There are some kinds of cable vibration phenomena occurred on transmission line. Notable vibration of them is called "Galloping". This vibration causes electrical outages and fatigue damages to these transmission lines, though this phenomena has not been clarified. Therefore, we have been studying and observing these galloping to comprehend the mechanism of this kind of vibration and confirm the effects of unti-galloping devices from 1950's. In 1975, galloping was defined as the low frequency self-excited vibration with large amplitude that is occurred by the lift force that is caused by the ice or snow accreted cable those shape is non-symmetric cross section under the wind velocity of more than 7m/s (10 minutes average). Thereafter, many kinds of field observations and experiments have been carried on using the full scale test lines as well as the operating lines. This paper denotes that these outline before mentioned and the characteristics of galloping phenomena.
At Tokyo Tower, wind observations have been carried out continuously at heights of 250m, 107m and 25m above the grand. In this paper, the authors have investigated the relationship between the vertical profile of the mean wind speed obtained from the data during a period of 1974 to1996 and both the building area ratio and the ratio of an area for buildings with four or more stories to that for all buildings obtained from the dimensions of all structures on the windward side of the observation points. When fitting a power low profile to the observation results, the power law exponent ranging from 0.48 to 0.56 was obtained. However, when a zero-plane displacement was considered in the evaluation of the profile, the power law exponent became 0.38 to 0.48. These values correspond well both to the plane density of the windward area and the abovementioned ratio of the area of buildings for four or more stories.