Quasi-modes multiphase transmission line model

This article presents a new model to represent transmission lines including the frequency dependence of longitudinal parameters. The model uses the natural modes, for ideally transposed lines, and 'quasi-modes' for non-transposed lines, and is applied to lines that have a vertical symmetry plane. The line is represented through pi-circuits, with one pi-circuit for each mode. The transformation matrix is modeled using ideal transformers. The model is described for three-phase lines, de lines, double three-phase lines and six phase lines. A 440 kV three-phase transmission line illustrates it and is compared with a frequency dependent EMTP line model, the Semlyen one. (C) 1999 Elsevier Science S.A. All rights reserved.