In considering the tentative results of the analysis, it should be kept 
in mind that the probable method of final power application to working tools 
at the bottom will be hydraulic, in the interest of reliability. The calculated 
efficiency of transmission may not reflect the desirability of asystem. A 
seawater hydraulic system pumping filtered water from the surface and using 
(and discharging) the water at the tool will require no later conversion and 
would therefore provide what appears to be a very simple and probably highly 
reliable system. On the other hand, presently available hydraulic motors are 
not adapted to use of a nonlubricating fluid such as seawater; development 
necessary to make the system feasible is currently underway (NCEL, 1969). 
The proposed taut cable systems would require a minimum of development 
for adapting existing oil well equipment and could develop high pressure in 
a hydraulic system with any type of fluid. 
Comparison of Electrical Systems 
The three-phase alternating-current system (Figure 1) and the 
single-conductor direct-current system (Figure 2) were analyzed using 
several different wire gages to deliver a terminal voltage of 440 volts and 
4,160 volts. 
The performance of the three-phase AC system was calculated using 
the basic equation: 
P = /3Elcos¢ (1) 
where P = power (watts) 
E 
| 
i 
voltage 
current 
@ =phase angle 
Balanced Y-connected loads were assumed and the slight line capacitance was 
disregarded. Figure 3 displays the various effects of wire size on a system with 
a terminal voltage of 440 volts AC. To reach at least 50% efficiency, OO-gage 
wires must be used. However, as seen in Figure 4, at 4,160 volts number 6 
wires will function with over 94% efficiency and number 14 wires will operate 
with an efficiency of 74%. The three-phase system, although performing with 
high efficiencies, has to insulate high voltages from a salt water environment. 
However, this voltage leakage problem is not as severe in the three-phase sys- 
tem as it is in the DC system. 
