This paper presents a computational analysis of the difference between the values of the self parameters (resistance, inductance and potential coefficient) of some typical transmission lines. The earth return effect is included. A new coefficient of unsymmetry for the untransposed transmission line parameters is proposed. The wave mode parameters as a function of the given coefficient of unsymmetry are deduced.The balancing of the parameters of both transposed and untransposed lines is applied. The percentage error in the calculated voltage at any point of the untransposed line, if considered as transposed, is formulated.