Z-transform electromagnetic transient analysis in power systems

The paper develops a new electromagnetic transient formulation for multiconductor power transmission lines based on the z-transform. Beginning with the basic relationships of propagation in the frequency domain, the successive steps of z-transform analysis are developed leading to recursive sequences for solution in the time domain. The case of lossless propagation is considered initially in introducing z-transform analysis in its application to transmission-line electromagnetic transient evaluations, following which a general formulation is derived into which series-path line parameter frequency-dependence is directly reflected. Test analyses based on a z-transform model complemented by a simplified equivalent-source representation and applied to a 160 km, 400 kV untransposed single-circuit transmission line confirm the high inherent accuracy and low computing-time requirements of the method.