Seismic Interaction in Cable-Connected Equipment Items

An electrical substation consists of a complex set of equipment items that are interconnected through conductor buses or cables. If the connections are not sufficiently flexible, significant dynamic interaction may occur between the connected equipment items during seismic excitations. This paper investigates the effect of interaction between two equipment items connected by a cable conductor. Analytical as well as large-deformation finite-element analyses are used to determine the nonlinear response of the cable-connected system to selected ground motions. Influences of the cable geometry and its axial extensibility, flexural stiffness, and inertia on the interaction effect are evaluated. It is found that the interaction may significantly amplify the responses of the equipment items relative to their stand-alone responses when the cable lacks sufficient slack. The amplification can be particularly large for the higher frequency equipment item. A parameter for predicting the interaction effect is introduced and evaluated for a large set of example systems.