Transient Thermal Response of Power Cables

This paper addresses procedures for power cable time-dependent rating calculations. Such calculations are required to obtain cable emergency ratings and also to observe the conductor temperature variations with time when subjected to variable loading. The calculation procedure is described in the IEC Standards 60853-1 and 2. A real difficulty in applying those procedures lies in an ability to take into account variation of the electrical resistances of the cable metallic components with temperature. The standard gives an approximate equation, developed by Goldenberg. However, this equation is applicable to a single current step applied to the cable. The paper shows that it cannot be easily applied to multiple current steps and proposes a new approximate algorithm providing an analytical solution to this problem. A comparison with a complex iterative procedure is also offered.