Transmission Line Transients

There is great need for a better understanding on the part of transmission engineers of the traveling waves on lines. The complete analysis of such waves is inherently complicated, but there are certain approximate relations by which the progress of waves on our ordinary systems may be readily studied. Before any theory is accepted for practical use, however, it is necessary to check it carefully by experiment. This paper gives quantitative checks of the principal aspects of the theory of the traveling waves due to suddenly applied continuous potentials, as originally given by Heaviside. It is shown that this theory based on fixed line constants predicts accurately the progress of waves as far as magnitudes, speed of propagation, and shape of wave except at the wave front are concerned. The effect of steepness of wave front is discussed with relation to its practical aspects. It is proposed to follow this paper shortly with similar results on alternating-current transients. Tests on artificial lines and on an aerial line in the field are compared with computed results. Working rules for considering the progress of transients are discussed, together with certain results that may be obtained by their use. An extension of approximate analysis is given in an appendix, which is sufficiently accurate for transmission lines of the present length, and which is sometimes easier to handle than the complete theory. Reflections at apparatus, and at line junctures, is discussed qualitatively. There are several cases in which extreme potentials may arise.