Power Line Carrier for Relaying and Joint Usage---Part I

1. Carrier relaying according to the present practice, or the equivalent, is needed, particularly, but not exclusively, for ground faults, and will be increasingly needed with adaptations for automatic reclosing and multiterminal lines. 2. Joint usages, which may be adopted in various degrees, will alleviate spectrum crowding, and for many installations such usages will provide either reductions in installation and maintenance costs, or improved performance, or both. 3. Various types of carrier control and modulation are available. 4. The problems of carrier transmission and reception can be discussed qualitatively, but quantitative knowledge is meager. 5. In comparing carrier types or systems there are distinctive characteristics in each, both as to function and performance, which may be advantageous. 6. The choice between the available systems will depend largely on the functional characteristics desired, but it appears that there are undeveloped potentialities in each, and possibilities of making combinations. 7. The nonrelay usages vary in their requirements, making each application a distinct problem. 8. Present standard relaying equipment provides for limited joint usages of a single carrier signal with possible consequences which do not seem to be generally recognized, namely, the wide receiver acceptance band, with corresponding inefficient use of carrier energy and spectrum space, and incomplete carrier control by primary relays. 9. Carrier relaying needs to evolve to meet new problems. Suggestions along that line, including solutions to the primary relay control problem, will be offered in the second paper.