Multiphysics approach to the boundary problems of power engineering and their application to the analysis of load-carrying capacity of power cable line

Many electrical problems involve the simultaneous solution of equations from different physical domains, i.e. require multiphysics solution. Multiphysics problems are typical for many electrical applications. Most of difficulties arising here are subject of study and classification. For example, for multi-physics analysis is typical to combine several physical models with different level of details. Another complicating factor is multiscaling, i.e. significant difference in space or time scale between different physical domains. The numerical strategy for multiphysics problem depends heavily on the assumptions made and level of physical details taken into account. In the paper some features of multidisciplinary problems are considered, typical problems are classified, and an approach to the solution is outlined. As a typical multiphysics problem we consider the modelling of current carrying capacity of underground three-phase power cable line. Such analysis demands the solution of the electromagnetic field equations, Kirchhoff´s equations for grounding circuitry, and the heat transfer equations coupled together. Each physical domain can be modeled with appropriate level of details. Several variants of geometric location of single-phase cables of three-phase are considered: in line, in triangle, and with separation of one phase from two others. One-sided and two-sided grounding of cable shield and armor is taken into account. The conducted study validates a number of the engineering simplifications, which are typical for multiphysics problems in the electrical engineering.