Wake-induced oscillations of two bundle conductors connected at intervals by spacers

Abstract

This paper discusses a finite element approach of modeling the wake-induced vibrations of the bundle conductors in transmission lines. An aeroelastic system consisting of two bundle conductors connected at intervals by spacers is considered. The wake coupling between subconductors is modeled with the modified Simpson’s theory. Deflection of an oscillating conductor from the straight line connecting a finite element ends is assumed to be small as compared with the element length; as a result the element tension can be estimated approximately as a constant as well as the tensile strain. The dependence of the strain on the transverse displacements is defined by the quadratic approximation. The coefficients of expansions of the element displacements and twisting angle in sine series with integer number of loops per element length are considered as generalized coordinates as well as their values at end points. The equations of motion of the conductor with nonlinear elastic, inertial and aerodynamic forces are formulated in the generalized coordinates, and the appropriate linearized equations for small aeroelastic oscillations around the static equilibrium position are derived. The latter equations allow one to determine the critical speed of the conductor flutter. Finally, bundled conductors’ susceptibility to wake-induced vibrations is illustrated on an exemplary twin- bundle, three-subspan model. Effects of bundle parameters and the means to account them when applying the approach are discussed.