Inductive Co-ordination of Common-Neutral Power-Distribution Systems and Telephone Circuits

Early installations of 3-phase 4-wire power distribution systems of the multigrounded or common-neutral type in some cases created noise problems involving neighbouring telephone circuits. Operating experience, studies of specific situations and comprehensive co-operative research over a period of years have developed means of largely avoiding difficulties of this character. The relative importance of various features of the power and telephone systems which have been found to affect the noise-induction problems involved is discussed here, and the general co-operative procedures most helpful in conversions to, or extensions of, these types of power distribution systems, are outlined.