Analysis of the Effect of Soil Thermal Resistivity on High-Voltage Cables Sizing

The determination of the ampacity of high voltage cables is most often done by standard, rather than measured values of soil thermal resistivity, as shown by a study published in a CIGRE technical brochure [1]. Since the sizing approach is generally conservative, cables tend to operate far below their transmission capacity [2]. The progressive increase of load, as well as the employment of cables in bulk power transmission requires a good knowledge of their thermal behavior as early as at the design stage, and the large capital investments require their optimum operation and the use of their full transmission capacity without risk of thermal failure. This paper presents case studies on the sensitivity of cable ampacity to soil thermal resistivity and analyzes the need for experimental verification to more accurately identify the initial computational conditions [3].