Improved Assessment of Power Cable Thermal Capability in Presence of Uncertainties

In the current tight economic situation, power cable engineers are trying to squeeze as much current carrying capability as possible from the installed underground cables. In the Saudi electricity system, extensive usage of underground transmission and distribution cables is a reality. As the demand levels continue to increase, power cables are more loaded to meet the growing demand, which result in higher cable temperatures approaching the thermal limit of the cable. On the other hand, the cable thermal circuit parameters, such as soil thermal resistivity and ambient temperature, are subject to random variations which traditionally forced the power cable engineers to use more conservative designs with associated higher costs. This paper presents an improved technique for assessing the loading capabilities of power cables in the presence of randomness in various parameters representing the thermal circuit of the cable. The technique is based on the finite element simulations which yield accurate evaluation of the cable temperature. The resulting probability distribution of the cable temperature is then used to assess the risk factors associated with different loading levels of the power cable. A practical application is also presented for one of the underground cable systems used in the Saudi electricity system.