• Title, Summary, Keyword: Galloping

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The Analysis of Power Line Galloping by Describing Function Method (Describing Function Method를 이용한 송전선의 전선도약(Galloping)현상 해석에 관한 연구)

  • 노창주;박한석;변기식
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.41 no.4
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    • pp.339-345
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    • 1992
  • Estimates of maximum amplitudes of conductor galloping are needed in order to determine appropriate phase-to-phase clearances on the overhead lines. One approach to obtaining these estimates is through the use of mathematical models of conductor galloping. Unfortunately, the models that consider both vertical conductor motion (Den Hartog type) and torsional conductor motion are often too complex for practical use. However, the estimates of maximum amplitude obtained from galloping models that assume only vertical (Den Hartog type) conductor motion tend to be too conservative. This paper presents the DF method to obtain the estimates of the amplitude and the frequency of galloping limit cycle, along with the wind pressure at which they occur, from a nonlinear dynamic model that considers both Den Hartog type and torsional conductor motion. From these results, the useful data for the line design guide and further insight into the mechanism of the conductor galloping are obtained.

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Galloping analysis of roof structures

  • Zhang, Xiangting;Zhang, Ray Ruichong
    • Wind and Structures
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    • v.6 no.2
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    • pp.141-150
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    • 2003
  • This paper presents galloping analysis of multiple-degree-of-freedom (MDOF) structural roofs with multiple orientations. Instead of using drag and lift coefficients and/or their combined coefficient in traditional galloping analysis for slender structures, this study uses wind pressure coefficients for wind force representation on each and every different orientation roof, facilitating the galloping analysis of multiple-orientation roof structures. In the study, influences of nonlinear aerodynamic forces are considered. An energy-based equivalent technique, together with the modal analysis, is used to solve the nonlinear MDOF vibration equations. The critical wind speed for galloping of roof structures is derived, which is then applied to galloping analysis of roofs of a stadium and a high-rise building in China. With the aid of various experimental results obtained in pertinent research, this study also shows that consideration of nonlinear aerodynamic forces in galloping analysis generally increases the critical wind speed, thus enhancing aerodynamic stability of structures.

Trajectory optimization for galloping quadruped robots (4 족보행 로봇의 갤로핑 궤적의 최적화)

  • Chae, Key-Gew;Park, Jong-Hyeon
    • Proceedings of the KSME Conference
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    • pp.831-836
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    • 2007
  • This paper proposes an optimal galloping trajectory which costs low energy and guarantees the stability of the quadruped robot. In the realization of the fast galloping, the trajectory design is important. As a galloping trajectory, we propose an elliptic leg trajectory, which provides simplified locomotion to complex galloping motions of animals. However, the elliptic trajectory, as an imitation of animal galloping motion, does not guarantee stability and minimal energy consumption. We propose optimization based on the energy and stability using a genetic algorithm, which provides the robust and global solution to a multi-body, highly nonlinear dynamic system. To evaluate and verify the effectiveness of the proposed trajectory, computer simulations were carried out.

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Galloping of overhead transmission lines in gusty wind

  • Ohkuma, Takeshi;Marukawa, Hisao
    • Wind and Structures
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    • v.3 no.4
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    • pp.243-253
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    • 2000
  • To develop galloping suppression devices, it is important to understand the effects of wind turbulence on galloping and to establish an evaluation method which takes 'large conductor deformations' into account. This paper introduces some findings on galloping in gusty wind obtained by numerical simulation using a model based on the Mogami Test Line of the Tokyo Electric Power Co. The equations of motion of the conductor are based on the Lagrangian formulations by Simpson, and they are made discrete in accordance with a finite element method.

Prediction of Galloping Accidents in Power Transmission Line Using Logistic Regression Analysis

