Modal analysis is widely approached in the classic theory of transmission line modeling. This technique is applied to model the three-phase representation of conventional electric systems taking into account their self and mutual electrical parameters. However the methodology has some particularities and inaccuracies for specific applications which are not clearly described in the basic references of this topic. This paper provides a thorough review of modal analysis theory applied to line models followed by an original and simple procedure to overcome the possible errors embedded in the modal decoupling through the three-phase system modeling. © 2012 IEEE. Dommel, H.W., A method for solving transient phenomena in multiphase system (1966) Proc. of Power System Computation ConferenceDommel, H.W., Digital computer solution of electromagnetic transients in single and multiphase networks (1969) IEEE Trans. on Power App. and Systems, PAS-88 (4)Tavares, M.C., Pissolato, J., Portela, C.M., Mode domain multiphase transmission line model-use in transient studies (1999) IEEE Trans. on Power Delivery, 14, pp. 1533-1533Wedephol, L.M., Nguyen, H.V., Irwin, G.D., Frequency-dependent transformation matrices for untransposed transmission lines using Newton-Raphson method (1996) IEEE Trans. on Power Systems, 11 (3), pp. 1538-1546Mingli, W., Yu, F., Numerical calculations of internal impedance of solid and tubular cylindrical conductors under large parameters (2004) IEE Proc. Gener. Transm. Distrib, 151 (1), pp. 67-72Dommel, H.W., (1989) Electromagnetic Transients Program Reference Manual (EMTP Theory Book), , Vancouver, Dept. of Electric Engineering, University of British ColumbiaCampos, J.C.C., Pissolato, J., Prado, A.J., Kurokawa, S., Single real transformation matrices applied to double three-phase transmission lines (2008) Electric Power Syst. Research, 78, pp. 1719-1725Gustavsen, B., Semlyen, A., Simulation of transmission line transients using vector fitting and modal decomposition (1998) IEEE Trans. Power Del., 13 (2), pp. 605-614. , AprMarti, J.R., Accurate modeling of frequency-dependent transmission lines in electromagnetic transients simulations (1982) IEEE Trans. on Power App. and Systems, PAS-101, pp. 147-157Morched, A., Gustavsen, B., Tartibi, M., A universal model for accurate calculation of electromagnetic transients on overhead lines and underground cables (1999) IEEE Trans. Power Del., 14 (3), pp. 1032-1038. , JulCosta, E.C.M., Kurokawa, S., Pissolato, J., Prado, A.J., Efficient procedure to evaluate electromagnetic transients on three-phase transmission lines (2010) IET Gener. Trans. & Distr., 4, pp. 1069-1081Costa, E.C.M., Kurokawa, S., Prado, A.J., Pissolato, J., Proposal of an alternative transmission line model for symmetrical and asymmetrical configurations (2011) Int. Journal of Elec. Power & Energy Sist., 33 (8), pp. 1375-1383Prado, A.J., Kurokawa, S., Pissolato, J., Bovolato, L.F., Step by step analyses of Clarke's matrix correction procedure for untransposed three-phase transmission line cases (2010) Proc. IEEE/PES General Meeting, , MinneapolisBudner, A., Introduction of frequency-dependent line parameters into an electromagnetic transients program (1970) IEEE Trans. on Power App. and Systems, 89 (1), pp. 88-97Wilcox, D.J., Numerical Laplace transformation and inversion (1978) Int J. Elect. Eng. Educ., 15, pp. 247-265Prado, A.J., Pissolato, J., Kurokawa, S., Bovolato, L.F., Modal transformation analysis for double three-phase lines (2007) IEEE Trans. Power Del., 22, pp. 1926-1936