A new approach to underground cable performance assessment

This paper presents a new approach to thermal field sensitivities and ampacity computations of underground power cables using a proposed algorithm of perturbed finite-element analysis. The new approach involves the use of derived sensitivity coefficients associated with various cable parameters of interest, and use these coefficients to achieve optimal cable performance. The proposed model provides a quick methodology, based on the finite-element model, to assess the cable thermal performance subject to variations in the cable thermal circuit parameters. The developed algorithm was applied to various practical cable systems. The effect of multilayered thermal conductivities and boundary parameters variations on the actual cable system ampacity was investigated using the proposed methodology. A comparison was made of the obtained results with the conventional finite-element approach in order to show the applicability and usefulness of the developed methodology. Our objective was to assess the effects of operating parameter variations in a straightforward manner, without repeating the thermal field analysis for each parameter change. The thermal field of an underground power cable sample directly buried in the soil was measured in the laboratory using a developed full-size experimental setup. The investigations involve all parts of the thermal circuit parameters representing cable composition, surrounding soil and boundary phenomena. The experimental setup was used to validate the simulation model by comparing the simulation results with the real laboratory measurements. Such experimental verification confirmed the accuracy of the new introduced finite-element sensitivity methodology.