Earth-Current Effects on Communication-Cable Power Subsystems

Earth potentials can be a serious threat to cable systems in areas of high magnetic-field activity. This paper describes analytical techniques for evaluating actual system susceptibility and precautions for minimizing outages The power equipments that energize modern, wideband cable-communication links are more vulnerable to this phenomenon than were the earlier versions. Recently, shutdowns have occurred in both landand sea-cable systems and fires have been started in communicationplant power equipments in Scandinavian countries where high-intensity magnetic distrubances occur. Analytical methods, which have been devised by magneto-teiluric prospectors for making deep soundings into the earth, have been adapted for estimating the amount of earth potential that would be applied to the power apparatus associated with communication cables. Results are presented showing the level of earth potentials which are developed and the mode of failure associated with the cable power equipment. Effects on both land and undersea cables are presented, and transatlantic cables are specifically discussed.