New multiphase transmission line model

This paper presents a new model to represent multiphase transmission lines in transient studies, including the frequency dependence of longitudinal parameters. The model uses the exact modes, for ideally transposed lines, and “quasi-modes” for nontransposed lines with a vertical symmetry plane. The frequency dependence is represented with synthetic circuits, with a cascade of π-circuit for each mode. A real transformation matrix is used for the entire frequency range and it is modeled through ideal transformers. The model is described for three-phase lines, double three-phase lines and DC lines. An application of the methodology is presented for a 440 kV single three-phase transmission line where some transients results simulated in EMTP are presented