• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.452-454
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• 2004

An accurate digital distance relaying algorithm which is immune to reactance effect of the fault resistance and the load current for phase-to-ground fault in 765kV untransposed transmission lines is proposed. The algorithm can estimate adaptively the impedance to a fault point independent of the fault resistance. To compensate the magnitude and phase of the apparent impedance, this algorithm uses the angle of an impedance deviation vector. The impedance correction algorithm for Phase-to-ground fault uses a voltage equation at fault point to compensate the fault current at fault point. A series of tests using EMTP output data in a 765kV untransposed transmission lines have proved the accuracy and effectiveness of the proposed algorithm.

• 조명전기설비학회논문지
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• 제20권9호
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• pp.70-77
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• 2006

We have fabricated an integrated three-phase flux-lock type SFCL, which consists of an YBCO($YB_a2Cu_3O_7$) thin film and a flux-lock reactor wound around an iron core of each phase. In order to apply the SFCL in a real power system, fault analyses for the three-phase system are essential. The short-circuit currents were effectively limited by adjusting the numbers of winding of each secondary coil and their winding directions. The flux flow generated in the iron core cancelled out under the normal operation due to the parallel connection between primary and secondary windings. However, the flux-lock type SFCL with same iron core was operated just after the fault due to the flux generating in the iron core. To analyze the current limiting characteristics, the additive polarity winding was compared with the subtractive one in the flux lock reactor. Whenever a single line-to-ground fault occurred in any phase, the peak value of the line current of the fault phase in the additive polarity winding increased up to about 12.87 times during the first-half cycle. On the other hand, the peak value in the subtractive polarity winding increased up to about 34.07 times under the same conditions. This is because the current flow between the primary and the secondary windings changed to additive or subtractive status according to the winding direction. We confirmed that the current limiting behavior in the additive polarity winding was more effective for a single-line-to-ground fault

• 조명전기설비학회논문지
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• 제22권2호
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• pp.107-113
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• 2008

22.9[kV]-y 배전 방식은 지중 케이블로 전력을 공급하고 있으며 선로 운영상 배전케이블 선로의 동심중성선을 케이블 접속 구간마다 3선 일괄 접지하는 다중 접지방식을 채택하고 있다. 그러나 지중 배전 선로에서 각 상의 부하가 평형일 경우에도 동심중성선에는 부하 전류의 약 40[%](전력구)${\sim}$50[%](관로)의 동심중성선 순환 전류가 발생되고 있기 때문에, 순환전류로 인한 손실이 도체 손실의 76[%]에 달한다. 이러한 손실 전력으로 케이블의 내부온도가 상승되어 케이블의 허용전류 용량이 관로의 경우 20[%] 정도 감소하게 된다. 본 논문은 이와 같은 문제점을 해결하기 위하여 새로운 동심중성선 접지방식을 제안하고 있다. 새로운 방법은 동심중성선의 순환전류를 효과적으로 제거하고 있으며, 그 방안을 직접 계통망에서 적용시켜서 실측하여 본 결과, 그 타당성과 유용성을 확인하였다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2006년도 춘계학술대회 논문집
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• pp.467-470
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• 2006

Superconducting fault current(SFCLs) are expected to improve not only reliability but also stability of real power systems. The analysis on the single line-to-ground fault current of the integrated three phase flux-lock type SFCL, which consists of three flux-lock reactor wound on an iron core in each single phase and three YBCO thin films, was investigated in current limiting operating characteristics. We compared additive polarity winding with the subtractive one in the flux lock reactor. Its turns ratio each phase between the primary and the secondary coils is 63:42. When a single line-to-ground fault occurred in any phase, the peak value of line current in the fault phase of the additive polarity winding increased up to 31.44[A] during first-half cycle. On the other hand, the peak value in the subtractive polarity winding increased up to 81.77[A] under the same conditions. This is because the current flow between the primary and the secondary windings becomes to be additive or subtractive in each winding direction. We confirmed that the current limiting behavior in the additive polarity winding was more effective for a single-line-to ground fault.

• 한국지반신소재학회논문집
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• 제11권4호
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• pp.45-53
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• 2012

지반굴착은 지반조사, 연약지반 개량, 선굴착 말뚝 시공 등 지반공학 분야에서 널리 사용되고 있다. 지반을 굴착하기 위해서는 오거의 상부에 설치된 구동모터를 회전시키는 전기에너지가 필요하게 된다. 본 논문에서는 지반굴착시 구동모터에 소요되는 전기에너지와 지반의 표준관입시험 N값의 상관관계를 분석하고자 하였다. 이를 위하여 지반굴착시 변화하는 전류값과 굴착깊이를 계측하기 위한 측정센서, 데이터 저장시스템, 굴착시스템 등의 실내실험 장치를 개발하였으며, 모형토조 실험을 수행하였다. 계측된 전류값과 굴착깊이는 표준관입시험 N값 추정에 이용되었으며 추정된 표준관입시험 N값은 실내실험으로부터 실측된 N값과 비교하였다. 비교결과 지반굴착에 소요되는 전기에너지를 이용하여 표준관입시험 N값을 추정할 수 있음을 확인하였다.

