A general method for predicting the electromagnetic interference field (EMI) performance from HV transmission lines has been proposed. The developed method utilizes a direct modal analysis using frequency dependent, electrical transmission line parameters. Carson's equivalent conductors representing the earth return were included in the line parameter calculation. The impact of transposed and untransposed lines on the EMI has been studied. Transposition has been represented with two models, namely, the equivalent model and the physical model;The EMI has been analyzed using the quasi-static method and the radiation method. The radiation method has been introduced to extend and validate the study of EMI spectrum to FM and television frequencies;A Fortran computer program has been developed. This program calculates the EMI based on the minimum input data.