To evaluate the seismic responses of bundled conductor interconnected electrical equipment, a model of the interconnected system was established. The bundled conductor model was incorporated into the interconnected model, and the electrical equipment was simplified as a 5-degrees of freedom structure. The bending stiffness of the sub-conductor and the constraint effects of the spacer, usually omitted in previous research, are considered in the paper. The iteration method was used to obtain the terminal forces and moments of the bundled conductor. Then, the model was validated by shaking table tests. We investigated the effects of the slackness and bending stiffness of the bundled conductor on the seismic responses of the interconnected system. Considering the bending stiffness of the sub-conductor and the effects of the spacer, the seismic response characteristics of the interconnected electrical equipment were much different from those connected by a flexible conductor without bending stiffness in previous research. Not only the terminal forces, but also the terminal bending moment should also be considered in the seismic performance evaluation of interconnected electrical equipment.