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Under the excitement of wind loads, UHV transmission lines are subject to two types of vibration phenomena, namely, sub-span oscillation and galloping. This phenomenon can easily lead to conductor breakage, interphase flashover, fatigue damage to fittings, and even lead to tower collapse and disconnection accidents. The numerical analysis method is used to analyze the sub-span oscillation characteristics of the eight-bundle conductor during galloping. The results of the numerical simulation are compared to explore the influence of wind speed, span length, initial angle of wind attack, and turbulence intensity on the galloping line, looking for movement characteristics between each sub-conductor. The results provide a reference for research on the galloping principle of UHV transmission line and anti-oscillation to further improve the resistance of the power grid against disaster ability.

In this article, the numerical model of the multi-span iced eight-bundle conductor is established using the nonlinear finite element method, the galloping of the line under different parameters is simulated, and the tension in the galloping process is analyzed. Based on the aerodynamic characteristics and galloping characteristics of conductors, the galloping modes, frequency characteristics, vibration amplitudes, and galloping orbits of multi-span lines under different wind velocities, span lengths, ice shape, and number of spans are analyzed, compared with those of single-span lines. It is demonstrated that there are differences in galloping characteristics between multi-span transmission lines and single-span lines. Each span of the transmission line is different, so it should be fully considered in the research of galloping prevention and control technology.

Pluronic F127, P123 and cross-linked F127 diacrylate micelles are photochemically deoxygenating nanocapsules in which oxygen could be removed by photochemical reaction with a surfactant and efficient triplet–triplet annihilation photon upconversion (TTA-UC) can be achieved in air. The efficiency of TTA-UC under air is comparable to that under deoxygenated conditions. [ABSTRACT FROM AUTHOR]

Major disasters and losses would be caused by the galloping of transmission lines. The basis for studying the galloping mechanism of transmission lines is to analyze the aerodynamic characteristics of iced conductors. The wind tunnel test is a traditional way to obtain the aerodynamic coefficients of an iced transmission line under wind load. Due to the high cost and long duration of wind tunnel tests, an experimental method based on machine learning to predict aerodynamic coefficients is proposed. Here, the steady and unsteady aerodynamic coefficients of an iced conductor under different parameters were obtained by wind tunnel test, and then the aerodynamic coefficients of the iced conductor under different parameters were predicted by machine learning. The aerodynamic coefficients of each iced conductor varied with the angle of wind attack by the wind tunnel test. The Den Hartog and Nigol coefficients determined based on the aerodynamic coefficients obtained by machine learning and wind tunnel test are in agreement. The results show the feasibility of the machine learning prediction method. [ABSTRACT FROM AUTHOR]

Two-dimensional air flows around a quad bundle conductor covered with crescent-shaped ice of different thickness are numerically simulated, based on which the aerodynamic coefficients of each iced subconductor vary with the angle of wind attack are determined. The numerically obtained aerodynamic coefficients are compared with those by the wind tunnel test carried out previously. It is seen that the laws of the aerodynamic coefficients against the angle of attack determined by the two methods are similar, and the corresponding Den Hartog coefficients and Nigol coefficients agree well. Moreover, the galloping frequencies, vibration modes, and galloping traces of a typical iced-quad bundle conductor line obtained by the finite-element method based on the aerodynamic coefficients, respectively, determined by the two methods are similar even though their vibration amplitudes are somewhat different. It is demonstrated that the aerodynamic coefficients determined by numerical simulation can be used to investigate galloping behavior and anti-galloping techniques of overhead transmission lines. [ABSTRACT FROM AUTHOR]