nautical miles were chosen as representative distances to reach the depths 

 selected for the study. Table 14 presents the selected AC or DC voltages 

 and includes all electrical costs, including costs for transformers, switchgear, 

 and conversion and inversion equipment. No system is shown for the 

 3,000-kw power level at 500 miles. This distance and power level must be 

 reached at a voltage level not considered practical with the present cable 

 technology. 



Table 14. Selected Voltages 



Power Level 

 (kw) 



Cable Lengths (miles) 



10 



50 



100 



500 



30 



100 



300 



1,000 



3,000 



4, 160 AC 



4, 160 AC 



13,800 AC 



13,800 AC 



13,800 AC 



13,800 DC 

 13,800 DC 

 13,800 DC 

 34,500 DC 

 34,500 AC 



13,800 DC 

 13,800 DC 

 34,500 DC 

 34,500 DC 

 34,500 DC 



34,500 DC 

 34,500 DC 

 34,500 DC 

 34,500 DC 



For shore-based plants, the available cable sizes are limited. The 

 maximum size of a three-conductor cable is determined by the maximum 

 diameter of the three conductors, the insulation requirements for the voltage 

 level, and the limitations of the cable manufacturing process. The minimum 

 cable conductor size required for each voltage level would be dictated by 

 voltage stress considerations. 



Voltage stress in a cable may be defined as the electrical pressure on 

 a unit thickness of insulation material and is usually expressed in volts per 

 mil thickness. The average value of voltage stress was determined by 

 dividing the voltage across the insulation by the insulation thickness in mils. 

 Voltage stress is not uniform in all parts of the insulation wall and is greatest 

 at the conductor-insulation interface. Voltage stress in any point of a cable 

 may be found by 



Voltage 



2.303 T log 



fe) 



72 



