Figure 5. Overhead line and Underground cable parameters.
For simplicity and without much loss in accuracy, multiple PI sections model have been used have been to represent both transmission lines and cables. Derivation of the underground cable PI section has been done as [29]. As a rule of thumb, each individual PI section should not be longer than (1) [27].
\begin{equation} \text{\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ }L_{\max}=\frac{v}{5\times f_{\max}}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ (1)\nonumber \\ \end{equation}