Effect of Concrete Duct Bank Dimension with Thermal Properties of Concrete on Sensitivity of Underground Power Cable Ampacity

Concrete duct banks have been used for protecting underground power cables from mechanical damage and for improving cable performance. Underground cable performance indices with parameters of the maximum cable temperature and ampacity are functions of installation conditions. In this work, the steady-state ampacity of an underground power cable system was evaluated by variation of concrete duct bank dimensions. To analyze ampacity dependence on temperature, a thermal model was developed with a two-dimensional finite element method. The system for simulation is a concrete duct bank installation containing power cables in casing pipes. The results show that the cross-sectional area allows a variation of cable spacing parameters. This is the most significant factor influencing ampacity because increased cable spacing can reduce the effect of Joule heating from neighboring cables. Reducing concrete resistivity also results in improved cable ampacity. However, this leads to the increased construction costs. Therefore, to improve ampacity of duct bank underground cable, the cross-sectional area for high ampacity must be balanced against increased construction costs. This is important for designing concrete duct banks.