New mode domain multiphase transmission line model applied to transient studies

This article presents a new model to represent multiphase transmission lines including the frequency dependence of longitudinal parameters. The model uses exact modes, for ideally transposed lines, and “quasi-modes” for nontransposed lines with a vertical symmetry plane. The line is represented through a cascade of π-circuits, with one π-circuit for each mode. The transformation matrix used is real and is modeled with ideal transformers. The model is described for three-phase lines, DC lines and double three-phase lines. An EMTP implementation of a 440 kV three-phase transmission line is performed to illustrate the model and a comparison with a frequency dependent EMTP line Semlyen model is made