• Structural Engineering and Mechanics
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• 제75권4호
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• pp.487-496
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• 2020

Most of the previous works on numerical analysis of galloping of transmission lines are generally based on the quasisteady theory. However, some wind tunnel tests of the rectangular section or hangers of suspension bridges have shown that the galloping phenomenon has a strong unsteady characteristic and the test results are quite different from the quasi-steady calculation results. Therefore, it is necessary to check the applicability of the quasi-static theory in galloping analysis of the ice-covered transmission line. Although some limited unsteady simulation researches have been conducted on the variation of parameters such as aerodynamic damping, aerodynamic coefficients with wind speed or wind attack angle, there is a need to investigate the numerical simulation of unsteady galloping of two-dimensional iced transmission line with comparison to wind tunnel test results. In this paper, it is proposed to conduct a two dimensional (2-D) unsteady numerical analysis of ice-covered transmission line galloping. First, wind tunnel tests of a typical crescent-shapes iced conductor are conducted firstly to check the subsequent quasisteady and unsteady numerical analysis results. Then, a numerical simulation model consistent with the aeroelastic model in the wind tunnel test is established. The weak coupling methodology is used to consider the fluid-structure interaction in investigating a two-dimension numerical simulation of unsteady galloping of the iced conductor. First, the flow field is simulated to obtain the pressure and velocity distribution of the flow field. The fluid action on the iced conduct at the coupling interface is treated as an external load to the conductor. Then, the movement of the conduct is analyzed separately. The software ANSYS FLUENT is employed and redeveloped to numerically analyze the model responses based on fluid-structure interaction theory. The numerical simulation results of unsteady galloping of the iced conduct are compared with the measured responses of wind tunnel tests and the numerical results by the conventional quasi-steady theory, respectively.

• Earthquakes and Structures
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• 제17권6호
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• pp.635-647
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• 2019

Tests and theoretical studies for seismic responses of a transmission tower-line system under coupled horizontal and tilt (CHT) ground motion were conducted. The method of obtaining the tilt component from seismic motion was based on comparisons from the Fourier spectrum of uncorrected seismic waves. The collected data were then applied in testing and theoretical analysis. Taking an actual transmission tower-line system as the prototype, shaking table tests of the scale model of a single transmission tower and towers-line systems under horizontal, tilt, and CHT ground motions were carried out. Dynamic equations under CHT ground motion were also derived. The additional P-∆ effect caused by tilt motion was considered as an equivalent horizontal lateral force, and it was added into the equations as the excitation. Test results were compared with the theoretical analysis and indicated some useful conclusions. First, the shaking table test results are consistent with the theoretical analysis from improved dynamic equations and proved its correctness. Second, the tilt component of ground motion has great influence on the seismic response of the transmission tower-line system, and the additional P-∆effect caused by the foundation tilt, not only increases the seismic response of the transmission tower-line system, but also leads to a remarkable asymmetric displacement effect. Third, for the tower-line system, transmission lines under ground motion weaken the horizontal displacement and acceleration responses of transmission towers. This weakening effect of transmission lines to the main structure, however, will be decreased with consideration of tilt component.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.105-113
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• 2018

This paper proposes pre-analysis on planning of high-voltage direct current (HVDC) transmission system applied to Korea electric power grid. HVDC transmission system for interface lines has been considered as alternative solution for high-voltage AC transmission line in South Korea since constructing new high-voltage AC transmission lines is challenging due to political, environmental and social acceptance problems. However, the installation of HVDC transmission system as interface line in AC grid must be examined carefully. Thus, this paper suggests three scenarios to examine the influences of the installation of HVDC transmission system in AC grid. The power flow and contingency analyses are carried out for the proposed scenarios. Power reserves in metro area are also evaluated. And then the transient stability analysis focusing on special protection scheme (SPS) operations is analyzed when critical lines, which are HVDC lines or high voltage AC lines, are tripped. The latest generic model of HVDC system is considered for evaluating the impacts of the SPS operations for introducing HVDC system in the AC grid. The analyses of proposed scenarios are evaluated by electromechanical simulation.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1144-1153
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• 2015

The resonant mechanism of reradiation interference (RRI) over 1.7MHz from power transmission lines cannot be obtained from IEEE standards, which are based on researches of field intensity. Hence, the resonance is ignored in National Standards of protecting distance between UHV power lines and radio stations in China, which would result in an excessive redundancy of protecting distance. Therefore, based on the generalized resonance theory, we proposed the idea of applying model-based parameter estimation (MBPE) to estimate the generalized resonance frequency of electrically large scattering objects. We also deduced equation expressions of the generalized resonance frequency and its quality factor Q in a lossy open electromagnetic system, i.e. an antenna-transmission line system in this paper. Taking the frequency band studied by IEEE and the frequency band over 1.7 MHz as object, we established three models of the RRI from transmission lines, namely the simplified line model, the tower line model considering cross arms and the line-surface mixed model. With the models, we calculated the scattering field of sampling points with equal intervals using method of moments, and then inferred expressions of Padé rational function. After calculating the zero-pole points of the Padé rational function, we eventually got the estimation of the RRI’s generalized resonant frequency. Our case studies indicate that the proposed estimation method is effective for predicting the generalized resonant frequency of RRI in medium frequency (MF, 0.3~3 MHz) band over 1.7 MHz, which expands the frequency band studied by IEEE.

