SG Undersea Cable System: Undersea System Power

The SG power-feed equipment is similar in system configuration to that which powers the SD1 and SF2 undersea cable systems previously developed and installed by the Bell System. As examples: (i) power-feed redundancy is achieved by connecting two load-sharing, independent, direct-current sources in series, with provision for the automatic assumption of the full load by the survivor should one current source fail, (ii) the cable is powered at each end with opposite polarities and a seaground power return, and (iii) the power supplies at both ends operate 2497 as current sources with their maximum output voltages restricted to be less than the voltage standoff capabilities of the repeaters. Despite the conceptual similarities among the SD, SF, and SG powerfeed systems, the techniques used to realize the system features have changed as the performance requirements have become successively more stringent and new circuit and physical design technologies have become available, or have been invented, to meet the performance requirements. Representative SG requirements are summarized in Table I. In this paper, we describe the SG power-feed system as applied to TAT-6, emphasizing the following new circuit and physical design features: (i) Inductive-input inverters in the power stages of the main power train. (ii) Pulse-position-modulation in the control and monitoring circuits. Table I -- Representative SG power-feed performance requirements for TAT-6 Output current: Nominal Set point resolution Variation within 24 hours Variation resulting from a ±1000-V load change Variation resulting from the failure of one of the two converters Output voltage: Nominal voltage Maximum voltage Tolerable earth potential Shutdowns: Current Voltage Alarms: Cable current Cable voltage Noise: Inverter harmonic tones Impulse (signal transmission path) 657.00 raA ±0.10 mA ±0.33 mA ±3.30 mA ±3.30 mA