Influence of soil humidity on the thermal impedance, time constant and structure function of underground cables: A laboratory experiment

The ampacity of power cables depends heavily on their ability to diffuse the resistive heating to the environment. This ability may vary significantly with time and is very sensitive to parameters such as soil moisture content, buried depth, cable arrangement and backfill material. Therefore, a downscaled laboratory model for an underground cable has been investigated experimentally with respect to these parameters. Having recorded the temperatures as a function of time, a dynamic thermal analysis has been conducted. Temperature curves are mathematically processed to provide the complex thermal impedance, thermal time constant distribution and cumulative structure function. Consequently, a theoretical analysis of the obtained results examines the relationship between the thermal impedance of the ground and the humidity, and explains the time constant distributions and the cumulative structure functions. (C) 2016 Elsevier Ltd. All rights reserved.