Mode domain multiphase transmission line model-use in transient studies

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. For the latter it is necessary to have a vertical symmetry plane. The frequency dependence is represented with synthetic circuits, with one π-circuit for each mode. The transformation matrix used for the entire frequency range is the Clarke´s one and as it is a real matrix it is modeled through ideal transformers. The model is described for three-phase lines and double three-phase lines. An application of the methodology is presented for a 440 kV single three-phase transmission line where it is made mode analysis, statistical energization and frequency scan analysis. The simulations are performed in EMTP with the proposed model and with a frequency dependent EMTP line model, the Semlyen one, supposing a transposed and nontransposed line