Non-linear dynamics of electrical equipment cables

In power substations, electrical cables are commonly observed in configurations that cannot be explained by tension stress states only. Moreover, during extreme excitations such as earthquakes, they can be subjected to large displacements and rotations, as well as forces that can lead to failure of both the cables and the equipment to which they are connected. In this paper a three-dimensional geometrically exact beam model is presented and used to describe the static and dynamic behavior of electrical equipment cables. The model is implemented in MATLAB and applied to a flexible conductor recently tested at the SEESL laboratory at the University at Buffalo. Both static and dynamic numerical applications are performed. First the initial configuration of the tests is obtained by imposing the end displacements and rotations to a straight and unstrained cable. Then the cable is subjected to resonant harmonic out-of-plane and in-plane horizontal ground motions. Due to the high frequency components resulting from the axial response of the cable, and to the fact that the Newmark time-integration algorithm used herein generally fails to conserve energy, very small time steps are needed for the algorithm to converge. Although algorithms have been proposed in the literature, which introduce numerical damping to stabilize the computations, the introduction of real forms of damping in the model and the simulation of the dynamic experimental tests performed at the University at Buffalo are object of current work.