MODAL PARAMETERS AND FAULT TRANSIENTS IN DOUBLE-CIRCUIT TRANSMISSION LINES: ON THE EFFECTS OF CONDUCTOR TRANSPOSITION, SHIELD WIRES, AND LOSSY SOIL MODELING
ATP/EMTP, conductor transposition, transmission line modeling, electromagnetic transients, frequency-dependent soil, modal parameters, sequence parameters, shield wire modeling.
This work analyzes the impact of conductor transposition, shield wires, and soil modeling on modal parameters of a double-circuit transmission line. Computational modeling routines are developed to represent transmission line parameters span by span, capturing parameter variation along the right-of-way. The circuit model is constructed using EMTP-type software, considering impedances and admittances calculated to account for conductive and displacement current eects on lossy earth. Transient studies are performed on a real 500 kV double-circuit transmission line, considering various scenarios of soil resistivity, transposition and shield wire modeling. Faults are applied at every 1% of the power line, which represents 100 faults per scenario. Results shows that a single average of deep-layer resistivity accurately represents heterogeneous resistivity distribution along the line, with less than 1% discrepancy. Transposition schemes rotating phases in opposite directions result in lower short-circuit currents, improving safety. The use of Kron reduction, as traditionally performed in line parameters calculations, yields conservative results in comparison with the realistic modal-decomposed model, overestimating fault branch currents and short-circuit contribution currents by 0.9 p.u. (600 A). Shield wire currents can reach up to 1.8 kA, highlighting their signicance in transmission line modeling.