Discussion at annual convention: Cable charge and discharge: Dielectric strength ratio between alternating and direct voltages: Cable geometry and the calculation of current carrying capacity

Abstract

J. B. Whitehead: The approximate exponential shape of the charge and discharge curves of composite dielectrics has long been recognized, and many efforts have been made to explain the departure of these curves from the pure exponential form, by various assumptions as to the structure of the dielectric in various arrangements of high resistance paths in conjunction with capacities. Several of these suggestions are in approximate conformity to the experimental observations of the charge and discharge curves as observed with continuous potentials. One of the simplest of all is that used by Dr. Steinmetz in which assumption is made of a very high resistance in series with a capacity, a number of such combinations being assumed with different relative values of the resistances and capacities. Another recent analysis of the problem has been given by K. W. Wagner who, with an entirely different method of approach, through a modification of Maxwell's suggestion of a mixture of two or more dielectrics, reaches the same conclusion as does Dr. Steinmetz, namely that the charge and discharge curves have one principal exponential term accompanied by one or more additional terms of relatively much smaller magnitudes.