Combined Resonance Phenomena due to Earth Wires Grounding and Conductor Sagging Effects in Overhead Transmission Lines

摘要

The periodic discrete bonding of earth wires to ground, on the one hand, and the distributed conductor sagging between towers, on the other, are mechanisms that have been reported before to be individually responsible for abnormal high-frequency responses of overhead power lines. In this paper we consider both effects superposed and then evaluate, as a function of the frequency, the even and odd mode propagation parameters characterizing a given transmission line section. We show that the two interacting mechanisms being combined do not annihilate each other; on the contrary, wave interference effects accumulate giving rise to broadband noticeable resonance phenomena for frequencies such that the line span gets close to one half wavelength, typically in the 400-600 kHz range.