The same pulsations take place in a tiiree-phase system in each of the 

 phases, but each phase of a three-phase circuit is separated by 120 electrical 

 degrees. When one phase is delivering zero power, the other two are supply- 

 ing the power requirements. Line losses are less in a three-phase circuit than 

 in a single-phase circuit. Three-phase circuits may be as much as 40% more 

 efficient. Conductor size and weight would be less for the three-phase circuit 

 for the same power level and cable length. A three-phase system was therefore 

 selected as the most cost effective for distributing AC power. 



Transmission Voltage. Transmission voltage is the most significant 

 electrical characteristic to be resolved since it will produce the most variation 

 in the cost and versatility of the basic electrical system. Incremental trans- 

 mission voltages of 480, 600, 2,400, 4, 1 60, and 1 3,800 volts were considered 

 appropriate for the study for cable lengths of 600 to 30,000 feet. Higher 

 voltages were only considered appropriate for long transmission cables in 

 excess of 10 miles, as required for shore-based plants. 



At each selected transmission voltage, the components and equipment 

 of the basic electrical system were added to the cable to arrive at an 

 acquisition cost. The acquisition cost was then compared for each possible 

 combination of transmission voltage, power level, and cable length. The 

 acquisition cost was used in this trade-off on the assumption that engineering 

 and deployment costs were the same for each voltage selected. The 5% 

 maximum voltage drop in the transmission cable created limitations in the 

 cost analysis of the selected voltage levels. 



Cable Connectors. The availability of connectors with respect to 

 voltage level and pin sizes was investigated in the selection of the most cost 

 effective transmission voltage. Wet connectors suitable for underwater mating 

 are nonexistent, and only a limited number of dry connectors are available for 

 underwater use at the power levels of interest. 



In an effort to reduce the number and types of connectors required 

 for the power transmission system, a study was conducted on the effects of 

 combining the secondary transformation and distribution equipment within 

 the load module. This concept would require high-voltage connectors and 

 hull fittings on the load module but would eliminate multiple sets of connectors 

 and hull fittings required on a separate hull for transformation and distribution 

 equipment. The separate pressure hull would also be eliminated. Consequently, 

 it was determined that it is most cost effective to transmit the higher voltages 

 directly to the load module. With this concept, additional weight and volume 

 requirements would be imposed on the load module. 



Electrical System Cost. A cost analysis was conducted on the 

 acquisition cost of the basic electrical system versus transmission voltage. 

 The costs of engineering, packaging, and protective circuits were considered 



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