A simplified real frequency independent modal transformation for overhead line switching transient computations

Modal transformation technique is a common tool for transmission line transient computations. A simplified modal decomposition of overhead transmission lines, suitable for time-domain switching (up to IO’ Hz) transient computations, is proposed. By neglecting residual terms in the ZY matrix. transformation matrices are approximated as real and frequency independent. The resulting propagation constants remain unaffected from the line being transposed or not, although the existing asymmetries affect transformation matrices. The method can be extended for double circuit lines, provided they have the same configuration. Propagation characteristics, mode decoripling and travelling-wave transmission effects have been investigated. Results are compared with those obtained from other methods in use.