The optimum design of an electrical distribution system (EDS) is based on the profound understanding and measurement of its thermal behavior, because this determines wire diameter and insulation material, has a major impact on the fusing strategy, and enables minimizing technical risk. Current methods of calculation require an extensive database, whereas the temperature measurements at selected points with normal sensors allow neither the precise rating of the actual insulation temperature within a wire bundle, nor the determination of the thermal impact of load currents.The presented approach is based on both a new measurement method and on a related evaluation algorithm. A common automotive wire is applied as a sensing device using its resistance temperature coefficient as the measurement principle. Sectioning of the wire provides the required spatial resolution, and variation of the measurement current determines both the thermal dynamic behavior and the impact of electrical losses. A model-based algorithm allows the non-destructive evaluation of overcurrent scenarios and the thermal rating of the other wires within the bundle. The paper presents initial experimental data followed by a discussion of the next steps and future potentials.