Investigation on the improvement method of ampacity for cable in duct bank: Using the mixed filler with high thermal conductivity material and phase change material.

• The simulation model of cable in duct bank with mixed filler was built. • The improved thermal model of cable in duct bank with mixed filler was proposed. • The accuracy of the improved method was verified by the real cable test. • The cable ampacity improvements of using different mixed fillers were discussed. • The basis for determining the performance of mixed filler was provided. Duct laying is a common cable laying way for the case of not meeting excavation conditions. However, due to the slow air flow rate in the duct, the cable section laying the duct becomes one ampacity bottleneck. Backfilling the duct with the mixed filler of high thermal conductivity material and phase change material is an effective method to solve the problem. In this paper, the simulation models of cable in ducts with backfilling the mixed filler were used to analysis the effect of relative position of cable and duct on temperature distribution and guide the thermal modeling of external environment. Then, the thermal model of cable in duct was conducted and the layered method was adopted to optimize the model. The real cable experiment was designed to verify the accuracy of proposed model. The improvement effect of mixed filler with different thermal conductivity and phase transition region on the cable ampacity were discussed by using the proposed model. The investigations in this paper show that the use of mixed filler material can have a great contribution to ensure the safe operation of cable in duct. [ABSTRACT FROM AUTHOR]