Radio Interference Studies on Extra-High-Voltage Lines

Investigations were carried out to determine the long-time average radio interference levels on ehv power lines. From an analysis of a large number of records, frequency distribution curves and typical r.i. levels for different weather conditions were established. The nature of line corona generation was studied oscillographically. Positive corona was found to be responsible for interference from conductors. Also, for a horizontal single-circuit construction, the centre phase conductor appeared to be the main contributor to the line noise. The tower proximity effect was found to be significant for both wood and steel structures. To aid in obtaining a correlation between a short and long line, lateral profiles for the test line were obtained and compared with those for operating lines. The effect of standing waves was also studied using artificial noise sources placed at a node and autinode points for a resonant frequency, and observing the behavior of the line and ground nodes.