This paper presents the proposition and justification of a new method for determining the presence of defects in electrically conductive ferromagnetic and non-ferromagnetic elements of a power cable, based on the excitation effect by means of an alternating-current electric field of the spin-based polarization in electrically conductive structures. This paper proposes the modification of the original on-line detector functioning in the impedance comparator mode. This paper considers the structure flow-chart of the technical implementation of the new method of on-line quality control for power cables. In this case, monitoring can be carried out both on a moving and stationary cable. The proposed method greatly simplifies the control process by providing a non-destructive diagnostics of various cable types by appropriate replacement of the reference cable length and, accordingly, does not require field calibration of the measuring units to eliminate the temperature effect or other external factors.