Traveling wave voltages in cables

WHEN a traveling wave on an overhead line reaches a cable, a wave of reduced voltage passes into the cable. This reduction is due to the fact that the surge impedance of a cable is less than that of an overhead line. In a traveling wave the electrostatic energy is equal to the electromagnetic energy, and the constants of a cable are such that the voltage of a traveling wave has a lower ratio to the current than in the case of a wave on an overhead line. After the wave enters the cable there are voltage and current reflections back and forth from each terminal. If the length of the original wave is great enough, there will be several superimposed waves at each point in the cable. The sum of these several waves will be dependent upon the shape of the original wave as well as upon the reflections.