• 한국전자파학회논문지
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• 제17권11호
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• pp.1132-1142
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• 2006

본 연구는 송전 선로 여러 가지 유형의 극저주파 자기장 저감 적용 모델을 조사하고 그 효과를 분석하였다. 본 연구에서는 154 kV 수평 배열 송전 선로를 기본으로 하여 적용 가능한 다양한 자기장 저감 모델에 대하여 적용시 얻게 되는 자기장 저감지수(Field Reduction Factor)를 검토하였다. 그 결과 compact 모델 채용시에는 상간거리 compact화 비율과 자기장 저감지수가 거의 비례하였으며, diamond 모델 및 transposed 선로 배치의 경우는 50 %에 근접한 자기장 저감이 가능하였다. 배전 선로에 적용이 가능한 삼각형 배열은 33 % 정도, 2회선 split는 50 % 정도 저감 효과가 나타나는 것으로 분석되었으며 수평 multi split 모델의 경우는 80 %까지 자기장 저감을 얻을 수 있었다.

• 한국측량학회지
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• 제37권2호
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• pp.63-70
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• 2019

Electric transmission towers are facilities to transport electrical power from a plant to an electrical substation. The towers are connected using wires considering the wire tension and the clearance from the ground or nearby objects. The wires are installed on a rights-of-way that is a strip of land used by electrical utilities to maintain the transmission line facilities. Trees and plants around transmission lines must be managed to keep the operation of these lines safe and reliable. This study proposed the use of a low-cost drone photogrammetry for the transmission line rights-of-way mapping. Aerial photogrammetry is carried out to generate a dense point cloud around the transmission lines from which a DSM (Digital Surface Model) and DTM (Digital Terrain Model) are created. The lines and nearby objects are separated using nDSM (normalized Digital Surface Model) and the noises are suppressed in the multiple image space for the geospatial analysis. The experimental result with drone images over two spans of transmission lines on a mountain area showed that the proposed method successfully generate the rights-of-way map with hazard nearby objects.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.90-97
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• 2014

Nash Cournot Equilibrium (NCE) has been widely used in a competitive electricity market to analyze generation firms' strategic production quantities. Congestion on a transmission network may lead to a mixed strategy NCE. Mixed strategy is complicated to understand, difficult to compute, and hard to implement in practical market. However, Stackelberg model based equilibrium does not have any mixed strategy, even under congestion in a transmission line. A guide to understanding mixed strategy equilibrium is given by analyzing a cycling phenomenon in the players' best choices. This paper connects the concept of leader-follower in Stackelberg model with relations between generation firms on both sides of the congested line. From the viewpoint of social welfare, the surplus analysis is presented for comparison between the NCE and the Stackelberg equilibrium (SE).

• 대한전기학회논문지:전력기술부문A
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• 제51권10호
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• pp.502-509
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• 2002

In the analysis of lightning surges, transmission towers are usually simulated by ATPDraw. The modeling of transmission towers is an essential part of the traveling wave analysis of lightning surges in transmission lines. The tower model is applied to the 154kV transmission tower of which surge performance characteristics are measured Tower surge response is computed using nonuniform, single-phase line models for both transmission tower and ground wire. The overvoltage will effect to the underground transmission line. The underground cable is combined by duct and trefoil type, and the each arrester is placed on the leading-in tube and outgoing tube. This paper analyzed the effect of lightning overvoltage on the underground cable system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.336-339
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• 2001

Transmission line data are very important for studying loadflow. Short circuit data(positive sequence, zero sequence) of 345kV and 154kV line were calulated and compared with KEPCO's line characteristics data. This Paper presents method of verification and complement of line data in PSS/E loadflow data using TMLC (Transmission Line Characteritics) program.

• 전기학회논문지
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• 제60권3호
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• pp.492-499
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• 2011

This paper describes that the evaluation on operation practicality of Al conductor cable will be used instead of Cu conductor cable. Analysis is divided into two kinds of cases as transmission and distribution. To evaluate that Al conductor line has the insulation strength indeed safely, various analysis and calculation such as single line-to-ground fault current, lightning surge and allowance current were carried. Model was established based on real combined transmission and distribution is being used in utility with EMTP. The analysis results on Al and Cu conductor line were compared each other. It was proved that Al conductor line can be operated instead of Cu conductor line without special insulation problem in transmission and distribution, in electrical view point such as overvoltage and allowance current.