POWER-FEED SYSTEM — NEWFOUNDLAND-NOVA SCOTIA LINK 283 



with normal double-end feeding, the broken lines (a) and (6) show 

 the distribution with single-end feeding from Sydney Mines and Claren- 

 ville respectively and the broken line (c) shows the distribution when a 

 power ground is connected at Terrenceville. 



DETAILS OF EQUIPMENTS 



Connection of the Equipment to the Cable 



Each station is provided with two power equipments and one cable- 

 terminating equipment interconnected as shown in Fig. 4. When the 

 live side of the output of the regular equipment is connected to the 

 cable via SWD and the link LKl, the alternate equipment output is 

 connected to its own dummy load (equi^'alent of RVl) and vice versa. 



The grounded sides of the regular and alternate equipments are made 

 common and then connected via a removable link, LK2, to the sea 

 ground. A safety resistor R2 connects the sea ground to the station 

 ground to restrict the rise in potential to 100 ^•olts if the sea ground 

 becomes disconnected. During maintenance on the sea-ground circuit 

 the link LK2 can connect the power equipment ground to the station 

 ground. 



If, for maintenance purposes, it is necessary to feed from the distant 

 end onl}^, the link LKl can connect the cable to the power-equipment 

 ground and disconnect the live side of both power equipments from the 

 line. 



Safety Inter-locks 



Safety interlock circuits are installed to protect the maintenance staff 

 if the equipments are used incorrectly and are not the normal methods 

 employed for controlling the power supplies. With double-end feeding, 

 dangerous ^'oltages are generated at both ends of the system, and when 

 access is gained to any point in the equipments personnel must be pro- 

 tected from the local and distant power sources. 



To minimize interruptions to traffic, the units of the cable-terminat- 

 ing equipment have been grouped under three headings (see Fig. 4), 

 namely 



(a) Transmission equipment (Si) isolated from the dc cable supply: 

 this includes cable simulators and monitoring facilities not associated 

 with the power supplies. 



(b) E(fuipment associated with the dc supply that can be made safe 

 without interrupting traffic. 



(c) Equipment that can be made safe only by intei-rupting traffic. 



