function of $L$ for $L>\lambda$. For what matters $R^{CM}$, its trend with the line length is logarithmic. Hence, $r^{CM}$ can be approximated with a piecewise constant value in order to correspond to a $R^{CM}$ with a piecewise linear trend. The number of approximation segments has to be chosen based on a trade-off between the computational complexity and the desired accuracy of the results.

Mode conversion and discontinuities {#sec:network_discontinuities}
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In this section, we explain the causes of mode conversion in power line networks, which eventually foster electromagnetic radiation and deteriorate the quality of the signal transmitted through the power line.

The main source of mode conversion in any electric or electronic circuit is system imbalance. Perfectly symmetric cables, circuits and loads would allow an independent transmission of CM and DM signals. While in integrated circuits advanced design strategies permit the physical minimization of mode conversions, few can be done in PLN, since there is no control on the wiring infrastructure, and only the load impedances corresponding to the power line modems can be optimized. Hence, the task of PLC engineers is not much about the minimization of the asymmetries, but it is more about the understanding of mode conversion and 