It is clear that during the manufacturing of the windings of an electric motor, enamel-insulated copper conductors are subjected to mechanical strain. The electrical performance of the enamel insulation could be adversely affected by this mechanical strain. Partial discharge inception voltage (PDIV) is a useful tool for comparing the performance of insulations. Therefore, PDIV tests along with breakdown voltage tests were performed for evaluating the effect of different levels of tensile-strain on the electrical properties of the enamel insulation of the copper conductor. In a previous work the enamel insulation was tested between two parallel-plate electrodes. In this study, however, unstrained and tensile-strained, enamel-insulated, copper conductors with rectangular cross-section were investigated and compared for their breakdown voltages and partial discharge behavior in a carbon powder medium.