Evaluation of the longitudinal parameters of an overhead transmission line with non-homogeneous cross section

• Series-impedance for multi-conductor overhead transmission lines is computed.
• Skin and proximity effects are taken into account.
• The conductors sections are completely arbitrary.
• Earth can be filled with heterogeneous conducting materials.
• Earth topography is completely arbitrary.

This paper presents an accurate method to evaluate the longitudinal parameters of multi-conductor overhead power lines, taking in account skin and proximity effects. This method has the foremost advantage of considering a non-homogeneous ground, composed by separate layers with different conductivities and having surface irregularities, such as hills or valleys. The method splits the system conductors (line and ground) into smaller sub-conductors, with variable rectangular cross-section. The method is validated by comparing the longitudinal impedance results with those obtained using both analytical equations and other numerical methods proposed in the literature. Analytical results presented are concerned to a cylindrical two-wire line and one-phase overhead line. Using the proposed method results are obtained for one-phase overhead line, considering the ground with different conductivity layers and with different topographies.