• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전력기술부문
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• pp.83-86
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• 2005

최근 가공 송전선로 건설에 대한 인근 지역주민들의 반대에 부딪쳐, 불가피하게 가옥이 밀집된 주거지역을 우회하거나 토지 활용도가 낮은 산악지를 이용하여 선로를 건설하는 경우가 대부분이다. 이와 같이 경과지의 제한성으로 인해 때때로 국지적인 기상현상 발생 우려가 있는 지역에 불가피하게 송전선로를 건설하는 경우가 있으며, 이상기상 현상이 발생하는 11월말에서 3월초 사이에 경기북부 지역의 국지성 돌풍에 의해 갤로핑(Galloping)현상이 종종 발생되었다 갤로핑은 바람으로 인해 전력선이 횡진과 출렁임이 발생되는 현상을 말한다. 송전선로의 지지물에는 주로 철탑이 사용되고, 전력선은 ACSR 410mm 복도체가 주로 사용된다. 송전선로는 경제성과 계통의 안전성을 고려하여 수직배열로 2회선용 표준철탑을 사용한다. 갤로핑 현상은 바람에 의해 전력설에 심한 진동을 일으켜, 수직 배열된 전력선 상간 단락 또는 전력선과 가공지선간의 지락으로 고장전류가 생기고, 고장전류에 의한 보호계전기 동작으로 선로가 트립(Trip)되며, 이로 인한 전력공급 중단이 발생된다. 또한 전력선의 기계적인 진동에 의하여 전력선의 단선 또는 지지물의 파손으로 영구고장을 일으킬 수도 있다. 본 논문에서는 경기북부지역의 산악지에 설치된 154kV 송전선로에서 산비탈면을 타고 오르는 상승 바람에 의한 갤로핑 사례를 국내 최초로 현장에서 촬영한 동영상 자료를 토대로 소개하고, 갤로핑 발생시 송전선로에 미친 영향 등 검토 결과를 설명하였다. 전력선에 생긴 아크 흔적을 토대로 전력선간의 단락이 발생했던 지점을 실제로 관측할 수 있었다. 최근 갤로핑으로 인한 상간 단락 고상 방지론 목적으로 개발된 폴리머 상간스페이서(Interphase spacer)의 시공 사례를 소개하고, 현재까지 상간스페이서가 설치된 송전선로의 점검 결과를 소개하고자 한다.

• 전자공학회논문지
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• 제50권2호
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• pp.114-121
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• 2013

Systems-On-Chips(SoC)에서 내장 메모리가 차지하는 비중은 비약적으로 증가하여 전체 트랜지스터 수의 80%~90%를 차지하고 있어, SoC에서 내장된 메모리에 대한 테스트 중요성이 증가하고 있다. 본 논문은 다양한 테스트 알고리즘을 지원하는 IEEE 1500 래퍼 기반의 프로그램 가능한 메모리 내장 자체 테스트(PMBIST) 구조를 제안한다. 제안하는 PMBIST는 March 알고리즘 및 Walking, Galloping과 같은 non-March 알고리즘을 지원하여 높은 flexibility, programmability 및 고장 검출률을 보장한다. PMBIST는 최적화된 프로그램 명령어와 작은 프로그램 메모리에 의해 최적의 하드웨어 오버헤드를 가진다. 또한 제안된 고장 정보 처리 기술은 수리와 고장 진단을 위해 2개의 진단 방법을 효과적으로 지원하여 메모리의 수율 향상을 보장한다.

• Wind and Structures
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• 제8권2호
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• pp.107-120
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• 2005

The quasi-steady approaches to simulate the wind induced vibrations of inclined cables, especially on the rain-wind induced vibration, have been tried by many researchers. However, the steady wind force coefficients used in those methods include only the effects of water rivulet, but not the axial flow effects. The problem is the direct application of the conventional techniques to the inclined cable aerodynamics. Therefore, in this study, the method to implement the axial flow effects in the quasi-steady theory is considered and its applicability to the inclined cable aerodynamics is investigated. Then, it becomes clear that the perforated splitter plate in the wake of non-yawed circular cylinder can include the effects of axial flow in the steady wind force coefficients for inclined cables to a certain extent. Using the lateral force coefficients measured in this study, the quasi-steady theory may explain the wind induced instabilities of the inclined cables only in the relatively high reduced wind velocity region. When the Scruton number is less than around 40, the high speed vortex-induced vibration occurs around the onset wind velocity region of the galloping, and then, the quasi-steady approach cannot be applied for estimating the response of wind-induced vibration of inclined cable.

• Wind and Structures
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• 제30권2호
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• pp.119-131
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• 2020

A butterfly web girder is a box-shaped girder with discretely distributed side openings along the spanwise direction. Until now, there have been few studies related to the aerodynamic performance of the butterfly web bridge. The objective of the current study was to clarify the effects of the side openings on the aerodynamic performance of the girder. Two butterfly web girders with side ratios B/D = 3.24 and 5, where B is the girder width and D is the depth, were examined through a series of wind tunnel tests. A comparison of the results for butterfly web girders and conventional box girders of the same shape confirmed that the side openings stabilized the vortex-induced vibration and galloping when B/D = 3.24, whereas the vortex-induced vibration and torsional flutter were stabilized when B/D = 5. The change in the flow field due to the side openings contributed to the stabilization against the vibration. These findings not only confirmed the good aerodynamic performance of the butterfly web bridge but also provided a new method to stabilize the box girder against aerodynamic instabilities via discretely distributed side openings.

