Computation of transmission line parameters for power flow studies

This work presents a general and simple method to obtain a single multiphase equivalent pi-circuit, suitable for power flow studies that takes the coupling effects into account for any line transposition scheme. The resulting circuit, suitable for use in connection with multiphase power flow programs is obtained from node reduction of all cascaded multiphase pi-circuits, each one representing the section in between transposition towers. For conventional power flow programs, symmetrical component coupled circuit parameters are obtained as well. A study carry out for a Brazilian electrical utility, in which two 230 kV transmission lines run at the same tower between Paulo Afonso and Fortaleza substations (678.90 km long), is presented. Power flow results have shown that the reactive power is strongly affected by the coupling between the two transmission lines