constant for the analysis. In addition to the costs of electrical equipment, 

 the cost of cable support systems was considered. This cost, a direct function 

 of the size of the cable and its overall length, favors the selection of higher 

 voltage. For cable lengths of 600 to 2,000 feet, the cost of the suspension 

 system must include additional buoyant support to maintain the cable in a 

 vertical orientation. Therefore, a cost constant was assigned to the cable 

 suspension systems. 



An analysis of the two armor strengths included in the study indicates 

 that the 125,000-psi armor costs about twice as much as the 30,000-psi armor 

 and provides a cable load capability four times greater than that of the 

 30,000-psi armor. The results of the analysis indicate that the most cost 

 effective cable support system would be 30,000-psi armor for cable lengths 

 of 600 to 1 0,000 feet and 1 25,000-psi armor for cable lengths of 1 5,000 

 feet or greater. 



Table 13 presents the most cost effective transmission voltages 

 selected as a function of power level and cable length. The voltages indicated 

 in Table 1 3 are acceptable for applications requiring long-term usage at a 

 specific power level and installation. However, for general utility purposes, 

 a block of power level conditions at various cable lengths can be selected and 

 satisfied by one or two specific transmission voltages. 



Table 13. Selected Transmission Voltages for Various Cable Lengths 



Power Level 

 (kw) 



Cable Lengths (ft) 



600 



1,000 



2,000 



6,000 



10,000 



1 5,000 



20,000 



30,000 



30 



100 



300 



1,000 



3,000 



480 



480 



480 



4,160 



4,160 



480 



480 



480 



4,160 



4,160 



480 



600 



600 



4,160 



4,160 



600 



4,160 



4,160 



4,160 



13,800 



4,160 

 4,160 

 4,160 

 4,160 

 13,800 



4,160 



4,160 



4,160 



13,800 



13,800 



4,160 



4,160 



1 3,800 



13,800 



13,800 



4,160 



4,160 



13,800 



13,800 



13,800 



Protection System. The protection of electrical systems can be 

 extremely complex. For this study, a constraint was established which 

 limited the electrical protection to the underwater power transmission 

 systems, excluding the load module or the specific safety needs of the mis- 

 sion. 



For faults within the generation area, such as a generator or prime 

 mover failure, it was determined that the generator plant would shut down 

 while at the same time the emergency power system would be activated if 

 available. All other faults on the transmission cable or at the load module 



69 