  • Lee, Junghoon;Jung, Ho-Yeon;Koo, J.R.;Yoon, Yoonjin;Jung, Hyung-Jo
    • Journal of Electrical Engineering and Technology
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    • v.12 no.2
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    • pp.969-980
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    • 2017
  • Galloping is one of the most serious vibration problems in transmission lines. Power lines can be extensively damaged owing to aerodynamic instabilities caused by ice accretion. In this study, the accident probability induced by galloping phenomenon was analyzed using logistic regression analysis. As former studies have generally concluded, main factors considered were local weather factors and physical factors of power delivery systems. Since the number of transmission towers outnumbers the number of weather observatories, interpolation of weather factors, Kriging to be more specific, has been conducted in prior to forming galloping accident estimation model. Physical factors have been provided by Korea Electric Power Corporation, however because of the large number of explanatory variables, variable selection has been conducted, leaving total 11 variables. Before forming estimation model, with 84 provided galloping cases, 840 non-galloped cases were chosen out of 13 billion cases. Prediction model for accidents by galloping has been formed with logistic regression model and validated with 4-fold validation method, corresponding AUC value of ROC curve has been used to assess the discrimination level of estimation models. As the result, logistic regression analysis effectively discriminated the power lines that experienced galloping accidents from those that did not.

A Study on the Analysis of Galloping for Power transmission line (송전선의 전선도약 해석에 관한 연구)

  • 김환성;변기식
    • Journal of the Korean Society of Marine Engineering
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    • v.25 no.5
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    • pp.1051-1057
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    • 2001
  • In this paper, we deal with three types of modelling method for the analysis of galloping in power transmission line (PTL). The single mass model is obtained under linearization method and it is applied into f-order model. On these models, the nature frequencies of PTL are obtained and it makes an effects on the galloping directly. In simulation, we verify that the maximum magnitude of nature frequency depends on the galloping distance of PTL. Also from the analysis of frequency response, a few of reduction method for galloping are introduced which is effected by distance of PTL, wind velocity and icing types.

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Effect Analysis of Spacer Stiffness and Interval on Galloping of Power Transmission Lines (스페이서 강성과 간격이 송전선 갤러핑에 미치는 영향분석)

  • Oh, Yun-Ji;Sohn, Jeong-Hyun
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.18 no.1
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    • pp.52-58
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    • 2019
  • Due to icing and snow, power transmission lines have asymmetric cross sections, and their motion becomes unstable. At this time, the vibration caused by the wind is called galloping. If galloping is continuous, short circuits or ground faults may occur. It is possible to prevent galloping by installing spacers between transmission lines. In this study, the transmission line is modeled as a mass-spring-damper system by using RecurDyn. To analyze the dynamic behavior of the transmission line, the damping coefficient is derived from the free vibration test of the transmission line and Rayleigh damping theory. The drag and lift coefficient for modeling the wind load are calculated from the flow analysis by using ANSYS Fluent. Galloping simulations according to spacer stiffness and interval are carried out. It is found that when the stiffness is 100 N/m and the interval around the support is dense, the galloping phenomenon is reduced the most.

Drift Compensation Algorithm of Acceleration Sensor for Galloping Measurement System (갤로핑 측정을 위한 가속도 센서 드리프트 보상 알고리즘)

  • 변기식;안영주;김환성
    • Journal of the Korean Society of Marine Engineering
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    • v.27 no.7
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    • pp.914-920
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    • 2003
  • In this paper, we deal with two drift compensation algorithms of acceleration sensor for measuring the galloping on power transmission line. Firstly, the block diagram of galloping measurement system is given and a galloping model is presented. Secondly, two compensation algorithms, a simple compensation and a period compensation, are proposed. A simple compensation algorithm uses the drifts of velocity and distance at fixed periods, so it is useful for constant drift case. Next, a period compensation algorithm can compensate a periodic drift. This algorithm uses the previous measured data and compensated data for constant period, where the period is obtained by FFT method. Lastly, the effectiveness of proposed algorithms is verified by comparing between two algorithms in simulation, and its characteristics and the drift error bound are shown, respectively.

An Experimental Study on the Galloping of Inclined Cables

  • Kim, Han-Soo;Lee, Do-Hyung;Kim, Seok-Jung
    • Journal of Industrial Technology
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    • v.22 no.A
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    • pp.137-144
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    • 2002
  • A series of wind tunnel tests was conducted to investigate the existence of the galloping instability of inclined dry cables and also to Identify the influence of some parameters on it. These parameters are the structural damping and cable surface roughness, which may have significant impact on the vibration characteristics. The test results showed both the divergent type of galloping instability and the limited amplitude high wind speed vortex shedding excitation. Galloping instability was observed in only one case. Parametric study shows that the vortex shedding oscillation can be easily suppressed with an increase of structural damping. It was also shown that the instability criterion indicated by earlier research was too conservative compared to the results obtained from the present study.

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