During the manufacturing of the windings of an electric motor, enamel-insulated copper conductors are subjected to mechanical strain. This strain may adversely affect the electrical performance of the enamel insulation. Partial discharge inception voltage is useful for comparing the performance of insulations. Therefore, experiments were done in evaluating partial discharge inception voltages in order to determine the effect of different levels of tensile-strain on the electrical properties of the insulation system. Within the scope of this study, unstrained and tensile-strained, enamel-insulated, copper conductors with rectangular cross-section were investigated and compared for their breakdown voltages and partial discharge behavior.