Analysis of influential factors on the underground cable ampacity

The extensive usage of underground cables is a typical feature of modern power distribution networks. To analyze the influential factors on the underground cable ampacity, a new numerical method to calculate the ampacity of the underground cable is described in this paper. It is programmed by COMSOL software, which is based on the principle of heat transfer and the Finite Element Method. This model completely takes into account the local cable conditions and complicated variable external environments. Its parameters can be updated according to the change of these influencing factors. The developed model is applied to analyze the impact of the different influential factors on the underground cable ampacity. The results show that the underground cable ampacity depends on many of the installation properties and conditions, of which the soil thermal resistance, the environment temperature, the laying way (the cable spacing and the cable number in the trench) and the external heat source are the main factors. The underground cable ampacity increases with the increase of the soil thermal conductivity and the distance from the external heat source, while it decreases linearly with the increases of the environment temperature.