Radio Interference from Isolated Noise Sources on Overhead Transmission Lines

An isolated noise source such as a cracked insulator on a multiconductor overhead EHV transmission line produces an electric field adjacent to the line by two separate paths. One is the transmission of the noise voltage along the line causing a lateral field and the other is the direct radiation from the source acting as a dipole antenna. The theory of natural modes has been applied to determine the line field while ordinary antenna theory has been used in the determination of the antenna field. The calculations have been carried out with a digital computer for a single circuit horizontal line although the program developed is general and applicable in the analysis of a practical line of any configuration and make up. It has been shown that the transmission line functions as an induction umbrella where the line field is strong and outside which the antenna field is predominant.