In this paper the propagation of pulse wave on and the mutual coupling between conductors of a multi-conductor transmission system are analysed from the basic voltage and current equations. It is found from the analysis that on a completely transposed double-circuit three-phase system there will exist four pulse waves of different velocities originated from a system disturbance, and accordingly there will be four different values of the characteristic impedance. With these relations obtained, some peculiar phenomena of pulse wave propagation on lines can be explained, and the distortion, reflection, and refraction, etc., of waves can be computed according to given boundary conditions, thus giving theoretical support to practical measurements on lines. Examples are given to illustrate the method of analysis.The pulse wave propagation analysis is further extended to the steady-state alternating current operating condition, and equivalent sequence networks are derived for power system studies.