• 한국강구조학회 논문집
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• 제20권6호
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• pp.741-750
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• 2008

본 연구의 목적은 3차원 풍동실험을 이용하여 합성형 사장교의 공기역학적 특성을 분석하는데 있다. 2차원 풍동실험에서 선정된 내풍개선 단면을 가지고 영각, 풍각에 대하여 3차원 모형의 내풍안정성을 평가한다. 설계풍속에서 수직, 비틀림 와류진동, 비틀림 플로터 등의 공기 역학적 특성을 규명하였다. 또한 사장교는 FCM으로 대부분 가설하므로 가설단계에서 강성이 부족하다. 따라서 실험은 완성계, 2개의 가설단계, 독립주탑의 단계별로 나누어 진행되었다. 원설계가 강상형교로 설계되었기 때문에 강상형교와 합성형교의 내풍특성을 비교하였다. 이 논문은 중소형 합성형 사장교의 내풍특성의 기초 자료로 활용될 수 있을 것이다

• 대한교통학회지
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• 제2권1호
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• pp.3-16
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• 1984

Development of para-transit is imminent in modern metropolis which are galloping toward motorization. Compared with other already industrialize countries, our metropolis can take a vantage of late starter in coping with urban transportation problem. Our metropolis are still heavily relying on public and/or pare-transit in modal split. Current government policy toward taxi-cab, however, seems to contradict with the objective of developing para-transit. If it is not adequately developed, the middle-class people of higher income would have no other option than having their own auto as already been observed. It will centainly accelerate our motorization process so that we follow the model of industrialized countries, and their problems too. Insisting that our transport policy should be drastically reformulated in favor of paratransit in addition to public transit, this study reappraise current policy on taxi-cab with respect to fare, prohibition of shared-ride, and other regulatory measures and propose and management model for taxi fare and operating policy in metropolis.

• Wind and Structures
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• 제15권6호
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• pp.495-508
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• 2012

The present paper is focused on the prediction of the acrosswind aeroelastic response of square tall buildings. In particular, a semi-analytical procedure is proposed based on the assumption that square tall buildings, for reduced velocities corresponding to operational conditions, do not experience vortex shedding resonance or galloping and fall in the range of positive aerodynamic damping. Under these conditions, aeroelastic wind tunnel tests can be unnecessary and the response can be correctly evaluated using wind tunnel tests on rigid models and analytical modeling of the aerodynamic damping. The proposed procedure consists of two phases. First, simultaneous measurements of the pressure time histories are carried out in the wind tunnel on rigid models, in order to obtain the aerodynamic forces. Then, aeroelastic forces are analytically evaluated and the structural response is computed through direct integration of the equations of motion considering the contribution of both the aerodynamic and aeroelastic forces. The procedure, which gives a conservative estimate of the aeroelastic response, has the advantage that aeroelastic tests are avoided, at least in the preliminary design phase.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.164-165
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• 2003

The problem of a bluff body oscillating in a fluid flow has been receiving a great deal of attention. When a bluff body is placed in a flow, it experiences fluctuating hydraulic forces in both transverse and stream-wise directions. It is caused by the formation of vortices behind the body, which could cause large damages of structures. It is called the flow-induced vibrations. In this article, it is investigated the effects of that side-jets and rear-jet, which is applied to control the vortex shedding. The rear-jet is available to control the flow-induced vibrations according as the body shapes and the velocity of fluid flow in which the galloping phenomena is not appeared.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 E
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• pp.1804-1806
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• 1997

Route conditions, applied voltage and the condition of stringing conductors should be considered in determining standard types and skeleton diagrams of towers. In skeleton diagrams the necessary number of insulators and the air clearance have been decided by the results of studies on insulation coordination. Galloping, sleet-jumping, sag characteristics and the possibility of closeness of conductors should be considered according to the condition of stringing conductor and the span. After reviewing those factors, it is necessary to determine the minimum vertical and horizontal distance for the safety of transmission lines under any circumstances. Also it should be economical.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.436-438
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• 2003

Wind-induced oscillations are known to cause damage to the conductors and related hardware through fatigue, clashing of the bundled conductors and bolt loosening. Wake-induced oscillations have been known since the advent of bundled conductors, they are caused by aerodynamically unstable forces acting on the leeward conductors in the wake of the windward conductors, They take the form of horizontal galloping, snaking or rolling, in which case all subconductors move together in unison. They can also take the form of the subspan oscillation, which appear as elliptical motions of the subconductors moving out of phase, mainly in the horizontal plane within a subspan. In order to decrease amplitudes of the oscillation, this paper examines the application status of the spacer dampers and suggests proper installation methods.