On-line Computation of the Underground Power Cable Core's Temperature and Ampacity based on FEM and Environment Detection

Dynamic line current rating and real time cable core's temperature have been proved to be the promising solution to increase the rating capacity of underground power cables. But the variation of environment temperature and the soil thermal resistance bring the difficult to realize the work. In order to detect the environment condition, a detect system was designed to monitor the real time environment temperature, the wind velocity and a setting point temperature in soil. The environment parameters were transmitted to the host computer by GPRS. With a hypothesis soil thermal resistance, FEM was used to analyze the temperature field of underground power cables in the host computer based on the environment parameters under given current condition. By iteration method, the real soil thermal resistance was confirmed when the setting point temperature in soil was equal to the FEM result. Therefor, the cable core's temperature was calculated by transfer matrix and the on-line current rating was solved by FEM.