Promoting cable ampacity by filling low thermal resistivity medium in ducts

The cable ampacity is closely related with its laying way and heat dissipation performance of the surrounding medium. With multi laying ways, the cable in ducts is the thermal bottleneck that constrains the whole cable line's ampacity. The cable conductor temperature could be reduced and the current-carrying capacity of the duct laying cable could be enhanced by filling medium with low thermal resistivity in duct. By ampacity calculation software which is tested in experiment of cable ampacity, the cable ampacity in different laying way and arrangement condition is calculated in this paper, and the relationships between thermal resistivity of the filling medium in the duct and the cable ampacity is analyzed. Meanwhile, the ampacity experiments of duct laying are carried out in the test field and operation lines which has a normal segment and a segment with duct filled with low thermal resistivity medium. Experiments and research show that the cable ampacity can increase by about 8 percent by filling this new material into the single-loop duct.