POWER-FEED SYSTEM — XEWFOUNDLAND-NOVA SCOTIA LINK 291 



terminal stations were operating into their dummy loads and daily- 

 current and voltage readings were well within the required specifications. 

 Since the laying of the sea section the eciuipments have satisfactorily 

 operated the completed link. When the link is in service the working 

 equipment at each end will be changed at 6-monthly periods and the 

 change-over time will be staggered by three months each end. The equip- 

 ment coming out of service will be immediately routine checked and 

 adjusted if necessary. 



The tests since installation confirm the laboratory and factor}' results 

 that the regulation is better than ±1 ma for anj^ alternating input volt- 

 age from 195-265 volts in the frequency range 40-70 cj'Cles for output 

 voltages of to 3 kv. The relatively long correction period of the mag- 

 netic-amplifier control circuit (about 0.5 sec) is satisfactory with the type 

 of no-break supply installed at the stations. 



Another useful by-product of double-end feeding is that, when there 

 is a shunt fault on the system, the voltages supplied from the two ter- 

 minal stations give an indication of the fault position. Manj^ factors will 

 control the accuracy of the location, e.g. magnitude and position of the 

 fault, and how nearly the currents fed from the two ends are equal. 

 Calculations, confirmed by tests made with shunt faults introduced at 

 Terrenceville, show that any continuous shunt fault that will affect 

 transmission (to the extent of operating the 1 db pilot alarms) will be 

 detected to an accuracy of ±1 per cent. The limit is set by the accuracy 

 with which the link voltage distribution can be measured. 



CONCLUSIONS 



The power-feeding system described is suitable for submerged-re- 

 peater schemes that can, in an emergency, be temporaril}' powered from 

 one end only. For locations within reasonable reach of a central catas- 

 trophe-spare store the equipment should be sufficientlj' reliable not to 

 need duplication at both terminal stations. For future schemes this will 

 provide a method which is economically attractive compared with the 

 present single-ended methods and which offers numerous electrical ad- 

 vantages. 



The routine maintenance required on the power equipment could be 

 further reduced if the few remaining electron tubes were replaced bj' 

 electromagnetic components. On schemes where short interruptions to 

 traffic do not involve a relatively high loss of revenue it would then be 

 unnecessary for the local staff to maintain the high-voltage equipment 

 and the expensive no-break ac supplies could be abandoned. The latter 



