Transient analysis of compact distribution lines with dielectric-coated phase cables

This paper studies wave propagation characteristics and the transient response of single-phase and three-phase compact distribution lines. Although compact line configurations present bare and dielectric-coated cables in relative proximity, it is shown that their external per-unit-length parameters can be calculated using simplified expressions valid for widely-spaced cables. An attempt is made to identify whether the insulating layer surrounding the phase cables must be included for an accurate simulation of switching and lightning transients on compact distribution lines. The results show that the dielectric coating reduces the propagation velocity of certain modes to values slightly below the speed of light. However, this reduction does not have a significant influence on the initial peak values of the calculated switching and lightning overvoltages. Only the wave tails of the resulting voltage waveforms are more strongly modified depending on the terminal conditions of the line.