This report presents new concept for modelling of high-voltage and extra-high voltage transmission systems, which provide higher accuracy for modelling of underground cables. The growing worldwide demand for electricity influences the transmission system in a way that requires the upgrade and construction of new transmission lines. Also, the high degree of urbanization, the growth of the cities and the social discontent with living nearby overhead lines leads to gradual transition from overhead lines to underground cables at all voltage levels. This paper presents the discrepancies between the real-world situation and the mathematical model due to the specific operation, construction and environment of the cable lines.
