Thermal environment design considerations for ampacity of buried power cables

The design and successful operation of underground power cable systems depend on a good understanding of the soil thermal characteristics along the cable route and the backfill materials that are put back in the cable trench during construction. Carefully evaluating these design considerations helps insure that the cable system will be able to achieve its full design capability and desired rating while assuring long-term operation without accelerating the thermal aging of the cable system. This paper summarizes the basic civil design considerations needed for cable ratings (ampacity) and how this important cable system parameter strongly relies on the proper characterization of the soil thermal resistivity (TR) and ambient temperature.