  This paper presents a detailed modeling and analysis regarding the dispersion
characteristics of multilayered open coaxial waveguides. The study is motivated
by the need of improved modeling and an increased physical understanding about
the wave propagation phenomena on very long power cables which has a potential
industrial application with fault localization and monitoring. The
electromagnetic model is based on a layer recursive computation of
axial-symmetric fields in connection with a magnetic frill generator excitation
that can be calibrated to the current measured at the input of the cable. The
layer recursive formulation enables a stable and efficient numerical
computation of the related dispersion functions as well as a detailed analysis
regarding the analytic and asymptotic properties of the associated
determinants. Modal contributions as well as the contribution from the
associated branch-cut (non-discrete radiating modes) are defined and analyzed.
Measurements and modeling of pulse propagation on an 82 km long HVDC power
cable are presented as a concrete example. In this example, it is concluded
that the contribution from the second TM mode as well as from the branch-cut is
negligible for all practical purposes. However, it is also shown that for
extremely long power cables the contribution from the branch-cut can in fact
dominate over the quasi-TEM mode for some frequency intervals. The main
contribution of this paper is to provide the necessary analysis tools for a
quantitative study of these phenomena.
