Application of Approximated Modal Analysis Methods for PLC System Design

In this paper recent developments rela ted to the analysis of electromagnetic waves propagation by means of modal analysis in H. V. transmission lines are presented. The developments showed here are concerned with the computation of the earth-return path impedance, pro posed earlier by Dubanton {1}, as well as the inclusion of the earth-wires in the impedance matrix. Three phase lines in horizontal and delta configuration (i.e. with centre-phase symmetry) are commonly used in H. V. and E. H. V. transmission. These lines are prone to modal cancellation phenomena. Formulae have been developed by Wedepohl for the calculation of their propagation constants and modal quantities. These formulae greatly simplify the computation of EM waves propagation. The graphical method proposed by Senn and Morf {2} and its application to assess coupling alternatives are discussed. This method is also used by the authors to evaluate non-conventional coupling arrangements.