Numerical Simulation Of Ice Shedding On Bundled Conductor Spacer System

Power system plays a great role in economic development of a country with transmission line transporting, regulating and distributing electric power as a lifeline project. External loads acting on transmission lines include wind load, seismic load, temperature load and uneven settlement of the foundation. Previous ice hazard investigations show that, ice load is one of the greatest threaten to transmission lines. Therefore, the study of loads induced by ice accreting and ice shedding on transmission lines is of great significance. Generally speaking, most power lines are bundle conductors. The response of ice-accreting and ice-shedding of bundle conductors due to the absence of spacers are more complex than that of single conductor. The analysis of transmission lines due to ice load in the past mostly goes to the single conductor but few to the bundle conductors, so, it is necessary to carry out the analysis of the response of bundle conductors due to ice load.Firstly, this paper comes up with a method of three dimensional finite element model of bundle-spacers system, and the equivalence problem of ice cover between bundle conductors and single conductor is studied, while an equivalent equation is derived. Then, the response of an existing three span transmission line with two kinds of uneven ice-shedding such as whole-span ice shedding and sub-span ice shedding from one sub-conductor in the middle span is also studied. Finally, by using finite element method, factors which influent the initial torsional stiffness is also emulated here.Results from this study show that, under the hypothesis of even ice-accreting, the displacement and stress of conductor after whole-span ice-shedding between bundle conductors and single conductor are equivalent, with the diameter and ice cover of single conductor√n times of those of bundle conductor. The maximum response of system after whole-span ice shedding always occurs in the middle of the ice shedding span, but the discipline after sub-span ice shedding is not so obvious. It is also found that the layout plan of spacers in bundle-spacers system due to controlling conductor galloping also helps to attenuate the torsion response of system after ice shedding. Initial torsional stiffness is the intrinsic attributes of bundles which have no bearing on the load from outside or the torsion angle of the system, but factors as the distance of sub-conductor and the level of conductor tension have a great effect on it.