• Energy Research

Abstract Wind tunnel tests on models of a 1000 ​kV super high-rise tubular steel transmission tower were carried out under two wind fields. In order that the boundary conditions for the tower section models be consistent with those of the actual structure, a new experimental method is proposed. The results show the drag coefficients in a thick turbulent boundary layer are generally less than those in uniform flow, as expected, the drag coefficient of a lattice tower section is related not only to the solidity ratio but also to its geometric shape and oncoming flow turbulence intensity. The effective projected areas (EPA) calculated by wind tunnel tests were compared to the regulations in some applicable codes. The results for the wind loads on the superstructure show that the calculation method should take into account the geometric shape, both in the transverse and longitudinal direction, and be distinguished from the methods for cross-arm and tower body. The test values for the cross-arm are in best agreement with the data from the Chinese code, while the results for the whole tower and tower sections match better with the values from the USA code. The European code generally underestimates the wind loads for all the test models.

Ice shedding of transmission lines may lead to interphase flashover and thereby endanger power transmission. The ice shedding of transmission lines is essentially an energy conversion process. Based on the vibration theory and energy method of cable structures, the iced load of a transmission line is regarded as the working load under the condition of a bare conductor. The theoretical analysis model of ice shedding for a single-span transmission line was established with a vertical symmetrical vibration mode configuration. Then the analytical solution of maximum jump height is given. The proposed formula makes clear the quantitative relationship among maximum jump height and the verticality of the conductor, the icing mass ratios, and the dimensionless frequency. The vibration of a single-span transmission line after ice shedding is investigated by the finite element method to validate the proposed formula. The results show that the maximum jump height calculated by the formula has a good agreement with the finite element analysis, which fully meets the engineering accuracy requirements. The total jump height calculated by the current method is only 1.6% lower than that from finite element method. The contribution of high-order vertical mode is small with a small sag. By considering the contribution of high-order vertical modes, the calculation formula was further modified to get more accurate results. Since the vertical modes are mainly determined by dimensionless parameters, a simplified calculation empirical formula for maximum jump height optimization was obtained by fitting based on parametric analysis results. The presented proposed formula can provide theoretical guidance and be employed to predict the maximum jump height after ice shedding for transmission line design.