Electrical conductors must be shielded to provide symmetrical radial 

 voltage stress distribution within the insulation and to eliminate tangential 

 and longitudinal voltage stress on the insulation surface. Tangential and 

 longitudinal voltage stress causes surface cracking and discharge to ground. 

 Shielding maintains a zero potential on the surface of the cable for the safety 

 of personnel and provides protection against lightning and switching surges. 

 The shield should be of conduction tape or wire material for increased fault 

 current capacity. Copper was selected for the shielding material, with the 

 shielding applied to each conductor of the three-conductor cable. 



Since each conductor of the cable would be shielded and grounded at 

 both ends, the first order of faults, if they occurred, would be phase to ground. 

 The important factor to consider in grounding a cable system is to detect 

 ground faults and effectively clear the faulted section from the source of 

 power. In the absence of an effective way to detect low ground currents, the 

 system should be effectively grounded to provide faults of greater magnitudes 

 for faster actuation of the system's protective equipment. 



Splicing of the three-conductor power transmission cable was not 

 considered necessary since the cable would connect directly to the power 

 source and the load module. The splicing, if required, would be by special 

 undersea connectors. 



Mechanical Properties 



The most important consideration in planning cable deployment for 

 minimum risk of damage is the selection of the cable route. Studies of cable 

 fault records indicate that many of the deep sea cable breaks occur where 

 cables pass over seamounts, canyons, and areas susceptible to turbidity 

 currents. 



Table 1 1 illustrates the frequency of cable casualties as compiled by 

 Bell Telephone Laboratories. Approximately 50% of the cable damage is 

 attributed to breaks caused by fishing trawlers and a majority of these in 

 depths less than 1 ,800 feet. 



The fundamental requirement in cable laying is to deposit sufficient 

 lengths of cable commensurate with the irregularities of the ocean bottom. 

 The most detailed knowledge of the bottom typography and of cable-laying 

 techniques is required to avoid introducing dangerous cable suspensions and 

 laying excess cable slack. 



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