impedances without actual measurements can be used in the design of grounding systems based on ground grids and the carbon ground electrodes.