The finite element method is a numerical technique for solving partial differential equations. Current rating calculations for power cables require a solution of heat transfer equations which define a functional relationship between the conductor current and the temperature within the cable and its surroundings.
Methods of solving the heat conduction equations are described in IEC 60287 (steady-state conditions) and IEC 60853 (cyclic conditions), for most practical applications. When these methods cannot be applied, the heat conduction equations can be solved using numerical approaches. One such approach, particularly suitable for the analysis of underground cables, is the finite element method presented PD IEC/TR 62095.
PD IEC/TR 62095 on ‘finite element method for current rating’ is useful for:
The current rating of the cable is defined as the maximum current carrying capacity of the power cable under normal operating conditions. The most important tasks in cable current rating calculations are the determination of the conductor temperature for a given current loading or, conversely, the determination of the tolerable load current for a given conductor temperature. In order to perform these tasks, the heat generated within the cable and the rate of its dissipation away from the conductor, for a given conductor material and given load, must be calculated.
For underground installations, the heat is transferred by conduction from the conductor, insulation, screens and other metallic parts. PD IEC/TR 62095 provides you with a heat transfer equation to quantify the heat transfer processes. PD IEC/TR 62095 also provides you with alternative numerical methods.
Graphs, detailed diagrams, and formulae have been provided in PD IEC/TR 62095 for a clear understanding of the finite element method for current rating. PD IEC/TR 62095 guidelines help you to calculate current rating in underground cables where regular formulae don’t apply. This helps you to provide practical power solutions to your customers and innovate new products.
IEC TR 62095:2003