Measurements of communication signal propagation on three phase power distribution lines

Abstract

Measurements of voltages and currents for distribution line carrier signals on a three-phase power distribution network are presented. Both symmetric and asymmetric lines are used under loaded and unloaded conditions. The measurements were made at 25 kHz on an unenergized 20847 ft overhead distribution line test site. The measurements show the existence of standing wave patterns on three-phase lines. Except in the simplest cases these standing waves patterns are difficult to predict using classical two-wire techniques along with the intuition, heuristics or Smith charts. There is significant interaction between phases. One phase can draw a disproportionate amount of current from the source; this is especially true when one of the phases is an odd number of quarter wavelengths. >