• 제어로봇시스템학회논문지
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• 제14권8호
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• pp.848-855
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• 2008

In this paper, we describe correspondence among multiple images taken by multiple cameras. The correspondence among multiple views is an interesting problem which often appears in the application like visual surveillance or gesture recognition system. We use the principal axis and the ground plane homography to estimate foot of human. The principal axis belongs to the subtracted silhouette-based region of human using subtraction of the predetermined multiple background models with current image which includes moving person. For the calculation of the ground plane homography, we use landmarks on the ground plane in 3D space. Thus the ground plane homography means the relation of two common points in different views. In the normal human being, the foot of human has an exactly same position in the 3D space and we represent it to the intersection in this paper. The intersection occurs when the principal axis in an image crosses to the transformed ground plane from other image. However the positions of the intersection are different depend on camera views. Therefore we construct the correspondence that means the relationship between the intersection in current image and the transformed intersection from other image by homography. Those correspondences should confirm within a short distance measuring in the top viewed plane. Thus, we track a person by these corresponding points on the ground plane. Experimental result shows the accuracy of the proposed algorithm has almost 90% of detecting person for tracking based on correspondence of intersections.

• 대한전기학회논문지:전력기술부문A
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• 제55권12호
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• pp.529-535
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• 2006

In DC tracking power supply system, ground faults are currently detected by the potential relay, 64P. Though 64P relay detects ground fault, it cannot identify the faulted region which causes long traffic delays and safety problem to passengers. A new ground fault protective relay scheme, ${\Delta}I$ ground fault protective relay, that can identify the faulted region is presented in this paper. In ${\Delta}I$ ground fault protective relaying scheme, ground fault is detected by 59, overvoltage relay, which operates ground switch installed between the negative bus and the ground. It preliminarily chooses the faulted feeder after comparing the current increases among feeders and trips the corresponding feeder breaker. After some time delay, it then recloses the breaker if it finds the preselected feeder is not the actual faulted feeder. Whether or not the preselected feeder is the actual faulted feeder is determined by checking the breaker trip status in the neighboring substation in the direction of the tripped breaker. If the corresponding breaker in the neighboring substation is also tripped, it finally judges the preselected feeder is actually a faulted feeder. Otherwise it recloses the tripped breaker. Its algorithms is presented and verified by EMTP simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.760-761
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• 2011

Ground differential relay is used to provide fast, sensitive, and selective protection for the wye connected and grounded electrical power equipment such as generators, power transformers, and grounding transformers. The ground differential protection only protects the ground faults within the protection zone, so that it can't protect the line-to-line fault. This paper proposes the algorithm to provide the protection for the line-to-line fault through the ground differential protection. The proposed algorithm detects the line-to-line fault of transformer using the comparison between the positive and the negative current, when the ground differential relay dose not operate. The performance of the algorithm is verified using a PSCAD/EMTDC simulator under various case studies.

• 전기학회논문지P
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• 제60권4호
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• pp.214-219
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• 2011

The substation grounding design,"IEEE Guide for Safety in AC Substation Grounding (ANSI / IEEE Std 80)"has been widely used. Substation grounding design and substation grounding resistance of grounding network site to predict the voltage at the risk of a very important task, which is a ground fault current due to the influx of the ground network and due to rise in the Earth's potential can be applied to human dangerous Voltage within safe tolerances be configured to be the ground because the network. IEEE Std. 80 for the substation construction safety equipment on the ground securing the ground electrode and the mesh around the boundary potential distribution in terms of risk analysis by the touch voltage and the reference was to clean up the definition and the basic steps of the voltage of the voltage limits the risk of peripheral grounding electrode Suppression by the simulator through a new secure from dangerous voltage design techniques were presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1741-1743
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• 2001

This paper presents the induced ground potential rise distributions on several ground electrodes buried nearby. These experiments were conducted with the impulse currents as a function of the ground electrodes types and distances from the current injection point. The ground potential is significantly induced in the vicinity of ground electrodes, and the induced ground potential rises can caused unwanted erratic operation of electronic device.